First CMOS image

I finally committed to getting a monochrome CMOS camera, ZWO ASI1600mm, with filter wheel and LRGB filters.

The learning curve was pretty steep and to date, my new work flow is something like:

1. Use unity gain (139). I used an offset of 2 1I think, but this should have been 50+.

2. My skies are Bortle 4, so using this table:

it means for F10, the luminance exposure should be 114s.

Having said that,  SGL advice seems to be :

 "For Gain 139 with 56 offset ,  background target ADU is 1386.  In order to find exposure times set  telescope  and at astro dark  take some test exposures at varying exposure times until you get one where the background level is 1386 and I do this for each filter and record times etc." (Pixel Aid in APT should allow the ADU to be measured)

3. Luminance filter : take flats, darks and dark flats

4. Red filter, take flats (exposure time? Not sure, but should be aiming to get a certain ADU reading)

5. Green filter, take flats (ditto)

6. Blue filter, take flats (ditto)

Take images of the target at L, R, G and B, using 1x1bin for L and 2x2 for R, G and B. Not sure what the exposure times should be for the R, G and B images,; using 114 s at the moment.

Processing:

Align and calibrate in DSS, using a reference frame 

Save as L, R , G and B

Use PS to:

 a) produce a RGB image and stretch it

b) produce a L image and stretch it

c) Combine them, using Luminosity as the blending mode

Use Lightroom to try and develop the colour more, set black ,etc.

This is my first image, based on around 4 hours of luminance  and 1 hour 20 mins of R, G and B. All exposure were at 114 (probably wrong for the colours). No calibration frames, hence the blotchiness.

NGC 4565 CMOS image

NGC 4565 The Needle Galaxy DSLR image

Compared with my DSLR image of the same galaxy, this has better resolution and less noise. Star colour is better but I think they are overexposed. Still, it is in colour and has only taken about 12 hours of fiddling to learn a technique that does actually give colour! There were a LOT of 'monochrome' moments on the way.