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View Full Version here: : How do I minimise cleaning requirements for an outdoor all-sky camera dome?


HunterGeo
11-03-2018, 09:23 PM
Hi everyone,

I am building an international network of astronomical all-sky cameras. The cameras will be protected from the elements with a clear plastic dome (and other environmental measures beyond the scope of this post).

(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?

Thanks in advance.
David

Wavytone
11-03-2018, 09:27 PM
David are you aware that quite a few weather stations have been installed by people that include a webcam, and provide weather data and images periodically to publicly accessible websites ? For example the hangliding and paragaligling community - and there are others.

Admittedly they don't use all-sky cameras but typically do have a pretty wide field which is easily compared on Google Earth if its unclear which way its facing.

HunterGeo
11-03-2018, 09:34 PM
Yup, I'm aware. Thanks, though. :)

JA
11-03-2018, 10:10 PM
1. Use clean fresh water to wash the dome and force dry with warm air on a regular basis. Do not allow to air dry unless air/water is very clean at the risk of leaving residue behind over many months.

2. Establish a program of remotely monitoring the dome cleanliness and setting the wash/dry cycle accordingly.

3. Consider adding detergent and/or rinse agent

4. Monitor dome for UV degradation of the plastic

5. Consider adding antibird spikes around dome.

6. You could even go crazy and automate a brush mechanism or lens visor tear-off protetcor if you were NASA


Best
JA

Wavytone
12-03-2018, 01:09 PM
Two solutions used in the rail industry - we have machine vision camera equipment embedded in the ballast looking up at the undersides of rolling stock to inspect brake pads and wheel wear. As you might expect it’s a dirty environment in addition to ordinary dust, rain, leaves, litter and other debris that can fall on the gear.

1. Use a mechanical shutter that protects the window from dirt and only opens before and closes after a picture is taken.

2. Windscreen wipers with fluid to wash the window before a shot is taken. Wipers have advantage that they will push small items off (leaves, etc) but also more of a maintenance problem in requiring regular replacement of the blades, water, and fail frequently.

3. Don’t face the camera up - place horizontally with wide angle lens and a hood over it, and accept the camera cannot view directly overhead.

Anything with moving parts or requiring consumables (wash liquid) is prone to failure and a maintenance headache. Making these solutions work this reliably long-term is neither trivial nor cheap.

Tear-off protectors are also used on motorcycle helmet visors.

Questions for you:

1. do you really need continuous video or would it be ok to take images periodically ?
2. Is this expected to operate automatically at a location which is unmanned for long periods or will there be someone nearby ?

As I hinted before I think you really should be talking to companies that do this for weather stations because what you’re proposing is not new, and has been solved before.

Imme
12-03-2018, 02:02 PM
Put them on their side and use a mirror on a 45’ angle.

To a point the mirror will self clean.....nor a perfect solution but it will significantly reduce cleaning requirements I’d guess

HunterGeo
19-03-2018, 02:12 PM
Hi everyone. Sorry for the slow reply - ended up being quite ill the last few days and completely forgot about this forum post. Apologies.

Thanks for the various suggestions. I'll reply to each message individually shortly...

HunterGeo
19-03-2018, 02:21 PM
Thanks for these suggestions. The automated brush idea is in line with what I was starting to realise would probably be necessary. I'm not looking forward to doing that but if it has to be, then so be it I guess.

In response to your point #1: do you think a tank of distilled water would be best, intermittently (e.g. weekly) spraying some of it onto the dome (along with e.g. Bars Bugs), and then warm-air-drying it?

Regarding your point #4. I thought I might have problems with the plastic yellowing and have since found a custom glass dome manufacturer. Waiting for a quote from them, but that'd presumably not degrade as rapidly as the plastic I was thinking of using.

Thanks for your help. :)

HunterGeo
19-03-2018, 02:39 PM
Thanks for these thoughts. I particularly like the shutter idea. However, given the dome is roughly a foot in diameter, it's going to be fairly large, and then we introduce problems with things possibly getting caught inside, motors failing, etc. Do you have any solutions for removing e.g. leaves, spiders, etc. from inside the camera housing protected by the shutter please?

Interesting idea regarding the windscreen wiper idea. I wonder if they make curved ones to suit this sort of dome, though. I have seen some CCTV dome wiper brushes, though, so they may be more easily used (i.e. they're commercially available). Just did a quick Google. Didn't find any commercially-available curved wiper blades, but I did find something that gave me an idea to run with that may actually be better than a wiper blade. :thumbsup: :thanx:

To answer your questions:



1. No, they're taking images every five minutes.
2. There will be people nearby, but the cameras are being installed on rooftops, so won't be easily accessible. The system needs to be fully autonomous for as long as possible. I realise I won't be able to get something that lasts forever, but if I can minimise cleaning and maintenance visits by a person to e.g. only once per year, then that'd be beneficial. :)

I am going to set up a prototype down at the beach soon. I figure that's probably the harshest environment (in terms of sea spray and wind-blown sand hitting the dome) and would be a good place to test these ideas out...

Thanks heaps for your help and ideas.
David

HunterGeo
19-03-2018, 02:40 PM
Thanks for that suggestion. :)