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

Discussion in 'STF Series CCD Cameras' started by JoshuaHufford, Apr 22, 2017.

  1. jerryyyyy

    jerryyyyy Cyanogen Customer

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    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
     
  2. brew

    brew Standard User

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    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.
     
  3. Colin Haig

    Colin Haig Staff Member

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    Brew, can you check what drivers and firmware you have for your ST-I ?
    Use the Upload a File button to the lower right to upload a PrtSc screen shot of the driver checker driver tab, and then on the driver checker firmware tab, Get Firmware.
     
  4. brew

    brew Standard User

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    I had updated drivers, etc last time.

    Rechecked drivers, it says firmware and drivers are up to date. Attached screen shots.
    DCFirmware.PNG DCMainStart.PNG DCUptoDate.PNG
     
  5. Colin Haig

    Colin Haig Staff Member

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    Ok thanks. This may take some digging.
    Can you zip up your MaxIm settings and attach using [Upload a File] button to the lower right?
    That way we can do a quick review and make sure nothing obviously wrong.
    Is this readily reproducible - or does it happen rarely?
    Does it happen when you run things fully manually or just under ACP control?
     
  6. brew

    brew Standard User

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    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? Halfblack.JPG AfterBlack.JPG

    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.
     
  7. Colin Haig

    Colin Haig Staff Member

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    Did you happen to get a FITS image of the half-white screen? This looks like something might be failing in the hardware like the shutter is slow/sticking. Can you pass along the serial number of the camera? (it's in tiny print on the back end of the ST-I).
     
  8. brew

    brew Standard User

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    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.
     
  9. Colin Haig

    Colin Haig Staff Member

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    The wave could be indicative of failing components in the ST-I, a bad cable/corrosion in the connectors.
    Maybe our expert @Bill can comment.
     
  10. Bill

    Bill SBIG Service and Repairs Staff Member

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    Highly unusual, perhaps it should come in.

    -Bill
     
  11. brew

    brew Standard User

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    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.
    Oscillate.JPG

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

    Attached Files:

  12. brew

    brew Standard User

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    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.
     
  13. Bill

    Bill SBIG Service and Repairs Staff Member

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    Ah yes, Robert. How are you? Sorry you're having troubles. Your ST-i images are like none I've seen before in this model. The image above looks like something that used to happen with the old ST-2000's when it would saturate. We called them Jail Bars or Grill Marks. That isn't what's happening here but the look is similar. Older ST-i's, like yours, sometimes had problems in the power circuitry (on the shorter board inside the tube). The usual failure mode is no shutter movement and/or black images but that doesn't seem to be what is happening here. If you'd like, call me tomorrow, 805 308-6979, maybe we can do a TeamViewer session and I can get a better idea about how the shutter is actually working. Just the ST-i, USB cable and the computer is all we'd need.

    Regards,

    Bill
     

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