#21  
Old 21-04-2017, 11:45 AM
NinetySix (Ian)
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Oh and lastly, getting her sealed up in a bag is a piece of cake now that I only have to deal with cables and tubes coming out of the camera when in use. The heatsink I was using was a real pain to get air tight, and it seemed that no matter how small the holes were, argon will find a way out and the sensor ices up.

But now I'll just have power, usb, shutter release cables, a small argon top-up tube and water flow+return tubes wrapped up in some closed cell foam and duct taped to one end of a food seller bag, with the other end taped around the base of the coma corrector.

Once I bag her up, she may never come back out
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  #22  
Old 21-04-2017, 11:47 AM
NinetySix (Ian)
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Originally Posted by rcheshire View Post
Looks like it's coming along well. Water cooling Argon and a PID controller. The dark says it all.

Yes... I've pretty much invented every step of the way with an Arduino and the ubiquitous TMP36 digital temp sensor. Trial and try again...

You can wind the voltage back on the sensor defroster depending on the megapixels of your sensor, providing your not cooling too low. -10C is the limit with low relative humidity.

At -5, I've never seen a drop of condensation. There is a but... the heater needs to be on as soon as cooling starts. It's designed to keep the glass clear but not to quickly recover a badly iced sensor glass. That takes ages.

I always get things up and running well before imaging and take a few sample shots. If there's any sign of frosting I up the setpoint by a few degrees. With Argon this is all academic.

EDIT: You can dispense with darks at 0 and below and forget about linear preprocessing methods and do a very simple;

Darks will very likely add noise to the images. It's possible to use linear processing but you need a program that does dark optimisation - personally, I avoid that style of processing with a cooled DSLR.

Have fun...
Cheers mate really appreciate the tips
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  #23  
Old 24-04-2017, 07:31 PM
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rcheshire (Rowland)
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Looks good Ian. I had the same problem with the argon bag. Gave up and went back to heating. Must try water cooling some day.
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  #24  
Old 26-04-2017, 10:20 AM
NinetySix (Ian)
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So after endless frustration with the argon bag technique, I was dragged kicking and screaming to the heated sensor club.

I used some really skinny 32 gauge kanthal/nichrome wire and applied it to some 10mm wide double sided tape, applied in a zigzag pattern. It took about 300mm of the stuff to get just on 21 ohms. I laid out a strip of tape longer than I need for the whole job on a table with the backing peeled off at the ends so it wouldn't move about, marked where the corners were and used tweezers to press the wire into the tape and fold it over for each zig and zag. Forgot to take a picture.

While I was there I relocated the temp sensor onto the aluminium sensor heatsink, should be a more accurate reading rather than directly from the cold finger. Still don't have a temp sensor that will fit on the sensor glass so I may well have to go without, just have to suck it and see.

I also whipped up a support bracket to prevent the cold finger from having to carry the weight of the heat exchanger & pipework. I used two pieces of 6mm depron foam between the bracket and the cold finger, it has proven to be a very good insulator with amazing compressive strength. Previously I used a piece of 8mm HDPE cutting board and the bracket was flexing quite a lot plus getting icy cold.

So I set everything up in the loungeroom this time instead of outside on the pier where it's either raining occasionally I'm distracted by stars poking out from behind the clouds. From 21c starting (and room) temp I struggled to get below -2c with the camera off completely and the sensor heater running on 5vdc, plus it was icing up a little still. The radiator was warm but hardly piping hot.

Then I realised that the cold finger is actually pressing hard up against the metal rear cover of the camera, which it wasn't doing before I fitted the support bracket. Explains why the screen was freezing cold to touch and covered in condensation

So any way I'll just have to cut it a bit wider, probably slot some depron into the gap too. Here's some slightly better pics.

Total weight as shown with SD card and external power battery adaptor is 1240g, standard weight is reported to be 780g so there may be very little weight saving to be had with water cooling. I bought the cheapest water block I could find locally, not the lightest, YMMV.

Full res pics here: https://goo.gl/photos/doQoFbUzSiKHuVS79
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  #25  
Old 26-04-2017, 03:56 PM
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rcheshire (Rowland)
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Who'd have thought of Argon as a hair loss treatment. You will loose a little cooling with the heater, but if it's working properly it should be good to -10. I used nichrome at one time. It works well enough.
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  #26  
Old 26-04-2017, 04:57 PM
glend (Glen)
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Over a year ago i setup water cooling on my mono Canon 450, it worked great at temperature control but issues arose once it was on the scope. The main problems were:
Even when using very flexible silicon tubing the flex decreased when filled with pumped coolant. This creates problems with scope movement and balance.
Secondly, the weight of the filled tubes ruins any attempt to balance the mount, unless the tubes can be supported by an arm attached to the dovetail.
Thirdly, positioning the pump unit was a problem, it was mounted on a box with its radiator and fan, it had to be manually moved from one side of the mount to the other when slewing required it.
I concluded that, despite great cooling performance, it was entirely impractical for use on a telescope, and went back to a fan cooling system.
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  #27  
Old 28-04-2017, 08:55 AM
NinetySix (Ian)
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Originally Posted by rcheshire View Post
Who'd have thought of Argon as a hair loss treatment. You will loose a little cooling with the heater, but if it's working properly it should be good to -10. I used nichrome at one time. It works well enough.
I felt the only option left with regard to argon would be to tape the bag around my neck, so I suppose it's a good thing I accidentally drained the bottle by leaving the reg slightly open

But on the bright side I think I've got the sensor heater pretty well nailed, previously I refitted the metal frame that held the dust off+ir/uv filter in place over the top of the double sided tape and it must have been making contact with the metal parts around the shutter box, which are thermally coupled to the sensor heatsink.

