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

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

  1. JoshuaHufford

    JoshuaHufford Cyanogen Customer

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    I'm not sure if this is a hardware or software problem, however the problem started when I switched from an Orion SSAG to the SBIG STi mono, so I'm guessing it is a hardware problem and posted it in the hardware section, however please move the thread if needed.

    Ever since I switched from a Orion SSAG on a Borg Mini 50 guide scope to a SBIG STi mono on an OAG8300 every so often at random times I get a guide image that is pretty much all noise and no star. This does not happen when I have a very bright star, only when it is a faint star, so I initially wrote it up to a dim star or possibly clouds from time to time. However my friend that I share the observatory with is having the exact same problem, we have had the problem happen at different times while imaging in the same area of the sky. I have also noticed several other users of the same hardware describing something very similar on this forum and others, so I decided to do some more investigating.

    I've uploaded some images, I'm no expert here but it seems to me that on some of the images the background level is much higher than others, when this happens it causes a star fade. All of these images were taken within a short time period, there were no clouds during this time. I also attached a screenshot of my current SBIG drivers. I also have a link to a movie that I made of some of my guide images where you can see this happening. I'm running version 6.12 of Maxim. I've also uploaded my settings folder.

    I've seen this problem or similar problems blamed on clouds, seeing, or other external problems, but I really can not see how such a drastic change in background levels on 3 second guide exposures could be blamed on sky conditions.

    This video was created with MaximDL, all are 3 second guide exposures, all the screen stretch is the same at low. It is a total of 176 images over about 12 minutes of time at 2 fps.

    https://www.dropbox.com/s/d7wk00bo1gh6yi7/Guide Image Movie.avi?dl=0

    Any other info that you need please let me know and I will be happy to provide it as I would like to get this problem fixed.
     

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    Last edited: Apr 22, 2017
  2. JoshuaHufford

    JoshuaHufford Cyanogen Customer

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    Anyone else seeing this?
     
  3. Dan Crowson

    Dan Crowson Standard User

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    Josh,

    I think I see something like this with my ST-i's as well. It only seems to happen on faint guide stars (with my OAG). I should keep my guide images over a night and see if this is really the case.

    Dan
     
  4. JoshuaHufford

    JoshuaHufford Cyanogen Customer

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    What seems to be happening is if the guide star is faint enough the background level spikes and it overwhelms the star, if the star is bright enough that doesn't happen. The next night I was able to image I was on a different target and I still saw the background level spike from time to time, but the star was bright enough to still be detected. Still I don't understand why this would be happening.
     
    Last edited: Apr 27, 2017
  5. JoshuaHufford

    JoshuaHufford Cyanogen Customer

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    Sure would like to hear from the staff on this one.
     
  6. JoshuaHufford

    JoshuaHufford Cyanogen Customer

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    I'm giving this a bump to hopefully get some attention, I see it was assigned to Tim but it has now been one week since I made my post with no response.

    Thanks.
     
  7. Doug

    Doug Staff Member

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    Sorry you didn't get an answer sooner. I'm guessing the guys weren't sure what to make of it.

    It really doesn't look right... I'm going to recommend sending it in to Bill @ Service.
     
  8. JoshuaHufford

    JoshuaHufford Cyanogen Customer

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    Thanks Doug. I'd be happy to send it it to Bill, however I know of one other Sti and maybe 2 doing the exact same thing, and I know I've heard others mentioning something similar. So either several of these cameras have the same problem or its software.
     
  9. Doug

    Doug Staff Member

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    Yours is the first report I am aware of. Please encourage the others to get in touch.
     
  10. JoshuaHufford

    JoshuaHufford Cyanogen Customer

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  11. JoshuaHufford

    JoshuaHufford Cyanogen Customer

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    Quick question. Isn't the chip in the STi the same chip that is built into other cameras/filter wheels? Could this possibly be related to all the other star fade problems?
     
  12. Doug

    Doug Staff Member

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    Yes it is the same sensor, and no, there isn't one single cause for star fade reports.

    "Star fade" has reached the level of urban mythology; it's not a single thing. We're going to expunge the term from the software, and replace it with more detailed reporting on what is going on.
     
  13. JoshuaHufford

    JoshuaHufford Cyanogen Customer

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    Well as of yet I don't have any updates because one guy that I know that sees this problem uses Maxim5 which can't save the guide images. And the other doesn't use Maxim at all with his camera. I might see if I can use my laptop on one of their setups and save some images with another camera that shows the same problem if that would be helpful?
     
  14. Doug

    Doug Staff Member

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    Yes it would be. It may be useful to get your camera back to Ottawa for investigation.
     
  15. JoshuaHufford

    JoshuaHufford Cyanogen Customer

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    What kind of cost would be involved in sending it in?
     
  16. Kevin Morefield

    Kevin Morefield Standard User

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  17. JoshuaHufford

    JoshuaHufford Cyanogen Customer

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    How many guide images do you have? Would you mind letting me see a series of them to compare to mine? DL suggested that I send in my camera for inspection, and I'm perfectly willing to do that if it isn't too much money to do compared to just a new camera. However you are not the only one seeing this problem so I'm thinking either a lot of cameras have this problem or it is a potential software problem. You are not using MaximDl for camera control correct?
     
  18. Kevin Morefield

    Kevin Morefield Standard User

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    I use TheSkyX for camera control and it only saves the current guide image I believe. So I have to sit watching the images and save them as they happen. I'll try to get a few more. But they will look just like the sample I posted.
     
  19. Kevin Morefield

    Kevin Morefield Standard User

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    OK, I watched about 10 minutes of guiding and caught 3 of the bad ones. I also save the next exposure after the bad ones. You can see how the guider moves the star off center after the bad subs. This is about how it normally goes - 3 bad ones in 10 minutes.

    See attached

    Kevin
     

    Attached Files:

  20. JoshuaHufford

    JoshuaHufford Cyanogen Customer

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    Well it certainly does seem similar to my problem although not as drastic. Hopefully this will help the staff find the problem.
     

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