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I am building an international network of astronomical all-sky cameras. The cameras will be protected from the elements with a clear plastic dome.

(To clarify, I will have a camera on a rooftop pointing upward, with a clear plastic dome protecting the camera)

Because the cameras are remote (and installed on rooftops), I need a way of keeping them clean for as long as possible.

  • Bird droppings
  • Dust
  • Rainwater
  • Sea spray
  • Grime, etc.

I have seen some hydrophilic coatings (designed for CCTV camera domes, which are installed upside down). But I'm not sure if this idea is going to be feasible, given that my camera is facing upward and facing directly into the rain. I'm also concerned that the coating may not be enough to repel bird droppings.

I'm also concerned that such coatings may affect the image quality. Obviously, in low-light conditions, I need to maximise the amount of light getting through the dome and into the camera. Is this concern justified or am I overthinking things?

Does anyone have any suggestions on how to keep this dome clean for as long as possible with as little human intervention as possible?

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    You need an automated cleaning system for the domes. A wiper with a motor and a little circuitry, probably a small water reservoir (or maybe a lens cleaning fluid depending on how seriously you take all this). Regarding low light issues, you'd need to explain the purpose of the shots - e.g. is long exposure OK, that kind of thing. – StephenG Mar 11 '18 at 17:50
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    You've told us about how good you need your solution to be but it would help to know how about the other two legs of your engineering triangle. How much fast do you need? Do you have time to deploy a series of prototypes over the period of months or years? How much cheap do you need? Do you have hundreds per unit and thousands of R&D money to develop a self aware robot cleaned camera? – PhotoScientist Mar 12 '18 at 17:32
  • Thanks for the comments. @PhotoScientist, I have time to prototype this. I am funding this myself so money is tight but I'm not afraid to learn how to do things myself rather than paying someone if needed. Budget is probably under $2k for the dome cleaning issue. – ZPMMaker Mar 19 '18 at 4:45
  • @StephenG, yes, the cameras are taking long-exposure photographs (30sec exposures, once every 5mins). – ZPMMaker Mar 19 '18 at 4:45
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Seems to me I've seen cameras on racing cars that have a thin plastic film (think Saran Wrap) in front of the lens that is rolled past every so often, from a clean roll to a take-up roll. An example of this in action is here. I don't know that this would be feasible for a 180 degree field of view (the roll structure would be at the edges of the frame), but depending on your needs it might work.

There are also superhydrophobic coatings that could be used for lenses or lens domes that might minimize any 'stickage' resulting from bird droppings, etc.

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  • +1 for those. I was going to mention tear-offs, but this idea is far more environmentally friendly. – OnBreak. Mar 13 '18 at 17:22
  • That's certainly an interesting idea (the film) I hadn't considered. However, as you say, the dome-shape could be problematic. I'll prototype it and see if it works and how bad the distortion is (if any). Thanks. :) I am also looking at those coatings you mentioned. In my original question, I wrote: "I'm also concerned that such coatings may affect the image quality. Obviously, in low-light conditions, I need to maximise the amount of light getting through the dome and into the camera. Is this concern justified or am I overthinking things?" Do you have any experience/thoughts about this? TY. – ZPMMaker Mar 19 '18 at 4:49
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    I don't have any experience with those coatings, optical or otherwise, I know that some form of hydrophobic coating is used to protect eyeglass lenses from grease, dirt, etc. One of the many options you can pay for when you purchase new glasses... – BobT Mar 19 '18 at 21:24
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Could you spin the dome?

High speed spinning windows are used on some boats where windscreen wipers would be ineffective. However even a slow speed spinning would remove most things that land on the dome, and would encourage water to move off. Bird droppings would likely still be an issue unless you were spinning really fast.

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  • Thanks for that thought, Harry. I considered this myself and most likely will incorporate this into the final design. I think between this and the hydrophobic coatings, I may have a solution that may delay the need for in-person cleaning. Thanks for your help. :) – ZPMMaker Mar 19 '18 at 4:50
  • @ZPMMaker spinning the dome fast enough while the shot is being taken may even blur any 'debris' on the cover enough that it becomes practically invisible to the photo – Harry Harrison Mar 19 '18 at 4:52
  • Yeah, it could do. Will have to test this idea out... – ZPMMaker Mar 19 '18 at 5:27

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