It seems as if from the factory the sensor heatsink is coupled all the way to the external base plate and the metal parts around the lens flange, makes sense as how else can the camera reject any heat the sensor generates. Maybe all cameras do this, just an observation.

But with that metal frame removed (it was completely unnecessary, the tape alone has more than enough grip, hot or cold) it's now performing much better. Before it would bring the sensor temperature up from ambient within seconds of being turned on, and it had very little effect on sensor dew.

Now with 5v on the sensor heater and the peltier running flat out at 12v with the pump & radiator fan also at full speed I've only got a ~10mm wide patch in the centre of the sensor that stays fogged. So once I actually get some control of the sensor temperature I'm confident it will do the job, at worst might need another volt or so just for head room.


The surface mount resistors look like they would do the job quite well, lots of surface area directly on the sensor. I think the foam of the double sided tape must be doing a reasonable job of helping to spread the heat around the sensor glass as well as insulating it from the air within the shutter box. I'll have to order a full set of screws for the camera if I have to go back in there again though plus some tiny easy outs
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  #28  
Old 28-04-2017, 09:17 AM
NinetySix (Ian)
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Originally Posted by glend View Post
Over a year ago i setup water cooling on my mono Canon 450, it worked great at temperature control but issues arose once it was on the scope. The main problems were:
Even when using very flexible silicon tubing the flex decreased when filled with pumped coolant. This creates problems with scope movement and balance.
Secondly, the weight of the filled tubes ruins any attempt to balance the mount, unless the tubes can be supported by an arm attached to the dovetail.
Thirdly, positioning the pump unit was a problem, it was mounted on a box with its radiator and fan, it had to be manually moved from one side of the mount to the other when slewing required it.
I concluded that, despite great cooling performance, it was entirely impractical for use on a telescope, and went back to a fan cooling system.
Just from bench testing it in the house I've had concerns about all of the issues you've listed there, plus the 10mm ID PVC tube I'm using is very happy to kink when warm.

Still, I'm not licked yet I plan to mount the pump with 125ml reservoir, radiator & fan to my extra long dovetail (which is actually ~40x20x3mm aluminium square tube bolted to an ADM puck) in a manner that will never allow the pump inlet to point down. The tubes will be affixed to the aluminium tube with elbows for any bends, and just enough slack for the focuser to travel in and out, plus hopefully get about 180 degrees of camera rotation. The 90 degree elbows coming straight off the heat exchanger can rotate 360 degrees freely.

The pump is very low on vibration and basically silent once all the air has bled off, and the fan is a noctua with nice rubber mounts and similarly bugger all vibration, so I'm feeling confident for now.

Any way I'll see how that goes before pulling the pin, I've also ordered a very cheap 40x40mm aluminium Northbridge heat exchanger from eBay that only weighs 30g, that should have the setup much lighter (as far as the focuser is concerned) than possible with air cooling.


Cheers
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  #29  
Old 28-04-2017, 10:37 AM
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Originally Posted by NinetySix View Post
Just from bench testing it in the house I've had concerns about all of the issues you've listed there, plus the 10mm ID PVC tube I'm using is very happy to kink when warm.

Still, I'm not licked yet I plan to mount the pump with 125ml reservoir, radiator & fan to my extra long dovetail (which is actually ~40x20x3mm aluminium square tube bolted to an ADM puck) in a manner that will never allow the pump inlet to point down. The tubes will be affixed to the aluminium tube with elbows for any bends, and just enough slack for the focuser to travel in and out, plus hopefully get about 180 degrees of camera rotation. The 90 degree elbows coming straight off the heat exchanger can rotate 360 degrees freely.

The pump is very low on vibration and basically silent once all the air has bled off, and the fan is a noctua with nice rubber mounts and similarly bugger all vibration, so I'm feeling confident for now.

Any way I'll see how that goes before pulling the pin, I've also ordered a very cheap 40x40mm aluminium Northbridge heat exchanger from eBay that only weighs 30g, that should have the setup much lighter (as far as the focuser is concerned) than possible with air cooling.


Cheers
Similar thoughts... but as you mention, vibration free...

Enough tube to rotate the camera and frame the target.
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Old 30-04-2017, 02:06 AM
NinetySix (Ian)
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With a heavy heart I must report that this project looks to have concluded far too early

Everything was looking good, except I realised I really needed a temp sensor on the sensor glass to control the dew heater, so despite my better judgement I pulled her to bits and got to work. Everything was looking good, the new sensor was in the perfect spot and I started reassembling her for what should have been the last time... And it all went south just as I was nearly finished, 3 (yes 3!) of the ribbon cable headers on the motherboard fell to bits on me, and the worst affected was the header for the shutter box assembly, the fingers were bent pretty bad and I lost a few of them trying to straighten them.

