Re: Flexure or tracking? (Another "cold night" from northern Indiana)


Ray Gralak
 

Joel,

However I now wonder about tilted optics. My collimation tests look good with round stars in the corners across a
full frame sensor.
You might want to verify that collimation holds throughout the sky by taking short images in different parts of the sky and checking the images for star roundness.

-Ray Gralak
Author of PEMPro
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver


-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Joel Short
Sent: Saturday, January 23, 2021 9:48 AM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Flexure or tracking? (Another "cold night" from northern Indiana)

Ray,
I use this same focuser (Feathertouch) on another scope with the same camera setup and I don't see this same
effect so I doubt it's focuser sag.
However I now wonder about tilted optics. My collimation tests look good with round stars in the corners across a
full frame sensor. However I have noticed that the diffraction spike on very bright stars has one spike (of 4) that
is much longer than the other 3. If I remember, next time I'm out I'll save an image of this. Any idea if that
indicates a mirror tilt issue? Again, collimation tests look good.

Rolando, I might look around for a replacement low vibration fan for the camera. That's an inexpensive and easy
thing to do so it can't hurt.
joel

On Sat, Jan 23, 2021 at 11:39 AM Ray Gralak <groups3@gralak.com> wrote:


Hi Joel,

> Guiding was quite good. I saw an average RMS RA of 0.4", Dec of 0.3".
> Also, I use an OAG for guiding.

Since auto-guiding looked good, that eliminates mount tracking as the problem. You need to look
elsewhere.

My first thought was tilted/moving optics, a sagging focuser, or a non-orthogonal camera sensor. Or some
mixture of these.

-Ray Gralak
Author of PEMPro
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver


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