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samtheeagle

Objective Lens Scratch (tiny) - Should I worry?

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HI all, I've just recently picked up a C80ED-R from off the forums here, and overall it's in great nick, but there does appear to be one very small scratch on the objective. Now my gut feeling is that this wont affect the performance one little bit, but it'd be nice if someone more knowledgeable could confirm that for me. :D

Thanks in advance.

post-16299-133877454339_thumb.jpg

Edited by samtheeagle

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I think thats very small to have any type of real effect, mind you I have seen worse.

BTW the C80ED & C100ED's are legends, too bad it's just the focuser which lets the scope down, but you could add some teflon pads to the drawtube or change the focuser altogether.

Nadeem..

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:D Thanks Nadeem. I spent an hour or so stripping the scope down last night. It was fairly dusty, and there was a scary amount of metal shards from the manufacturing process floating about in there. It's pretty immaculately clean now, and it's only really that small scratch that is a bit of a concern. Just using it visually on some distant trees I couldn't see any kind of problem caused by the scratch, so I assume that imaging probably wont be affected either.

I've only ever had rack an pinion focusers, so I guess I don't know what I'm missing out on, but as R&Ps go this one seems quite nice. And yup, I've already regreased and added teflon strips to the rails inside the focuser. It's rather more solid feeling now :D

Just wish that this cloud would clear off for a night!

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I wouldn't worry too much about it- think of it as a piece of dust; it will have little or no effect on the final image.

Ken

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my gut feeling is that this wont affect the performance one little bit

Your gut is perfectly correct. If the scratch was considerably worse than this, there might be a barely noticeable loss of contrast. A scratch that small will have no effect whatsoever, unless you wish to use the scope for a coronagraph, when scattered light is at an absolute premium.

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Thanks guys, my mind is suitably at ease now :D

Nadeem, as a C80 veteran I might have to pick your brains as to accessories! Not that I can afford any right now, but high up on the shopping list is a flattener / reducer. I think you've said previously that the WO FFII is a good match, but they're hard to come by these days. What do you use? In fact does the scope even need a flattener?

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The WO Flattener is a good match for it, but their hard to get hold off as thet have been discontinued. The next best thing which is meant to be optically matched for the scope is the SW 0.85x Focal Reducers, Steve from FLO, is meant to be arranging some 2" push fit adaptors to fit onto the reducers so they can be used with other scopes. Or you can try a televue reducer... Tell you the truth, I never imaged without the reducer, so I cant comment what the effects were without one.

Nadeem..

Edited by Deneb

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Well I guess I'll find out what field curvature you get at some point. Forecast suggests there might be a chance on Friday night, which will be too good to pass up if it happens. Shame I need to be up early Saturday morning :S

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Well, i think i'll have a bash with C80ED on friday night, then get mak-newt out on saturday or vice versa, depending what the weather man says..

Nadeem.

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You can always use CCDInspector to verify the field curvature and squareness.

Ken

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...get mak-newt out on saturday or vice versa, depending what the weather man says..

Nadeem.

Ah so that was your "last" scope... Nice choice :D

Peter...

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