Sh2-140 and Lynds 2304

[gorann]

Finally, after a month I had half a night with clear sky on Sunday morning, although a bit hazy. I was also a bit too eager to get the scopes up on the rig so I noticed afterwards that balancing was not perfect. Balancing is also a bit tricky with a dual rig. So my EQ8 had to fight a bit and I had to throw out a bunch of subs due to jumps in the guiding. So I ended up with 48 x 3 min RGB from the ASI071 (gain 200, offset 30, -15°C) sitting on Esprit 150, and 67 x 3 min Ha (Baader 7nm) from the ASI1600 (gain 139, offset 59, -20°C) sitting on Esprit 100, so totally nearly 6 hours from when the sky cleared between 02.30 to 06.00. My plan was to get more data last night but the weather report lied and the clouds stayed on.

Far from a master piece but it is the first in a while and of an object I never tried before so I could not resist posting it. Stacking and calibration (only master dark subtraction) in PI, processing in PS.

Sh2-140 is apparently largely hidden by the dark nebula called Lynds 2304. If you want to see a nice close up (caught with an 8" SCT) of the central part of the nebula, with some clear pillar structures, and an interesting write-up about it, have a look at Jason Guenzel recent post. He calls it the Hidden Nebula:

https://www.astrobin.com/377160/

[Rodd]

Interesting target Goran  I am not familiar with it.  It kind of looks like an inverted Christmas Tree Cluster--very cone nebula-ish ( only the stars). Without knowing, I f I had to guess, I would think this was shot at a long focal length--I guess the 150 is fairly long--but not much over 1000mm right?  

If the central dark region is what you are referring to as a foreground dark nebula--it looks more like background space--maybe clipped a tad?  More data will resolve this issue.  

Rodd

[gorann]

3 hours ago, Rodd said:

Interesting target Goran  I am not familiar with it.  It kind of looks like an inverted Christmas Tree Cluster--very cone nebula-ish ( only the stars). Without knowing, I f I had to guess, I would think this was shot at a long focal length--I guess the 150 is fairly long--but not much over 1000mm right?  

If the central dark region is what you are referring to as a foreground dark nebula--it looks more like background space--maybe clipped a tad?  More data will resolve this issue.  

Rodd

Thanks Rodd. Yes it was new to me too until recently. The Esprit 150 is an f/7 scope so 1050 mm FL for the RGB (0,94" / pix with the ASI071). The Ha was collected with an Esprit 100, which has 550 mm FL, so 1.42" / pix with the ASI1600, so I scaled the Ha up before adding it to the red channel.

I am quite sure I did not clip anything but more data would help. Maybe you can see the dark nebula a bit better after this tweak? You can also conclude that something must be obscuring the background since there are so few stars there.

 

 

[Rodd]

21 minutes ago, gorann said:

Maybe you can see the dark nebula a bit better after this tweak?

Yes--Now I see.  It could be a screen thing too--monitors are all different.  How do you combine different focal lengths?  Whenever I try, the smaller FOV always gets the data--so a shorter FL will be put into the longer FL--which is the opposite of what you want for increased resolution.

Rodd

[gorann]

38 minutes ago, Rodd said:

Yes--Now I see.  It could be a screen thing too--monitors are all different.  How do you combine different focal lengths?  Whenever I try, the smaller FOV always gets the data--so a shorter FL will be put into the longer FL--which is the opposite of what you want for increased resolution.

Rodd

Worked a bit more on it so I just edited my last post - the dark nebula is even less dark now.

I do it in PS. I first did some basic stretching to both images. Then I used the ruler tool to measure the distance (in pixels) between the same two stars en each image. Dividing one value with the other gives me a conversion factor that I use to put both images on the same pixel scale (done in Image Size in PS). Then I use PI star alignment. In this case I used the RGB image as template and aligned the Ha to it. That also cropped the Ha image (with the larger FV) so they become exactly the same size and with all stars aligned. Back to PS again: I took a copy of the RGB image and deleted all channels except the red. Then I added the stretched Ha data to the red channel using lighten mode (so only Ha areas that are brighter than the red is added - a trick Olly uses). Then I took this new red channel and paste in as a new red channel in the RGB image, now becoming HaRGB. I also added a bit of the Ha image as lum to selected parts (also playing with the opacity slider of the layer to get the best result).

[Rodd]

8 minutes ago, gorann said:

hat also cropped the Ha image (with the larger FV)

But this means that the larger FOV data is being put into the smaller FOV data.  I want to put smaller FOV data (higher resolution) into larger FOV data--you know supplement key areas with higher resolution data.  The problem is the higher resolution data is a smaller FOV--so I don't know how to do this in PI

Rodd   

[gorann]

42 minutes ago, Rodd said:

But this means that the larger FOV data is being put into the smaller FOV data.  I want to put smaller FOV data (higher resolution) into larger FOV data--you know supplement key areas with higher resolution data.  The problem is the higher resolution data is a smaller FOV--so I don't know how to do this in PI

Rodd   

Yes, it is not ideal but it would be even worse if I had the ASI071 on the Esprit 100 and the ASI1600 on the Esprit 150. The reason I do it is that I can run two telescopes. I could of course collect the Ha and RGB on the same scope but then it would take twice the time. When I get my more study Mesu mount I may put my 5" ES refractor next  to the 6 " Esprit.

[gorann]

1 hour ago, Rodd said:

But this means that the larger FOV data is being put into the smaller FOV data.  I want to put smaller FOV data (higher resolution) into larger FOV data--you know supplement key areas with higher resolution data.  The problem is the higher resolution data is a smaller FOV--so I don't know how to do this in PI

Rodd   

PS. One way of solving this would be to start playing with reducers but SW does not sell anything but flatteners for their Esprit series so I have not yet figured out what reducer to get.

[Rodd]

55 minutes ago, gorann said:

Yes, it is not ideal but it would be even worse if I had the ASI071 on the Esprit 100 and the ASI1600 on the Esprit 150

You have the option of shooting a widefield with the 100 then supplementing high detail/structural areas with the 150.  Its done all the time--Olly does it quite often (but this is what I do not know how to do).  

Rodd

[gorann]

Just now, Rodd said:

You have the option of shooting a widefield with the 100 then supplementing high detail/structural areas with the 150.  Its done all the time--Olly does it quite often (but this is what I do not know how to do).  

Rodd

Yes, but it depends on the target, i.e. if all the interesting things are in the centre. It would not be a problem if I had clear skies all the time. Then I could move the cameras between the scopes and get it all - a wide field with all the channels and a close up with all the channels. As I said it could be partly solved with a reducer on the long FL scope. Even better would be if there was a larger mono CMOS camera to be bought than the ASI1600.

[Rodd]

13 minutes ago, gorann said:

Yes, but it depends on the target, i.e. if all the interesting things are in the centre. It would not be a problem if I had clear skies all the time.

I might not be articulating this very well.     I mean--you can insert high-resolution data into a wide FOV image, only affecting the high-resolution region while preserving the large FOV with the wide filed, lower resolution.  Take a wide field shot of the Bubble Nebula region for instance.  Some folks shoot a wide FOV with a 71mm scope, then insert data for the bubble itself shot with a 17" Planewave CDK.  This gives you a big FOV with the Bubble looking like a higher resolution region upon zoom.   

Rodd

[gorann]

Yes, I got it first time Rodd and I have done that several times since I am addicted to double and triple rigs, but it is a compromise that works ok with things like the bubble. So, next time I aim for such an object I will switch cameras, using the 1600 on the 1050mm Esprit.