Luna Incognita

Imaging bright objects

2007-05-19T13:11:00.000-07:00

How I take images depends on the object in question. I usually use a webcam for bright objects inside our solar system, and a sensitive cooled camera for everything else.

The reason is that even though the webcam is much less sensitive than my main camera and has a much smaller dynamic range (brightness levels), it can take up to 25 frames a second, whereas the main camera is limited to one 0.1 second frame each second. To minimize the effects of seeing (air turbulence), I can therefore use the technique of "lucky imaging" with the webcam. This is a technique with exposure times short enough so that the changes in the atmosphere during the exposure are minimal. From these images (a movie really), I select the frames least affected by the atmosphere and combine them into a single image by shifting and adding the short exposures. This yields a much higher resolution than would be possible with a single, longer exposure and allows me to reach the diffraction limit of my telescope, about 0.5 arc seconds (one arc second is the apparent size of a dime about 3.7 kilometers away). By adding hundreds of individual frames like this, the effective dynamic range of the webcam increases, reducing the effects of noise, and I can apply advanced image processing techniques to further increase the resolution of the final image.

Because the exposures are short, I can also use the simpler ALT-AZ setup for the telescope, which is less sensitive to disturbances and vibrations by the wind. During the exposures, the telescope is passively tracking the object to counter the effects of the rotation of the Earth. The Earth's rotation moves objects with a speed of up to 15 arc seconds each second out of view or, with the image scale generally used for these images, between 30-60 pixels each second. The telescope mount can counter the effects of this rotation, but with my telescope, the remaining tracking errors have an eight minute periodic component of 21 arc seconds in them. With the built-in software of the telescope mount I reduced that to an eight minute periodic error of 7 arc seconds peak to peak (in polar mode; I never measured it in ALT-AZ mode but it sure is much higher).

But, because the individual exposures are very short, this remaining periodic tracking error in an 8 minute time period does not lead to image smearing.

Another benefit of the webcam for these kinds of objects is that, unlike my main camera, it is not a monochrome but a color camera. The 640x480 pixel CCD contains a Bayer filter (50% of the pixels have a green filter, 25% have a red filter and 25% have a blue filter). Although this means that each RGB pixel has at least two interpolated color components, it does have the benefit that the colors are shot at the same time. The only post processing required is relative shifting of the color channels, as the Earth's atmosphere refracts light at a slightly different angle for each color, which amounts up to several pixels on the image scale used.

The maximum number of frames that can be combined using this method is limited to a few thousand. Only a certain percentage, like 10%, of the frames can be used to maximize the resolution of the result. My wish to use an ALT-AZ setup for these kind of images also limits the total exposure time because of the effects of field-rotation in this mode. In addition, the imaged objects themselves rotate too, which leads to smearing if the movies are longer than about 10 minutes.

April Fool's Night

2005-04-01T06:20:00.000-08:00

I obtained a tripod mounting block for use with mounting rings and used it to mount the 80ED refractor (with 2" diagonal and 19mm eyepiece, 31x) on the Paragon-Plus XHD tripod. The scope still is out of balance, but a bit less than before, making this combination a little more comfortable to use. This time I also attached the Rigel QuikFinder.

From my light polluted patio, I observed M97 with the refractor. I could only detect it by using the UHC filter. It looked like a featureless roundish smudge of a few arcminutes across near a triangle of stars. M97 forms a right triangle with two if these stars.

Globular Cluster M3 was easy to find. It is visible as round nebulosity that gets dimmer towards the edge. In the same view, two bright magnitude 6 and 7 stars are visible, and M3 itself sits in the "center of mass" of three other stars (mag 8.4, 9.8 and 10.6). M3 is about 3' across in the refractor. No stars of M3 itself were resolved. I am rather surprised that even though I am observing from my patio and high clouds are sometimes reducing the visibility, the limiting magnitude at this magnification is about 11 (towards the east, at about 50 degrees altitude).

At 22:30 I observed Saturn in the Western sky. Its moons Titan (mag 8.4) and Rhea (mag 9.8) were easily visible. I did not detect any other moons. Besides the rings, Saturn did not show any details. At 31x I could not detect the cassini division (which is not surprising with such a low magnification). The effects of atmospheric diffraction were visible when Saturn was slightly out of focus.

I also observed Castor. I could not resolve this double stars (mag 1.9 and 2.9 separated 2.5") at this magnification. I could easily see the mag 9.8 star 72" away and a mag 10.4 star 3' away.

Double star nu-Draconis was an easy target as well. These mag 4.9 stars are 62" separated. They appear white. I was confused for a moment, thinking I was looking at the wrong object, but then I realized magnitude 6.5 GSC 3893:353 is a non-existent object. After realizing that, the star field made sense (field of view is 2 degrees across with this configuration).

At 00:25 I also observed Albireo while it was rising above the East horizon. Even though it was only 10 degrees above the horizon, the orange and blue components were easily separated (34"). This double star is always a joy to observe.

Finally, I observed Jupiter and four of its brightest moons in the Soutern sky. Two cloudbands of Jupiter were obvious, but no other details on Jupiter were observed. Again I noticed the effects of atmospheric diffraction on Jupiter, which surprised me at 50 degrees altidude. I didn't notice color fringe, but had trouble focussing Jupiter. It more looked like a focus problem of my own eyes than bad seeing. I wonder if the Panoptic is to blame.

Polaris and the Ring Nebula

2005-03-25T06:27:00.000-08:00

This evening I mounted the 80ED refractor on a Paragon-Plus XHD tripod. Attaching the 2" diagonal and 19mm eyepiece result in a tail-heavy combination that is too much out of balance for comfortable use. I need to get a tripod mounting block for use with mounting rings so I can balance it properly.

I pointed the telescope towards Polaris and had no trouble splitting this binary at 31x. Later I also observed the Ring Nebula M57. It was not difficult to find, even though I had not mounted the Rigel QuikFinder. At 31x it was not more than a tiny smudge from my light-polluted patio. Adding a UHC filter improved the contrast somewhat.

Airplane!

2004-12-04T00:44:00.000-08:00

An airplane heading for SJC while imaging the M81/M82 mosaic. This is a single 60 second frame through the V filter.

NGC 1502

2004-12-04T00:36:00.000-08:00

NGC 1502 on December 3, 2004. A 10 minute exposure (20x30s) through a V filter using the 80ED. The camera was cooled to -15°C.

I also imaged it with an I filter. I still have to perform photometry.

The Double Cluster in Perseus

2004-12-04T00:25:00.000-08:00

NGC 869 and NGC 884. Mosaic of two images taken on December 3, 2004 through a V filter with the 80ED telescope. One of 57x30s and the other of 31x30s. The camera was cooled to -15°C.

