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Barcon and CA

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#1 jtaylor996

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Posted 16 November 2012 - 11:50 AM

I've noticed some CA on my scope when using the Denk II's on jupiter lately.

Since I don't have a ton of EP pairs yet, I was sort of assuming this had to do with the barlows I've been using. At lower mag I could barely detect any, but on higher mags it was clearly there.

It's not like I've been using poor quality barlows, either: seibert 3x and 4x, TMB 1.8x. However, they all had some CA.

This was leading me to think it may be the prisms or the D21's. I'm still not sure where the CA is coming from.

Yesterday I got a pair of Paradigm 12mm and a BARCON in the mail. Viewing with the BARCON and paradigms at higher magnifications I noticed a remarkable drop in observed CA (other than some serious lateral CA present on the outer 10% of the paradigm field, which was clearly due to the eyepiece).

I suppose I can put some of my known CA-free mono EPs in one side to test things further, but has anyone here noticed a similar remarkable reduction in CA from using the BARCON barlow? Or do you think it's possibly an issue with the D21's vs ATP12's?

#2 Mike B

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Posted 16 November 2012 - 02:00 PM

Couldn't say. But i *could* ask: Which scope is the CA exhibited in? If the Dob in your sigline, then are you also using the Denk Newt OCA? And you don't see the same effect with the same EP(s) used "mono"? Perhaps it's then a prism alignment issue?

I use a Denk II also, and not in my former SCT, nor in my current Dob (w/ the Newt OCA), have i seen what you're describing. Now, i'm growing to suspect there may be a twinge of prism-induced SA? But that's another issue, and a fairly well-known one. But no CA here.

Hope you can get that tracked down & remedied!
:grin:

#3 jtaylor996

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Posted 16 November 2012 - 02:42 PM

I'm using one of these. So CA shouldn't really be a problem ;)

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Mine is XC0007, you know, cause the sky is falling, and someone as cool as James Bond like me has got to be watching :cool:

#4 Mike B

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Posted 16 November 2012 - 03:00 PM

Yeah, ya wouldn't think, eh?

Perhaps Moneypenny dropped your Denks before you received them? Maybe have Russ give 'em a thorough check-up?... before they explode.

M

#5 jtaylor996

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Posted 16 November 2012 - 03:51 PM

I bought them used, and then sent them off for a 'Russ'ing about 2 years ago. They mostly been in storage since. I can't quite imagine there's anything wrong with them.

I'll have to do some more testing in mono mode tonight to get a better idea of the component that may be causing the issue.






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