Repeated FocusMax Errors = Star is too bright

[Bob Denny]

I just saw this and a few light bulbs went on:

(1) Steve, you responded to Eric as though you saw that AcquireStar was not on in ACP (and it was not),, however it appeared that the FocusMax log Eric passed to me in the initial post indicates that AcquireStar was being used? If not then I am a doofus in reading the FocusMax log :-) and may have confused Eric. For that I apologize.

(2) Eric - Once you switch to AcquireStar, FocusMax is in charge of the entire autofocus process including the star selection and exposure duration selection. FocusMax assumes you have selected the desired filter before asking it to do the AcquireStar-Focus. ACP does this, selecting the "reference filter" from your filter focus offsets table.

(3) The "issue of the run stopping before the first exposure" can't be diagnosed without a log from one of those runs. I can't guess, and I am not going to assume that the issue is exactly the same as it was for the run night before last.

(4) Eric, you're right to wonder why this "just started happening"... software doesn't corrode or wear out, so something changed.

(5) Eric, is this a "sample of one" or is this happening on all of your targets now? What if you try a different target (in other words some different conditions)?

(4) You have to love the responsiveness of Steve (and me) on this :-) however I'll feel much better when you're back in business imaging.

[Eric Coles]

Bob,

I reset the star brightness settings in FocusMax per Steve's suggestions. Let's see if that helps. I still don't understand why FocusMax fails after it apparently does a successful focus run.

The ACP log I uploaded this morning was from last night's run where it failed just when it was suppose to start the first exposure.

These events (the focus problem and now the stopping before first exposure) are both new. I can try another target, but I did get 24 exposures two nights ago with this target, even with the focus issue. So the "stopping" issue is new.

(4) And I will also feel better to be back in business.

Eric

[Bob Denny]

Sorry I missed the log. The stop at the end of the log is unrelated to AutoFocus.

05:10:00 (starting exposure)
05:19:38 **Imaging error: Exposure Aborted
05:19:39 (stopping the autoguider)
05:19:40 (turning tracking off for safety)
05:19:41 End of run.

This indicates that someone (effectively) pushed the Stop button on the MaxIm Camera control. It wasn't killed inside ACP or you would see a Script Error abort. If it's not that simple, let please start a separate ticket/thread so this won't get conflated with autoguiding problems, since they are not related at all.

[Steve Brady]

Eric--

I doubt that mag 7-8 are optimum for each of your LRGB filters for AcquireStar. I would expect L will require dimmer star, B brighter etc. Please plan to experiment with these settings some night unless you use filter offsets for all of your filters.

As to the question what changed...
Is it possible that the stars that ACP has been selecting are in or near the summer Milky Way which contains a denser star field? Unless AcquireStr is in control, FMx will always select the brightest star in the image, not necessarily near the center of the chip. The only counter measure is to reduce the FMx CCD Central Region used in the initial image to 50% (or less) to limit brighter stars in the field. I think your best bet is to AcquireStar. Perhaps you can go through your ACP Logs on your desktop and slew the Simulator telescope in TSX to each star with the FOV set to ~ 1 degree to determine if there are bright stars nearby.

In looking further at your Logs the Total Flux at 0.1 sec with Red filter are 7+ million against a target of 300,000. The star used was way too bright.
Under these circumstances this leaves two options to consider:
1) abort the focus run early if the star is too bright using the minimum user defined exposure
2) use the final focus positon even though the star was saturated with possibly poor focus
Right now FMx chugs through the focus process using the minimum exposure time with the hopes that the final focus verification will pass which it may if the final flux is reasonable near target.
I am open to suggestions here...

You may be interested to know that AcquireStar will select 3 or more suitable stars from the star catalog. If the focus attempt with the first star fails, then it moves to the second in the list, etc which increases the odds of success!


Steve

[Eric Coles]

Bob,

Exposure Aborted. That's interesting. It was midnight my time and I was fast asleep. Does this mean someone there or remotely pushed the Stop button? What else could it be?

[Bob Denny]

Exposure Aborted. That's interesting. It was midnight my time and I was fast asleep. Does this mean someone there or remotely pushed the Stop button? What else could it be?

I don't know. Let's see if it happens again. If it becomes chronic we're going to need help from Diffraction to find out what might cause that to happen apart from activation of the Stop button on MaxIm. (That's the only reason I know of anyway).

Since this is unrelated to focusing, and this is a Steve Brady ticket, I've split this off into a separate conversation back in the ACP section.

[Eric Coles]

Steve,
You suggested I send you a PM. What address should I use?
Eric

[Eric Coles]

Steve, Bob,

Thank you both for working through the odd focusing issue with me.

Steve, thanks again for getting on the system and configuring FocusMax. I set up ACP to Use FocusMax Acquire Star feature and take advantage of those functions

Last night I stayed up until midnight to watch the script run. I ran perfectly. Not sure if it was the reconfiguration of FocusMax or the use of the Acquire Star feature (using focus stars from a different region of the sky) that made the difference. In the end, we are apparently running like we should and that's most important. I am going to run tonight with the same target using the WaitUntil function. If it runs without and error, then I will make a note and close this thread.

Eric

[Eric Coles]

Let's close this thread.

[Bob Denny]

Will do and thanks for your patience. Steve, your help is definitely appreciated.