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Old Tuesday 9th August 2016, 08:11   #1
Binoseeker
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Pentax PF-80 EDA vs PR-80 EDA experiences ?

Hello,

I am interested in some info/experiences comparing Pentax PF-80 EDA vs PR-80 EDA, please. Which has best image quality? Cromatic abberation may differ?
Best zoom eye piece recommended?
Overall build quality?

Any comments compared to Celestron regal M2 80ED?

I am looking for a back up scope and one with astro ep could be a choice :-).

Thanks,
Anders
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Old Saturday 13th August 2016, 21:23   #2
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Star test PR-80 EDA

I star tested a PR-80EDA today.
When defocus i got this image, any ideas why it looks like that?

I rotated the EP but the vertical lines oriented the same direction.
I rotated the scope in the collar 90 degrees, the image/lines rotated same way.

Thanks,

Anders
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Old Sunday 14th August 2016, 18:24   #3
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Apart from the star test and I can't help you with that, what was the view like?
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Old Sunday 14th August 2016, 19:58   #4
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Hi,

this looks not too great... apart from that vertical line which according to your rotation tests is either a problem with the objective or with the image erecting prism, the rings are elliptic rather that round, which could mean astigmatism. How does the image change if you defocus the other way? With astigmatism the ellipse should change its orientation...

I would return this instrument if possible...

Joachim
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Old Sunday 14th August 2016, 22:47   #5
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Giosblue, Jring,

The image was ok at 20x, at 60x i thought it was a bit dark, with same CA.
There was some heat in the air so that caused some problems trying to judge image quality, and the wind was blowing shaking the scope a bit, so that made the star test image not as circular as it could be, i guess.

The vertical lines was there in the image on both sides of focus point.

The zoom was parfocal. No slack in the zoom wheel. Supplied zoom was PR-XL 8-24 mm (no 51040).

It was a bit hard to acheive best focus, i had to go back and forth a bit to find best focus....focus hunting.... No slack in the focus wheel.

I felt that eye placement even at 20x was a bit tricky, like i had to keep the eye in the middle, and if deviating just a bit sideways it effected image quality. Not as easy viewing as my meopta S2 scope....:-)

I hope there is a optical fault in this example of the scope since i like it overall. I will contact the seller to see what to do...

The version i got had the focus wheel much closer to the body, so i guess there is a version 2 of the PR-80 EDA.

Here is some info about the PR-80 EDA and PR-65 EDA :
http://www.mynewsdesk.com/se/focus_n...kationer-26014

Here is a cut through image of the PR-80 EDA: http://www.astroshop.eu/pentax-spott...l-8-24/p,48866



Here is some info about PF-80EDA : http://www.digiscopingitalia.it/test...txpf80_01.html
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Old Monday 15th August 2016, 15:38   #6
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The vertical line in the star-test image is caused by a poorly made roof edge on the Schmidt prism shown in the cutaway image in your first link. That's enough to return the scope even without anything else being wrong, but as Joachim mentioned the non-circular appearance of the diffraction pattern suggests that there are probably other problems, possibly astigmatism and/or pinched optics. The slightly flat area between 4:00 and 6:00 might be the intrusion of a prism edge into the exit pupil.

Your photo is too far out of focus (10+ rings) to show all the defects. To evaluate things like spherical aberration, astigmatism, pinching, coma, etc. we need two photos, one from each side of focus and each about 4 rings out of focus.

Henry

Last edited by henry link : Monday 15th August 2016 at 16:00.
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Old Monday 15th August 2016, 22:11   #7
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Henry, thanks for your comments.

I looked today at a video i took and the ring is sometimes round so the irregular exterior shape in the image is mostly due to hot air.

I don´t have that kind of image with only four rings.
If they send me a replacement then i will try to get that kind of image.
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