Methods and madness

BASS Presentation

Sun, 22 Mar 2009 19:23:03 -0600

Last night I had the privilege of giving a presentation about astrophotography titled “Astrophotography for Non Millionaires” at the Boulder Astronomy and Space Societies monthly meeting at the Sommers Bausch observatory on the CU campus. As the title would indicate it is all about doing astrophotography with affordable gear. I think it was well received and I really enjoyed doing it. Thanks very much to the BASS folks for being such a good audience. As promised here are the slides from the presentation.

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M45 the Pleiades

Wed, 26 Nov 2008 16:20:36 -0700

Well I completed my first deep space photograph. And apparently I picked a real doozie of an object to start with. I chose the pleiades because I think they are neat especially in a photograph. I also chose it because it was a good match for the camera and telescope combo being a nice wide field object . And also because it is available right now in the early evening sky. I have come to understand how difficult it is to image the pleiades and get the nebulosity to show up. I basically had to beat this image in to submission in processing. With three hours of total exposure I think I could have used about a hundred more. I will come back to this and try to collect more photons next time. I used a light pollution suppression filter (Orion Skyglow Imaging) and I am wondering what effect that may have had on the number of photons I collected on this object I have seen lesser exposure times in other images even other 80mm telescope images show more of the nebulosity. So I am wondering where I may be losing photons. I figure it could be either my suburban skies, the LPS filter, or my processing. I will try next time without the LPS filter as a test. So basically I am sorta happy with this image at least for now. You can check out a larger version with capture details in the star clusters album.

Lunar imaging

Sat, 8 Nov 2008 14:19:56 -0700

Well, after much hard labor I finally completed my back yard observatory a couple of weeks ago. The last two weeks have been consumed with move in housekeeping. And last night I finally got an opportunity to do some imaging. And since the moon is out and waxing gibbous. That seemed a logical place to begin.

I decided to use my small Orion EON 80mm ED refractor mounted to my modest Celestron CG-5 german equatorial mount. It has a 500mm focal length and fine optics which are largely free of chromatic aberration. So it would give me a good field of view for this wide field object as well as good contrast. I chose to use my Orion Starshoot Solar System Color Imager II camera which I bought specifically for Lunar and Solar work. It’s CMOS sensor while not as sensitive as a CCD webcam is certainly sensitive enough for Lunar and Solar work. And it’s high resolution (1280x1024), allows you to fit the entirety of either the Sun or moon on to the chip when combined with the wide field of the EON.

This camera is actually a webcam that has been modified specifically for use in planetary imaging. Video cameras are preferred for planetary imaging over still cameras even high end DSLRs. The reason for this is that planetary objects are fairly bright and the biggest impediment in planetary imaging is atmospheric turbulence known as seeing. By using a camera that can capture many frames per second we can cheat the seeing by capturing those fleeting glimpses of steadiness. Incidentally this is very similar to how our own brain works when looking at the moon through a telescope eyepiece. Once captured the AVI can be analyzed by specialized software and the highest quality frames separated out and stacked. The stacking of the good frames increases the signal to noise ratio. That is to say it increases the signal that we want while at the same time reducing noise we do not.

For software I used virtualdub for AVI capture and Registax for stacking (both open source and free) and Lightroom and Photoshop for final tweaking. I captured several AVI files of different lengths some as short as 2 or 3 minutes and some as long as 10 minutes. I learned by doing this that registax has a 2GB file limit. Most of my files were well over 2GB (The Orion SSSSCI II gives you raw uncompressed video). And every time I would try to align them Registax would give me an error (failed to decompress AVI frame). I used virtualdub to cut the big AVIs in to smaller AVIs and then processing went fine. The upshot for me is that at 1280x1024 with this camera I need to limit the frames to about 500 per AVI.

I also tried using OnOne’s Genuine Fractals to enlarge this one megapixel image to 11x14 240 dpi print size or 3360x2640 pixels. Genuine fractals is a Photoshop plugin used by photographers to enlarge photos to be used on billboards or the side of buses. For the most part the enlargement seemed to work well. In theory I could print this out on 11x14 and hang it on the wall.

My next Lunar project which I will try is to use the same camera with my larger Celestron C-8 telescope which has a 2000mm focal length. With this setup I will try and capture the moon with a multi shot mosaic which should give me a large high resolution image without enlargement.