14 Hour Leo Triplet

[DaveS]

And it's *still* not right.

130mm f/7 TS Photoline triplet apo / ASI  1600 in Max DR / Baader LRGB filters on ASA DDM 60

3 Hours Blue and Green in 600 sec subs, 1 Hour Red in 300 sec subs (A mistake in exposure settings) plus 2 Hours Red in 600 sec subs, 5 Hours Luminance in 600 sec subs. Sigma Add stacking in AstroArt 7, Gradient Removal and align All. Luminance given DDP, Histogram Stretch and Denoise. RGB combination then DDP, Histogram Stretch and Denoise. Finally LRGB synthesis, crop, colour Curve (To reduce a green tinge), Saturation Boost and final Denoise.

The Tidal Tail off the Hamburger is proving elusive. Although I can see it in the stacks (Especially the Luminance) during processing, in the final stack it's almost invisible. Need more data, but realistically at least the same again, but I doubt if I'll get it.

[Gina]

Nice.

[MarkAR]

Well done.

[michael.h.f.wilkinson]

Lots of detail there. Like the fact that you got the tidal tail of NGC 3628

[geoflewis]

Well done Dave, whatever you think, it’s a very nice result and the tidal tail is showing, even viewing on my iPhone. Does it show better if you raise the black point a bit as the sky background looks pretty dark (on my phone that is)?

[DaveS]

Thanks.

The Tidal Tail is fainter than I thought it was going to be, perhaps at a truly dark site it might show more. If I raise the black point there is more of the tail showing, but also a heck of a lot of noise, plus uneven background colour mottling. Maybe actually using the right flats for each stack, instead of being lazy and just using a set of Red flats will help. ATM it's too light / warm but later I may have a go at getting the real ones.

[DaveS]

11 minutes ago, geoflewis said:

Well done Dave, whatever you think, it’s a very nice result and the tidal tail is showing, even viewing on my iPhone. Does it show better if you raise the black point a bit as the sky background looks pretty dark (on my phone that is)?

This is with the Black Point lowered, curves applied in Histogram Stretch and another Denoise. Do need proper flats, as there's a nasty great dust bunny showing.

I'm also seeing a bit of a green tinge in the background.

[geoflewis]

Maybe somewhere in between and yes, it's always best to shoot flats and flat-darks for each filter. I reuse mine for several weeks, even months so long as the camera hasn't been removed or rotated; sometimes even if it has been rotated together with the Optec lens, as anything further up the optical train away from the sensor really doesn't show.

Edited April 16, 2020 by geoflewis

[DaveS]

Thanks Geof.

Yes, I did brighten the background a tad more than perhaps I should have, but I wanted to see just how much of the Tail was actually there, more than I thought.

Will bite the bullet and take a comprehensive set of Flats and Dark Flats.

[DaveS]

I did a medium Black Point version that looks better, but I think I'll wait until I've assembled something with real Flats and Dark Flats before posting another image. Hopefully it may be the definitive version unless I get a shed load more data.

[bob-c]

Well done Dave ,can see the tail in first pic on my monitor, it is faint though.

Bob.

[DaveS]

Thanks Bob. Yes, the tail is faint, more so than I expected, though hopefully showing clearer on the second version. More work needed.

[kirkster501]

I like this.  I prefer the second version where you did not raise the black point quite so aggressively, despite the dust bunny.  Is there an in between version?  You could up the colour saturation more I think.  I think there is more in this data set you've painstakingly collected, screaming to be let out.

That is nit-picking on a great image and composition.

[DaveS]

Nit-pick away!

One big issue I had was from using just one set of Flats for all the channels. I have now captured individual Flats and matching Dark Flats for each, so hopefully will have a cleaner background to work from.

There are also a few more clear nights forecast so will hopefully get more LRGB data.

To avoid overloading the thread with images I will wait until I have something definite to post.

[DaveS]

OK, I got some calibration frames and ran stacks with properly calibrated data. This is the result

Still looking a touch blue on here, was looking neutral during processing, but there was a rather nasty red mottling gradient that was proving obdurate. Tried to put the Black Point between the last two versions.

Will go away fro a bit before having another go.

[DaveS]

Let's see how this version compares. Used Colour Curves again to get rid of the red background mottling and used Histogram Stretch to adjust both Black and White points. This may be as far as my processing skills can take this data. If I should get a significant amount of new data I will start a new thread toavoid confusing this one.

Hmm...Still a touch Blue, and a brighter background than on my monitor, possibly a colour space problem.

[geoflewis]

Hi Dave, I agree it’s a bit blue, but it’s a huge improvement on the first pass that you posted, so I’m sure that it was worth recalibrating the data with correct flats for each filter, plus what ever other processing modifications you incorporated. I don’t think the background is overly bright, but then I prefer backgrounds that are not too black. All in all it’s a great image, well done.

[DaveS]

1 hour ago, geoflewis said:

Hi Dave, I agree it’s a bit blue, but it’s a huge improvement on the first pass that you posted, so I’m sure that it was worth recalibrating the data with correct flats for each filter, plus what ever other processing modifications you incorporated. I don’t think the background is overly bright, but then I prefer backgrounds that are not too black. All in all it’s a great image, well done.

Thanks Geof.

Getting the background to neutrality has been a real test of my control, as well as colour acuity, even with a calibrated wide-gamut monitor. I think I'll leave this here, accepting the slight blue cast.

Maybe getting more data will help, if it's of good enough quality, no point in trying to add dodgy data as I found out the hard way with 6+ hours of duff Hydrogen that just messed up the Red channel and would have been better spent getting RGB or L data instead.

[kirkster501]

Very much better.  A tad blue but OK.  The background sky is now very good. 

It is very evident that there is a lot of data in here.  I think you could use a tiny bit of HDR with a heavy mask to bring out some more detail in the galaxies.  It would respond well to this I think.

Edited April 18, 2020 by kirkster501

[DaveS]

Thanks Steve.

Not sure how to do HDR in AstroArt, which is all I use ATM, though I will download GIMP again, now I have a larger boot drive. I can do masks in AA7 though. will look into it.

Theoretically (Yeah, right) a big dollop of *good* H-alpha might help define the spiral arms in M65 and 66. Looking at the H-apha data that I captured it looks like my autofocus offset for the Hydrogen filter was off as the stars look bigger than they should with a 3nm filter. If it *was* out of focus that would also explain why the signal was so weak.

[kirkster501]

2 hours ago, DaveS said:

Thanks Steve.

Not sure how to do HDR in AstroArt, which is all I use ATM, though I will download GIMP again, now I have a larger boot drive. I can do masks in AA7 though. will look into it.

Theoretically (Yeah, right) a big dollop of *good* H-alpha might help define the spiral arms in M65 and 66. Looking at the H-apha data that I captured it looks like my autofocus offset for the Hydrogen filter was off as the stars look bigger than they should with a 3nm filter. If it *was* out of focus that would also explain why the signal was so weak.

You can also get more out of the HII regions by sampling the red in you image and building a layer mask from it.  Then, use curves and saturation on Red only exposed through the mask to bring them out more.  I sometimes "cheat" like that if I don't have any Ha data.  My recent post of NGC2403 is a recent example.

[DaveS]

Well, I just made some calibration frames for the H-alpha data. It did make a difference to the Hydrogen stack, but when I added it to the existing Red stack I could see little effect.

I may try doing a DDP on the individual stacks before Trichomy but I've encountered problems with colour balance doing this in the past.