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First Night Flop with Filter Wheel Test

astrophotography CMOS EAA dso filters optics
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#1 GaryShaw

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Posted 22 September 2020 - 02:08 PM

Hi All:

Having started EEA Observing just over 2 years ago, I finally felt far enough along to acquire a 5-station ZWO filter wheel and set it up for a shake-down run last night in my Bortle 8 (SQM 18.5) skies.

 

As I was setting up the filter wheel, spacers/adaptors and coma corrector, I found I was missing the ZWO M48 T2 16.5 mm extender needed to get the optics train to be as ZWO recommends - 55mm from the coma corrector. I managed to cobble together some spacers as shown below and managed to get about 51mm. See Image 1 below.

 

So Question 1 is: Given that I was able to achieve focus, how sacred is the 55 mm versus the 51mm that I used? I do have the missing extender on order so I'll have it at 55mm in a few days.

 

My Question 2 relates to focusing. Right now I have 2 empty slots in the wheel. One will remain empty, the other will be occupied by a OIII filter. I noticed that I had to adjust my focus between viewing with no filter versus when either the L-eNhance or H alpha was in use. Will I soon also notice that I'll also need to refocus for each individual filter?

 

Take a look at the first screenshot below - See Image 2 . This was taken while attempting to adjust the Live Stack Histo with the L-eNhance filter in place. You can barely see the nebula and there's virtually no color.

Attached Thumbnails

  • IMG_4950.jpg
  • L-eNhance W Veil copy.jpg

Edited by GaryShaw, 22 September 2020 - 03:01 PM.

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#2 wrnchhead

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Posted 22 September 2020 - 02:19 PM

My Question 2 relates to focusing. Right now I have 2 empty slots in the wheel. One will remain empty, the other will be occupied by a OIII filter. I noticed that I had to adjust my focus between viewing with no filter versus when either the L-eNhance or H alpha was in use. Will I soon also notice that I'll also need to refocus for each individual filter?

I have an answer for this one, and it is yes. Filter vs no filter will take quite a bit of focusing. Filter to filter will likely take some. My Astrodon Ha and SII have been parfocal (I still check every time though) but any other switching requires refocus. 


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#3 GaryShaw

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Posted 22 September 2020 - 02:33 PM

Now take a look at a screenshot showing the H Alpha version of the same view - Image 3. In addition to being barely visible, you can see what looks like 'amp glow' on the upper right side of the image. This didn't appear on the L-eNhance filter screenshot.

 

Image 4 below shows the Western Veil as I captured in last year using a smaller, 142mm Schmidt Newtonian. I have the L-eNhance filter directly installed on the camera for this image. While not AP grade, its fine for EAA and is far more colorful and contains a lot more contrast. 

 

So my last questions for now are:

 

Question 3: Why is the amp glow happening when never observed before and why only on the H Alpha screenshot?

 

Question 4: Was I missing something or doing something incorrectly when trying to adjust the histograms on both images? The last image clearly shows how the filter can boost both color and contrast on this object, but, with a larger, 203mm F4 newtonian with filter wheel, spacers and coma corrector, I was unable to work the histogram well enough to get a decent image to observe.

 

Question 5: We are currently engulfed by some of the smoke from fires out west. Could that be impacting the observing/imaging process?

 

 

 

Perhaps the problems getting viewable images ties back in some way to not having adequate space between the sensor and the coma corrector. This is all new territory for me so I'm hoping some of you smarter folks in the CN community can provide some ideas and input on what I can do to get better at this.

 

Thanks for you help!

Gary

 

ps: Another thought that just came up is whether the gain and/or exposures were just not sufficient. I was using my typical range of 275-325 gain and 10-15 seconds of exposure.....

Attached Thumbnails

  • H alpha W Veil copy.jpg
  • WesternVeilNebula_Stack_113frames_1377s.jpg

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