Autofocus can shift the camera which will cause the star to jump. Try turning off Autofocus and see if you still get the jump.

Rolando

-----Original Message-----
From: Brian Valente <bvalente@...>
To: main@ap-gto.groups.io
Sent: Tue, Nov 23, 2021 10:52 pm
Subject: Re: [ap-gto] Guide star lost after dithering

There's one other thing you can test

disable dithering and take a few images, but leave everything else the same (i.e., continue guiding during download). If the issue persists, you know it's unrelated to dithering

If that's the case, you could then try imaging without guiding and downloading and see what happens

On Tue, Nov 23, 2021 at 6:39 PM yanzhe liu <liuyanzhe@...> wrote:

Download takes 10-20s. Yes, guiding is still on during download, but not during auto focus.

On Tue, Nov 23, 2021 at 6:31 PM Brian Valente <bvalente@...> wrote:

Regarding your image download when exposure complete, are you still guiding while image is downloading? Does download take a while?

On Tue, Nov 23, 2021 at 6:28 PM yanzhe liu <liuyanzhe@...> wrote:

Yes, exposure time was 900s.

On Tue, Nov 23, 2021 at 6:25 PM Brian Valente <bvalente@...> wrote:

Are you doing 15 minute exposures?

The dither distances and settling look fine from a PHD perspective, although I can see a big spike in guidestar SNR roughly every 900 seconds

On Tue, Nov 23, 2021 at 5:49 PM yanzhe liu <liuyanzhe@...> wrote:

Here is the log:

https://openphdguiding.org/logs/dl/PHD2_logs_xGZF.zip

I have not used the log before but I think this is the dither causing issue. I then restarted the sequence by turning dither off.

19:29:39.383 00.003 2112 PhdController::Dither begins

19:29:39.386 00.003 2112 dither: size=1.00, dRA=-0.61 dDec=0.00

19:29:39.389 00.003 2112 MountToCamera -- mountTheta (3.14) + m_xAngle (-1.59) = xAngle (1.55 = 1.55)

19:29:39.392 00.003 2112 MountToCamera -- mountX=-0.61 mountY=0.00 hyp=0.61 mountTheta=3.14 cameraX=0.01, cameraY=0.61 cameraTheta=1.55

19:29:39.395 00.003 2112 setting lock position to (121.19, 18.76)

19:29:39.398 00.003 2112 Mount: notify guiding dithered (0.0, 0.6)

19:29:39.401 00.003 2112 MultiStar: stabilizing after lock position change

19:29:39.403 00.002 2112 Status Line: Dither by -0.61,0.00

--

Brian 

Brian Valente

portfolio brianvalentephotography.com 

--

Brian 

Brian Valente

portfolio brianvalentephotography.com 

--

Brian 

Brian Valente

portfolio brianvalentephotography.com 

--
Roland Christen
Astro-Physics