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Pleiades with more subs, and a problem

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#1 Stricnine

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Posted 21 November 2020 - 08:04 PM

I managed to get a "full" night on M45, but the images weren't 'compatible' with the images from a few night before thanks to some stars with diffraction spikes that were at different angles between the two sets.

 

I'm not sure what's causing the diffraction spikes to begin with, the telescope is a refractor, and only some stars have them.

 

So instead of close to 9 hours, here's ~6 hours on M45 instead.

 

M45 2020-11-19 v1b

 

Astrobin:

get.jpg?insecure


Edited by Stricnine, 21 November 2020 - 08:05 PM.

  • H-Alfa, Jim Waters, zxx and 5 others like this

#2 andysea

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Posted 21 November 2020 - 08:22 PM

That's an excellent image! I get spikes from refractors too. They could be caused by the micro lenses on the sensor.



#3 imtl

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Posted 21 November 2020 - 09:05 PM

If that was the case then it would have shown up in all of the stars. Only a handful of them have it here.

Can you see if it shows up in all the subs?

 

If you don't have that in either sub and it sounds like you're combining two data sets with difference in angel. Then this is a processing artifact. You should look into your stacking process.



#4 Stricnine

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Posted 22 November 2020 - 03:47 AM

If that was the case then it would have shown up in all of the stars. Only a handful of them have it here.

Can you see if it shows up in all the subs?

 

If you don't have that in either sub and it sounds like you're combining two data sets with difference in angel. Then this is a processing artifact. You should look into your stacking process.

The diffraction spikes appear in most subs, but the stars that have them change after the meridian flip and begin to reduce/disappear in subsequent subs.  There are no power lines or tree limbs remotely close to cause it.

 

The rotation angle was off about 9 deg between the two nights, which showed up in the spikes.



#5 imtl

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Posted 22 November 2020 - 03:52 AM

You had an intrusion to the light path. Maybe something inside your tube. It can create partial diffraction patterns.



#6 Stricnine

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Posted 22 November 2020 - 04:39 AM

You had an intrusion to the light path. Maybe something inside your tube. It can create partial diffraction patterns.

Yeah, I already reached that conclusion.



#7 sn2006gy

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Posted 22 November 2020 - 10:49 AM

I think i have some bolts in my lens cell on my esprit 120 that cause the iron cross spikes in my photos.  My scope is remote so i can't do much about it but I am asking SkyWatcher if there is an aperture mask i can print or something i can try..  I don't hate them, but i'd prefer rounder stars after all my hard work :)   (but.. i also can't tell if its a symptom of my reducer... hmm)



#8 Jim Thommes

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Posted 22 November 2020 - 09:06 PM

I see the stars with the spikes. But overall, the image looks great. Nicely processed too.

 

This doesn't look a problem I would want to troubleshoot. Seems to happen on so few stars - probably happens differently in different areas of the sky. if it happens intermittently or is different in other parts of the sky, I'll bet it would be difficult to come up with an actionable diagnosis.



#9 jgraham

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Posted 23 November 2020 - 12:33 PM

Beautiful image. I get spikes around bright stars with my refractors if I have the slightest intrusion into the light path like one of the lens spacers. Another common problem that I have are wires the cross by backyard. I'll get a nasty set of spikes as the target passes behind one of the wires.

 

Nicely done!




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