Guide Star Fade Problem using an AO-8T

[Dan Simpson]

Hi Bob,
Thanks for the update. I think things are progressing at DL but I appreciate your giving the issue a boost. It's been three months now so I'm hoping that we can make some progress soon.
Take Care,

[Dan Simpson]

Hi Bob,
I'm game to get together most any time whether by phone or TeamView. I do think having you run through the steps on my equipment would be the most productive. Who knows, you might see something I'm missing altogether. I'm assuming that you would need to actually acquire an image or two in real time. Unfortunately, the weather forecast is looking pretty grim for the next week or so. When I see a few nights of clear skies coming up I'll let you know and we can schedule a time. Let me know if we're on the same page.
Thanks,

[Bob Denny]

It will be TeamView where I can get a few hours shooting in the dark to see if I can identify what activities of ACP are upsetting the AO. I have no clue how it operates internally and some of the info I have gotten from Diffraction/SBIG confuses me. So I am just going to start stripping logic, dropping features one at a time, making it dumber and dumber until i hit the thing that is doing it. Then at least I might find a way forward.

Right now the weather looks really bad, snow to the north and a few openings between rain in Santa Fe. I can't do it tomorrow night, and at present the first day with precip probability below 40% after that is next Thursday the 16th. So I will bookmark that evening and then come back and look Monday or so. May 22 is showing 0% but that's far in the future and could be anything ha ha.

[Dan Simpson]

Hi Bob, Just a quick weather update. Skies tonight look good starting around10pm and then clear until dawn. Tomorrow night starts clear with a partly cloudy blip around 1am and then clear until dawn. I'm available either night. The next few days after that don't look very promising. Just an fyi.
Thanks,

[Bob Denny]

I can make it tonight 8:30PM your (MDT) time. Shall I call on the -5219 number?

[Dan Simpson]

Yes, that number will work. Tonight and tomorrow night now look pretty good.

[Bob Denny]

It will be tonight 8:30PM your time (MDT).

[Bob Denny]

I determined why ACP can't start the AO at all unless the guide star is right smack centered on the full frame guider image. Dan had the Autoguider Image set to "Flip Horizontally". This caused ACP to pick up the guide stars on the opposite side of the detector and after measuring the SNR, it gave the wrong coordinates to the guider for tracking. The track box was always empty.

Snap1.png

After getting past that one, we are now at the same problem being experienced by many other AO users... as soon as the main exposure starts, the AP stops tracking. I did some experimenting and videotaping, and what's actually happening is that the AO is losing a great deal of sensitivity at the moment the main imager starts exposing. You can see this when ACP is set to force the AO to greatly over-expose the guide star.

I will produce a video that will make this crystal clear.

[Bob Denny]

Here's the post I made to the Diffraction forum about this. There is a video with it.

http://www.diffractionlimited.com/forum/threads/ao-guiding-under-automation-guidestar-fade-issue.5340/page-5#post-31405​

[Dan Simpson]

Hi Bob,
I was going to try running some images with the exposure delay. I'd need to modify the script and was hoping you could show me where to insert the delay. Somehow I didn't end up with the MDL log files from our session. I think it would be helpful for Owen and D. George to see what we saw in action.
Thanks,