New STT-8300 Image Defect Problems Continue - amp glow?

Discussion in 'STT Series (retired)' started by Dean J., Apr 3, 2016.

  1. Doug

    Doug Staff Member

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    So far it appears that the long guide exposures combined with slew-before-download operation is the cause of the extra amp glow. So far we've not been able to to suss out the exact circumstances; the whole sequence is very complicated.

    What I would recommend is going to 3 second guiding, and if you're worried about chasing seeing then reduce your Aggressiveness (say to 3). That will create a "rolling average" effect, which will essentially do the same thing as taking long exposures.
     
  2. Dean J.

    Dean J. Standard User

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    OK, back from collecting more data last night with the STT-8300 & FW8G-STT.

    Using The Sky X Professional with the camera control module.

    3 second guide exposures again [because it worked 2 nights ago].

    36 subexposures and no appearance of amp glow.

    Tested out 4 second guide exposures for about 40 minutes of 300 sec. test images with no appearance of amp glow in this small sample set.

    So, it looks like I will be able to avoid amp glow issues with 3 sec. and probably 4 sec. guide exposures... as long as there are good guide stars in the field that will support 3 or 4 second exposures.

    Sometimes I need to go up to 5 or 6 seconds, sometimes a little more, to get good guiding.

    I'm glad to get a handle on this issue but I was wondering if there may be a more permanent fix in the works that won't restrict my options for guide exposure length?

    Dean J.
     
  3. Adam Robichaud

    Adam Robichaud Staff Member

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    Thanks for the update Dean. We're still working on the issue, but the tests we're running are giving results that are a little perplexing. Apologies for the delay.
     
  4. Samuel Lising

    Samuel Lising Cyanogen Customer

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    Hi Adam.

    I was looking at CCDOPS5 to check some camera settings today and I noticed a setting that doesn't seem to be in Maxim or other imaging apps. It's a checkbox setting in the Camera/Customer Options dialog box called "Vdd Normally Off". The description in the help file says:

    Vdd Normally Off
    When this item is checked the Imaging CCD's Vdd (Readout Amplified Power) is off all the time except when it's required for readout. When this item is unchecked the Vdd is on all the time except for long exposures. The reason Vdd is turned off is that the Readout Amplifier emits a weak glow that can show up in the upper-left corner of long exposures

    This sounds like exactly what's happening to our images. I have the setting enabled which means it's off. I don't know if this is a setting that is specific to the application or if it's saved onto the camera hardware.

    Dean, your glow comes from a completely different use case than mine so I'm wondering if you can check to see if this check box is enabled in CCDOPS5.

    Adam, Even though I have this enabled and still get the glow when I have ACP running without "disabling slew during image download", I am wondering if Vdd is causing issues when an external app is accessing Maxim or the camera directly. Just a thought.

    Sam
     
  5. Adam Robichaud

    Adam Robichaud Staff Member

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    We turn VDD off during acquisition in all modern cameras with exposures longer than 3 seconds, so that setting doesn't really do much except possibly speed up start exposure responsiveness. Without getting into specifics, there's a very tricky timing problem involved with how we control the camera, and we're still working to sort that out.
     
  6. Dean J.

    Dean J. Standard User

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    Hi Sam,

    I found that setting a year ago or so when I was trying to figure out my situation. Based on Adam's response it looks like it doesn't have any present applicability... However, I did turn the switch on when I was looking at it. Whether it has any persistence when using another camera control software - The Sky X in my case - only Adam or Doug can say.

    I have made some changes in my imaging computer for this new moon session. I had been running The Sky X on a Windows 7 machine. I have now switched over to The Sky X on a Linux machine with the camera control and the telescope control all being handled via the Linux machine. We will see now whether the problem continues for me when I attempt longer exposure times - 5 or 6 seconds - with the new setup.

    Regards,

    Dean Jacobsen
    http://astrophoto.net
     
  7. Dean J.

    Dean J. Standard User

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    Back again,

    Made it out for a single night imaging session this month.

    Using The Sky X Professional for Linux with the camera control module.

    3 second guide exposures again.

    38 subexposures and no appearance of amp glow.

    I haven't seen any instances of image corruption with amp glow for the last few imaging sessions since I started using 3 second guide exposures.

    Dean Jacobsen
    http://astrophoto.net
     

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