Click the image to see the full mosaic.

Equipment

2004-12-01T00:30:00.000-08:00

Telescopes

Oberwerk 10.5x70mm Ultra Series binoculars. I selected 10.5x instead of the more common 15x because I assumed this would allow me to use it without tripod. It also has a larger exit pupil distance. However, although these are great binoculars, I regret not buying the 15x variant instead. It's too heavy to not use with a tripod anyway, I find the 10.5x magnification too low and, more importantly, the exit pupil diameter of the 10.5x variant is too big. Since 2010 I use it with an Orion binocular mount on the Orion XHD Paragon Plus tripod I originally bought for the 80ED. Its weight is really pushing the limits, especially when viewing near zenith, because of the poor design of the binocular attachment on that mount. This binocular mount is far from perfect, but it does make observing with the binoculars more convenient;
My main telescope is a 254mm f/10 Meade UHTC LX200GPS. It has the standard electrical focuser and primary mirror lock. A nice feature of this telescope is the upgradable firmware (older versions and history can be found here). To reduce the slewing noise and load on the gears, I use a maximum slewing speed of only 1 degree per second;
For wide field imaging, I have an 80mm f/7.5 Orion 80ED. I usually mount it on top of the main telescope;
7x50 binoculars of an unknown brand bought mid-nineties. The optics were never properly aligned, but I wasn't actively observing in this period anyway. In 2001 I picked up the observing again but when I bought the LX200GPS, a GOTO telescope, I stopped using it again. I replaced it in 2008 with 10.5x70mm binoculars;
115mm f/9 Newton telescope bought in 1981 through Gerard Keijzers from N.J.R.S for a 10% reduced price from Ganymedes in Amstelveen, The Netherlands. I still remember my excitement when Gerard helped me setting up this telescope and I viewed through its 20mm eyepiece for the first time. It has a aluminum OTA and equatorial mount on a wooden tripod.
It's a decent telescope but it has its flaws. The equatorial mount is inadequate for the OTA. The slightest breeze or touch causes the OTA to wobble and it takes several seconds to dampen. Also its 30mm finder is of very poor quality and I rarely used it. The telescope is rebranded as "Vesta", but I think it is a predecessor of the now discontinued Celestron Firstscope 4.5" Newton on a CG-3 mount (model 31044) with .965 inch Huygens 20mm (magnification 45x) and 6mm (magnification 150x) eyepieces. Later I also added a Huygens Mittenzwey 9mm (magnification 100x) and a Symmetrical Ramsden 4mm (magnification 225x). The ones I used most were the 20mm and the 9mm eyepieces. From my old drawings it is clear that my eyes and the telescope optics once were pretty good. I did see the casinni division and a cloud belt on Saturn with it for example. Nowadays the mirrors are very much in need for a recoating;
40mm refractor. I was really my brother's, but I used it for many years instead. It had a cardboard OTA, wooden ALT-AZ mount and probably because of the heavy use by me its achromatic doublet developed an air bubble between its crown and flint lenses which made it a poor performer. I also ruined the single Huygens eyepiece at one point, but continued to use it. In addition I ruined most of the negatives of my family's pictures in my Sun spot viewing sessions (usually at sunset), but I don't think anyone but me ever realized that.

Cameras

SBIG ST-7XE NABG CCD camera. This is a dual CCD camera with a full-frame NABG 765x510 (9x9μm) pixel Kodak KAF-0401E imaging CCD and a full-frame ABG 192 x 164 (13.75x16μm) pixel TC-211 CCD tracking CCD. Mine can cool up to -40°C from abient without using the water cooling. I usually set it to -35°C. In San Jose, CA, this means that the CCD temperature is around -25°C (-13F) on a "cold" winter night, and around -15°C (5F) during summer.
SBIG CFW8A color filter wheel. This automatic filter wheel has room for 5 1.25 inch filters, which is 5 too few, because besides the standard R, G, B and clear filters (and an empty slot), I also own Bessel V and I filters for photometry and narrowband H-alpha, OIII and SII filters.
SBIG AO-7 Adaptive Optics. This is a high speed tip-tilt mirror system. My laptop limits it to 30 corrections a second. I usually use it at 7Hz - 15Hz.
Philips ToUCam Pro webcam for planetary imaging;
Meade Superwedge. Instead of the standard knobs, I use replacements from Scopestuff so I don't have to use tools.
Meade f/6.3 and f/3.3 focal reducers.
Cable (Radioshack)
Jumpstarter (Walmart). I never even tried to use the telescope with internal batteries. From the start, I used a 12V 17AH battery.
25ft serial cable for connecting the telescope to the laptop (Radioshack).
Springy Thingy (parts from Home Depot)
Pizza pan. I found it a pain to try to put the telescope on its tipod for ALT-AZ. As I didn't want to spend $95 on a scopesaver table, I bought a $2.95 pizza pan instead, drilled an off-center hole in it and marked the outline of the telescope base on it.
Dew shield (Orion)
Quick Rigel finder
Collimation thumbscrews (Scopestuff)
Balancing kits and weights (Scopestuff)
Dew heater. I bought the convenient Dew Buster. To recover the costs, I made all the heaters (telescope, finder and eyepiece) myself.
Case (JMI).
350 Watt inverter (Walmart).
The next thing I will buy is the ASO optical cleaning kit. After almost one year of use, the corrector of the SCT is dirtier than my car's wind-shield.

I generally use this equipment in the following combination:

Telescope - focuser - camera
This combination fits through the forks and results in a f/10 system. The image scale is 1.028"/pixel??? in 1x1 binning mode and field of view is 10'x9'.
f/6.3 reducer - focuser - camera
Focuser, F/3.3 reducer, 15mm spacer, camera
Focuser, F/3.3 reducer, 30mm spacer, camera
This results in a F3.3 system.
Telescope - focuser - AO-7 - camera
F/11.3???
Telescope - Focuser - f/6.3 reducer - AO-7 - camera
This results in a f/7 (1774mm) system. The image scale is 1.04"/pixel in 1x1 binning mode and the field of view is 13.3'x8.8'. 1.033avg-1.030+1.035??
Telescope - Focuser - f/6.3 reducer - 15mm spacer - AO-7 - camera

The image scales were determined using actual images. I used the formula:
focal length [mm] = 205 * pixel size [micrometers] / image scale ["/pixel]
to compute the effective focal length.

My reasons for not using other combinations,are:

Telescope - AO-7 - camera.
This combination fits through the forks, but without microfocuser it is pretty useless.
Telescope - f/6.3 reducer - focuser - AO-7 - camera
This results in a f/4.9 (1253mm) system. The image scale is 2.098"/pixel??? and the field of view is 26.7'x 17.8'. This combination results in off center vignetting with a brightness difference of about 30%. For this reason, I will not use this combination anymore.

