Cold weather problem

Discussion in 'STF Series CCD Cameras' started by Richard Willits, Dec 21, 2016.

  1. Richard Willits

    Richard Willits Standard User

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    My STF 8300 Loses it's sensitivity at about -3˚F (-20˚C) ambient. Last winter I had this problem and was able to control it with scarves. If I wrap a scarf around the camera and am able to keep the % of power to keep the sensor at -30˚C to 12% or higher the camera will stay warm enough to keep working correctly. I have to stay diligent, because if it gets colder. I have to move the scarf a bit, and if I fall asleep and the camera starts warming, it will generates more heat then needed. and keeps getting warmer and warmer. I woke up and found it at 95% and climbing. It was a major pain to keep the camera body at the proper temperature. It worked great in the summer.
    this winter I have an OAG on my telescope and the scarf trick doesn't work well. where I live it is warm and snowing or cold and clear. I do most all my imaging at below -20˚C . Has anyone had this problem and if so, what did you do.
     
  2. Richard Willits

    Richard Willits Standard User

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    I may have made my original post in the wrong place. this is a copy of a post I made in "General".

    My STF 8300 Loses it's sensitivity at about -3˚F (-20˚C) ambient. Last winter I had this problem and was able to control it with scarves. If I wrap a scarf around the camera and am able to keep the % of power to keep the sensor at -30˚C to 12% or higher the camera will stay warm enough to keep working correctly. I have to stay diligent, because if it gets colder. I have to move the scarf a bit, and if I fall asleep and the camera starts warming, it will generates more heat then needed. and keeps getting warmer and warmer. I woke up and found it at 95% and climbing. It was a major pain to keep the camera body at the proper temperature. It worked great in the summer.
    this winter I have an OAG on my telescope and the scarf trick doesn't work well. where I live it is warm and snowing or cold and clear. I do most all my imaging at below -20˚C . Has anyone had this problem and if so, what did you do.
     
  3. Colin Haig

    Colin Haig Staff Member

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    I'm curious - when you say it "loses it's sensitivity", can you explain, or provide some sample images?
     
  4. Richard Willits

    Richard Willits Standard User

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    When it is working properly, the image has small stars and nebulosity. But when the camera gets to cold a 10 minute exposure looks like a 1 minute exposure. all that is on the subs is the brightest stars, and they don't look very bright.
     
  5. Doug

    Doug Staff Member

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    Can you provide a FITS light frame from the camera - when cold?
     
  6. Richard Willits

    Richard Willits Standard User

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  7. Richard Willits

    Richard Willits Standard User

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    I actually have 4 of the good subs and 20 of the bad subs, all taken the same night and all are identical. I use SGPro for capture, and because of the cold, I use TeamView to monitor the telescope which does not have very good resolution. I was careless and didn't pay close enough attention.
     
  8. Tim

    Tim Staff Member

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    Do you know the approx. temperature inside the observatory? Are you saying the ambient temp inside your observatory is -20C, and you cool the camera to -30C (based on the information in the FITS headers)?
     
  9. Richard Willits

    Richard Willits Standard User

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    I setup my telescope outside, and the outside ambient was between -3˚F (-20˚C) to -8˚F (-22˚C) when these subs where taken. It was also a bit windy.
     
  10. Doug

    Doug Staff Member

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    That does not sound normal. We're going to run a couple of tests on an identical camera in our environmental chamber, just to check. Hopefully we can get that done before the Xmas break.
     
  11. Richard Willits

    Richard Willits Standard User

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    I could send in my camera now, if that will help. I was thinking of sending it in after Christmas anyway.
     
  12. Doug

    Doug Staff Member

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    You would have to RMA it to Ottawa, because Bill doesn't have an environmental chamber. Contact Carla at our office.
     
  13. Richard Willits

    Richard Willits Standard User

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    I will check into that tomorrow morning. Thank you for the prompt replay, and resolve to my problems.
     
  14. Colin Haig

    Colin Haig Staff Member

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    Richard, as a "crazy idea" is there any chance the imaging chip is frosting over inside? I'm wondering if the problem shows up after its been quite a while with the cooler on and cold outside temperatures? Or if it shows up right away? Thinking dessicant might needs to be baked. I know this isnt too likely given what you've explained, but thought I should ask.
     
  15. Doug

    Doug Staff Member

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    Actually, looking over your FITS files I think the problem is that the camera isn't set up properly. There's an offset value programmed into the EEPROM, which adjusts the offset from the A/D converter. I think that value has somehow been corrupted. The firmware is trying to compensate but it's on the hairy edge of working, and lower temperature puts it out of compensation range.

    The camera needs to have a "gain/offset" run on it. This determines the appropriate settings for the A/D converter and programs it into the EEPROM.

    It might be possible for one of our staff to do this remotely with your assistance, but I'd have to check with Tim on that. I'm not certain if he'll be in tomorrow or not due to a family situation. Unfortunately we're shut down next week.

    Failing that Bill @ Service would be able to reset it for you.
     
  16. Richard Willits

    Richard Willits Standard User

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    Doug, I like your Idea. I do have TeamView. We could wait until after the Holidays if you think that is best. I don't think that the US postal Service will insure packages leaving the country. UPS and Fedex offices are 60 miles away, and I don't want to go to the city until after the holidays. After the New Year will be fine with me if it works for you.
    I also have an issue with a vertical gradient that appears on the left side on occasions. In reading through the posts, I see that this could also be a software problem. Other than these, I love the camera.
     
    Last edited: Dec 23, 2016
  17. Christopher Duffey

    Christopher Duffey Standard User

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    I've had to make electronics work at very cold temperatures -my suggestion would be to adapt a dew heater to heat your STF-8300 - you could put the heater around the fan inlet and try and heat the air a bit before it enters the camera, a heater around the camera body might work as well - if the dew heater has a controller you should be able to balance the temperatures to run without intervention in your extreme temps
     
  18. Richard Willits

    Richard Willits Standard User

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    Thank you Christopher. that will be on my list. every suggestion is valuable. (the Americans spent one million dollars to develop a pen to work in space, the Russians use a pencil.)
     

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