Luckily I had a spare motherboard as I had recently replaced mine a few weeks earlier, that one had a dicky ribbon socket that still worked. No dice, can't get into live view or take a photo, constantly flashing ERR on the top LCD.

I have it one last shot to pull it apart, inspected every ribbon and ribbon socket with a loupe and made sure everything was where it should be and foreign object free, and now the bugger won't even turn on at all, zero signs of life.

So at this point my sanity, patience (and more importantly, the Mrs') and spare time have been fully depleted so although I may get this Nikon going again in the distant future, I'm now in the market for a mono CMOS and filter wheel.

I believe that the issue I've run into is almost certainly a result of it being pulled apart so many times rather than the presence of the cold finger.

My main motivation for posting this up was to show that it could be done reasonably easily on a Nikon D7000, so c'mon Nikon users don't let her (temporary) death be in vain, treat yourself to a cold fingering!


See you on the next one, Cheers
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  #31  
Old 01-05-2017, 07:18 AM
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Several of us have a 'casualty' in the spare parts drawer. Usually, a consequence of over modification. Though, the older Canons do seem to be more tolerant.
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Old 01-05-2017, 08:50 AM
glend (Glen)
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Yes, i had a box of old Canon boards that i managed to destroy during mods. Those ribbon cable lock bars are notorious for falling to bits if disturbed. I tried various ways to secure the ribbons, but without the lock bar they simply will not make a connection. If you can source dead boards cheaply you might be able to salvage the lock bars but they are likely to break trying to get them off and back on your board. Buy a replacement board if your keen. I lost track of how many Canon 450D sensors that i bought from Aliexpress, when i was doing mono debayering. It is so frustrating when you put so much time, and care, into a camera mod and then on assembly it doesn't work. I used a camera repair shop in Chicago for Canon board spares but can't remember their name now, not exactly cheap either but you get a working board. My frustration ended when i added up the cost of what i was doing and realised i could have bought an ultra low noise, mono, cooled, astro camera for that investment. I purchased a ASI1600MM-C and have had a great time with it, actually imaging. My original cold finger full spectrum Canon 450D is still with me, still works great, and i get it out now and then, but the ASI is much easier to use, requires less power, cools much deeper, etc.
Move on, is my advice.
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  #33  
Old 01-05-2017, 09:02 AM
NinetySix (Ian)
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Several of us have a 'casualty' in the spare parts drawer. Usually, a consequence of over modification. Though, the older Canons do seem to be more tolerant.
I'm not quite ready to call it a casualty just yet, and if my asi1600mm-c, filter wheel and filters don't arrive before the weekend I'll be sure to have one last go at it, it may just be a plug that I forgot to plug back in.

There comes a time when you have to accept that the Mrs is right, you've been spending way to much time on that stupid bloody camera! And wipe up the thermal grease you stepped in and walked around the house.

Money isn't a problem (sparky with no kids, Mrs works plus we run a business from home) but time absolutely is, and even with a working camera astrophotography has proven to be very time hungry. Luckily it's interchangeable with sleeping
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Old 01-05-2017, 09:34 AM
NinetySix (Ian)
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.... I purchased a ASI1600MM-C and have had a great time with it, actually imaging....
Move on, is my advice.
I have to say that sounds pretty bleak, but I'll just have to make my own fun of it I just worry that I might not appreciate the better images quite as much without them being tainted with my own blood sweat and tears.

I wanted to stick with a CMOS sensor for my own personal, uninformed reasons so the asi1600 looks like the one to have, though the imx071 from the d7000 (and a few others) is still an absolute cracker of a sensor, which makes it so hard to let go! But mono with filters sounds like just what I need.

This here is really the only good shot I got from it with cooling:

https://goo.gl/photos/C9i3RcBy8bbRWG2X8

A single 4 minute sub with the sensor around -5c, no dark no bias and no flat frames. Star eater disabled and true dark current enabled in firmware and quickly tweaked in Lightroom. Huge dust bunnies but it was the one time the argon bag actually worked. Still a few optical issues such as secondary mirror alignment, collimation and coma corrector spacing plus erratic guiding from my neq6 which is also suffering from excessive disassembly syndrome (EDS).


I was already on my second motherboard, though the damage on the first was basically superficial. One of the ribbon sockets for the display had lost its lock bar, but luckily it was the type where the lock bar is on the other side of the socket to where the ribbon goes in, and the ribbon could still be pushed in and pulled out without too much fuss. The damage on the second board was quite a bit worse though.

You can pickup replacement boards from eBay for 90 bucks, seems to be a steady supply of them from China plus the USA for a few bucks more.

I was worried that the damage may have actually been to the shutter from the sensor heater temp sensor pushing into it, or the mirror actuator because neither were working initially. You can get a brand new mirror box assembly including shutter for about 110 delivered or without shutter for 65 bucks so spares aren't a huge issue, but it's kind labour intensive.
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