M17 Data Set

[Rodd]

For my northern comrades (or anyone who is in need of some data).  This is narrowband M17.  Next time I will try to post LRGB data. The number of subs for each stack is in the stack name.  All subs were 5 min.  Taken with TOA 130 at F7.7 and ASI 1600mmcool pro with Astrodon 3um filters.  Fully calibrated. This is one target that I wished I had used the .7x reducer--I think the framing would have been much better.  But overall I am pleased with the data.  Conditions weren't great, and I think that manifests in a slightly soft appearance.  I also think that more subs would help.  As a fairly bright target, I thought I could get away with fewer than normal for the ASI 1600. 

Ha-66.fit

O23.fit

S33.fit

Good Luck.....Have fun!!!!

[Ceph]

Thanks Rodd, been thinking of narrow band for a while as I lives in a little light polluted area and far to travel to avoid it. Will give your pics a try and see what comes out

[simmo39]

Thanks, will try  my first attempt at narrow band too.

[Rodd]

3 hours ago, Ceph said:

Thanks Rodd, been thinking of narrow band for a while as I lives in a little light polluted area and far to travel to avoid it. Will give your pics a try and see what comes out

Looing forward to seeing the results

Rodd

2 hours ago, simmo39 said:

Thanks, will try  my first attempt at narrow band too.

Can't wait to see it!

Rodd

[wimvb]

Ok, I'll go first. I mapped the filters to SHO. The oxygen master had most noise, so I used MLT on that during the linear stage. Also DBE on the masters. Masked stretch followed by HT, then combined (right image). The left image got an extra dosage of boost in the Sulphur master before combination. Haven't even started looking at the stars yet, but these will need more attention. NB is uncharted territory for me. Only a screen shot so far.

Is it just me, or is there a ghost head with a big bright mouth in this image?

[Rodd]

1 hour ago, wimvb said:

s it just me, or is there a ghost head with a big bright mouth in this image?

This image is a veritable zoo--spiders, horses, jockeys, fish, a swan (I am told), so why not a ghost? So far it is looking familiar.

Rodd

[simmo39]

1 hour ago, wimvb said:

Ok, I'll go first. I mapped the filters to SHO. The oxygen master had most noise, so I used MLT on that during the linear stage. Also DBE on the masters. Masked stretch followed by HT, then combined (right image). The left image got an extra dosage of boost in the Sulphur master before combination. Haven't even started looking at the stars yet, but these will need more attention. NB is uncharted territory for me. Only a screen shot so far.

Is it just me, or is there a ghost head with a big bright mouth in this image?

That looks so good, only had a quick play last night but will post my efforts when i think they are good enough.

[wimvb]

Version 1, mostly about learning NB processing. It's a "whole new ballgame" to me.

This is the SHO palette with boosted S. That's why the fat star has such a bright diffraction halo.

As always: messed in PixInsight

 

[Rodd]

22 minutes ago, wimvb said:

As always: messed in PixInsight

Hit it with SCNR green, average neutral, max strength to get rid of the green

Rodd

[wimvb]

2 minutes ago, Rodd said:

Hit it with SCNR green, average neutral, max strength to get rid of the green

Rodd

I thought of doing that, but since Ha is mapped to green and it isn't natural colour to start with, isn't that just killing signal?

Atm, I'm redoing and adding deconvolution of the three masters. I will try scnr, to see what it does.

[Rodd]

3 minutes ago, wimvb said:

I thought of doing that, but since Ha is mapped to green and it isn't natural colour to start with, isn't that just killing signal?

Atm, I'm redoing and adding deconvolution of the three masters. I will try scnr, to see what it does.

No--It changers the hue not the signal strength I think.  I always remove the green by using SCNR--it produces the gold colors usually seen in the Hubble Palette.  I usually do it directly after the histogram stretch,

Rodd

[wimvb]

Ok, so here's v 1.5 then

[Rodd]

35 minutes ago, wimvb said:

Ok, so here's v 1.5 then

Looks very familiar.  Here is my attempt, very similar to yours in allot of ways.--except it took me weeks to do and you did yours in a few minutes!  

 

 

[wimvb]

1 hour ago, Rodd said:

Looks very familiar.  Here is my attempt, very similar to yours in allot of ways.--except it took me weeks to do and you did yours in a few minutes!  

You pulled out more detail in the background, and got lots more colour out of it. That only works if you have a good foundation. The red diffraction halo around that star at the top is a result of stretching Sii. To keep the stars under control, I used MaskedStretch, mainly.In my first version, I had to use a colour mask to target just that star and desaturate it.

Here's my v2. Deconvolution on the 3 masters. Masked stretch to background 0.125. Tweaked with HT. Combined and then SCNR, which still seems very counterintuitive, but it works. Thanks for that tip.

I was a little more carefull with stretching this time, and was able to keep the stars under control. Only a little star reduction at the end. And no noise reduction; Quality data!

[Rodd]

13 minutes ago, wimvb said:

Here's my v2.

