Posts Made By: Joe Baldwin

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=22-504

Trying it but not having really good success. CCD sensitivity falls off fast above 800nm - have to use a lot of gain which equals poor S/N ratio. Haven't tried it with the Sony Exview yet, maybe some potential there. Also hard to find reasonably priced bandpass filters in the near-IR and none of them are in a standard 1.25" or 2" astro format.

Great job for such low elevation. BTW, I've been out of the loop awhile. What kinds of issues did you have with your C9.25?

Very nice. Very smooth with little noise, I'd say the exposure was set perfectly.

I've not found any improvement on Saturn or Jupiter, I did not have the filter for the last Mars opposition so the jury is still out on that one.

Really Nice! I like the color balance

The rebel and the 10D have around 6M pixels the 20D is around 8M. Noise levels are supposed to be slightly better in the 20D. The rebel and the 10D are the same internally, the rebel has some advanced functions neutered. the program DSLR focus does not work with the 20D (yet). You need that or one of the Knife edge type thingies ($$) to focus.



Go here for a full-blown comparison.

www.dpreview.com

Dick Suiter's book " Star Testing Astronomical Telescopes" addresses this very issue. He examines each optical defect in detail and its impact on resolution. While a central obstruction is not a defect per se, he evaluates this as well. To answer your question you would need to quantify the terms better quality and average quality . In general, errors tend to suppress higher spatial frequencies which contain the information for fine detail and sharp edges. Bigger apertures have higher spatial frequencies. The optical quality determines how much of the higher frequencies make it to your eye ( or CCD)

I recently bought a pair of 16mm UO Konigs for binoviewing. They are great performers BUT the eye relief is microscopic. Eye lens was coated with eyelash marks after one use. Anybody else have this same issue?

Floyd,

Suiter's treatment of diffraction theory is quite complete making the book read more like a college text than a how-to guide. But, if you read the material on each kind of optical defect and study the pictures of the diffraction patterns you can get a very good feel for the kinds of patterns to look for when at the eyepiece. Most, if not all, of the derivations and wave theory explanations could be skipped without losing any value when comparing star patterns. The gory mathematical details are fascinating to some, while others, unable to grasp them, find them unnecessary(empty).

I spent the better part of 2 nights looking at my setup and comparing to his diagrams. Some very important things to keep in mind:

- To compare the star test patterns, you need to defocus approximately the same amount as Suiter's diagrams. He explains how to calculate the focus movement for a particular F#.

- The patterns in the book usually illustrate the diffraction pattern inside, outside and in focus. Note the in-focus pattern is greatly magnified w.r.t. the out of focus images- I really had to look hard to see characteristics of the diffraction rings in focus.

- I never had seeing conditions good enough to do a decent star test. I made an artificial star using a white LED flashlight and a pinhole - worked great.