Problems

Although the LX200GPS is an incredibly value for the money, it does have a few problems.

The fork mount is heavy. swing
The OTA of my telescope is not mounted parallel to the fork arms. When I put it in polar home position and rotate the telescope back and forth in RA, I will never find position (by adjusting the declination) where the stars move around a center.
The optical axis is not aligned with the mechanical axis of my optics. When I use the f/3.3 reducer or the f/6.3 reducer with a big spacer, the vignetting is off center. Coma is visible in one corner when I use the f/3.3 reducer.

Hardware Issues

2004-11-30T22:10:00.000-08:00

A list of issues encountered:

The OTA of my telescope is not mounted parallel to the fork arms. When I put it in polar home position and rotate the telescope back and forth in RA, I will never find position (by adjusting the declination) where the stars move around a center.
The optical axis is not aligned with the mechanical axis of my optics. When I use the f/3.3 reducer or the f/6.3 reducer with a big spacer, the vignetting is off center. Coma is visible in one corner when I use the f/3.3 reducer.

Internal reflection caused by the visual back.
Telescope didn't fit in the JMI case.
The handy microfocuser mounting thumbscrews that were included with the JMI case ruined the original visual back and many of my images.

Planetary Nebula M76

2004-10-30T03:35:00.000-07:00

M76 on October 30, 2004. Four 30 minutes exposures combined for a total exposure of 2 hours.

Equipment used: 254mm SCT @ f/6.1, ST-7XE @ -15C, AO7 @ 7.5Hz (RMS wander 0.1x0.1, activation level 10%, bump 0.30s, dither 3), 656.3/4.5 nm H-alpha filter. Location: San Jose, CA.

The Moon

2004-09-07T02:27:00.000-07:00

The Moon. This image is a mosaic of 8 frames captured on September 6th, 2004 around 1am PST. Each frame was exposed 0.2 seconds through a 656.3/4.5 nm H-alpha filter.

Equipment used: 254mm SCT @ f/6.1, ST-7XE @ -15C. Location: San Jose, CA.

Click the image to see the full 1650x1650 mosaic.

Crab Nebula (M1)

2004-09-05T23:08:00.000-07:00

2004-09-05: 40 minute exposure (4x600s) through H-alpha filter. Camera cooled to -15°C.

Minor Planet (1316) Kasan

2004-08-19T23:03:00.000-07:00

Asteroid 1316 Kasan was discovered on November 17, 1933 by the Russian astronomer Grigoriy Nikolaevich Neujmin (1886-1946). He is credited with the discovery of 74 asteroids, including 951 Gaspra and 762 Pulcova. He also discovered or co-discovered the periodic comets 25D/Neujmin, 28P/Neujmin, 42P/Neujmin, 57P/du Toit-Neujmin-Delporte and 58P/Jackson-Neujmin.

This movie was created from 11 images, each having an exposure of 2 minutes, taken over a 35 minute timespan on the night of 2004-08-19 (around 11PM PST). Each image was taken through an infrared filter. 1316 Kasan is marked at the start of the sequence and can be seen moving towards the West (North is up and East is to the left). At the time the images were taken, the asteroid distance from the earth was almost 1 AU, and its distance from the Sun was 1.8 AU.

The bright star on the upper-left of this movie is magnitude 9 SAO 71737 in the constellation Cygnus. The star immediately east of the asteroid is of magnitude 12.5. Because the images were not obtained using a V filter, but using an I filter, the differential photometric magnitude of 16.2 for the asteroid is not accurate (but it is still close to the expected magnitude of 15.8).

The center of the images as reported by the telescope was RA 21h 48m 48s, DEC +38d 14' 19''. A plate solution found RA 21 48m 43.78s, DEC +38d 13' 30.7''. The image scale is 2.35 arcsecs/pixel (the whole image is about 15' x 10'). During the 35 minute sequence, the asteroid moved almost 21 arcseconds.

The animation is noisy because I did not have matching bias/dark frames, nor did I have flat frames. I downscaled other bias/dark frames, and used strong dead/hot pixel removal to reduce the remaining noise.

Polar Alignment using a CCD Camera

2004-07-18T03:21:00.000-07:00

The polar alignment technique as described in the LX200 GPS manual is too inaccurate for CCD imaging. Although many people are recommending the Drift Alignment technique instead, I find it too cumbersome. I always use the following technique:
After setting up the telescope, attaching the camera, balance, level it, and turning everything on:

Disengage the locks and manually point the telescope to zenith.
Switch the image acquisition software to Focus Mode, and focus.
Set the guiding speed to 100% (Autostar II: SETUP - TELESCOPE - GUIDE SPEED).
Take an image of 35 seconds:
1. Don't touch the Autostar for the first 5 seconds.
2. Press the E (left) button for 15 seconds.
3. Press the W (right) button for 15 seconds.
You will now see two star trails for each star (see IMAGE). One trail is caused by the fact that the telescope was not moving, and the other one is caused by the telescope moving at twice the sidereal speed. The angle between the lines is an indication of the amount of misalignment in the azimuth direction.
Turn the azimuth knobs and repeat the previous step. From the angle between the lines, yo will quickly learn how far you have to turn (and in which direction).
When the two trails are falling on top of each other, then take an image of 65 seconds:
1. Don't touch the Autostar for the first 5 seconds.
2. Press the E (left) button for 30 seconds.
3. Press the W (right) button for 30 seconds.
Repeat again until the difference is too small and take an image of 125 seconds:
1. Don't touch the Autostar for the first 5 seconds.
2. Press the E (left) button for 60 seconds.
3. Press the W (right) button for 60 seconds.
I usually stop after this.
Now disengage the locks and manually point the telescope towards the east direction (or west).
Repeat the same method, but adjust the altitude knob. Because the telescope is level, this step is much faster.
Disengage the locks again and manually point the telescope towards a bright known star.
Sync Autostar. as an Autostar SYNC resets both the RA and DEC values to the ones of the currently selected object, a SYNC is all that needs to be done when the telescope is properly aligned. (Autostar II: MODE - 5, select star. Sync by holding ENTER).
Set the guiding speed back to 66% (Autostar II: SETUP - TELESCOPE - GUIDE SPEED).

TODO
At f/7 ?? (St7XE,CFW8,AO7,FR6.3) and the 125 seconds exposure, the accuracy is about 6 arc minutes (500 pixels length, 1 pixel about 1 arc second). Another excellent description of this method can be found here. Using this method, I also discovered the AO-7 wiggle, that was caused by a defect in the ST-7XE camera. Fine tuning can be done using the Single Axis Mount Dynamics command of CCDOps.

