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Alnitak the beast - advice please!

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#1 Chrisofweden

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Posted 24 January 2022 - 02:55 AM

 

After finally "biting the bullet" and starting to use my reducer that's been in its box, unopened, for six months, I'm quickly learning that imaging at 410mm and f3,9 is a completely different animal than 600mm and f5,6!

To compound things, I decided to go for a target I've never shot before: The Horsehead and Flame nebulae, containing the infamous Alnitak foreheadslap.gif   

Even though I had read-up in advance and tried to follow the advice I found, I'm still struggling with processing what I humbly believe is an otherwise pretty good image but which is "ruined" by that monster - would appreciate advice and input regarding both how to capture better data next time and how to make the best of what I got this time! 

 

Capture:

- Askar FRA600 with 0,7 reducer

- ZWO 294MC Pro, unity gain, cooled -10C

- IR Cut filter

- 61 x 120s subs

- Guiding around 1.0

- Autofocus

- Bortle 4-ish

- Darks, Dark Flats, Flats

Processing: 

- PI WBPP

- Color Calib

- EZ Suite: Deconv, Denoise

- Game script (multi-point gradient mask)

- Soft Stretch

- StarXterminator

- Process Stars and Starless individually (Arcsinh, MMT, Color etc etc)

- Pixelmath recombine

- Photoshop "touch up" and finish


Edited by Chrisofweden, 24 January 2022 - 03:03 AM.

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#2 the Elf

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Posted 24 January 2022 - 04:07 AM

Here is your image vs. my shot from 2019. This is what can be achieved though you don't have the spices.

 

compare.jpg

 

I can only guess what is going wrong. My first guess is exposure time. My image is 2 min subs at f/6.5 for OSC. That makes Alnitak controllable but will not show much of the Ha in an OSC camera. My image is an OSC Ha composite using 15min subs. So using an Ha filter or some dual bandpass like L-extreme and combine the two data sets. Last but not least I see a lot of blue in the halos. This may or may not be caused by the telescope. Basically if a star is very bright an the exposure time is long there always is a halo. It the star is blue the halo is blue.

You can download my data from this page:

https://www.elf-of-l.../Downloads.html

There are two sets, the OSC data and "additional Ha data" for this image. Have look and compare it to your data. You will find that the Ha filter dramatically reduces the star intensity, so my suggestion is to go for a filter.

If you post a link to you data I'll have a lock if it can be processed better.

 

CS

the Elf



#3 the Elf

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Posted 24 January 2022 - 04:28 AM

Oh, one more point: Why unity gain? First you will find a lot of input that there is no magic wand in unity gain and if there is one it is more for dim objects, that is the other school of thought. Anyway, high gain is low dynamic range and fast saturation, so a lower gain will probably tame Alnitak. Yes, on the other hand the red stuff might suffer. I'd do a few test shots at lower gain.



#4 Chrisofweden

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Posted 24 January 2022 - 04:33 AM

Hi again Elf and thanks for your feedback and the advice regarding use of a filter. I have an L-Extreme also still in it's little box, but am a little wary of using it at the relatively fast f/3.9 that my reducer gives me. That said, I will of course give it a try!

Will also download your data and experiment processing on that - very appreciated!

 

Thanks for offering to take a stab at my data - if you are still willing and have the time, you'll find the master light as a TIFF from PI here: 

https://www.dropbox....n 2022.tif?dl=0

 

Regards and Clear Skies,

Chris

 

EDIT: Just saw your PS - I have run on unity gain since "Day 1" and never really considered not doing so. Lack of understanding is my excuse and reading your explanation now, together with a little more experience these last months, it really makes sense and I will definitely try again, at 0 smile.gif  


Edited by Chrisofweden, 24 January 2022 - 04:37 AM.


#5 matt_astro_tx

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Posted 24 January 2022 - 06:05 AM

Some cameras don't like gain 0.  For example my ASI183MC Pro freaks out and introduces banding across the image at gain 0.  Not all cameras are the same and you may have better luck than me.  But yes, I agree a lower gain and potentially shorter exposures will help tame the beast.


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#6 happylimpet

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Posted 24 January 2022 - 06:29 AM

I cant see anything wrong with your image. Alnitak is a bright star. Trying to make it look faint just seems daft. It plays a central role in exciting the nebula and making it shine, so pretending it isnt the beast it truly is seems odd.

 

If it was actually ruining the part of the image with the horsehead i'd understand, but this is just a great image with a bright star in it.


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#7 Bretw01

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Posted 24 January 2022 - 07:16 AM

To me the focus looks a bit soft. I see you are using autofocus, but I am not familiar with the ASI EAF. I could be wrong, but you might want to check the accuracy of the calibration (step size). And as others have said, shorten up the exposures. F3.9 is fast!

 

You could share your stack to see what others might be able to get from it.


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#8 the Elf

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Posted 24 January 2022 - 07:35 AM

My processing of your above link:

 

ChrisOfSweden.jpg

 

Let me know what you think.


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#9 Chrisofweden

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Posted 24 January 2022 - 09:13 AM

Thank you Elf - I like it a lot!

You succeeded in bringing the stars under control, both in intensity and color - the blue is gone, which makes for a far more aesthetically appealing look in my view :)

I will look at your tutorial and images to try and understand how you achieved this, but would also be very grateful if you would link me the full size version of your "product" from my data bow.gif

 

Thank you too to the others who chipped in, not least HappyLimpet for the compliment and your point of view regarding Alnitak - I think Elfs version is the "compromise" I was hoping for, where the magnitude is very apparent but doesn't dominate the whole image!  

 

Clear skies!

