27 hours on M27

[DaveS]

This is 9 hours each on [NII], HII. and [OIII] captured over multiple nights in in varying combinations. 

130mm f/7 triplet apo, ASI1600MM cool, 3nm Astrodon filters. Processing in AstroArt 7, GIMP and Affinity Photo. Combined as N>red, H>green, O>blue immediately after stacking, then levels in GIMP, Selective Colour in Affinity Photo then back to GIMP for titivating.

Although there are 27 hours here the data is a bit miffy, due to some being captured in Nautical Dark, and with M27 very low in the sky towards the end of the night, leading to gradients all over the place. The sky clarity has been suboptimal too.  I've pushed this a bit more than I should I think to pull out the outer halo, which should be stronger with this much data.

Will park this as far as data capture is concerned, but will revisit the processing.

[andrew s]

No excuses needed @DaveS cracking image.

Regards Andrew 

[MarkAR]

Superb.

[DaveS]

Thanks guys.

Those outer lobes are surprisingly feint. Unfortunately M27 is now starting to get very low after a reasonable imaging session, so may have to revisit this next year, depending on what I have rigged up. Really needed to have started in August to get a long run.

I think I will revisit the processing after a break to give myself a fresh perspective.

[michael.h.f.wilkinson]

Very nice indeed, lots of detail showing. I am also working on a longer integration of M27, but only have 10.5 hours with the Optolong L-eNhance filter on an OSC camera. Currently grabbing a last batch of 2.5 h before clouds roll in tomorrow. 

[ollypenrice]

I think the outer halo would be helped by a more neutral background sky. It's pretty blue 'as is' and, since the outer halo has also emerged as blue in your mapping, the contrast is diminished. As you say, I think this will be a processing job to tinker with.

Olly

[DaveS]

Thanks Olly.

I'll come back to it in a bit. I originally had a rather yellowish background, in trying to take it out I may have gone too far.

[Laurin Dave]

Nice one Dave...  it'd be interesting to see what the individual channels look like, especially the NII

Dave

[DaveS]

Here we go, for @Laurin Dave

9 Hours H, linear stretch in GIMP

9 Hours N, linear stretch

And 9 Hours O, linear stretch

Faugh, the JPEGS uploaded here look nothing like they do in the GIMP window, but I hope they show that the outer wings are nearly all [OIII], with just a bit og [NII].

[DaveS]

And a second NHO combination using the pre-stretched TIFFs Gradient Reduction after cropping, White Balance, DDP, Histo Stretch, Colour Balance and Unsharp Mask

Still a bit meh

 

[peter shah]

16 minutes ago, DaveS said:

 

Still a bit meh

 

Dave everything you need is there, Just need to tame the core and push the colour a bit......still a great image

[DaveS]

OK, I've been bashing my head against this to the point that my eyes ache and my head hurts.

So here are the three unstretched but calibrated and aligned stacks. There are alignment edges but can't crop them off without messing up the other processes in AstroArt

9 Hours H.tif

9 Hours N.tif

9 Hours O.tif

Replaced the 32 bit(?) FITS with 16 bit TIFFS which should open reliably

If you have any success could you post here for comparison, thanks.

 

 

 

Edited September 25, 2020 by DaveS
Replace dodgy FITS with TIFF

[DaveS]

And now I'm done with this until I can get better data, probably next year now.

This is the latest process using a more extreme DDP in AA7  than I would normally use, lots of masked stretches, colour work in Affinity, and masked denoise and unsharp mask in AA7.

[kirkster501]

This is what I got in a quick ten mins in PI before a Zoom meeting. Might have a go ignoring the N channel and stick with HOO.

I don't like the colorless stars in this palette. Be good to get an hour each of RGB so you can use RGB stars in the background.  In fact I have my own RGB image of this so can have a proper go later.

[DaveS]

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.

[DaveS]

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.

[kirkster501]

16 minutes ago, DaveS said:

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.

I think your main channels are superb.  Not too sure about this palette personally though, different strokes for different folks......  I have my own LRGB version of this so will see if I can blend your M27 core object with my stars from my RGB version of M27.

[ollypenrice]

I've just had a go at the Ha with three objectives: drag out the outer shell, give the core more attitude, flatten the background. I don't know if I've succeeded...

I found it was a devil to flatten and never entirely got there with DBE. I ended up finishing the background sky by hand in Photoshop which is easy if you have empty sky round a central object. This was, as usual for me, a Ps Layers job, one for the background and stars, one for the outer shell and one for the core. I might not process quite as 'hard' as this for real but I thought it would be more useful to the thread to give it some welly!

Olly

[DaveS]

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.

[CCD-Freak]

I agree...Astro Art 7 gradient removal routines are great.  I have been using AA since v2 when I got my first commercial camera...the mighty MX-516 🙂 which replaced my DIY Cook book 245.

AA just keeps getting better and better.

 

John Love
CCD-Freak
WD5IKX

Edited October 5, 2020 by CCD-Freak

[kirkster501]

A quick ten mins In the HOO Palette, here is mine and yours.  Mine is using 3nm Astrodon filters. Not sure about yours Dave? That N channel is doing something weird to the colour so I removed it - I am not familiar with the HNO workflow at all.  I do not have RGB in as wide a field as yours Dave so I can;t combine my stars with yours.

[DaveS]

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.

[ollypenrice]

Dave, I was all set to get cracking on an HOO because the OIII shell looked brilliant. However, the OIII stack as it is isn't workable. It has a significant patch which is fully saturated and contains no information as a consequence. The crop below is linear.

 

This comes as a surprise, particularly in narrowband. Could it be that you were shooting in moonlight some of the time? The background sky is quite light so that might have eaten into your well depth. If so you might be able to make a separate stack of just the darkest subs and use it as a repair patch. You wouldn't need a lot of subs to get a good S/N ratio because the region is so bright. Failing that, you'd need to shoot a set of short subs to fill the saturated parts, as is always necessary for M42.

Olly

 

Edited October 6, 2020 by ollypenrice
Typo

[DaveS]

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.

[Laurin Dave]

Hi Dave, I've had a look too and noticed what Olly saw on the Oiii.   I looked back at my own data taken with Esprit150 ASI1600 Unity gain and 300s subs (not sure what you used) and compared the ADUs across the nebula and on the stars...  on the nebula for both Ha and Oiii my unstretched ADUs are less than a tenth of yours, whilst my stars are lower but more similar...  this makes me wonder whether you have posted partially stretched images rather than overexposing.  Also when I look at your processed images I see no signs of the Oiii being saturated.   If you have one maybe put your raw stacks into a Dropbox.  Also if you'd like to have a go I have it in RGB although at a different orientation and slightly smaller.

HTH 

Dave