PEC training using a CCD camera

2004-07-18T03:19:00.000-07:00

TODO

The Bubble Nebula Revisited

2004-06-25T22:58:00.000-07:00

NGC 7635 on June 25, 2004. My first SII Ha OIII image attempt.

2004-06-25:

The Bubble Nebula

2004-06-05T04:12:00.000-07:00

NGC7635 on June 4, 2004. A combination of eight 20 minutes exposures through a 656.3/4.5 nm H-alpha filter for a total exposure time of more than 2.5 hours. The ST-7XE camera was cooled to -20C.

The Cocoon Nebula

2004-05-30T04:05:00.000-07:00

IC5146 on May 29, 2004. A star-forming region of glowing hydrogen at an approximate distance of 3000 light years, surrounded by a sparse star cluster. The hydrogen is lit by the type B0 star of magnitude 9.6 in the center of the nebula.

This is an 80 minute exposure, consisting of four 20 minutes individual exposures, through a 656.3/4.5 nm H-alpha filter. The ST-7XE camera was cooled to -20C.

NGC 6888

2004-05-29T22:48:00.000-07:00

NGC 6888 on May 29,2004. This is a mosaic of two 100 minute exposures, each consisting of five 20 minutes individual exposures (2x5x1200s) through a 656.3/4.5 nm H-alpha filter. The ST-7XE camera was cooled to -20°C.

Dumb Focuser Thumbscrews

2004-04-24T08:59:00.000-07:00

Last night I realized that much of the flexure in the optical train I have been noticing many times before is really caused by the focuser. It is never snug to the back of the telescope. So today I took a closer look and noticed something I should have noticed a year ago. The damage to the optical back is not caused by over tightening, but by the focuser thumbscrews that were included in the JMI case itself! Comparing them to the original ones that came with the telescope, it is obvious that these replacements have a flat head instead of a round one, and they do not properly fit in the optical back.

So I filed them. And indeed now the focuser connects well. Moving forward, this should reduce the elongated stars I have been seeing in so many of my images.

Planetary Nebula M57 Revisited

2004-04-09T08:48:00.000-07:00

My first image using my new AO-7. Not perfect yet, but sure an improvement on my previous image.

2003-04-08: 4 minute exposure (2x120s). Camera cooled to -10-20°C.

Saturn

2004-03-09T11:28:00.000-08:00

Saturn on March 8, 2004.

Jupiter

2004-03-09T03:18:00.000-08:00

Planet Jupiter floating in space on March 8, 2004. A combination of 662 frames taken with a ToUCam Pro webcam through the 254mm SCT. A total exposure time of 44 seconds.

Please note how this exposure is expressed in seconds, while most others of this blog are expressed in minutes or even hours. Jupiter's apparent brightness is extremely high compared to objects outside our solar system. In fact, only the Sun, Moon, Venus and Mars can reach a higher apparent brightness.

I clearly improved my technique compared to my first attempt of this planet with this telescope.

Eye Opener II

2004-03-07T02:08:00.000-08:00

On several occasions when using the SCT visually, I noticed a significant glare around bright objects (e.g. planets). This is caused by internal reflections in the optical system. I also ran into this problem during imaging several time. For example the January 21 raw frames of M109 are completely ruined by the reflections of the light of a nearby star.
I found that the standard visual back of the SCT is a major cause of this. Flocking it is however not an option as this increases vignetting. To test this theory, I took some flats on December 26, 2003. Indeed, with the standard visual back my replacement f/3.3 focal reducer has an ADU drop of 7% across the field when used with the ST-7XE camera. But, after flocking the inside of this original visual back, this increased to 12%.
I figured that although an Eye Opener II would theoretically not have any benefits with my 1.25 inch eye pieces, nor with my cameras, it may actually lead to a reduction of the reflections. So I bought one, and found that it was actually even more reflective than the original visual back. Indeed, it is slightly worse than the original visual back in regard to the glare.
However, after flocking the inside of the Eye Opener II, it is actually much better than the original visual back. When using the camera with the f/3.3 focal reducer flocking the Eye Opener II doesn't have any negative effects (the 7% ADU drop remains). However, the glare is very significantly reduced when using it visually with bright objects.

So, for my purposes the Eye Opener II isn't beneficial because it reduces vignetting, but it is only because I have more room to add some flocking to suppress the reflections.

Determining Declination Backlash Using a CCD Camera

2004-02-06T20:42:00.000-08:00

By using a 4mm eyepiece, speed 3 (8x sidereal) in ALT-AZ mode I found that my DEC axis backlash can be compensated by entering a value of 30 . This is the value I have been using until now. But, most of the time

The telescope is used in a completely different configuration while imaging (heavy camera, counter weights, etc);
I am using polar mode, not ALT-AZ;
I am using a guiding speed of 66% sidereal (sidereal is 15 arcsec/sec, so I am guiding at 10 arcsec/sec), not 8x sidereal while imaging;
For any speed other than guiding speed, the UP/DOWN buttons behave different. For guiding speed UP/DOWN moves the Declination axis only, but for any other speed, this moves the telescope Altitude. In ALT-AZ mode, Dec movements cause both axis to move, while in Polar mode, an Altitude movement causes both axis to move.

So, for a proper backlash compensation, the amount of backlash should really be determined in the same configuration as that will be used for imaging.

A more accurate approach to determine the DEC backlash compensation in polar mode is:

Set up the telescope with the camera attached as usual (but not with focal reducer for increased accuracy).
Turn off tracking (SETTINGS - TELESCOPE - ...).
Point the telescope to east.
Set the guiding speed to 66% (or whatever what you usually use).
Select guiding speed (MODE - 1)
Take an image of 60 second, while doing that, do the following:
1. Press UP key for 10 seconds.
2. Wait 10 seconds
3. Press DOWN key for 10 seconds
4. Wait 10 seconds
5. Press UP key for 10 seconds
TODO

This is how I came to use the value 100 instead.

Of course, backlash is only a problem if the the guiding direction is changed, so, with a proper polar alignment and an AO7 all this is not really a problem. Also, as long as the direction is not change, the issue of retrograde motion also doesn't appear (this is the problem of a drive, usually the Dec drive, to move a bit in the opposite direction selected by the keypad, before resuming in the correct direction).

On the night of 2004-02-07 I set out to improve my DEC backlash correction using the Single Axis Mount Dynamics command of CCDOps. The telescope was mounted in polar mode.

