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star testing c80 powerseeker

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#1 rob1986

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Posted 26 October 2021 - 06:45 PM

After finally reviving my EPs from the states (and a new diagonal) I've set to trying to star test my telescope.

 

inside of focus is producing beautiful diffraction rings, really perfect  (the 45mm vixen is outperforming the japanese meade EPs)

 

But outside of focus is a different story. I'll try to get pictures later. There certainly is turbulence. the Meade UWA 4.7 is showing a very small, perfectly round disc in focus, but i'm not seeing the diffraction rings out of focus. there is a bright halo, and the seeing is much more apparent outside of focus than in. With the 45mm and the barlow, I could just see a hint of a bright outside ring and nice inside rings, much like the other-side of focus, but i'm not sure. the inside focus ring is relatively clear of CA, but the outside disc has a clear differentiation. also outside of focus is much dimmer than inside

 

is this a standard achromat problem, or a more serious CA problem?

 

is outside of focus that different from inside?

 

(as an aside, the 45 performs outstanding with the f11.4 system. they really are a match made in heaven. but i'm reminded whats annoying about the really long eye relief, as nice as it may be on the astigmatism.)


Edited by rob1986, 26 October 2021 - 06:47 PM.


#2 ngc7319_20

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Posted 26 October 2021 - 07:23 PM

 

is this a standard achromat problem, or a more serious CA problem?

 

is outside of focus that different from inside?

 

(as an aside, the 45 performs outstanding with the f11.4 system. they really are a match made in heaven. but i'm reminded whats annoying about the really long eye relief, as nice as it may be on the astigmatism.)

Yes different star test patterns inside and outside focus is perfectly normal for a refractor.  You should test with a green filter.

 

There are also differences due to seeing.  Outside best focus the atmospheric cells are in focus -- there less blurring but more image motion than inside focus.




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