Hi Debbie, thanks too for the off-list reply: I started shooting astro photos over 30 years ago, I am aware of all the caveats; airplanes, sky-fog, tracking limits, etc. My current set-up is homemade (actually a heavily modified commercial mount from the '70s), I do not use PEC, autoguiders or any digital aids, although I do have a couple of the old Astro-Physics autoguiders. They took all the fun out of it! :( I guide manually, strictly; I've become rather good at it and enjoy it (it's not hard, really. Really!). Go-to mounts and other commercial astro-hardware "for the masses" are not needed here. Old habits I guess. I just had a question about trailing near the edge of the field with a wide-angle lens due to differential atmospheric refraction. (much wider than a 50mm, I'm talking about something shorter than 17mm). You can get the zenith AND horizon in the same shot! What-if stuff. Rob, thanks for your off-list reply also, but the digest just came-through anyway. I use a pair of ancient Pentax K bodies, the fisheye lens in this case is the Russian Zenitar K2,8/16, got for pennies on the dollar on eBay a couple of years ago. Yes, I know it's "student" gear, but I am not going to replace it with high-dollar stuff because it works, works well, I'm used to it, it's paid-for, all my adapters fit it, and money for all-new equipment isn't likely unless it falls from the sky, so any suggestions would have to refrain from including new commercial hardware to be useful. Thanks again!

From: <astrodeb@charter.net> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Date: Tue, 7 Dec 2004 12:00:30 -0700 Subject: Re: [Utah-astronomy] Fisheye lens

First of all, you would need a very dark sky to avoid sky fog. My last batch of slides were limited to 10 minutes because of the sky conditions. With my two-star alignment with my polar scope, I could have gone up to 30 minutes unguided with my 50mm lens if the sky conditions would of allowed it. A fish-eye lens would be even more forgiving as far as tracking goes.

Does your mount have PEC? The best mounts, provided they are accurately polar-aligned and PEC trained, can be left to track unattended and unguided for 30 minutes or more. Of course, the longer exposure the more there is a chance of getting airplane trails.

My 2 cents,

Debbie

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