TODO

No backlash compensation Backlash 8s, Y [-7.87,34.56]	Backlash compensation 25 Backlash 6s, Y [-7.33,48.56]
Backlash compensation 50 Backlash 4.5s, Y [-10.57,45.69]	Backlash compensation 75 Backlash 2.5s, Y [-33.86,33.80]
Backlash compensation 100 Backlash 1.5s, Y [-25.32,38.82]	Backlash compensation 150

Galaxy M109 in Ursa Major

2004-01-22T03:59:00.000-08:00

The aurora in this image is the result of a reflection in the optical system caused by a star just outside the field of view. After taking this image I have been flocking the inside of the AO-7 adapter ring, which was a major contributor to this problem.

For this image, I have used a longer exposure time for the blue filter than for the other two, to compensate for the lower sensitivity of the main CCD for this color.

This is the first image I used my newly built light box for to do flat field correction.

2004-01-21: Luminance 50 minute exposure (5x600s). R and G binned 2x2 10 minutes (1x600s), B binned 2x2 16 minutes (1x960s). Camera cooled to -20°C.

MPL 2860 Pasacenten

2003-11-01T09:29:00.000-08:00

A preliminary light curve spanning 4 hours for Minor Planet 2860 Pasacenten. Determined from 81 frames obtained on 2003-11-01. Each 3 minute frame was binned 2x2. The camera was cooled to -20°C. The telescope used was the 254mm SCT in a f/12 configuration (focuser/AO-7/CFW-8/ST-7XE). No focal reducer was used to minimize vignetting. The image scale is 1.23 arc seconds per binned pixel.

As can be seen from the light curve, the rotational period of this minor planet is around 2.5 hours. I used GSC3674:761 (mag 14.1) and GSC3674:3 (mag 13.5) as K,C stars for the photometry.

I also determined from these Pasacenten frames that I can go until magnitude 18.5 in 3 minutes when binning 2x2 at F/12 from my San Jose patio, and possibly a bit deeper. By combining all 81 images (243 minutes = 4 hours), I determined that I can go until magnitude 20 in that period. Possibly even deeper if during the last hour the frames were not out of focus due to the dropping temperature.

Moon

2003-10-17T04:50:00.000-07:00

A combination of 4 of the best images, automatically selected using CCDOps. Partially overexposed. Click on the image to see the full version.

2003-10-16:

The Bubble Nebula NGC 7635

2003-10-12T04:47:00.000-07:00

My first true LRGB image.

2003-10-11:

Uranus, Umbriel, Oberon and Titania

2003-10-11T04:26:00.000-07:00

The following image of Uranus and three of its moons was taken on the night of October 11, 2003 in front of my apartement in San Jose, CA. In this image, North is down, and East is left. Uranus has a computed magnitude of 5.75, and an apparent angular diameter of 3.62 arc seconds. Known stars of the GSC catalog are marked with their GSC magnitudes (decimal dot before last digit removed).

Using AIP4WIN (star aperture 4, inner sky annulus 6, outer sky annulus 10) and the magnitude 11.2 GSC 5805:40 star at the top left of the image (chosen because it is the faintest one mentioned in the Tycho catalog, and therefore assumed to have a more reliable magnitude: Vt=11.265), it was determined that the three moons had the following magnitude:


Object	Magnitude
Umbriel	-
Oberon	13.9
Titania	13.8

Umbriel is too close to Uranus in the image for an accurate magnitude determination. These values are close to the values calculated using the NASA Ephiremide generator:


Object	Magnitude
Umbriel	15.0
Oberon	14.2
Titania	14.0

The difference is caused by the fact that the image was obtained through a RGB red filter, while the comparisment star magnitude is a V magnitude. Another reason is that the difference in brightness between the moons and the comparisent star is almost 3 magnitudes, which reduces the accuracy.

2003-10-10: 8 minute exposure (50x10s). Camera cooled to -20°C.

Using the known positions of the GSC stars, it was determined that the center of the image is located at 22h 06m 18.67s -12d 29m 56.55s. Similary, the locations of Uranus and its moons were determined as:


Object	RA             Dec
Uranus	22h 06m 17.00s -12d 29m 39.79s
Umbriel	22h 06m 16.79s -12d 28m 20.68s*
Oberon	22h 06m 17.10s -12d 29m 06.70s
Titania	22h 06m 16.24s -12d 29m 19.85s

*The position of Umbriel is only an approximation, as it could not be determined accurately.
The apparent angular distance between the objects in arc seconds and their position angle is:


Object   Uranus     Umbriel Oberon    Titania
Uranus   -          ?       33.1 2.6  22.9 330.8
Umbriel  ?          -       ?         ?
Oberon   33.1 357.4 ?       -         18.2 316.1
Titania  22.9 29.2  ?       18.2 43.9 -

Miranda & Ariel are too close to Uranus (8 arc seconds from center) and could not be imaged. The star left under of Uranus can be found in the USNO-SA2.0 database as a mag 15.3 star. The object right of Uranus doesn't exist in this database (in other words, I do not know yet what it is).

Galaxy NGC 891

2003-10-11T04:20:00.000-07:00

A clear improvement of my first attempt, 9 months earlier on my third imaging session.

2003-10-10: 15 minute exposure (3x300s). Camera cooled to -20°C.

Planetary Nebula NGC 246

2003-10-11T03:55:00.000-07:00

This planetary nebula was discovered in 1785 by William Herschel. It is of relatively low surface brightness. As can be seen in this image, the central star of this nebula is actually two stars close in angular separation. The central star is of magnitude 11.9. Its companion at 3.8 arcseconds distance is of magnitude 14.

The planetary nebula has an apparent diameter of 4 arcminutes. Compare this to the moon, which has an apparent diameter of 30 arcminutes. Several stars are superimposed on this nebula.

2003-10-10: 30 minute exposure through a red, green and blue filter each (3x3x600s). Camera cooled to -20°C.

Galaxy M77 (NGC 1068)

2003-10-11T03:47:00.000-07:00

M77 is a magnitude 9.6 (8.9?), type Sb spiral galaxy in the constellation Cetus. It is over 170,000 light years across (bright part measuring about 120,000 light years,) and over 49 million light years away (60000 (kly)?).

It is the nearest and brightest example of a type II Seyfert galaxy, showing broad and strong emission lines due to high velocity gas in the galaxy's inner regions. A strong radio source (probably a supermassive blackhole) known as Cetus A sits in the nucleus.

The foreground star to the left of M77 is the magnitude 10.81 HIP 12668, on a distance of 982.40 light years and spectral type G0. Using this image, I determined the angular separation between this star and the galaxy core is 88.1 arcseconds (PA 295°).

2003-10-10: 30 minute exposure through a red, green and blue filter each (3x3x600s). Camera cooled to -20°C.

