Moving On from STT8300M

Discussion in 'STT Series (obsolete)' started by Greg Crawford, Feb 26, 2019.

  1. Greg Crawford

    Greg Crawford Cyanogen Customer

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    I have a STT8300M which has now been in for repair three times. I have been using it with a self-guiding 8 filter, filter wheel and an AO-8T , so that guiding is placed in front of the filters and with an AO-8T. If I want to move on from the superseded line of STT cameras, what model line should I look at to maintain the guiding advantage?
     
  2. Doug

    Doug Staff Member

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    The STT series has been replaced by the Aluma models.

    The AO-8T can be upgraded to AO-8A simply by replacing the cable (the connector is different).
     
  3. Colin Haig

    Colin Haig Staff Member

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    Greg, I had a chat w Bill Lynch our service wizard, and he shared some photos of the corrosion on the boards.
    Can you tell me a bit about the environment the camera was in ? Did you leave it on or power it off when not in use?
    The Aluma might be a better way to go, as the boards aren't in the "open air" as much as the prior generations of SBIG cameras.
     
  4. Doug

    Doug Staff Member

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    Since you're a good customer, maybe we can do something special for you. The FW8G Aluma is actually very similar to the FW8G-STT; perhaps we can work out some upgrade pricing and rebuild your wheel to work with Aluma. And certainly the AO-8 is trivially converted by replacing the cable.

    To echo Colin's comment about corrosion, my design philosophy is to minimize the exposure of electronics to the atmosphere. Especially in salt environments (i.e. within 30 miles of the ocean), salt gets gradually deposited on exposed surfaces and it can eventually corrode the circuit boards.

    Aluma's cooling is via a separate channel that contains the forced air within the heat sink. The fans do not circulate air around the circuit boards.
    Aluma_FrontC-e1501280576452-600x600.jpg
    Also a recommendation: if you have your camera permanently installed in an observatory, it's a good idea to leave it powered up with the cooler off when not in use. This helps prevent condensation within the camera.
     
  5. rockenrock

    rockenrock Cyanogen Customer

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    I like this thread.
    I also had my STT8300M camera back to Bill, and he expressed that some components were corroded. I have always carefully covered my camera, telescope and mount controller with several layers of polybag, you know the type. Then I have a large PVC/canvas cover over all. that is pulled tight around the pier. No water gets directly onto the OTA or the electronics.
    After painfully buying a new board from Bill I put more thought into what I was doing. I think that dew got trapped was getting trapped inside. Then as the temperature dropped the moisture would condense on different components. My current solution is to improve the polybag sealing with 2 pcs 50 gram bags of silica gel. When the weight gets to 66 grams I know it is time to dry out again at home.
    I bought my camera/filter/AO used. So maybe it was not pristine when I bought it.
    It is easy to say, why leave >$5,000 astronomy electronics outside, and not disassemble and take inside after each use. I say, why would a company design a >$5,000 system and fail to protect the PCB with a simple to do lacquer conformal coating that will not corrode in the known high humidity environment of astrophotography. Dew shields are used to fight the humidity near the lens. Electronics need something too, IMO.
    Yes, I would love a permanently housed observatory or roll off. But alas it is not allowed on top the building where I live.
    Roger
     
  6. Doug

    Doug Staff Member

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    Conformal coating has several issues, including (a) it makes it very difficult or impossible to repair the board and thus increases repair costs significantly, (b) it can have pinholes that allow corrosion to proceed, and (c) it does absolutely nothing to protect the internal connectors. At best it slows down the problem. The only real solution is to avoid getting moisture on the hardware.

    Even in an observatory moisture can be an issue. We have terrible humidity here year-round. My approach is to leave all the equipment powered up but with the CCD cooler off. This allows the electronics to self-heat slightly. As long as the hardware is a few degrees above ambient dew will not form on it.

    We do not recommend leaving cameras outdoors, even in a bag.
     
  7. Colin Haig

    Colin Haig Staff Member

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    The other trick is to park the scope in an orientation such that the camera and electronics aren't at the lowest point. Condensation that runs will find the lowest spot.
     
  8. Greg Crawford

    Greg Crawford Cyanogen Customer

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    I have wondered about leaving the camera on all the time. It is what I do with my observatory computer and my telescope mount, and they have both rewarded me with long years of service. If the camera is left turned on, should the fans be left running, or will that lead to them burning out early?
     
  9. Colin Haig

    Colin Haig Staff Member

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    If the cooler is OFF, fans can be OFF too.
    There is going to be some wear-and-tear on the fan bearings if left running.
     
  10. Doug

    Doug Staff Member

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    Aluma now has an auto fan speed mode.
     
