The Squid and Bat after 6 hours with RASA8

[gorann]

I posted my first two hours here Friday night and now I magaged to get four 4 more hours last night so now with 6.2 hours (75 x 5 min) and there is clearly less noise and more details. Quite happy with the result with this extremely faint object. I think the image reveals that the RASA 8 is a real light bucket, that the ASI2600MC is a very sensitive camera, and that a dual band filter works quite well on modern OSC cameras. More info on the system in my previous post:

 

[Laurin Dave]

Clearly even better Goran..  what increase in SNR did you get, it looks quite significant..  well done..  Do you run more than one system at the same time?

Dave

[gorann]

21 minutes ago, Laurin Dave said:

Clearly even better Goran..  what increase in SNR did you get, it looks quite significant..  well done..  Do you run more than one system at the same time?

Dave

Thans Dave! How do I calculate/measure my SNR? Last night was Saturday and I have a wife, so I only run one obsy. Tonight I may also fire up the double-Esprit obsy while the RASA is ticking away on a dark nebula. Well, at least that is the plan......

[Sunshine]

WOW, very beautiful! which begs the question I've asked before, is there no end to imageable nebulae up there? it seems every time i open SGL theres a nebula i haven't seen before.

[Kinch]

I never had much luck with this one.....🙄. You have used your gear well....can't believe how little time there is in this!

[Laurin Dave]

27 minutes ago, gorann said:

Thans Dave! How do I calculate/measure my SNR? Last night was Saturday and I have a wife, so I only run one obsy. Tonight I may also fire up the double-Esprit obsy while the RASA is ticking away on a dark nebula. Well, at least that is the plan......

Assuming you have Pixinsight then  in the process menu got to Image Inspection .. Subframe Selector and run it on the unstretched stacks ..   good luck tonight..  cloud here 

[gorann]

2 hours ago, Sunshine said:

WOW, very beautiful! which begs the question I've asked before, is there no end to imageable nebulae up there? it seems every time i open SGL theres a nebula i haven't seen before.

Thanks! If there is an end to them, it will take a long time to reach it, fortuantely.

[gorann]

2 hours ago, Kinch said:

I never had much luck with this one.....🙄. You have used your gear well....can't believe how little time there is in this!

Thanks Kinch! You should have a go at it with your new Sharpstar light bucket. The data does need a lot of stretching.

[andrew s]

Fine image,  although I prefer the more muted colour of the H alpha in the original.

Regards Andrew 

Edited November 22, 2020 by andrew s

[gorann]

2 minutes ago, andrew s said:

Fine image,  although I prefer the more muted colour of the H alpha in the original.

Regards Andrew 

Thanks Andrew. I thought about that and could not decide. More signal made it more red, but I could easily desaturate it a bit. Will have a look again.

[Craney]

This one drove me mad last year.  The bat came out fine.....( as they do on a night !!)...... but I could not for the put the hours in to wrestle the squid out of the images.

This is a great image.  May I ask which "Dual Band filter" you used on this ??     

I am trying out the L-enhance from Optolong tonight with my old QHY8-pro, since my  go-to mono camera is a bit unreliable at the moment.

 

Sean.

 

[gorann]

12 hours ago, andrew s said:

Fine image,  although I prefer the more muted colour of the H alpha in the original.

Regards Andrew 

You were right Andrew, so here is a version with reduced red saturation. I like it better.

 

Edited November 23, 2020 by gorann

[gorann]

25 minutes ago, Craney said:

This one drove me mad last year.  The bat came out fine.....( as they do on a night !!)...... but I could not for the put the hours in to wrestle the squid out of the images.

This is a great image.  May I ask which "Dual Band filter" you used on this ??     

I am trying out the L-enhance from Optolong tonight with my old QHY8-pro, since my  go-to mono camera is a bit unreliable at the moment.

 

Sean.

 

Thanks Sean!

A light bucket like the RASA 8 helps a lot on a faint object like the squid. And then you have to stretch a lot but still carefully. I used the IDAS NBX that is ment for high speed scopes like the RASA (which is f/2).

[Phillyo]

Well now, this is rather nice Göran! I had a very quick look at this a couple of nights ago, just a single 10min sub to see if I could even see anything and it was there...though very faint. I'm very tempted to give this a go with my ASI533 and Samyang at 2.4 to see what I can get. I'm also using the NBX, which I think it's doing REALLY well, so I'm very quietly optimistic that I might get something...if I get another clear night. I think it would need to be without a moon though as it is fainter than a faint thing so I need all the help I can get in capturing the detail.

Great image! I too prefer the slightly desaturated reds image.

Phil 

[ollypenrice]

The improvement is considerable over an image which was already excellent.

Olly

[gorann]

2 hours ago, Phillyo said:

Well now, this is rather nice Göran! I had a very quick look at this a couple of nights ago, just a single 10min sub to see if I could even see anything and it was there...though very faint. I'm very tempted to give this a go with my ASI533 and Samyang at 2.4 to see what I can get. I'm also using the NBX, which I think it's doing REALLY well, so I'm very quietly optimistic that I might get something...if I get another clear night. I think it would need to be without a moon though as it is fainter than a faint thing so I need all the help I can get in capturing the detail.

Great image! I too prefer the slightly desaturated reds image.

Phil 

Thanks Phil! If only the clouds cooperate then your set-up should be excellent for the task. You should get the whole bat in without a problem.

[gorann]

41 minutes ago, ollypenrice said:

The improvement is considerable over an image which was already excellent.

Olly

Thanks Olly! I have started looking at other images of the Squid and noticed that people have it from deep violet-blue, to cyan, and green. Then I found this old thread on SGL telling me that Oiii is really green. How can that be when we all say there is no green in space (except for those small green men) while there is plenty of Oiii. I am no big fan of green things in images and I am addicted to SCNR-green in PI. Maybe I should tweak the colours of my squid? Wonder what Valiv's @vlaiv opinion is.