Galaxy M31

2003-10-11T03:38:00.000-07:00

Last night I did my first attempts to color imaging with my ST-7XE. This LRGB image depicts the central region of M31. The dust is clearly visible, but the coma in the source images made it impossible for me to properly line up the individual images.

2003-10-10: Camera cooled to -20°C.

Mars Revisited

2003-08-25T10:16:00.000-07:00

2003-08-26:

AO-7 Wiggle

2003-07-26T03:20:00.000-07:00

TODO

Setting up for CCD imaging

2003-07-26T03:15:00.000-07:00

Setup the tripod, attach the wedge and roughly level it.
Table south of telescope
Attach te telescope. Make sure the locks are disengaged. The OTA is kept in place by a piece of velcro that's wrapped around it.
Attach the finder, microfocuser, diagonal and 19mm eyepiece.
Attach all the cables to the camera, telescope and laptop. I always put the bulky camera power supply on the wedge.
Level the combination more accurately (using the wedge level).
Attach the dew shield and camera. Dynamically balance the telescope, disengaging the locks whenever necessary.
If necessary, cover the telescope and let it cool down for one hour.
Turn on the laptop, camera and telescope, in that order.
Make sure Autostar is set to Polar mode. I have told Autostar to do a GPS sync on startup.
Point the telescope to a bright star, align the finder and focus.
If necessary, remote the dew shield, collimate the telescope using the camera and attach the dew shield.
Usually, the camera equipment will not fit through the forks, so the Autostar polar alignment functions cannot be used. But, as an Autostar SYNC resets both the RA and DEC values to the ones of the currently selected object, a SYNC is all that needs to be done when the telescope is properly aligned. Not using any Autostar alignment function, move the telescope to a known star and do an Autostar sync.
Using the camera, do an accurate alignment.
Do the Autostar sync afterwards.
When I turn off the equipment, I first turn off the telescope.
Determine the seeing condition by taking a well focused 0.01s exposure of a bright star and determine its FWHM.
If possible, I modify the setup such that the FWHM on this short exposure is between 2 and 2.5 pixels. I find a larger (e.g. 3 pixels) FWHM visually much less pleasing, and smaller would result in undersampling. As the typical rms stellar wander is about half of the FWHM, I reduce the system further to a FWHM of at most 2 pixels when I am not using the AO-7.

Techniques

Do a PEC before each long exposure, overwriting previous one. This will compensate RA drift caused by imperfect polar alignment. Also gives most accurate PEC I believe.
Disable X/Y corrections of drive while autoguiding. All corrections should be done by AO-7 only. With proper alignment and PEC, this should be all that's necessary.

Mars

2003-07-13T09:55:00.000-07:00

2003-07-13: 12 second exposure (300x1/25s) using ToUCam Pro webcam at f/20.

Uranus

2003-07-13T09:43:00.000-07:00

2003-07-13: 4 second exposure (100x1/25s) using ToUCam Pro webcam at f/20.

Globular Cluster NGC 6229

2003-05-12T09:05:00.000-07:00

2003-05-11: 50 minute exposure (5x600s). Camera cooled to -20°C. Image scale 1.03 arc secs/pixel.

Planetary Nebula NGC 6210 (PLN 43+37.1)

2003-03-07T02:25:00.000-08:00

This planetary nebula in Hercules is claimed to have a distance of about 6500 light years. Its central star has designation HD 151121, and according to the Tycho catalog, its distance is 136.7 light years, which doesn't add up.

A SIMBAD search reveals the central star is of type O7, the radial velocity is -35.6 Km/s (moving away from our solar system) and the parallax is an unreliable -4.0±11.00 mas (!), which corresponds to 250pc, or 815 light years.

2003-03-06: 1 minute exposure (1x60s). Camera cooled to -20°C.

Planetary Nebula NGC 6058

2003-03-07T02:22:00.000-08:00

2003-03-06: 3 minute exposure (3x60s). Camera cooled to -20°C.

Seyfert's Sextet (NGC 6027)

2003-03-07T02:16:00.000-08:00

Flat field subtracted using a flat that was constructed from all the session's images as described here.

2003-03-06: 3 minute exposure (3x60s). Camera cooled to -20°C.

Galaxy NGC 5474

2003-03-07T02:11:00.000-08:00

Obviously in need for a much longer exposure.

2003-03-06: 1 minute exposure (1x60s). Camera cooled to -20°C.

Galaxy M101

2003-03-07T02:07:00.000-08:00

2003-03-06: 4 minute exposure (4x60s). Camera cooled to -20°C.

Globular Cluster M92

2003-03-07T02:04:00.000-08:00

2003-03-06: 1 minute exposure (1x60s). Camera cooled to -20°C.

Planetary Nebula M57

2003-03-07T01:51:00.000-08:00

The famous Ring Nebula, imaged using the horribly bad .33 focal reducer. I had to reduce the size of the image just to cover up the extended coma. The field of view with this focal reducer is great, but because the vignetting and coma is so severe, if not resizing it I would have to crop the image so extensively that I could as well just use the .63 focal reducer!

2003-03-06: 3 minute exposure (3x60s). Camera cooled to -20°C.

Spiral Galaxy M51 (NGC 5194) Revisited

2003-03-07T01:30:00.000-08:00

A second attempt of this galaxy, this time using the .33 focal reducer. Only a two minute exposure (the previous one was 25 minutes), but the increased field of view is rather nice. The low quality of the reducer spoils it though (notice the strong coma at the bottom half of this image).

2003-03-06: 2 minute exposure (2x60s). Camera cooled to -20°C.

Globular Cluster M13

2003-03-07T01:24:00.000-08:00

Coma is noticeable at the bottom left of the image.

2003-03-06: 2 minute exposure (2x60s). Camera cooled to -20°C.

Galaxies MCG +9-23-50, +9-23-51, +9-23-52, +9-23-56 and CGCG 272-40, 272-42 in Ursa Major

2003-03-07T01:20:00.000-08:00

2003-03-06: 3 minute exposure (3x60s). Camera cooled to -20°C.

Creating a flat field from light exposures

2003-03-06T23:40:00.000-08:00

On the 2003-03-06 imaging session, I used my newly obtained FR/0.33 focal reducer for the first time. The images obtained using it show severe vignetting. For example, the following image is of Seyfert's Sextet (50% of original size):

At the lower left, the average ADU is 24% less than in the center of the image. Also, the vignetting is off-center.

By combining 49 images from different fields that night, all with the same camera orientation, and applying a dust and scratches filter with radius 30 and blurring with radius 30, the result is:

Applying this flat field to the above image, the image now looks like this:

Here the black and white points remained the same. There is still some residu of the vignetting, but it is not very severe.
The difference of the average ADU is now much smaller. There is now only a difference of 1.4% between the center and the border. I don't know why this central area is overcorrected by this amount. It is not a replacement for a real flat field of course, as the noise is much higher (not half full-well limit).

