The focus doesn't change during the night. The only thing that changes is the FWHM which starts out at 1.25 arc sec and then slowly creeps up to around 1.7 as the sky scintillation gets worse by the hour. That's the local conditions here unfortunately. In a reall steady night I might get around 1 arc sec resolution with the QSI683 camera.

Rolando

-----Original Message-----
From: Bill Long <bill@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Fri, Oct 1, 2021 9:39 pm
Subject: Re: [ap-gto] Thor's Hammer

Looks solid. I had a RCOS made with sitall mirrors. Once you focused it for the night, it never needed it again. 

---

From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Roland Christen via groups.io <chris1011=aol.com@groups.io>
Sent: Friday, October 1, 2021 7:34 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>; main@ap-ug.groups.io <main@ap-ug.groups.io>
Subject: [ap-gto] Thor's Hammer

 

At least that's what I call it, the outstretched hand and hammer in the neck of the Pelican Nebula, also known as IC 5070. It appears next to a cliff with what looks like a waterfall:

https://www.astrobin.com/6lbi12/C/

Testing out an older 12" F12.5 Mak-Cass which we built about 15 years ago but never put to use or sold. The mirror and corrector lens optics were made by Intes Micro when they were still operating. They are zero-expansion Sital. The rest of the mechanical parts were fabricated here. The tube is carbon fiber.

To take the image I added a CCD67 telecompressor in order to get a larger field. I took it in one night with just over 2 hours of H-a narrowband. It really needs longer exposure.

Rolando

--
Roland Christen
Astro-Physics

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Roland Christen
Astro-Physics