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wokka Tuesday 24th September 2019 18:34

First go at star test, help with results
2 Attachment(s)
Good evening,

Iíve just conducted an artificial star test on my second hand Kowa 773 with a 1.6 extender at 96x

Could anyone give me some advice on what Iím seeing, how good the scope is and especially what is the yellow line through the picture. Iím hoping to get a 883 next year and want to ensure I get a descent one by star testing it.

Thanks for any help you might be able to give.



Binastro Tuesday 24th September 2019 19:49

Looks like a prism line.
Maybe the stars are defocused too much?


jring Tuesday 24th September 2019 20:22


much less defocus is needed, you want 5 rings or so.

As for the line - roof prism edge was my first thought too, but it would be shocking if it was that visible... Also quite a coincidence to get it so nicely centered... As a first measure I would try to rotate the artificial star and check the line...


henry link Tuesday 24th September 2019 20:44

I agree there's far too much defocus. As for the line, if it's the roof edge of the scope it should be vertical unless the scope barrel has been rotated. Are you photographing through a roof prism binocular or small scope placed behind the 773's eyepiece?

wokka Tuesday 24th September 2019 21:14

Iíll give it another go tomorrow. Iím taking the picture with an iPhone Kowa scope attachment.

Any tips for taking pictures/ getting usable results with this setup?



jring Tuesday 24th September 2019 22:00

Hi Pete,

apart from too much defocus the images look very usable. What distance is your artificial star at? 30m or so would be great.


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