Gina

I may be confused but surely you must compare pixel with pixel not the sum of 3 pixels with the value of 1. If we average over the quad, the sum of the OSC version is R + 2xG + B = 38321. Now lets add the mono pixels = 4 x 13363 = 53452. So comparing like with like, before debayering the sum of 4 is 38321 and after debayering it is 53452. This shows an increase in sensitivity of 1.36 times. Of course if we could somehow retain or replace the micro lenses the benefit of debayering would be even greater. Apart that is from the doubling of resolution in both axes.

Yes - this is what I meant

I think I've pretty much settled on a 4 position FW for my debayered 1100D with Ha, OIII, SII and L filters. The L is useful both as high res luminance and for setting up. I could use an 1100D with untouched CFA for RGB simultaneous imaging. This would almost make up for the smaller, less sensitive pixels compared with mono separate RGB subs binned 2x2 if this were possible with a DSLR (which it isn't AFAIK). This is a cheaper option than a single 1100D with 7 filters as I won't need to buy RGB filters.

From the graphs the KAF8300 mono is actually more sensitive at Ha and SII wavelengths and the same at OIII But as has been said this is a CCD sensor and not CMOS - whether they're the same or different in this respect I have no idea.

Very little then.

40% increase in sensitivity is about half a stop - not a lot Though "every little helps" I guess. I'm not losing any sleep over losing a 40% sensitivity increase

Thank you for that -= I'll look through the links with interest and reply later

Yes, I have. I don't think this blocks much light though and variations in the amount of this layer removed should be able to be compensated by using flats.

450D example - there is a strip on the RHS where the sensor is untouched which may be compared with the centre region with CFA and micro lenses removed. This is a flat using white light in greyscale. CR2 image converted to TIFF and then resized in Ps and saved as PNG. (I'm still looking for representative examples among my dozens of debayering images in various folders ).

Here's some images image taken when I was debayering 1000D and 1100D sensors. These are standard capture using the SD card. When I get going onto debayering an 1100D sensor again I'll provide a better example. 3 1000D examples and 2 1100D. I think the first 1100D image (annotated) shows that the area with CFA removed is lighter than that with normal sensor but with the colour change it's difficult to tell just how much.

I really don't think it's as much as 3 times. When I was debayering and testing the results with side-by-side areas of untouched sensor, micro lenses removed and both removed and while the difference between micro lenses removed and not with CFA intact was noticeable, the improvement in sensitivity due to CFA removal seemed more to me. I'll dig out some sample photos... The effect is subjective and I have not actually measured it - I didn't know how to. You really need to do measurements with a narrow spectrum and compare single pixels at the different wavelengths. With a standard scene it is difficult to tell.

I hope someone understands all that about the BARC layer because I sure don't!

I may have those comparisons one day

I haven't got round to trying the buffing tool dry as yet and I have no idea how to remove that layer below the CFA. I shall endeavour to get the sensor as flat as I can, hoping not to go too far. I think that if I can remove all the CFA over most of the image area, I shall make do with that and use flats to clean up the final image. I've been trying to get my dreaded 3D printer to produce usable prints! I'm up to the 17th attempt at a reasonable frame for holding the sensor for drying and replacing the cover glass and the 4th attempt at the lever that holds the glass and applies it to the sensor frame I'm daft really - in the time I've spent on it I could have made one from sheet plastic or wood with hand tools and hot melt glue! And in fact, thinking about it, I may give up and make it by hand! I'm sure it would be far less frustrating.

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.