Following on from the work done last year on my colour, full spectrum, cooled 450D I've decided to use the spare 450D that I have on hand to build a mono version with updates to the cold finger setup.
First I have to thank Rowland (rchesire) for all the work he did developing and sharing the copper cold finger design.
Recently CentralDS (in South Korea) have started to offer debayering of CMOS sensors as one of their services. Normally this debayering is offered in conjunction with one of their camera products, but is also offered as a standalone mod on some recent models. In discussions with Yun Lee at CentralDS they have agreed to debayer my 450D sensor. Rather than attempt the debayering myself I decided to trust the work to them. The sensor assembly has been sent off to them for debayering. Cost of this is $300USD. Note that JTW does not offer a debayering service anymore, but still publish the instructions for people wishing to try it themselves at their own risk.
The debayering will give me a 12 megapixel (5.2 micron) mono sensor. This is a significant improvement on the resolution available in the bayer matrix colour version, as all the pixels will be collecting photons all the time; unlike the colour version which has some red, some blue, and more green. For a detailed explanation of how the bayer matrix works look here:
https://en.wikipedia.org/wiki/Bayer_filter
The initial plan is to use the mono camera for B&W luminance imaging, and narrowband from my observatory. I am leaving RGB imaging for later, once I get through the learning curve for B&W and narrowband - and decide how I would manage filter swaps.
Just a note on RGB filters for mono DSLRs, Astromonik is now offering EOS clip-in RGB filter sets for mono Canons:
http://www.astronomik.com/en/news/RG...er-as-Clip_EN/
So, to the build, I have attached some photos of the strip down of my spare 450D, which is basically as per Gary Honis' excellent guide to DSLR mods which I used last year. My sensor was already full spectrum so there was no need to do any work to it before it went off to CentralDS (and saved alittle money as I don't need to pay them to do that).
The copper cold finger shown in the photo below, is exactly the same as the one in my colour camera (and in Rowland's). I have two possible TECs to be tested: the same 40v40mm 5.8Amp unit used in my colour camera, and a 8amp unit of the same size. I expect the 5.8amp unit will be the final choice for power efficiency as it gives an adeqaure delta T of -25C, and there is really no reason to push the cooling below -5C.
The temperature setpoint controller and power management will be the same unit I built for the colour camera, and as it is attached to the camera by a six wire cable I can simply use the same wiring scheme on the mono camera and just have a single controller for both cameras.
While the sensor is off in South Korea I will be rethinking the argon system and condensation/frost management. Bagging the camera works really well but requires changing from time to time as leaks develop in use, and it makes camera port access an issue. I'd like to create an argon chamber around the sensor and this maybe feasible.
I have included a photo of my step by step tear down "Run Sheet", which I find very helpful in managing all the little screws that need to be removed in a certain order, as reassembly is made easy by just going backwards through the run sheet. Regardless of how many times I tear down a camera I always use this "Run Sheet" to manage the parts and steps. The removed components are kept in a sealed bag until needed again.
More to come.