I returned this focal reducer, because the 24% vignetting is unacceptable. In addition it also created severe coma. Not only in the corners of the main CCD, but especially in the tracking CCD all stars had a V shape. The replacement only exhibits a 7% vignetting and much less coma.

Minor Planet (1951) Lick

2003-03-06T23:08:00.000-08:00

On March 7, 2003 I took 14 successive 60 second images of an area the size of about one quarter of the full moon in Hercules, near the borders of Draco and Bootes. Each image was taken with a delay of 60 seconds, except for the second image, which was taken after a delay of about 4 minutes. The movie below depicts this sequence, in reality lasting a little more than 30 minutes, accelerated 480 times.

Look closely, and you'll find asteroid (1951) Lick moving in front of the background stars. This asteroid was discovered on July 26, 1949, by Carl A. Wirtanen (Lick Observatory, CA, USA, I guess that's why it was named Lick). He also discovered comet 46P/Wirtanen, that originally would be visited by the European Rosetta spacecraft, before it was delayed and a different target was chosen. Unlike many other asteroids, it does not move around the Sun in an orbit that lies between those of planets Mars and Jupiter, but one that is a little closer to the Sun and one that does not lie in the ecliptic plane, but is inclined 39° [1]. It has an eccentricity of 0.0615. The distance of Mars to the Sun is about 1.52 AU (228 million kilometers), whereas that of the asteroid is up to 1.39 AU (209 million kilometers) [1]. Because the Earth moves around the Sun too (at a distance of 1 AU, or 150 million kilometers), the distance between the asteroid and Earth varies a lot, and at the time of these images, it was about 0.74 AU (111 million kilometers). The positions of the planets and the asteroid at the time of imaging, is depicted in the following graph. The planets and asteroid (the square) move clockwise in this orientation.

The bright star in the images is the V magnitude 8.5 HIP 78421, which has a distance of 492.68 light-years (4661 trillion kilometers) [2]. The star below the center of the image is magnitude 14.43 GSC 3497:1453. Using the latter star for unfiltered differential photometry, I determined that the magnitude of the asteroid was about 16.4 at the time. I estimate the accuracy of this to be only about 0.5 magnitude, as a result of a combination of severe vignetting (this was before I exchanged the poor focal reducer), and field rotation (ALT-AZ mount). Nonetheless the measured magnitude matches the computed magnitude 16.5 well.

This inaccuracy did also not allow me to determine a light curve for the asteroid. It is known to have a rotational period of 5.3016 hours [3;4;5;6] (secure result with no ambiguity, full lightcurve coverage), and a V magnitude variation of 0.17-0.27. Using GSC 3497:1453 (mag 14.43) and GSC 3497:1319 (mag 14.09) as C and K stars, I found the variation of C-K to be of the order of 0.4 magnitude, which is larger than the expected variation of the asteroid. Of course, half an hour of imaging would be too short for confirming this rotational period anyway.

The asteroid moved 57.02 arcseconds between the first and last image, which corresponds to an apparent speed of 0.0313 arcsecs/sec (taking half exposure as the time of an image, the first and last image were 1824 seconds apart). This is slightly less than the computed 0.0382 arcsecs/sec (computed RA rate of 0.0294 and dec rate of 0.0244). This difference is likely caused by the small change in image scale during imaging (clearly visible in the above movie).

Using my measured value of 0.0313 arcsecs/sec, and the computed distance of 111 million kilometers, this means the asteroid was moving at a speed of at least 16.8 Km/sec relative to the Earth.

The parallactic angle (angle between the top of the image and true North) of the aligned images is 273.43°. Combined with the positional differences between the first and last images, I found the angle of the asteroid move to be 329.67°.

The last image is an averaged combination of all 14 images. It shows fainter stars, up to about magnitude 17.5, and a trail for the asteroid (in case you still didn't find it). The uneven background is a result of vignetting and processing.

2003-03-06: 14 minute exposure (14x60s). Camera cooled to -20°C.

Bibliography

[1] Minor Planet Center Orbit Database (MPCORB); 2003.
[2] Hipparcos Catalog.
[3] IAU Minor Planet lightcurve parameters list; 2003-12-15.
[4] Velichko, F.P., Krugly, Yu.N., Lupishko, D.F., Mohamed, R.A.; 1989, Astron. Tsirk. 1546, 39-40.
[5] Wisniewski, W.Z., Michalowski, T.M., Harris, A.W., McMillan, R. S.; 1997, Icarus 126, 395-449; 1995, Lunar & Planetary Science XXVI, 1511-1512.
[6] Pravec, P., Wolf, M., Sarounova, L.: 2003, posted on WWW; http://sunkl.asu.cas.cz/~ppravec/neo.htm.

Spiral Galaxy M51 (NGC 5194)

2003-02-03T22:58:00.000-08:00

2003-02-03: 25 minute exposure (5x300s). Camera cooled to -25°C.

Planetary Nebula M97

2003-02-03T22:55:00.000-08:00

2003-02-03: 15 minute exposure (3x300s). Camera cooled to -25°C.

Spiral Galaxy M108 (NGC 3556) Revisited

2003-02-03T22:45:00.000-08:00

This image was taken just two days after the previous one. The effects of much improved tracking and a longer exposure (40 minutes instead of 10) are clearly visible. Notice the difference in details of the dust in the galaxy.

2003-02-03: 40 minute exposure (4x600s). Camera cooled to -25°C.

Spiral Galaxy M108 (NGC 3556)

2003-02-02T07:22:00.000-08:00

I am obviously having trouble with tracking.

2003-02-01: 10 minute exposure (5x120s). Camera cooled to -25°C.

SAO 24929 (7 Camelopardalis)

2003-01-26T06:59:00.000-08:00

While I was looking for galaxy UGC3217 on the 2003-01-25 imaging session (which I didn't find), I took this overexposed image of SAO 24929. Nothing interesting to see here, but the only result of that session.

Galaxy NGC3631

2003-01-19T06:53:00.000-08:00

Another binning test.

2003-01-18: 4 minute 2x2 binned exposure (4x60s). Camera cooled to -29°C.

Galaxy NGC 891

2003-01-19T06:37:00.000-08:00

On my third imaging session I have been experimenting with binning. This image was made with 2x2 binning. Because the ST-7XE main CCD doesn't have many pixels to begin with, then resulting image is rather small. However, the sensitivity for each pixel is increased fourfold, and the well depth twofold. For LRGB imaging and photometry this will certainly have its uses. In this case, with normal binning I would only have reached the depth of this image after 42 minutes, instead of the 10.5 minutes used here.

