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M1 and M27 pictures


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#1 fjhdavid

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Posted 02 April 2020 - 02:05 AM

Hi,

 

Pictures with a meade LS6 ACF:

 

M1 is the sum of 1000 sub frames of 5s

M27 is the sum of 360 sub frames of 5s

 

I use a f/6.3 reducer for SC  (as the LS6 is ACF, stars at the edge are a little bit elongated, but you can work up to a 10mm centered circle)

I use a zwo 1600MM (not cooled, as 5s is not a long time)

 

==> résolution is 0.75" /pixel

 

clear skies

 

François

 

ps: I use Iris (from C. Buill) and photoshop

Attached Thumbnails

  • M27.jpg
  • M1 nb.jpg

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#2 MistrBadgr

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Posted 02 April 2020 - 10:19 AM

This is really nice work, Francois!

 

I think you have nailed contrast, at least to me.  The reason I say this is that the images definitely look three dimensional to my eyes.  There is good contrast and detail in the nebula as well.

 

Though not designed with imaging in mind, the LS 6 has proven to do much better in that capacity than expected.  I think, in part, to the inventiveness of the people who have tried it.  Due to a heavier scope on the same basic mount and tripod, the LS 8 cannot do as well in that activity.

 

Best Regards,

 

Bill


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#3 fjhdavid

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Posted 03 April 2020 - 12:51 AM

1- the pre-processing script I wrote with Iris is very complete but basic (no lucy richardson alogorithm, or enhanced contrast) but takes 8hours to compute 1000 frames. But when you choose the 2 or 3 initial parameters, everything is then fully automatic.

 

2- the script under photoshop asks for 3 questions during the process, but use very standard functions (there is a lot of litterature about them).

To answer Bill comment, I soften a little bit the external shape of the stars with a gaussian filter, otherwise stars would have been more contrasted!!!

 

3- the seeing these nights was very good (under 2arc sec) and with 5s exposure time, you record crisped details you won't be able to record even with guiding and 30s exposure time!


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#4 Cezar

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Posted 16 April 2020 - 10:30 AM

Very nice pictures. Great work Francois!

Yes, you are right. A black clear sky is the most important. You can try to stay in range of 15-20 sec. Here is a nice topic I have read for Alt-Az imaging: https://stargazerslo...-dso-challenge/


Meade LT-8


#5 fjhdavid

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Posted 17 April 2020 - 02:06 AM

thanks a lot, I will read your link

 

in fact, with a focal of 1050mm (F/7), I noticed that 5s is really the max exposure time before trailing (of course it depends of the exact DSO localisation)

 

stars are three dimensional because, even with a 1.2e- readout noise, the readout noise is more important than the background noise, then you don't have gaussian noise in the background picture ( you can add it with photoshop of course but I didn't do it)

 

My next step is to use a f/4 reducer!

 

this will reduce trailing and increase sensitivity; I even computed that I should have background gaussian noise even with a mag 21 background level






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