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New C8-A and optics question

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#1 AJK 547

AJK 547

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Posted 15 May 2019 - 04:50 PM

Since last Aug. I've been having lots of fun using my then new 6SE on Solar, Doubles, bright DSO's,etc. The views have been highly rewarding. I did numerous 'Star tests' @ 150X and the little 'scope gives me a distinct star 'snap test'... no astigmatism, no 'pinched optics'... and excellent concentric rings on both sides of focus. Happy camper.

Just this Mon. I recv'd a new C8-A (XLT) and the weather cooperated with very good transparency and 'seeing'. After letting the C8-A cool for 6 hrs to ambient, I turned the C8-A on Polaris @ 200X... got a great star 'snap test'... no astigmatism... no pinched optics... excellent concentric ring pattern around the CO (outside focus), BUT as I racked the focus to 'inside' there was only a slight development of concentric 'rings' between the bright outer ring and inner ring around the CO. The C8-A is also in VG collimation. The initial Lunar views late last Mon. were EXCELLENT with great contrast and resolution. Easily better than the 6SE. The initial views of Jupiter gave me my first ever view of the general detail of the GRS (well actually the 'faded' GRS) at 2:40am... smile.gif

Question, with a good 'snap test' and resolution capabilities of this C8-A, does a lack of total development of a concentric ring patterns on only one side of focus mean anything is amiss?

Thanks for any insight in advance!

Edited by AJK 547, 16 May 2019 - 03:00 AM.


#2 Eddgie

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Posted 15 May 2019 - 07:50 PM

Normal.  When you rack out so that 4 or 5 rings can be seen the inside and outside rings will be bright (and if the optic is good, they will appear equally bright) and the 2 or 3 interior rings will be fainter and thinner.  That is normal behavior.


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#3 AJK 547

AJK 547

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Posted 15 May 2019 - 08:46 PM

Thanks Eddgie! I was pulling 4 to 5 sharp concentric rings (of equal brightness) on one side of focus which really pleased me. Polaris A/B is again tack sharp with Pol. B being a nice tiny sharp point of light.

FWIW, the 'seeing' tonight in Chicago is VG and I just finished a lunar session at 450X. I'm very pleased with the resolution and contrast of this new C8-A, and hope to further test on Jupiter and Saturn again at 2am this coming morning.

Thanks again so much for your reply!

Edited by AJK 547, 15 May 2019 - 09:41 PM.



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