Guider Problem Star Fade (exposure interval -1)

[Mike Pooler]

I am having a problem getting my new guider setup and working. I just upgraded my OBS system to Windows 7 Pro 64bit,,,Maxim5.18 and guider to SBig STI Color.
From the guider tab in Maxim I can expose fine and calibrate just fine. From ACP I am able to use the calibrate guider script (east side of pier). I am able to track just fine on the West side and East side of the pier (using a very bright star).

The problem starts when I am trying to guide on normal guide stars lets say under Mag 1.
See attached file for screen snapshots.
I can see the stars in the image and they look good to me. Maxim or ACP (test guider script) won't locate any stars to guider from the initial exposure.
For some reason the log reads "exposure interval -1". My min exposure in ACP is 2 sec my max is 15 seconds.
I was wondering if there are settings in Acquire Support or Acquire Scheduler I need to adjust.

Once I do get a star to start tracking,,,I can see it in the guide box and it looks good (white star black background). Maxim never latches on it just reads Star Fade on every cycle.

Anyone see this before?
Thanks
Mike Pooler

[Dick Berg]

Mike,

Perplexing. Your settings look almost identically like mine, except I see you have readout mode set to RAW (or it's set somehow automagically) - mine is blank. What kind of camera is the guider camera?

I thought you might need to hit the "Reset" in the Guider Settings box, but your third image of the five you sent looks like you're using the whole guider chip.

Another thing to consider - don't connect MaxIm to the ACP Hub, to the telescope directly, or to anything. This is probably not your issue. (If ACP is running the show, ACP is connected directly through the appropriate driver to the telescope. ACP uses MaxIm to take pictures in the guider frame (MaxIm does the guiding) and the regular imaging frame. ACP tells Focus Max to move the focuser or to take focus images, and FocusMax will get the images it needs through its direct API interface to MaxIm. FocusMax connects to the ACP Hub. The only reason to ever connect MaxIm to the ACP Hub is so that MaxIm can get telescope coordinates if you want to use MaxIm's built in planetarium program. I personally do this and don't have any problems, but Bob's general advice is to not connect MaxIm to the ACP Hub.)

I'm grasping at straws!

[Mike Pooler]

Dick
The camera I am using to guide is the new ST-I Color kinda like the load star but sbig and color.
My choice from the camera window was raw or color,,raw was default.

I am using simple auto dark in Maxim (the ST-I acutaly has a sutter that lets me do this without covering the scope).
I am using a seperate guide scope.
I am almost sure that it is a maxim issue with the camera. The only thing is I can't see what the problem might be.
I have guided with my old starshot (it is dead or I would try it) on a lot worse stars than in the images I am getting now.
I do have a ticket open with maxim now I will see what they say.

The one thing that I don't understand was when i watch ACP call out for the guider,, it goes out and takes a picture and no mater what comes back I get something like this.

05:48:25 Ready for NGC 4631 (# 1 of 1 in set 1)
05:48:25 [flip check: Tn=660s HAc=-3383s GW=T HAz=-2456s DWz=T WF=no]
05:48:25 Updating pointing...
05:48:25 (long exp, trying to autoguide)
05:48:31 **No stars found in guider image
05:48:31 (initial exposure interval -1)
05:48:31 No usable stars in guider image; trying again at max guider exposure
05:48:53 **No stars found in guider image
05:48:53 (exposure interval -1)
05:48:53 **No usable stars at max guider exposure interval
05:48:53 **Autoguiding failed.

I don't understand where the -1 comes from.

[Jim McMillan]

Hi Mike,

One question, what is the minimum SNR set to in ACP? It typically should be something like 3.0 or 4.0. If it's a lot higher than that, it could be the cause of what you're seeing.

The exposure interval of -1 is something ACP puts there when it can't find a star. It's kind of a diagnostic for Bob.

Jim

[Mike Pooler]

Jim
The SNR is @ 3 I tried 1.5 ,,2,,,3,,,4 with out much difference.
Seems 1.5 was more sinsitve but still the same results.

When I chose 1.5 it would find the star some times but after Maxim took over it would only readout Star Fade.
I was looking on the Yahoo Maxim Group and A few other people have had this problem with 5.18
If I can't find a star from ACP the I should go down from 3 to 2 if I remeber correctly.

[Jim McMillan]

Hi Mike,

Reducing the SNR below 3 will allow the use of dimmer stars, but the quality of the centroiding algorithm isn't all that great with a star that dim. I keep my minimum SNR = 4.0.

FYI, ACP uses PinPoint to select the guide star, then tells MaxIm the coordinates of that star to guide on.

If I understand what you've said, guiding may or may not start using ACP. And, in MaxIm, even if it starts, you'll usually get a "guide star fade" error - unless using a very bright guide star. I wonder if there's something going on with your STi color guider and MaxIm. I don't really know how well either PinPoint or MaxIm guides with a color camera.

Sorry I'm not much help.

Jim

[Mike Pooler]

Thanks for the try Jim
I am not sure about guiding with color mabey that is the issue. The camera is new and I am sure that is part of the problem.
When The SSAG died I ordered the ST-I-C and was down for about 6 months waiting for Sbig to send it to me after month 5 I ordered a load star to get me by. I haven't seen it yet. When it comes in I will test it and see if things are different.

[Dick Berg]

Mike, I would change the RAW to Color - it's worth a shot. I think the RAW image is actually the Bayer matrix image (your star images on one of the enclosures above was VERY softly focused and textured, and it made me wonder if you were using a color camera - which you are), and that could give the guider grief. It's worth trying it, anyway.

[Bob Denny]

I think you'll love the Lodestar!