Changing background values on STi images. Causing guiding problems and star fades.

Thanks for the response... I already found my user name has caps in one machine and not the other

On the centroid. Thinking of the relationship to binning I suspect without looking at the math in detail that the centroid is probably only slightly different with the binning different.

I do not know how you select the stars for the multi-star but a suggestion might be that if you could get some measure of variance of the individual stars centroids, you could just use the stars with the lowest variance... I know when I look at the autoguider images some stars are clearly more stable than others (at the edges).

If you had this measure of variance across multiple images... like the RMS cumulative measure, a user could vary the binning and select the binning with the lowest variance. You also might allow the user to set the maximum number of stars used in multi-star and then again look at the RMS and see what happens.

I am big on variance. In the old days when i ran a flight simulator we tested pilots with marijuana (yes THC- you can look it up). What we found was that the THC affects pilot performance more on the variance or performance than on the mean performance, i.e. they became less reliable in the control movements.....

Typical study: https://www.ncbi.nlm.nih.gov/pubmed/1849400

Cheers

 

So, is there a fix for this problem yet (the varying guider images from the St-i)?

I upgraded to Maxim 6.20, and am still seeing problems. This has been going on for 3 years now?

It usually guides for awhile but eventually flakes out enough that ACP either runs unguided images (wasted time) or just gives up.

I can see the varying images as each guider image is taken; most are good images but every so often a white one shows up.

I use either multi-star or single star, doesn't seem to matter. Either way I keep seeing White Screen of Death images which can confuse guiding.

 

I had updated drivers, etc last time.

Rechecked drivers, it says firmware and drivers are up to date. Attached screen shots.

 

OK, here is my Documents/Maxim DL6 folder. I did the whole folder, rather than just Settings. Again, I am running 6.20 Maxim.

The brightening of images occurs with or without ACP. I am guiding with multistar in the vague hope of better survival of the guider, but the issues clearly occur with both single and multi star guiding.

Trying to watch the intensities of the guide images, the typical guide exposure is roughly 1000-1200 ADU. When the image goes white the average intensity is maybe 4000 ADU or more. This prevents using Simple Autodark - if the autodark image happens to be a high value one, the guider images will have almost all zeros and no guide star is found. If I flush the autodarks or change the exposure slightly (generating a new dark), images will be OK other than when a white screen is encountered.

I have been saving guider exposures, trying to see the issues. Oddly, the saved images do not seem to show the whitening as drastically, although I am not completely sure of this (I keep changing things to try and get something to work). It may be that the images presented on the screen are not completely processed / stretched?

Another odd thing - If guiding is stopped for a bit, for example to go autofocus, when it starts up again I get a weird half-white screen (attached above). This shows no stars and fails with no guide star found. The next exposure will be normal (in this example the mount was not yet tracking, hence the star trails). When guiding manually in Maxim guiding will fail after the Half Black screen; I have to manually re-expose a frame. ACP is usually able to recover and get guiding going although sometimes it gives up and runs unguided.

 

I don't have a fits file; when I zipped my Settings file I had several thousand guider images, so the file was over 1Gb. I deleted those images to keep the zip manageable.

Your shutter theory is interesting. Another pattern I see looks like an oscilloscope wave, kind of a filled in sine wave alternating white black. Maybe that is due to the shutter "stuttering" as it moves across or something...

I will see if I can create the half image again and capture the file. I assume that manual guider exposures get saved...

My serial is 11279.

 

Attached are the HalfBlack fits file, and the exposure after it which is normal.
This happens when in Guiding tab:
No calibration being used.
Expose image 3 seconds. Get HalfBlack.
Expose image 3 seconds. Normal.
Track. OK, except for occasional White screens where the intensity goes from Normal ~1000 to ~4000 or more.
Stop Tracking.
Expose - Get HalfBlack again.
Expose - normal again.

I also attached a screen grab of the Oscillating pattern. I didn't manage to grab the fits, didn't realize it wasn't saving the Expose images (only the tracking images). This pattern popped up when I was doing Expose operations, but I can't reproduce it.


If I send it in, what do I expect it to cost? I worry I might be pouring money down a rabbit hole.

