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Been sold the incorrect type of 2" diagonal for a SCT OTA, please help.


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Hello everyone, I've just bought this diagonal from a fellow forum member, Celestron 2-inch XLT Diagonal (Refractor) 93526

He sold it as a 2" diagonal for a SCT OTA, a genuine mistake. Hi is willing to return the cheque, but I was thinking if its possible to buy an adaptor to make it fit my new C9.25 OTA. What part would I have to buy to make the item fit?

Thank you.

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Will this increase the focal length of the scope?

No, the focal length won't change. The focus position will change a bit but an SCT has lots of focus travel so that should not be a problem. I used one on a C8 and it worked fine.

I think it's actually a better solution than using an SCT-specific diagonal although it's a little heavier I suppose with the adapter contributing a few more grams.

If you get 2" filters you can screw them onto the end of the diagonal then you can change eyepieces leaving the filter in place.

Edited by John
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One thing you need to be careful about is will all your eyepieces come into focus? I have a similar diagonal and adapter but when using the focal reducer and a 30mm 2" eyepiece it wouldn't quite come into focus so I did need a proper SCT diagonal which does work fine with reducer and all eyepieces.

Mostly it is fine but did not work with that particular combination.

Dave

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The diagonal should have been a direct SCT fit one... unscrew the visual back (the piece on the back of the scope you put the EP's or diagonal into) and put the diagonal on in its place?

http://www.celestron.com/c3/product.php?ProdID=403

We bought them the same time.. and they were SCT fit ones unless Kev had bought a different one since of course....

Edited by Psychobilly
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One thing you need to be careful about is will all your eyepieces come into focus? I have a similar diagonal and adapter but when using the focal reducer and a 30mm 2" eyepiece it wouldn't quite come into focus so I did need a proper SCT diagonal which does work fine with reducer and all eyepieces.

Mostly it is fine but did not work with that particular combination.

Dave

Thinking about it, you are right Dave - the only problem I had was using the focal reducer. But because I'd moved to a 2" diagonal and could take advantage of the wider FoV of 2" eyepieces I didn't need to use the FR any more anyway.

That was for visual though, the situation for imaging might be different :eek:

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Would you like to swap what you have for a standard Meade 2 inch screw fit SCT diagonal? I have one of these and don't use it because I now have an aftermarket Crayford focuser which takes your type of diagonal. I no longer use the SCT one. Just a thought.

Olly

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Thinking about it, you are right Dave - the only problem I had was using the focal reducer. But because I'd moved to a 2" diagonal and could take advantage of the wider FoV of 2" eyepieces I didn't need to use the FR any more anyway.

That was for visual though, the situation for imaging might be different :eek:

I am using 2" diagonals, but I just wanted that wide view.

Dave

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The diagonal should have been a direct SCT fit one... unscrew the visual back (the piece on the back of the scope you put the EP's or diagonal into) and put the diagonal on in its place?

2-inch XLT Diagonal (SCT) (item #93527) / Optical Accessories / Accessories / Products / Celestron.com

We bought them the same time.. and they were SCT fit ones unless Kev had bought a different one since of course....

yeah its the same one, its weird cos i thought it was for SCT......KEV

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Hello everyone, I have removed the visual back, no way will it fit. Celestron did sell two different types of diagonals. This is the type that I have received, Celestron 2-inch XLT Diagonal (Refractor) 93526, made for a refractor type scope.

And this is the correct SCT type, David Hinds Ltd, as you can see. The OTA end is totally a different fixture, or am I missing something simple.

Thanks.

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It seems you do have the wrong type. I would either return it or accept Oly's offer or get the adapter but risk an eyepiece not coming into focus.

Dave

Edited by Dave Smith
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I use a 2" adapter (from OO) for my diagonal. I have no problems at all with focussing any of my eyepieces (se sig for details).

You can see it in this pic:

_D3H2178small.jpg

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would this fit into a normal 2" drawtube (e.g. for a newt?) and convert set screw to compression?

No, it's for SCT's only.

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Does the O O adaptor thread into the rear cell unit? Do you happen to remember where you bought it from and if you remember the part number?

Thanks.

Yes, you unscrew the 31.7mm and the 50.8mm replaces it. I've just had a look at OO's website and can't see it anywhere. Maybe as the new scopes are all fitted with 50.8mm now they have stopped making it?

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