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Tales from Night 1 - mostly positive; a few snowflake star flurries

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#1 Tim0116

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Posted 24 February 2021 - 07:52 PM

Successful first night, 2/23/21!  Actually flabbergasted by how well it went.  When you're in test mode with new gear you don't even mind that big moon lighting up your work space.  I acquired my first mount and telescope in Nov/Dec and promised myself I'd spend time using the scope visually and learning the basics of the mount before jumping right into astrophotography.  Really did enjoy those sky tours (wife did too!), but I was dying to set up a guide scope and see how well this puppy (EQ6-R) would perform tracking.  Give me some METRICS!  

 

So my definition of "first night" in imaging mode was based not just on running some exposures with the ASI1600, but on the BIG TEST of having placed a reducer/flattener into the optical path, and the filter wheel.  How would the stars look??  Petrified about all the things I'd read regarding the woes of setting up back focus, and here I was trying to add all this extra stuff as a first-timer.  I must thank John (bridgman) for giving me the courage to purchase a WO 6AIII to use with my AT 115EDT.  I knew nothing about this subject.  Jumping ahead in the narrative, the frames look astonishingly good to my amateur eye.  Full zoom into those corners and I can discern no meaningful elongation (for me- beginner guy).  Round stars everywhere.  Now maybe somebody would plug it into an analyzer and show me what's "really going on."  For now, I'll take what I'm seeing very happily.  I will keep evaluating and adjust if needed. 

 

I guess the success with guiding was the biggest pleasant surprise.  No tiny starter scope for me, let's just dive right in!  I did use a PoleMaster for alignment and really love that gizmo.  Other than that I set my looping exposure time to 2.0s and sat back and stared as it kicked in.  Really could not believe when it settled into 0.26 - 0.28 total RMS and never went above 0.33 or so for a couple of hours.  These new mounts are incredible.   I ran a 6 minute exposure at one point and had beautifully round stars.  

 

So.  If not for the last 15 minutes of the session I would have been feeling like it was an almost flawless first experience.  The wonder of plate solving in NINA with ASTAP-- wow!  Slews were so accurate.  Then I thought... hmmmmm, despite this moon, I should just try out the different filters and see how things look.  I had been using L and Ha for the entire time.  Everything looked great.  Then I took an exposure with the R filter and ..... huh?  What's that?  Well it was Alnitak, of course, looking very.... not good.  Does anyone have a notion?  I will say that I did not refocus between filter changes, but that doesn't look like a focus issue.  I'm going to be totally miffed if someone says it's filter-related reflections.  I double-triple checked my filter sides when installing-- reflective surface to the telescope side.  I also found a similarly weird pattern with Alnitak from the O3 filter.  The linked photos are 120s exposures.  I stupidly did not go ahead and try ALL the filters, but it was clear that something wasn't right. Bummer.

 

So after feeling so good about things and thinking I was "ready to roll," I seem to be stuck until that situation is worked out.  Don't want to spend hours imaging with hideous stars in the final result.  But really-- can't complain about all the stuff that went right!

 

R image:

https://imgur.com/a/43TITgk

 

O3 image:

https://imgur.com/a/nbR8rEY


Edited by Tim0116, 24 February 2021 - 07:53 PM.


#2 jonnybravo0311

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Posted 24 February 2021 - 08:22 PM

That's the microlensing effect of the 1600. It's not your filters. The halo around Alnitak is your O3 filter. Antlia's new 3nm O3 filter does a better job - at least according to the comparison image I saw and now can't find again.

 

Edit: this is probably one of the best posts I've read on it: https://www.cloudyni...fect-explained/

Edit 2: and here's that comparison between the 3.5 and 3nm Antlia O3 filters: https://www.cloudyni...alo-comparison/


Edited by jonnybravo0311, 24 February 2021 - 08:26 PM.

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#3 Tim0116

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Posted 24 February 2021 - 08:46 PM

That's the microlensing effect of the 1600. It's not your filters. The halo around Alnitak is your O3 filter. Antlia's new 3nm O3 filter does a better job - at least according to the comparison image I saw and now can't find again.

 

Edit: this is probably one of the best posts I've read on it: https://www.cloudyni...fect-explained/

Edit 2: and here's that comparison between the 3.5 and 3nm Antlia O3 filters: https://www.cloudyni...alo-comparison/

Wow.  Thanks, Jonny!  Something I missed in all my reading.  Glad to at least know the cause and it not be a deep, unsolved mystery.  So this affects *ALL* ASI 1600s??  Such a raved-about camera.  I need to start researching.  Seems like I may have a camera to sell with some disclosure.  That ain't gonna work for me.  



#4 Tim0116

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Posted 24 February 2021 - 08:49 PM

And yes, it looks like Antlia came out with 3nm filters immediately after I purchased mine!  Go figure.  I can deal with the O3 halo since it seems so common, but that microlensing in the O3 image... nope.



#5 Tim0116

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Posted 24 February 2021 - 08:51 PM

And I bought this camera from a CN member :).  If it's common to all of the 1600's then so be it.  



#6 jonnybravo0311

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Posted 24 February 2021 - 08:53 PM

And I bought this camera from a CN member smile.gif.  If it's common to all of the 1600's then so be it.  

Yes, it's common to the 1600s - you didn't get duped.


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#7 Tim0116

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Posted 24 February 2021 - 09:02 PM

This is so interesting, because I'm looking through my images and the Ha filter shots have none of this effect around Alnitak.  Even the 6 minute exposure.  




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