Gina

That's radical I think it would be difficult to get a clean changeover and also half sensor size partly negates the benefit of a DSLR with it's relatively large image sensor.

I'm still of two minds regarding using a debayered DSLR for LRGB. I'm definitely going for NB as the main reason for CFA removal but I'm weighing up what I would image. My experience with the transparency (or lack of it) and seeing we have in this country, the image resolution is limited by the sky and there is no point in going for small pixels for longer focal lengths. OK the DSLR image size will cover a greater FOV but AFAICT there are few DSOs warranting this frame size and LRGB. In fact the only DSOs I use LRGB for are galaxies and maybe adding star colour to NB. In view of the number of 1100Ds I seem to have I'm thinking I might keep one for use as an OSC camera (assuming I don't destroy all the 1100D sensors I have in total). This would save me buying a set of 36mm unmounted LRGB filters and at the same time mean I would need only a 4 position filter wheel on the debayered camera. The result would be a smaller and sturdier all singing, all dancing camera for narrow band imaging.

The sensitivity to Ha is definitely increased, presumably because the spectral response of CFA red pixels falls off in the deep red. Likewise the sensitivity to OIII is increased because the spectral line of OIII falls between the green and blue responses. SII is even deeper in the red than Ha. So a debayered DSLR achieves better sensitivity for NB as well as having twice the resolution in both axes. For RGB the sensitivity may be slightly lower but the resolution is still doubled. This is definitely a very worthwhile mod for astro use. I have yet to compare a debayered 1100D directly with a mono CCD astro camera but would still expect the CCD camera to win, particularly with regard to noise. But the cost of a 12mp astro camera is considerable. Even with the cost of all the DSLRs I've bought for this project it is still only a small proportion of the cost of a 12mp astro CCD camera. But also, of course, I enjoy the experimenting

Been sorting out 1100Ds. That non-working one I bought recently works fine with external power The one with the cold finger had a duff sensor in it - one I had been debayering. There was a broken gold wire where my debayering managed to creep under the filter frame (that I was using as a guard) and catch a wire. I did test it - with short exposures up to 1/50th sec the image was black and at 1s and more in daylight, all white. Usually after destroying by debayering the sensor won't work at all. The sensor assembly that was untouched (without even filter removal) works fine and I have taken the shield off, snipped off a lug that was in the way and slipped a cold finger in together with plastic insulator to prevent shorting on the SMD components on the back of the image processor board. That's now ready for cooling test. I have tested it with the cold finger and it's still working. Now I need to look out a DS18B20 to measure the CF temperature and rig up a cooling circuit. I've made further progress on the cover glass replacement rig, sorting out a design for a printed plastic frame to hold the sensor. Now I know which cold finger I'm using I can finalise the design. I have the 3D printer working well enough to do the printing

Yes, it has. And yes, the sensitivity is reduced but every pixel will respond to all colours. I thought the reduction was more than that Nice to have actual figures.

Good - the sketch is alright then Anyway, I shall be testing with low temperature so we shall see how good it is. I have virtually no doubt about achieving -10C without misting up and that's fine

I think that might have been the one I bought (well bought 2 actually). I think it was a 2A one. EDIT --- Found it - and yes, it was MCPE-127-10-25 Works very well though I forget what temperature I got down to. It will be in one of my cooling threads I'll have the answer again soon though when I put an 1100D in the cooler instead of the 450D,

Transferred most of the smaller pot of resin to a 60mL syringe and put the rest in the other pot. So here is what I have now. Hardener still in its bag to be accessed by hyperdermic needle, one plastic pot of resin, 55mL of resin in syringe, 20mL resin in syringe and 2mL of hardener in syringe with needle. To use I plan to squirt out a 5:1 ratio by volume of resin and hardener, mix thoroughly and suck up with either a 2mL or 5mL syringe to apply to the sensor gold wires. The latter will require a fair bit of practice I suspect Now in view the arrival of the replacement control board I'm switching my attention to the 3D printer

There's a possibility that I may get the 3D printer working shortly - the replacement control board came this afternoon

I have sucked up resin into a 20mL syringe and also taken a 2mL syringe with needle and poked that into the bag of hardener and sucked up 2mL of hardener. I sealed up the bag again where the tiny hole is with Sellotape. The resin was too viscous to suck up with a needle on the syringe even though it was quite a big needle. I had to cut the needle off the syringe as it was stuck firmly on - that's why the tube is shorter than usual. Two photos - 1. syringes filled and 2. after cleaning off and piece of balse wood to seal the hardener needle and prevent a nasty accident.

