Comet images and an education

I've decided to create a summary of my Comet Holmes images in chronological order in this posting with the plan of adding to them here as time goes on. I'm not particularly proud of them, but they have taught me a lot and others may find some of what I've learned useful. None of this is earth-shattering, but it's been news to me. The highlights so far:

1. I need to use quality pastel papers to do pastel sketches of diffuse objects. 9Been sketching on some fairly smooth, cheap black paper.)

2. The Canon Digital Rebel does a great job with exposures up to 30 seconds long when you simply piggyback it on the LX90.

3. The zoom lens I bought for the MallinCam is usable, but extremely poor in several respects.

4. The MallinCam delivers incredible depth - sensitivity - even when shooting through 3-inch scopes.

5. The NexStar 5 SE mount can be used to hold a ShortTube 80 or other scope, but it also seems more erractic than when the 5-inch is mounted that way. (Still experimenting, but now with the larger NexStar 8 mount.)

6. Keeping in mind that the goal of the MallinCam video camera is to produce live video - not still images , I have found that the simplest way to get crude, but useful still images is to simply snap a picture of the video screen.

7. Such screen shots should be taken at between 1/8th and 1/4th of a second to avoid artifacts from the way the image is created on the screen. This means using an image-stabilized lens or a tripod.

8. With a growing comet I have been experimenting with ways to get wider and wider shots. I have found that on the F10 SCTs I can double up the MallinCam MFR3 focal reducer with a Celestron focal reducer that mounts directly on the SCT.

9. Adding spacers between the MFR3 focal reducer and the CCD in the camera helps - knew this - but I didn't know how much space could be added. More experiments coming shortly after anew spacer arrives.

10. The easy way to quickly focus the MallinCam is to brighten the video screen way past what you should - then once you have focus, darken the screen. This is very helpful when you are switching the camera from telescope to telescope and finding focus can be difficult.

THIS POST IS A WORK IN PROGRESS. I PLAN TO EXPAND ON THESE POINTS AND RELATE THEM TO THE IMAGES WHERE USEFUL. BUT FOR NOW . . .

Above taken November 19, 2007 - about 11:44 pm. Used 5-inch, MFR-3 plus 10mm and 5mm rings. Mirfak is the bright star on right. Screen shot at 1/6th second with Canon Rebel and a 300mm IS lens.

I first looked at Comet Holmes this night in the 8-inch Nexstar SE. It's still right next to Mirfak and Mirfak was so bright it seemed like it was taking a big chunk out of one side of the comet. Keep in mind I was contending with high clouds that some times totally obscured Mirfak to the naked eye and throughout my observing session it was never absolutely clear. Oh - and a waxing moon maybe 70% full and pretty bright in the west as well.

But the naked eye view was good enough to send me back into the house to get the NexStar 5 SE and put it on the same mount - didn't have to do another two-star that way - and set-up the video camera. I watched for about an hour taking pictures of the video screen with the Canon Rebel. Most of the shots were six second integrations. Some were 12 seconds, but the mount wasn't tracking well enough to really handle the 12-seconds. In fact it dragged stars some on some of the six second shots.

Also - I could just squeeze the comet into the fov even though I have two focal reducers and two extensions (a 10mm and 5mm) on the scope giving me perhaps an F3 or faster. Another 10mm extension is due in tomorrow's mail. This should widen the field a bit more, since it puts more space between the optical elements of the focal reducer and the CCD chip.