Re: [APML] First halfway decent cassigrain image

["Bradley" <bhope@thorngarden.net>]

Thanks, Alan;

I based the starting exposure on Covington's AstroCalc giving me 12min to
sky fog..and estimating based on my old piggyback work. I'm guessing that
due to the length of the optical train it's probably more like f8 or f10
rather than f6.3...10" f10 - Meade microfocuser - .63 focal reducer - Vixen
off-axis guider - camera...and that gives me 20min at f8, 30min at f10. I'll
find out the next clear night...as well as bracketing the focus a bit...and
trying to use a star higher in the sky in clearer air which should,
hopefully, make it easier to find the sweet spot for focus (it's going to be
a while before I can get the knife edge adapter from STI, I already have a
list almost as long as my arm).

Clear skies

Bradley
48°07'12.72" N 123°27'29.16" W
http://astronomy.thorngarden.net


----- Original Message ----- 
From: "Alan Voetsch" <alanv12952@yahoo.com>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Thursday, January 06, 2005 12:23 PM
Subject: Re: [APML] First halfway decent cassigrain image


> Hey Bradley,
>
> That's a really nice shot. You're right, looks like the focus could be
> better. But that will come with experience.
>
> Unless you're in a SEVERLY light polluted area, you should be able to
> expose far longer. Up your exposure times until you find the breaking
> point. Their is a lot more nebulosity waiting for you if you do.
>
> Keep 'em coming,
> Alan

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