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Wide Field Auriga in Ha - C&C requested

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#1 mikefulb

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Posted 09 February 2018 - 05:27 PM

This is a 2 x 1 mosaic I've been working on in Ha for Auriga including IC405/IC410 and Simeis 147:
 
get.jpg?insecure
 
I've been mainly dealing with blending the two frames together so they appear seamless.
 
I think I have that mostly licked.
 
Now I've been working on bring out the nebulosity and part of that process for me has always been to de-emphasize the stars.
 
In this case it was tricky because with my Canon 100mm lens/ASI1600MM setup I have tilt and so stars look great on half the frame and not so good in the other side - mostly the corner.
 
I have treated this so far by the standard method of reducing star sizes.  To handle the "bad side" I layered several additional star reduction layers which I masked to only treat the problem areas.
 
As a result I like the general balance of stars to nebula but if you pixel peep you will be blinded by the small scale disaster area left behind!
 
I suspect I need to work on further de-emphasizing the sea of smaller stars that remain.  I'm usually not a fan of starless images but maybe I need to go that far for this subject.
 
I'm mostly satisfied with the result but would appreciate any feedback from fresh sets of eyes.


Edited by mikefulb, 09 February 2018 - 10:53 PM.

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#2 HarryRik9

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Posted 09 February 2018 - 05:56 PM

Needs more contrast.



#3 scopenitout

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Posted 10 February 2018 - 12:19 PM

This is a 2 x 1 mosaic I've been working on in Ha for Auriga including IC405/IC410 and Simeis 147:

get.jpg?insecure

I've been mainly dealing with blending the two frames together so they appear seamless.

I think I have that mostly licked.

Now I've been working on bring out the nebulosity and part of that process for me has always been to de-emphasize the stars.

In this case it was tricky because with my Canon 100mm lens/ASI1600MM setup I have tilt and so stars look great on half the frame and not so good in the other side - mostly the corner.

I have treated this so far by the standard method of reducing star sizes. To handle the "bad side" I layered several additional star reduction layers which I masked to only treat the problem areas.

As a result I like the general balance of stars to nebula but if you pixel peep you will be blinded by the small scale disaster area left behind!

I suspect I need to work on further de-emphasizing the sea of smaller stars that remain. I'm usually not a fan of starless images but maybe I need to go that far for this subject.

I'm mostly satisfied with the result but would appreciate any feedback from fresh sets of eyes.


I enjoyed looking at your full res image on AB. Well done Mike!

#4 StarFood

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Posted 10 February 2018 - 01:13 PM

I had an almost identical setup with a canon 100L and an Atik 383L. Wonderful lens ( I think the best deal in the L family of canon lenses) and I never had any issues with tilt in my setup.  I’ve had friends who have attempted to use a ZWO with a lens and been met with tilt issues.  It seems a tilt adjuster goes a long way if you have the back focus for it.  

 

You could always flip the panel and reshoot, sometimes that’s the best case when it comes to mosaics.  From what I can see you handled it well and I can’t really pixel peep it and honestly as someone who does mosaics frequently, pp can onl cause you pain lol.  You can see some of my work a few posts down from yours here.  

 

How are you assembling it?  Are you using pixinsight to solve it and assemble in mosaic by coordinates?  That would be my suggestion to use some of pixinsights refinement tools in the edges.  

 

Having said all that you did a tremendous jobs on what is arguably one of the most beautiful areas of the sky.  Capturing spaghetti is no joke, it’s a tough thing to do!  Good work on all accounts.  :) 



#5 mikefulb

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Posted 10 February 2018 - 10:30 PM

Thank you for the feedback - I'll try to address your comments...

 

I 3D printed a support for the lens as it doesn't have a lens foot available I could find and has a tapered body which makes it tricky but I'm pretty sure everything is solid.

 

I've been playing with tilt control using some of the aluminum from the side of a soda can.  It is pretty thin.  So I slightly unthread the ASI1600MM from the EFW8 and insert 1 or 2 thicknesses of shim and take a shot of a dense star field.  I use software to look at star sizes across the field as well as just inspecting the corners.  Then I move the shim 90 degrees around the ASI and try again.  After a few tries it is amazing what you can take out.

 

Because focusing the lens so such a chore I lost patience (and rare dark clear sky) trying to shim it so I just started shooting data and figured I'd fix it in post.

 

Next full moon I'll try to get it shimmed better.

 

For combining I used Pixinsight.  I actually just used StarAlignment and it did fine as I had good overlap.

 

GradientMergeMosaic really blew up when I tried to combine the 2 frames.  It did some odd things in places where it looked like a black hole was eating itself. 

 

So I made two masks which were equal to 1 in the independent parts of the 2 frames and linearly blended the two in the overlap region.  Since it was a vertical blend it was easy to make a PixelMath rule to generate the blended region of the mask.

 

I had StarAlignment do frame adaptation and it was pretty close.  I added an addition offset (determined by measuring median of background of two frames in overlap region) and scaling (determined by trial and error) to one of the frames when I combined them with PixelMath and my masks to get it pretty close.

 

Then I did a non-aggressive stretch in PI and exported it to Photoshop where I find it much easier to work on the rest of the steps.

 

I can make a great star mask in PS in no time whereas the StarMask tool in PI has eluded my mastery for about a decade now.  :)

 

I reduced the stars using the minimum filter.  Where the stars were extra elongated I did some extra layers in PS where I reduced the stars several times and then used a mask to blend in the more reduced stars as needed while leaving the initially OK stars alone.


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#6 StarFood

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Posted 11 February 2018 - 12:46 AM

I found thes invaluable with the canon 100. wink.gif

 

https://www.teleskop...to-D-135mm.html

 

also, sending you a PM. 


Edited by StarFood, 11 February 2018 - 12:47 AM.


#7 mikefulb

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Posted 11 February 2018 - 06:00 PM

That is a cool gadget.  I have a lens gear and a small stepper controlling focus on mine and I can get it fairly well focused.  I use a Bahtinov initially to get the center focused and then take test shots and analyze the center and corner FWHM and move the focus in 1 step at a time until I have it fairly balanced around the field.  I have the lens stopped down to f/4 and yet it seems to have field curvature as well as some tilt still.




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