2003-01-18: 630s 2x2 binned exposure (21x30s). Camera cooled to -30°C.

Mirach (β Andromeda)

2003-01-19T06:33:00.000-08:00

I found this overexposed image of Mirach between my images of the 2003-01-18 imaging session. Nothing interesting to see here, except for the faint star at 11h relative to and close by Mirach, which is the magnitude 14.2 GSC 2286:693. After all, this is only a one second exposure.

Galaxy M63

2003-01-19T06:30:00.000-08:00

2003-01-18: 150s exposure (5x30s). Camera cooled to -30°C.

Globular Cluster M3 (NGC5272)

2003-01-19T05:46:00.000-08:00

2003-01-18: 150s exposure (15x10s). Camera cooled to -30°C.

Galaxy M81

2003-01-07T01:15:00.000-08:00

While experimenting with automatic tracking and stacking, I took this image of galaxy M81. The polar alignment of the telescope was poor, hence the common part of all sub-images was relatively small. So I ended up with a galaxy not even fitting in the final image.

Anyway, the spiral arms and dust in this galaxy are obvious.

30x30s exposures combined (total 15 minutes). Camera cooled to -25°C.

Planetary Nebula M76 (NGC 650) in Perseus

2003-01-07T01:05:00.000-08:00

For the second imaging night with the ST-7XE, I mounted the telescope in Polar Mode. This is the first time I used the tracking CCD of the camera for automatic guiding of the telescope and I experimented with automatic tracking and stacking. The striping in this final image is the result of poor polar alignment and the sub-exposures being too short.

In this image of M76, commonly known as the Little Dumbbell Nebula, the bright expanding elliptical ring seen almost edge-on is quite obvious. The dim "wings" along the axis perpendicular to this ring are visible as well, although barely in this image. Both of these structures are expanding.

20x15s exposures combined (total 5 minutes). Camera cooled to -25°C.

Galaxy M82

2003-01-05T00:49:00.000-08:00

That same night I pointed the telescope towards the irregular Galaxy M82 (NGC 3034), in Ursa Major (Big Dipper). Its visual brightness is magnitude 8.4 and apparent dimension 11.2' x 4.3' (Uranometria 2000 2nd ed.).

For this object I enabled the telescope tracking and used a focal reducer. With the ALT-AZ mounted telescope, the longest exposure I can take in this area of the sky at this focal length (about f/6.9), without the effects of field rotation causing the stars to streak too much, is about 30 seconds. This single unguided 60 second automatically dark subtracted image is the best result of this night. The camera was cooled to -25°C.

The amorphous galaxy M82 contains a starbursting nucleus. Images in the light of ionized Hydrogen and Sulfur show vast filaments of ionized gas streaming away from the galaxy. In the image below, this ionized gas is not visible, but dark dust lanes and patches in the central part of M82 are. The central dark dust lane can be observed visually as well with the same telescope. The stars in this image are all part of our own galaxy. Their distances are up to a few hundred light years. M82 itself lies far beyond the borders of our galaxy, at a distance of about 12 million light years.

One minute exposure. Camera cooled to -25°C.

Polaris (North Star)

2003-01-05T00:23:00.000-08:00

This is the first image of an astronomical object I ever took with my ST-7XE camera. Last night, I mounted the telescope in ALT-AZ mode, attached the camera, pointed the telescope to Polaris, roughly focused it, and shot this 10 second exposed image. The camera was cooled to -10°C.

As this was just a simple camera check, even the telescope tracking was completely turned off.
Polaris itself is completely overexposed in this image, and the raw image contains blooming streaks above and below the star, proving that this camera indeed has a NABG sensor. You see, Astronomics initially sent me an ABG version, which I returned immediately after discovering this using a pin-hole test.

I manually cleaned the blooming streaks (some artifacts are still visible), and used non-linear histogram stretching to improve the visibility of the companion.

Polaris is a binary star at a distance of 431 light years, consisting of a bright magnitude 2 supergiant and a much dimmer magnitude 9 main sequence star, separated by about 18 arcsecs. Even though this 7 magnitude difference makes it a bit harder, I found on 2005-03-25 that I could easily resolve the binary with my 80mm refractor at a magnification of 31x.

From the original (bloomed) image, I determined that the apparent distance between the two components is 26.7 pixels. Attaching the camera directly to the focuser therefore results in a system with a focal ratio close to f/11.

The same night, I also took my first image of galaxy M82.

Coe

2002-11-01T23:42:00.000-08:00

I went to Coe last night and stayed until around 3:30am. The overflow parking lot was locked again, so I set up the 254mm SCT at the parking lot near the entrance. The limiting magnitude was at least 5.5 and M31 was easily visible with the naked eye. It was the first time I actually could easily see M1 and truly recognize it. M82 showed an obvious dust lane about in the middle. M42 had too much detail to describe, the trapezium components E and F were easily visible.

My object for the night, NGC 7662 (Blue snowball, Caldwell 22, in Andromeda) looked to me like a ball with a brighter inner ring. I did not see a central star, but one close to it (distance about the same as the size of the disc) and with averted vision two other nearby stars popped up. I don't know their magnitude, but you can see the three I mean here.

Jupiter

2002-09-23T23:49:00.000-07:00

A first attempt on September 22, 2002 of imaging planet Jupiter with my new 254mm SCT. It sure looked a lot crispier when viewed through the telescope, but the shadow of one of its moons can still seen projected on the sphere here. A combination of many frames taken with a ToUCam Pro webcam in prime focus. No Barlow lens was used.

Saturn

2002-09-18T10:03:00.000-07:00

A first attempt on September 18, 2002 to image planet Saturn with my new 254mm SCT using a ToUCam Pro webcam at f/10.

Mizar through my old Newton telescope

2002-04-14T00:25:00.000-07:00

A single webcam frame of Mizar and Alcor in the constellation Ursa Major through the 115mm Newton telescope on April 13, 2002. I wasn't (manually) tracking, so the stars appear slightly elongated, even with this short exposure.

Imaging with a 21 year old 115mm Newton

2002-03-20T22:00:00.000-08:00

Jupiter on March 19, 2002. The average of many frames taken with a ToUCam Pro webcam in the prime focus of my 1981 115mm/f9 Newton telescope. The mirrors of this telescope are very much in need for re-coating. The views through the telescope are not close to what they once were.

Saturn through the same telescope. Back then I could easily see the Cassini Division and Saturn's cloud belt. Not so anymore.

A shot of the moon.

And one more, but this time using eyepiece projection.