 

By the way, Bill: I am the guy that sent in my STF 8300 a couple of times for the problem of getting half the light on the St-i. I finally figured out what the problem is.

When the camera is disassembled (removed from the mount, remove the top plate to see the prism, etc) there is no problem.
Reassemble, the top plate (with the T-thread) covers half of the prism, blocking the light. The top plate extends over the prism! The design prevents light from hitting the entire prism.

I can extend the prism a very slight amount before blocking the imaging chip, but not nearly enough to get the whole prism in view.

 

So I realize I'm bumping an old thread here, but since I'm still having the same problem and I started this thread I saw no reason to start a new one.

After taking a couple year break from imaging due to mount problems and being very busy I'm getting back into it again. I'm currently running version 6.30 and I still have this problem with the STi camera where the background value randomly increases to the point where the star is lost in the noise. And without a doubt the problem is worse when the ambient temperature is warmer. When temps are below 0C it would happen maybe once every 3-5 minutes, with temps 10-15C it happens about once every 30 seconds. Is this just going to be a fact of life with this camera? I don't think the camera has enough value to send it in for repair and frankly with all the other reports of the same behavior from others it seems more like a design problem of the chip and not a malfunction.

I'll be happy to help out with any testing if there is something that can be done to help fix this. And my mount usually tracks well enough that loosing a guide sub from time to time doesn't ruin an image. The biggest annoyance with this problem is I turn off the audible alarm of a guide star fade because with it turned on using this camera it gets old constantly hearing the warning sound going off. But now if I really do loose the guide star because of clouds or whatever other problem, I don't have the warning sound.

 

Josh,

I'd add that I continue to have this issue as well and it is just as you mention - worse when warmer. I have three of these ST-i's and different setups. I sometimes have better luck if I increase the exposure length. With my mount, I can and tend to use 9-10s guide exposures which helps to minimize the issue unless the guiding program picks up something in the bad exposure and and attempts a big move.

This hasn't annoyed me enough to move to a different camera but the (non-SBIG) CMOS setup I have ready to go will use a different guide camera.

Dan

 

Bumping this in case it was missed.

 

Colin, thanks for the detailed response.

If you go back to the beginning of this thread you can see that this problem has been ongoing since I bought the camera. I realize it is well past the warranty and now even discontinued, however considering many others have had the same problem, and I've had the problem using 3 different computers across 2 different identical cameras I think it is in the best interests of DL to help with this problem to keep customer loyalty in tact.

I know for a fact that I have had the problem using the original supplied USB cable, and I am 98% sure that I am still using that cable, and I currently have that cable connected directly to the PC. However, can you provide a link to a 15ft. cable that will provide the proper supply power, I will gladly buy a new one just to be sure.

My current cable setup has a strain relief at both the pier and at the dovetail so there is no chance of any strain on any connectors, I was VERY particular about this.

I am current with all Windows Updates, I'm currently running Windows 10, and the same problem persisted on 2 different Windows 7 PCs that I used previously.

USB selective suspend is turned off, I've checked this multiple times.

I'm currently running Maxim 6.30, again this has been happing for years over several versions of Maxim.

I've attached a current screenshot of my SBIG drivers, when I check the firmware I simply get a message saying the camera doesn't require firmware updates.

I will check to see if there are any Bios or other PC updates that are available, however I prefer to not do that remotely incase something goes wrong. However the fact that several users all report that the problem is worse the higher the ambient temp really points to a hardware not a software problem.

I will get the camera serial number next time I'm at the observatory.

As far as reproducing the problem, simply taking autoguide images is all that is needed. Please look at my initial posts in this thread, there is a lot of detailed information including guide images. If you need new images I will gladly supply them. I know there is a problem when the star disappears in a wash of background noise that shouldn't be there and I get a guide star fade warning.

I realize this is not a cooled camera, but when say 1 of every 20 guide images has substantially more noise that the previous, then the very next image is back to normal, that is not explained by simple thermal noise.

 

I've posted a picture with the STi serial number and other information, and I've also managed to update the driver by your tip of disabling the camera. Please let me know if all of my drivers are up to date?

Next night of imaging I will be sure to record all of my guide images.