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Dark nebulas next to Iris.

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#1 gezak22

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Posted 04 August 2014 - 10:21 AM

Hey guys,

 

We have seen some nice examples of the Iris and Sh2-136 this year. I wanted to share my take on the area, by imaging the dark nebulas to the west of the Iris. Conditions were mediocre, and imaging L with a doublet is certainly a handycap, but I am quite happy with the results. This is also my first try at processing with CCDStack, not with DSS. I am pretty impressed with CCDStack so far.

 

Link

 

Thanks for looking.



#2 vpcirc

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Posted 04 August 2014 - 04:32 PM

Your stars look way over exposed to me, how are you strectching your data?



#3 gezak22

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Posted 04 August 2014 - 07:40 PM

Your stars look way over exposed to me, how are you strectching your data?

No doubt about that. The fact that I am imaging L data with a doulet certainly is not helping. And notice the ugly flares too.

 

Stretchig was done by adjusting the black and white points in CCDStack and playing with the DDP slider until the dark nebulas looked ok. I should probably leave the white point alone, right?



#4 vpcirc

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Posted 04 August 2014 - 07:48 PM

Masked stretch, but that's just my 2 cents. Most people would never touch the white point, only the mid range, but everyone processes to what they think looks the best. Many times I love what I did only to have mentors suggest a different approach, but they're saying how they like it. 



#5 gezak22

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Posted 04 August 2014 - 10:39 PM

Masked stretch, but that's just my 2 cents. Most people would never touch the white point, only the mid range, but everyone processes to what they think looks the best. Many times I love what I did only to have mentors suggest a different approach, but they're saying how they like it. 

 

Back when I was doing OSC imaging, I frequently produced images I thought were great, but once I looked at them an hour later I realized that the color balance was way off. As they say, I had spent too much time in the monkey cage. :) I have since then been cheating by doing monochrome luminance and narrowband images.

 

Could you provide a link to a tutorial on masked stretching or should I just get Adam Block's processing DVD?

 

Finally, I am indepted to your clear post on how to process in CCDStack in this old thread. Without it, I would have given up on CCDStack within 30 minutes. I owe you at least one beer.

 

Cheers.



#6 vpcirc

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Posted 05 August 2014 - 07:45 AM

You make a star mask, in PixInsight or Photoshop, then put it over the image and adjust your curves so you don't effect the stars when stretching. I don't know of a way to do it in CCDStack. Adam typically doesn't finish any image in ccdstack. After combining he then takes it into PixInsight and or Photoshop. Creating a star mask is simple in PixInsight since they have a function for it. Photoshop is a bit more complicated. Unless you have a friend with a college email address, photoshop is pretty spendy, which is why PixInsight has become so popular. It can do every function almost that photoshop can, but at this point the UI isn't is simple at times. 



#7 gezak22

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Posted 05 August 2014 - 10:18 AM

 

You make a star mask, in PixInsight or Photoshop, then put it over the image and adjust your curves so you don't effect the stars when stretching. I don't know of a way to do it in CCDStack. Adam typically doesn't finish any image in ccdstack. After combining he then takes it into PixInsight and or Photoshop. Creating a star mask is simple in PixInsight since they have a function for it. Photoshop is a bit more complicated. Unless you have a friend with a college email address, photoshop is pretty spendy, which is why PixInsight has become so popular. It can do every function almost that photoshop can, but at this point the UI isn't is simple at times. 

 

I do have photoshop and I do some tweaking in it. When I was using DSS I did a lot more levels/curves in PS than was necessary in this image as the bulk of the stretching of this image was done in CCDStack. I'll look into star masks.

Thanks.

#8 Leonardo70

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Posted 05 August 2014 - 10:44 AM

Geza, in CCDSTACK  try to lower the Gamma value and pump the DDP effect ... this reduce the star size and leave the dust in evidence. You lost a general contrast but you can adjust after on PS.

 

All the best,

Leo



#9 gezak22

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Posted 05 August 2014 - 03:30 PM

Geza, in CCDSTACK  try to lower the Gamma value and pump the DDP effect ... this reduce the star size and leave the dust in evidence. You lost a general contrast but you can adjust after on PS.

 

All the best,

Leo

Thanks Leo, I'll give that a try.



#10 gezak22

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Posted 07 August 2014 - 12:50 AM

deleted


Edited by gezak22, 07 August 2014 - 12:55 AM.


#11 gezak22

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Posted 07 August 2014 - 12:51 AM

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Edited by gezak22, 07 August 2014 - 12:55 AM.


#12 gezak22

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Posted 07 August 2014 - 12:54 AM

I gave Leo's suggestion a go, and I am now stuck with the halos that are inherent in a fast doublet (Here). Using a star mask indeed seems to be the better way to deal with this.

 

I can't really blame the 90 mm Tak - I bought this scope primarily for NB work, and I didn't expect to get hooked on dark nebulas this quickly. Thankfully the next scope upgrade (by the end of the year) should take care of this issue.

 

Thanks again for all the feedback.








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