Friday, January 26, 2007

Saturn

It's that time of year again when Saturn makes an appearance late in the evening. Last night I spent an hour or so trying to get a better photo of it than last year. Out of the 112 shots that I didn't immediately delete, this was the best.



Not too bad I thought, the rings are distinct and the banding is visible. I suspect it's about as good as I'm going to get with my current equipment. It's a bit of an elaborate procedure to take these photos, and goes something like this:

1. Get Saturn in the telescope's field of view and focus
2. Line up camera on tripod, get Saturn in camera's field of view
3. Manually focus camera
4. Set shutter release on timer to allow vibration of telescope and camera to dampen out
5. Take as many shots as possible before it wanders out of the field of view
6. Go to 1.

Trying various shutter speeds, I found 1/40th to 1/80th of a second to be about optimum. Any faster is badly underexposed, any slower and you get too much motion blur. Actually, all the shots are underexposed, the camera is already maxed out in terms of aperture (f2.5) and ISO (400) so there's no where else to go. Short of building/buying a bigger telescope with an equatorial or microprocesser controlled mount, I could possibly make a simple powered mount with rollers acting directly on the ball of the telescope. I'm sure this would work, but the programming to achieve true tracking would be a challenge. However, I think for relatively short exposures of a few seconds or so it might be possible to get away with a simple linear drive, rather than one that tracks the correct curved path..

At the other end of the astrophotography spectrum, make sure you have a look at The Most Detailed Image Of The Orion Nebula Ever Taken. Mindblowing.

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