Gina

Another way of getting relatively dry air up to the ASC for cooling I though of was an air duct from the scope room with a fan at the scope room end but I think this would be quite difficult to implement.

Central heating systems have problems with airlocks - radiators need venting occasionally as do the highest parts of the pipework.

Air can be dissolved in the water but should be released in the reservoir, again if a sufficient flow to get over the reduced pressure in the waterblock.

The possible problem with water cooling is that the waterblock is going to be the highest part of the system and could suffer from an airlock unless the pump is powerful enough to flush the air out. I think I shall have to do some experiments. I do have the necessary parts. A copper waterblock 40mm x 40mm x 10mm, 12v pump, plastic pipes, etc.

Vibration may be a problem with cheap fans whilst high quality ones with low vibration probably wouldn't stand up to the environment. I'm going off fan cooling. The passive cooler looks like being the easiest though water cooling is interesting and would make for a smaller, more streamlined unit with less windage. This is a very exposed location particularly from the SE.

These photos show last year's ASC before it was destroyed in a fierce storm. This uses a passive cooler about 4" square and 3" high. The cooler survived the storm and is a contender for the next build.

Possibly.

But they're huge!

Yes, water cooling is one of the ideas mentioned above but is not so easy with the waterblock so high up. I have used water cooling in the past for camera cooling and use it currently in one of my 3D printers. I am well familiar with it.

Some nice images of the sky including the Milky Way with star colours showing. I can also see approaching clouds long before I can see them out of the window. (Or approaching clear sky.) Sorry, the images aren't better documented though there is info in my ASC Blog. Also, I haven't had the opportunity to do a more extensive report on noise v temperature. I just know that the camera needs cooling to somewhere near freezing to get the noise down. The camera can get down to a few degrees above ambient without cooling so is alright uncooled in winter but temperatures can get to 20°C to even 30°C in summer and the noise would swamp the image.

So sorry to see you lost your wife Kev ? If it would help you to post me your problems in PM I'll be happy to reply. I think I'm known as a good pair of ears/eyes. But if you would rather not I respect that too. I wish you the best of luck - life has a habit of throwing nasties at us!!

Some test images at various temperatures and exposures. Best images are with temperature of <2°C the worst is with no cooling and around 15°C. Exposures are from 10s last pic @ 15°C up to 60s on the lightest one. I estimate that 15s exposures with temperature cooled to near freezing would be good with the ASI 120MC-S camera (which is more sensitive then the ASI 185MC that I was using last year having larger pixels). 60s exposure at 2°C 15s exposure at 2°C. 10s at 15°C. (Focus was well out)

Experience has shown that cooling is necessary. This applies to the ASI 120MC-S, ASI 178MM and ASI 185MC with an f1.8 lens. I'll see if I have some images.

Following on from a couple of other threads I thought I would start one on the specific topic of cooling the astro camera in an all sky camera (ASC) to reduce noise for longer exposures for use at night. An ASC by its nature is isolated up a pole/mast or maybe attached to the highest point of a roof and out in the open. This means normal cooling methods may not be suitable. Cooling the astro camera is provided by a Peltier TEC but the problem is getting rid of the heat from the hot side of the TEC. The standard cooling method is a finned heatsink with a fan to blow cooling air over it but this camera cooling system is outdoors in the often damp/wet atmosphere we have in the UK. This then needs the question asking "Are cooling fans alright when used in a damp environment as they are designed to be used indoors?". I don't know - does anyone? It seems likely that damp may cause rusting of iron rotors or maybe affect the electronics inside the fan. There are other ways of dissipating the heat such as a large passive cooler which relies on convection for cooling or even water cooling. Plus it might be possible to provide a supply of dry air. All these ideas and maybe others are what I wish to explore in this thread.

Blimey!! All these posh observatories... ? Mine works - nuff said!!

In view of the way the prime Fujinon fisheye lens seems to be getting scarcer and more expensive as time goes on I have decided to buy a used one from ENS optical as linked to above. Not an OTT price for an astro item, I guess. I have an ASI 178MM camera I can use with it and upgrade to the colour version later on when/if funds permit. The zoom lens and ASI 120MC-S should be adequate for daytime. Alternatively, I could team up the prime lens with the ASI 120 for nighttime to get the star colours. It's all "still in the melting pot".

Thanks. That looks like a neater way to do it than using an intermediate Arduino. Found tutorial on using Python with INDI.

I've been doing more searching of the internet and it seems nobody has achieved what I desire in an ASC at any price. Even the Oculus ASC at around £750 doesn't achieve full sky coverage. Seems there is no fisheye lens at any price that will do what I want though the Fujinon DF1.4HB-L1 that I was using before,comes closest, in combination with the ASI 178 camera. That lens is several hundred UK pounds new though used ones are available much cheaper, as I said above. Of course, getting both nighttime and daytime decent images out of the same ASC is asking a lot. One solution to this would be to have two ASCs. The daytime one would still want a super wide angle fisheye lens but clouds don't need high resolution.

Have to say I'm not happy with the Fujinon zoom lens nor really with the other Fujinon lens. The zoom lens is poor quality and awkward to control whilst the bigger fixed focal length lens has no facility for focussing, making this difficult and it cannot be used with the ASI 120MC-S camera for daytime use as the minimum camera sensitivity is too high and any sun in the FOV causes whiteout. The ASI 178MC with smaller pixels and half the minimum exposure will cope with the f1.8 lens in daylight. Unfortunately, even with the new month and input of funds into my bank account I can't afford a new lens and ASI 178MC camera as well as pay the bills so I shall have to put up with the zoom lens somehow. I now have the two servo motors I ordered and these are very much better then the tiny micro server motors though considerably bigger. The ASC will need quite a large casing. I have to arrange mechanical coupling from servo motor to the little levers on the zoom lens and also sort out how to operate the servos from the RPi. If I can't drive the servos directly from the RPi I could use an Arduino Nano between them so using servo motors is certainly possible. For use with the ASI 120MC-S camera the lens focal length has to be 1.4mm or less to cover the amount of sky I want (though still not all of it). There are 1.55mm focal length lenses available but these don't cover the sky with the small image sensor in the ASI 120. For those with buildings and trees restricting their view of the sky these lenses would be adequate.

And of course - rain tonight so no stars!

Increased exposure to 1ms.

Strange!! It's gone green!! ?

Nice video ?

Eyebolt for stopping my observatory roof lifting up and off in a storm.

Since I'm currently stymied with the WiFi problem, I've connected by cable, set everything up with KStars etc., focused the image and put the bare camera plus lens rig up on the pole outside the living room window, hung on the house guttering (yes, it is secure!). Lots of clear blue sky ATM.