How To ~

A Beginner's Guide to Astro-Videophotography

By Phil Hoyle
September 1999
One of the best things about astro-videophotography as compared to other forms of astrophotography is that it can be done with very simple equipment. It can also be very easy. I am writing this to tell you how you can do it with equipment you may already have.

Nearly any "modern" commercial video camera can be used. My camera is about five years old. It is VERY modest as far as video cameras go, even for commercial ones. It has a 1 "lux" rating. (The lux rating is a measure of how much light the camera needs in order to takes pictures. The lower the lux rating, the less light required.) For most astronomical needs, a low lux rating is desired. There are also now commercially available video cameras designed specifically for astronomy. Some people have also used security cameras. I have never used either of these, and therefore I won't talk about them much. Besides, I want to talk about the things YOU can do with simple stuff. 

You can take video through your telescope simply by hand holding the camera over the eyepiece. The camera can also be mounted to the telescope in some fashion, but it is not really necessary. Best of all, a hand held camera can be used with ANY kind of telescope -- even Dobsonian mounted telescopes -- even (should I say) department store telescopes! (Please do not write or call me, I'm not suggesting you go out and buy a department store telescope.) A tracking telescope will make things a little easier, since you won't have to stop every few minutes to readjust the pointing, but I've done it with my LX200 with the power turned off, and with the power turned off, an LX200 is just an expensive Dobsonian. After all, who really cares on a video if the object your shooting slowly moves across the field of view. And, if you intend to download video frames to your computer, it's really not important at all. The only drawback that I have experienced with hand-holding the camera is the resulting shakiness of the video. (Remember my camera is very modest; it doesn't have the steady-cam features that some of yours may have.)

Probably the biggest drawback to video astro-photography is that it is basically limited to the brighter objects like the Moon and planets. Image intensifiers have recently come onto the market that will also allow video photography of deep-space objects, but for now at least, they are beyond my puny budget. Besides, for many of us, the Moon and planets are the most interesting objects in the sky anyway, right? Other targets that I haven't tried yet, but should be easy are: occultations (are you listening Dave?), and the Sun, with the proper filters of course. I only wish I could have had the means and knowledge to do this kind of video-photography when comet Shoemaker-Levy-9 crashed into Jupiter. To this day, I haven't seen real-time video of that event.

To actually take video through your telescope, this is what you do: First get the object into the field of view of your telescope and focus the eyepiece for your eye. Wear your glasses if you have them. Then with the camera in manual focus mode, focus the camera at infinity. Use a very distant object, or the Moon or a very bright planet. For my camera, Jupiter was bright enough to focus on without the telescope this past fall, but Saturn wasn't. Bring the focus just slightly closer than infinity. Then hold the camera directly over the eyepiece. Using wide angle, tilt your camera in different directions until the object you want is in the view finder. The focus should be pretty close right now, but not exact. Use the focuser of the telescope to get a "rough" focus. Then, use the focus adjustment of the camera to get a "fine" focus. Once you're satisfied with the focus, start the video tape. You can speak your observing notes now. They are being recorded on the soundtrack of the video. The things I always try to remember to record are the time and date, what eyepiece and resulting telescope magnification I am using, what my target is and where I am observing from.

Some general observations from my short experience doing this are: Use the zoom feature of your video camera. Anyone who has spent some time visually observing planets knows that the higher you go in magnification, the steadier the atmosphere has to be. It seems to me that the seeing conditions are much more sensitive to an increase in magnification from the eyepiece than an increase in magnification from the video zoom. This allows you to fill the frame with the disk of Jupiter with a relatively low power eyepiece. My camera has a zoom magnification of 8x. Many cameras available today have optical zoom capability of 18x or higher.

I normally use the automatic exposure feature of my camera. For Jupiter and Saturn, this is going to mean that the exposures will normally be as long as the camera shutter allows (1/60 of a second). The automatic exposure feature will also get the proper exposure of the Moon. I would encourage any of you to experiment though. After all, all it costs is a few minutes worth of video tape. Keep in mind that the higher the magnification you use, the dimmer the object will appear. This happens regardless of whether you are increasing the magnification with the eyepiece or with the video zoom. It may not hold true for the Moon; since it is so bright, a higher magnification will just cause your automatic exposure to compensate. 

One of the advantages of using a commercial video camera is that you automatically get color without using filters. To get the proper color, do not use the automatic white balance feature of your camera. This will cause the Moon and Jupiter and Saturn all to have a very pale color. My camera has three white balance settings. One for sunlight, one for yellow (incandescent) light and one for blue (mercury vapor) light. To get the proper color, I use the sunlight setting of my camera. When increasing the magnification so that the object begins to dim, you will lose some of the color. All commercially available cameras as well as the Human eye lose their ability to accurately distinguish color when there is not much light available. If, as you are recording, you notice the object getting dimmer, you might want to zoom out to maintain the proper color. If you want to record as much detail as you can and don't really care about the color, you might want to zoom in. Experiment! See what your camera does in combination with your telescope and with different eyepieces. With a video camera, you don't have to worry about how expensive the gas-hypersensitized film is. You're recording on videotape! If you really don't like what you get, you can erase it and try again! You can also try a lot of different things in a really short period of time. Your shots don't have to last more than a few seconds unless you want them to. So shoot it one way, try something else, then shoot again.

I hope I've encouraged some of you to get out and try this. It really isn't that hard. If you know how to use your video camera, and if you know how to use your telescope, you really shouldn't have any problem. Good luck!

Part II: Downloading video frames and processing them on your computer.

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