DaveS

It was *supposed* to be set at 2 seconds, which I determined by trial exposures, but somewhere along the line I must have left the exposure in Maxim on zero seconds, without realising it.

Oh, and the stack without flats looks no different to the one with.

OK, single Dark frame. Not worth posting a Flat is it is effectively a Bias frame. Histo shows just a few spaced out bars. ASI1600 10M-0001Dark.fit

OK, just doing a trial stack without Flats and Dark Flats to see what happens. Will post single Darks in a mo

This is the 12 sub master dark Master Dark.fit I've just found out all my Flat frames were taken with an exposure of 0 seconds, instead of the 2 sec that I thought. The Dark Flats are at 2 sec. Argh! Will have to do a load of Flats as well and the weather is rubbish for doing T-shirt flats

Now here's a think I should have clocked, my lights were taken at -20c, but the dark and flats were at -25c. I know PI would have thrown a wobbly but AA is quite happy with mismatched temps. I can take some more -20c Darks, not sure about the flats and dark flats.

Again single dark and flat, or the stack used for calibration. Sorry for the questions.

@andrew s I will check tomorrow when I can reboot the platform computer

OK. It looks like I may have a clear moonless slot on Saturday, so I'll see what gain 139 looks like, but I don't have any Dark frames for that.

OK, single uncalibrated Oxygen sub. Dumbbell-Oxygen-0018.fits

OK, single sub? or stack?

This is the histogram I get of the 9 hour unstretched stack

When I look at the [OIII] Sigma Average stack in AA the histogram says 12 bit, but looking at the Sigma Add stack it says 17 bit, hence why the FITS is 32 bit rather than 16 bit. My head hurts. My next big purchase will be a QHY 268, which does, at least, have a decent 16 bit ADC and 14+ stop DR. But this is no nearer solving the problem or producing a believable image. Edit: The single calibrated sub says 9 bit on the histo. Now my head really *does* hurt.

Here you are Single O Sub Cal.fit Single H Sub Cal.fit As it happens I've noticed the low end of the histogram "combing". I ought to check the settings, that I wasn't inadvertently capturing 8 bit data, but I haven't rebooted the platform computer since a power cut a couple of days ago. Will do it tomorrow and check the settings.

This is a native 16 bit FITS from a Sigma Average stretch. Might have fewer problems. 9 Hours O Sigma Average.fit

Just to say I used zero gain, AKA the Max DR setting in the ZWO ASCOM driver.

Ha yes, sorry they are a bit big. When I opened the FITS file in AA7, I could see structure that was blocked up in the TIFF file.

OK, @ollypenrice and @Laurin Dave, I think the problem occured when I saved the files as 16 bit TIFFs. The originals are 32 bit FITS, so when I saved as TIFFs the high values were truncated. Here are the original 32 bit FITS if your software can handle them. 9 Hours H.fit 9 Hours N.fit 9 Hours O.fit I can do a Sigma Average stack which will produce 16 bit FITS which won't truncate.

Hi and thanks. I have my cousin and her hubby coming for a socially distanced meet while it's still legal, so it might be this afternoon before I can have a bash at the data.

Thanks Olly, I'll have a run through the individual subs when I get the chance. I timed the oxygen capture to avoid moonlight, but it might have been getting low in the west, drifting in to the Bridport LP.

Hi, yes I have 3nm Astrodons (Bought when they were merely expensive rather than "How much???!!!"). Will see if I can put together a HOO version. Mine is analogous to the Hubble Palette with [NII] replacing [SII] Looking at the spectra I've seen, and at my data, the H-apha, [NII} and [OIII] are of similar intensities.

That's brilliant Olly, shows how much I have to learn. I found gradients all over the place in my stacks and RGB assembly, but AstroArt's "Adaptive Subtract"gradient removal got rid of them once I cropped off the alignment edges.

And I've just realised that my 5 place wheel is full of NB filters, I'd have to strip it down, replace the filters, and recalibrate the filter offsets.

Well no, but the question was about the QHY600 vs the QHY268, nothing about the ASI1600.

Thanks Steve, that's the first one that looks different to the original. I've been all round the block with my processing, but TBH I can't see much, if any difference between the first and last. I think any more data will have to wait until next year, as by the time we get anything like a clear moonless night for capture M27 will have disappeared.