  11. rockenrock

    rockenrock Cyanogen Customer

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    Hi Colin, Great idea for parking the scope.
    Currently I have a little different method to keep low moisture inside the scope and camera. I park the scope, CWD, add several 50g SiO2 desiccant bags in the scope (RC-10 so it is open) seal a plastic bag over the dew shield end of the scope with a velcro strap around that end of scope. At STT camera end I remove all cables, put 2 desiccant bags in a plastic bag and then seal it to the outside diameter of the back plate with another velcro strap. I think the sealing is pretty good because if I try squeeze the air out of the plastic bag it is tight.
    After those 2 bags are installed I cover the entire scope in a big polybag plus a custom canvas cover. I like this system with the desiccant because any dew on anything will not get locked into the scope or the electronics. It is sucked into the desiccant. No water will condense on the mirrors or electronics with the daily night/day temperature fluctuations.
    Roger
     
  12. Jason

    Jason Cyanogen Customer

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    I have a STT-3200 and have just set up a permanent observatory in the past few weeks. I have added to my procedure the following:

    Startup
    Connect
    Turn the fans on for ~15 seconds
    Turn on cooler

    Shutdown
    Warm up
    Turn fans off
    Disconnect

    The camera is on a remote power switch, with which I can disconnect power; however, I have left the camera powered up for convenience.

    First, I'm glad to read that this can be considered good standard operating procedure.

    Now to my question:

    To turn fans on/off, I am doing this with the "Enable fan" checkbox on the "Setup" tab on the "SBIG AO Control" popup in Maxim DL.

    Is there a way to script fan on/off control, either with ACP or another way?
     
  13. Doug

    Doug Staff Member

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    I recommend using the Auto fan speed mode. That way when the coolers off the fans do continue running, but at a very slow speed. It automatically raises the speed as required to maintain cooling.
     
  14. Jason

    Jason Cyanogen Customer

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    OK, that is the setting I'm already using and will keep doing so; I was just wondering about powering the fans all the way off.
     
  15. Doug

    Doug Staff Member

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    At this time that is not possible via scripting.
     
  16. jerryyyyy

    jerryyyyy Cyanogen Customer

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    Well, I just talked to Bill who is sending my STT 8300M back after the second episode of replacing the very expensive board due to humidity. It did last 5 years but still.

    There is no getting around that fact that San Francisco is Fog City. SO what are the countermeasures. I can reprogram the shutdown script in ACP to delay shut down for a couple hours to leave the camera power on? Will that help.... will the fans keep running?
     
  17. Colin Haig

    Colin Haig Staff Member

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    As a possibility, you could keep the camera powered up, with the cooler off and fan turned off. Heat from the internal electronics may be enough to keep it warm and dry.
    Am aware of one person who has a dew strap around their camera's body, (I thought this was silly - the body is quite large and is designed to dissipate heat).
     
  18. jerryyyyy

    jerryyyyy Cyanogen Customer

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    Seems the dew strap would be counterproductive to the cooler's efforts. Crucial part is to keep the moisture off the printed circuit board. If I could figure out a way to heat it in the morning that might help.

    I'll try the fan. I think 4 hours of fan after shutting down would be a good start. I can just add a delay in Bob's script...

    Does the desiccant plug play any role...?

    Finally I assume your new models will have the same problem?

    Interesting Bob's scrip has these lines in it:

    //Console.PrintLine("Shutting down CCD and Dew Heater in 200 minutes");

    //Console.PrintLine("Shutting down CCD and Dew Heater in 200 minutes");

    //Console.PrintLine("Shutting down CCD and Dew Heater in 200 minutes");
     
  19. Doug

    Doug Staff Member

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    The desiccant plug keeps the CCD chamber dry. It has no impact on the electronics.

    You could wrap a dew heater around the camera, and turn it ON when you shut down. Just keeping the camera powered up with the cooler and fans off should keep humidity off the boards in most conditions.

    This is why I designed the Aluma cameras to keep the circuit boards out of the air flow. Same thing with all future models.
     
  20. Colin Haig

    Colin Haig Staff Member

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    That's the essential thing.
    If you leave the camera powered up, with the cooler off, and the fan stopped, then it's on-board electronics will usually keep it above ambient and hopefully the dewpoint.
    The fan is going to cause airflow into the camera, including the damp outside air, and if it runs sufficiently fast, that damp air will condense on the aluminum and on the circuit board as it gets below the dew point.
    The order might be like this:
    - shut down the cooler, eg Warm Up (let it come up to ambient).
    - shut down fan a couple minutes later
    - then let heat from electronics in the camera keep the pcb warm

    No. The desiccant is inside the sealed chamber of the sensor, and keeps the air inside the chamber dry. It has no bearing on the outside electronics.

    The Aluma series are a complete redesign, with less outside air reaching the PCB. It's not totally sealed, but much better than the prior designs.
    The dual fans blow air against the massive heatsink, and none of that blows against the PCB. So any heat in the electronics tends to stay there in the blue box, while the TEC heat gets out through the heatsink.

    The other issue you have is that the SFO sea air is somewhat corrosive, not much to be done about that.
     

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