Star test 70mm F6 achromat doublet. with and without central obstruction. + green filter

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realflow100 United States of America
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Star test 70mm F6 achromat doublet. with and without central obstruction. + green filter

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Post by realflow100 »


I'm attempting to interpret the results of my star test and tried multiple strategies.
With or without a green filter. its clear one side of focus of a star at very high magnification has a noticably softer/blurrier out of focus disk. with hard to see concentric rings.
and the other side of focus is sharper. but its not REALLY bad or anything.
in aberrator its 0.1 to 0.2 waves approximately what it appears to look like when i input my scope specs and play with the spherical aberration value. that matches approximately the appearance of what I see.
The in-focus image of terrestrial. or stars seem to look reasonably fine. just a bit fiddly to get it focused at high magnifications.

but with the central obstruction. i can't tell anything. it looks identical/the same either side. not even the smallest particular difference I can tell from it.
smoothly transitions between either side of focus. and infocus. and looks identical. even when just barely out of focus. a bit more out of focus. and a lot out of focus.
I'm using recommende central obstruction size also. which turns out to be very similar in size to an eyepiece dust cover/cap so convenient.
I also tried with the green filter with the central obstuction but got the same results too. just darker image.

Any idea what my results here would mean for my 70mm F6 achromat doublet telescope? in terms of image quality and whatnot?
Svbony SV503 70mm ED F6 420mm FL refractor telescope (New)
Canon EOS 100D/SL1
Tamron 18-200mm F3.5-F6.3 II VC lens
canon 50mm STM F1.8
svbony 8-24mm zoom eyepiece
svbony goldline 66 degree 9mm and 6mm + 40mm plossl + 2x barlow.
svbony UHC 1.25 filter + astromania 1.25" O-3 filter + also an svbony H-B filter.
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Re: Star test 70mm F6 achromat doublet. with and without central obstruction. + green filter

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Post by realflow100 »


double double is splittable at 140x but I wouldn't say its a clean split. More of I can just see them as a peanut shape. their airy disks are just touching. from what I can see.
Svbony SV503 70mm ED F6 420mm FL refractor telescope (New)
Canon EOS 100D/SL1
Tamron 18-200mm F3.5-F6.3 II VC lens
canon 50mm STM F1.8
svbony 8-24mm zoom eyepiece
svbony goldline 66 degree 9mm and 6mm + 40mm plossl + 2x barlow.
svbony UHC 1.25 filter + astromania 1.25" O-3 filter + also an svbony H-B filter.
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realflow100 United States of America
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Re: Star test 70mm F6 achromat doublet. with and without central obstruction. + green filter

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Post by realflow100 »


I usually find the atmosphere is more of a problem than the optical quality of the telescope itself. at 70x or higher sometimes the atmosphere is really bad. causing significantly more degredation to the image than the telescopes optical quality.
and 140x can be horrible if the atmosphere is really bad. No detail at all. even hard to focus on bright stars.

Sometimes its so bad even 40x doesnt look very good. and very difficult to focus.

I one time had atmosphere turbulence SO BAD even 11x had tons of turbulence visible on the moon. very hard to focus.
Svbony SV503 70mm ED F6 420mm FL refractor telescope (New)
Canon EOS 100D/SL1
Tamron 18-200mm F3.5-F6.3 II VC lens
canon 50mm STM F1.8
svbony 8-24mm zoom eyepiece
svbony goldline 66 degree 9mm and 6mm + 40mm plossl + 2x barlow.
svbony UHC 1.25 filter + astromania 1.25" O-3 filter + also an svbony H-B filter.
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