 

/Chris 



#10 the Elf

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Posted 24 January 2022 - 12:42 PM

Here is my processing you YT. Send you a PM with the link to the data.

Sorry for the poor quality, got the screen recorder settings wrong. Technically it's full HD but a bit too compressed. *G*

 

https://youtu.be/kCesBxbhzIM


Edited by the Elf, 24 January 2022 - 12:46 PM.

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#11 rj144

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Posted 24 January 2022 - 01:34 PM

Here's my version (colors are a bit different than yours):

 

IC434-Jan-2022.png

 

This was simply using Siril and Affinity (with James Ritson's excellent macros, Astroflat Pro and Topaz Denoise plugins).  It was about a 10 to 15 minute edit.

 

Excellent data again... good job.  See here:

 

https://www.cloudyni...some-your-data/


Edited by rj144, 24 January 2022 - 01:35 PM.

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#12 F.Meiresonne

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Posted 24 January 2022 - 01:58 PM

Could not realy tame Alnitak but could take some annoying blue color away...

 

Image seems a little out of focus ...

Attached Thumbnails

  • IC4343.jpg

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#13 bobzeq25

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Posted 24 January 2022 - 02:16 PM

Main thing to do.

 

Recognize Alnitak is an unusual case, as just accept it.


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#14 Chrisofweden

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Posted 24 January 2022 - 02:24 PM

Guys, what can I say but "wow!"

 

You are all the best and I can only try to express how happy I am for your input and feedback  - gratitude!

My conclusions from all your comments:

- take a look at my settings for my EAF

- I have a good setup than can collect good data

- I have  long way to go with regard to processing

- I love this hobby!

 

 

/Chris


Edited by Chrisofweden, 24 January 2022 - 02:32 PM.

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#15 jonnybravo0311

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Posted 24 January 2022 - 02:26 PM

You all do realize that Alnitak is a BLUE supergiant star, right? Seems a bit odd to try and remove the blue from it... :)


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#16 rj144

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Posted 24 January 2022 - 02:46 PM

Guys, what can I say but "wow!"

 

You are all the best and I can only try to express how happy I am for your input and feedback  - gratitude!

My conclusions from all your comments:

- take a look at my settings for my EAF

- I have a good setup than can collect good data

- I have  long way to go with regard to processing

- I love this hobby!

 

 

/Chris

Simply curious because everyone has different tastes, but did you like my edit or were the colors too far off compared to your edit?


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#17 F.Meiresonne

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Posted 24 January 2022 - 04:08 PM

You all do realize that Alnitak is a BLUE supergiant star, right? Seems a bit odd to try and remove the blue from it... smile.gif

It was an ugly blue i got wink.gif  wanted to get a bit rid of it....lol.gif


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#18 the Elf

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Posted 24 January 2022 - 04:57 PM

I don't like the ugly yellowish white of our star. But I'm lucky, where I life it is hidden behind the clouds most of the time. As are all other stars. ;-)

Freddy, if you image with your mono only you don't have to worry about blue stars. Trash the 800D. No wait, send it to me.....


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#19 JMeddings

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Posted 24 January 2022 - 07:15 PM

Lots of great processing here.  I think the data is actually pretty good.  Here is a quick processing with PI and then taken to PS to quickly highlight the starless image and then readd the stars.

Attached Thumbnails

  • IC434 Jan 2022.jpg


#20 JMeddings

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Posted 24 January 2022 - 07:17 PM

Lots of great processing here.  I think the data is actually pretty good.  Here is a quick processing with PI and then taken to PS to quickly highlight the starless image and then readd the stars.

Gawd..... the jpg compression completely made the colors far too red!  I'll try a better compression.

Attached Thumbnails

  • IC434 Jan 2022.jpg

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#21 Bretw01

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Posted 24 January 2022 - 09:04 PM

 
 

Thanks for sharing, my take using PI and PS:

 

Chrisofweden's flame
 
You definitely want to click on image!

Edited by Bretw01, 24 January 2022 - 09:05 PM.

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#22 happylimpet

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Posted 25 January 2022 - 04:28 AM

Thank you Elf - I like it a lot!

You succeeded in bringing the stars under control, both in intensity and color - the blue is gone, which makes for a far more aesthetically appealing look in my view smile.gif

Well done, you got rid of the blue colour of those, er very blue stars.

 

What the **** is the point of this if we take images of bright blue stars and want them to appear as faint white stars? This is a spectacular, massive, OB supergiant star. Why not celebrate that? Why try to diminish it?  The whole reason that IC434 is shining is because this amazing star is bathing it in UV light. Because its a very bright blue star.

 

To answer my own question, I think this is because everyone is trying to reproduce the previous caricature of this object, and has lost sight of reality.


Edited by happylimpet, 25 January 2022 - 04:29 AM.


#23 Tim J Fowler

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Posted 25 January 2022 - 05:59 AM

Mice data! My usual run through Siril and GIMP. No Starnet++ this time. Thanks for sharing!

Attached Thumbnails

  • small Siril GIMP Chrisofweden Horsehead Flame IC434 Jan 2022.jpg

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#24 Professor2112

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Posted 25 January 2022 - 06:10 AM

IMHO, it’s up to the imager what they want to do with their stars.  Heck, they can make ‘em all green if they want.  If you’re going for a “realistic” image though, it’s all a matter of finding the right balance that leaves you satisfied with your work.  Nice image regardless of what Alnitak looks like.  


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#25 F.Meiresonne

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Posted 25 January 2022 - 06:19 AM

Gawd..... the jpg compression completely made the colors far too red!  I'll try a better compression.

Yeah, that really can play tricks...




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