I'm sorry but after an extensive search, I can't find the link to the Farnell Peltier TECs I'll post if I come across it.

Yes, quite sufficient. I'll look for the link to the Farnel ones.

Now received the epoxy potting resin from Maplin and started transfering to containers. These two photos show the resin pack as supplied and the resin part of the pack transferred to two plastic pots with screw lids. Or most of it there is a little bit left in the bag but I don't think it's worth pushing it. I may put the hardener straight into a syringe or another pot - not sure yet.

I've just checked the figures my Arduino sketch is providing with an online calculator for dewpoint and the calculator shows about -25C whereas my sketch is showing -11 for temp of 18C and RH of 13 I got the DP calculation sketch from the Arduino web site!

So it would seem Tested the 1100D with cold finger in normal mode with SD card and battery, and although it apperared to work normally there was no image on the SD card. So I'm going to bring the laptop in from the warm room and test it with APT. Just realised that I probably turned off "Save to SD card" in the optiond Didn't think of that when I tried it last night - doh

Found the other 1100D body with the cold finger coming out the back So one option is to use that and perform all the removal of unwanted parts anew. However, I should have all the bits that went into the last cooled 1100D system and that would save work and laeve some complete parts (as it were) for selling off (if I can be bothered ). I've also found another complete untouched 1100D body that appears to be in full working order. BTW - I am imaging tonight - adding Ha to the M51 data Still upping the exposure time to get more data ah the signal is much lower with Ha even binned 2x2.

Thank you Cath

Yes, I remember reading that. I don't think there's any doubt that I can get the humidity low enough. Next thing I'm working on is the cooling. Now where's that 1100D with the cold finger hiding???

With the box sealed and 8 bags of silica gel in it the dewpoint has now reached -10C after 30m. It is still slowly going down so I'm hopeful of reaching -15C in time I think this will be quite sufficient. In my tests a year or two ago I went down to -20C but the noise reduction between -10C and -20C was small. I am now content that I can achieve low enough humidity - next I need to perfect the machanism for replacing the cover glass within the dry box. It may not be necessary to use that many bags - the main point will be to reduce the amount of free air. In that way the amount of moisture in the box after closing the lid will also be reduced.

A small advance on the cover glass replacement mechanism design. A soft sponge pad connects the cover glass to a flat piece of plastic or metal which in turn is attached to the shaft. If I don't have the 3D printer I plan to use a sleeve on the shaft with the flat plate glued to it. If printed in plastic this can be all one piece - a tight fit on the shaft. The pad, placed in the centre of the glass will provide equal pressure all round the edge to ensure it sticks well, allowing for a slight misalignment.

There may be a slim chance of imaging tonight - keeping fingers crossed I shall do my best to try and provide as reliable a method as possible - I realise that others may follow my example and the responsibility this entails

It seems that after an hour the RH has stabilised at around 15% at 20C giving a dewpoint of -7C. I think the limit may be due to the fact that there is currently a gap where the wires to the DHT22 go past the box top seal. I shall have to seal the box before any futher testing to be meaningful.

A bit later and the humidity is getting back to where it was but with a lower temperature.

You may be right but I opened the lid in the living room and changed the air and immediately got RH or 47% at about the same temperature when the lid was back on. I think the silica gel held the temperature.

Not true actually - RH = 74% for air from freezer Living room RH = 43% according to my wal thermometer and humidity meter.