 

[vlaiv]

8 minutes ago, gorann said:

Thanks Olly! I have started looking at other images of the Squid and noticed that people have it from deep violet-blue, to cyan, and green. Then I found this old thread on SGL telling me that Oiii is really green. How can that be when we all say there is no green in space (except for those small green men) while there is plenty of Oiii. I am no big fan of green things in images and I am addicted to SCNR-green in PI. Maybe I should tweak the colours of my squid? Wonder what Valiv's @vlaiv opinion is.

 

Thing with OIII is that you can't really display that color on computer screen or any other device as all display devices have limited color gamut and can't display pure spectral colors.

Here is simple way to display color that is closest to OIII. Take XY chromaticity diagram with sRGB color space marked on it and draw a line from D65 to outer spectral locus at 500nm like so:

Take first color this line "runs into" - color in sRGB triangle that is closest to 500nm. That is color that is visually closest to true OIII color. True OIII color will be "deeper" / "richer"/ more saturated than this, but this color will have closest hue to it.

You can check the OIII color yourself by looking thru OIII filter at a light source (even against sky in daylight), just make sure you keep filter perpendicular to your eye and not at an angle - because interference filters shift they bands depending on angle and you want it to stay on band.

Green is often neutralized in astronomical images because indeed there is no green - in star colors. Presence of green cast usually means poor color balance. Star colors are in Planckian locus:

You'll notice that sRGB can't show very cool red stars as well and that Planckian locus is below green part - there is no green color in stars:

(main spectral classes OBAFGKM)

This however does not mean that there are no green objects in outer space - most emission nebulae will end up having some green hue in true color because of OIII in them.

[gorann]

Thanks Vlaiv👍 Amazing how you can set up a whole lecture with graphs in a few minutes, or maybe you have answered this question many times before😉

[Stuf1978]

Outstanding work, beautiful 😎

[gorann]

1 minute ago, Stuf1978 said:

Outstanding work, beautiful 😎

Thanks, much appreciated!

[vlaiv]

59 minutes ago, gorann said:

Thanks Vlaiv👍 Amazing how you can set up a whole lecture with graphs in a few minutes, or maybe you have answered this question many times before😉

Google usually prepares graphs for me so it is simple copy paste (there is a small software called lightshot that enables you to take annotated screen captures and save to file or to clipboard and SGL post editor allows for paste operation) - knowing what to search for, well, yes, you can say that I touched upon this subject once or twice before

 

[ollypenrice]

3 hours ago, gorann said:

Thanks Olly! I have started looking at other images of the Squid and noticed that people have it from deep violet-blue, to cyan, and green. Then I found this old thread on SGL telling me that Oiii is really green. How can that be when we all say there is no green in space (except for those small green men) while there is plenty of Oiii. I am no big fan of green things in images and I am addicted to SCNR-green in PI. Maybe I should tweak the colours of my squid? Wonder what Valiv's @vlaiv opinion is.

 

I agree wth Vlaiv. It's very much on the green-blue border. When I look through my own OIII CCD filter at the daylight sky the angle of the filter makes a dramatic difference so that I see blue sometimes and green sometimes, but certainly never anything like cyan. In a nutshell this is where the spectrum puts it. What I do with objects in which the OIII is visible in the RGB layer is keep the RGB on the screen for reference. I then add OIII to HaLRGB green channel in one version and add it to HaLRGB blue channel in a second version. When I put these into Ps layers I can balance the green-blue contribution of the OIII with the RGB as my reference just by moving the opacity sliders. In the case of the Squid, the darned thing is only visible in OIII so I just made it greenish blue or blueish green.

There are lots of greens in planetary nebulae, many of which are stronger in OIII than Ha. Thor's Helmet, for instance (if you consider it a planetary since Wolf-Rayets are a special case, perhaps.)

When I was a relative beginner, and before SCNR green and Hasta La Vista Green appeared on the scene, I posted the notion that green was the root of all evil in AP colour.  The idea didn't seem to strike any chords at the time but I think I do now feel vindicated... 😄 There used to be a green grinning emoticon but that one will have to do!!!

Olly

[vlaiv]

25 minutes ago, ollypenrice said:

There used to be a green grinning emoticon but that one will have to do!!!

One just needs to smile in particular way

[gorann]

30 minutes ago, ollypenrice said:

I agree wth Vlaiv. It's very much on the green-blue border. When I look through my own OIII CCD filter at the daylight sky the angle of the filter makes a dramatic difference so that I see blue sometimes and green sometimes, but certainly never anything like cyan. In a nutshell this is where the spectrum puts it. What I do with objects in which the OIII is visible in the RGB layer is keep the RGB on the screen for reference. I then add OIII to HaLRGB green channel in one version and add it to HaLRGB blue channel in a second version. When I put these into Ps layers I can balance the green-blue contribution of the OIII with the RGB as my reference just by moving the opacity sliders. In the case of the Squid, the darned thing is only visible in OIII so I just made it greenish blue or blueish green.

There are lots of greens in planetary nebulae, many of which are stronger in OIII than Ha. Thor's Helmet, for instance (if you consider it a planetary since Wolf-Rayets are a special case, perhaps.)

When I was a relative beginner, and before SCNR green and Hasta La Vista Green appeared on the scene, I posted the notion that green was the root of all evil in AP colour.  The idea didn't seem to strike any chords at the time but I think I do now feel vindicated... 😄 There used to be a green grinning emoticon but that one will have to do!!!

Olly

So, what about the colour of my Squid Olly?