Very nice.  You got what I got, but yours does not look like it was pushed too far, as mine does.  I tried deconvolution on the Ha master--but not the others--I guess I should do that.  I find decon in the linear state pretty tricky.  I have used masked stretch, but have never preferred the results over manual histogram stretches.  But you have shown that it was the way to go here.

Rodd

[wimvb]

The Sii data needs to be pushed hard. Since Ha signal is stronger than Sii, you need more of the latter to compensate. Ideally it would need 10 minute subs and possibly more of them.

Deconvolution on Ha was straightforward, but I had to keep it back on the Oiii and Sii, because the data was noisier.

Don Brecher (AstroDoc) had a talk about deconvolution on the Astro Imaging channel recently. His explanation is very easy to follow.

https://www.youtube.com/watch?v=GIeRT_lkjTQ

The talk is intended for "newbies", but maybe you get a few pointers. I did.

[Rodd]

18 minutes ago, wimvb said:

The Sii data needs to be pushed hard. Since Ha signal is stronger than Sii, you need more of the latter to compensate. Ideally it would need 10 minute subs and possibly more of them.

Deconvolution on Ha was straightforward, but I had to keep it back on the Oiii and Sii, because the data was noisier.

Don Brecher (AstroDoc) had a talk about deconvolution on the Astro Imaging channel recently. His explanation is very easy to follow.

https://www.youtube.com/watch?v=GIeRT_lkjTQ

The talk is intended for "newbies", but maybe you get a few pointers. I did.

I'll give that a look, thanks.  

Rodd

[simmo39]

Ok, here is my go with the data. Just to say thanks Rodd i did enjoy this try before you jump in!

 

First SHO

HOS

And finally HOO

[simmo39]

A slight tweak of the SHO mix. A little better I think.

[Rodd]

3 hours ago, simmo39 said:

Ok, here is my go with the data. Just to say thanks Rodd i did enjoy this try before you jump in!

That looks great.  I did not think my pale image was correct so I boosted saturation....a big mistake, as yours and Wim's are both more natural looking.  I will have to revisit this one (AGAIN!) and reprocess it wit this in mind.  I see your second attempt popped up while I was writing this--yes, much better.  Nice image.

Rodd

[simmo39]

36 minutes ago, Rodd said:

That looks great.  I did not think my pale image was correct so I boosted saturation....a big mistake, as yours and Wim's are both more natural looking.  I will have to revisit this one (AGAIN!) and reprocess it wit this in mind.  I see your second attempt popped up while I was writing this--yes, much better.  Nice image.

Rodd

Thanks and thank you for the data to play with been most enlightening.

[Rodd]

14 hours ago, wimvb said:

The talk is intended for "newbies", but maybe you get a few pointers. I did.

I watched it and am trying it now on another image (not quite ready to revisit M17 yet!)  Thank you--I did not know the depth of preparation required.  I have always used decon as a fine sharpening tool late in the wokflow (it can work if you use a mask and are careful), but I see I was way off the mark--(it is not a sharpening tool per se).  Hopefully I can get it to work for me

Rodd

[MarsG76]

17 hours ago, wimvb said:

You pulled out more detail in the background, and got lots more colour out of it. That only works if you have a good foundation. The red diffraction halo around that star at the top is a result of stretching Sii. To keep the stars under control, I used MaskedStretch, mainly.In my first version, I had to use a colour mask to target just that star and desaturate it.

Here's my v2. Deconvolution on the 3 masters. Masked stretch to background 0.125. Tweaked with HT. Combined and then SCNR, which still seems very counterintuitive, but it works. Thanks for that tip.

I was a little more carefull with stretching this time, and was able to keep the stars under control. Only a little star reduction at the end. And no noise reduction; Quality data!

To me on my screen this one looks the best... 

[wimvb]

2 hours ago, Rodd said:

Hopefully I can get it to work for me

The trick is not to try to overdo it. The central idea behind deconvolution is that it corrects the very slight blurring that occurs due to seeing (mainly). The effect of deconvolution should be subtle. As soon as you get artefacts in the bright areas or the background (assuming you don't use a mask), you need to back off. There are three indicators that I always look for:

Dark rings around stars in bright areas; increase global deringing

Squiggles in bright areas (I believe Don calls these "worms"): decrease iterrations

Increased noise in the background, as if normal salt 'n pepoar noise starts to clump together; use a (stronger) mask or increase the deregularization parameters.

Hope this helps.

[Rodd]

1 minute ago, wimvb said:

The trick is not to try to overdo it. The central idea behind deconvolution is that it corrects the very slight blurring that occurs due to seeing (mainly). The effect of deconvolution should be subtle. As soon as you get artefacts in the bright areas or the background (assuming you don't use a mask), you need to back off. There are three indicators that I always look for:

Dark rings around stars in bright areas; increase global deringing

Squiggles in bright areas (I believe Don calls these "worms"): decrease iterrations

Increased noise in the background, as if normal salt 'n pepoar noise starts to clump together; use a (stronger) mask or increase the deregularization parameters.

Hope this helps.

Check out my most recent Sh2-119 on another post--I redid it using decon.  I like.  Thanks,

Rodd