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NGC 6559

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Re: 5" Achro Optical Test

Started by 1953, 10/17/2006 02:56PM
Posted 10/17/2006 02:56PM Opening Post

I too would choose a less bright, more yellow star. Regardless, it sounds as if the optical system (including primary, diagonal & eyepiece) may be under-corrected. What you describe is exactly what I saw with my AR5. The real trick is judging just how under-corrected it is. Then is it really a "problem"? Try for 4 rings inside and outside of focus. Are the inside of focus rings a whole lot sharper than the outside ones? If it's fairly subtle (and you have to look past or ignore the color distortions as much as you can) youre scope is only mildly undercorrected.

Of course, if it gives nice sharp images of the moon and planets, who cares as that's what really matters.

Also, you might be able to snag a used Chromacor O1. With carefull set up, it will reduce the under-correction (which will sharpen up the image even more)and greatly reduce the secondary color as well. Of course it will cost you ~3 times what you paid for the AR5 8O , but IMHO, it's worth it.


"Don't sweat the petty things and don't pet the sweaty things" 8O