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11-05-2006, 01:01 PM
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Registered User
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Join Date: Mar 2006
Location: Geeveston, Tasmania
Posts: 889
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2" eyepieces on a Celestron C8 SCT
The subject pretty much says it all. Can this be done and if so, why would it be a bad idea?
I'm in the process of ordering some new eyepieces and was considering 2" as opposed to 1.25" with a view to the future where I may want to upgrade my telescope.
The scope is a Celestron C8, SCT about 14 years old.
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11-05-2006, 01:09 PM
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~Dust bunny breeder~
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Join Date: Nov 2004
Location: The town of campbells
Posts: 12,359
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so does the c8 take 2" eps? if not then you could get an 1.25"-2" diagonal.
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11-05-2006, 01:34 PM
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Moderator
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Join Date: Apr 2005
Location: NEWCASTLE NSW Australia
Posts: 33,369
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It would be beautiful, if you can afford it get a WO 2" diagonal and then some good 2" eyepieces (don't have to be Nags, could be University optics, even a few GS ones would be ok to start with) , you will love it. if you can meet a few people in sydney area to have a look through their eyepieces then you will see the difference. This is of course entirely a personal viewpoint from me. You will know what you like after a look through one or two.
I personally like 2" EP's because I normally wear glasses to read etc, the eye relief is wonderful, the downside they can be heavy, filters are dearer, and you get guys like me drooling over them.................
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11-05-2006, 01:57 PM
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Join Date: Jul 2005
Location: Wentworth Falls NSW
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You would probably also need to get a 2" visual back.
As h0ughy say get a good 2" diagonal, these come with an insert so you can still use the 1.25 eyepieces until you replace them all.
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11-05-2006, 03:16 PM
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Join Date: Mar 2006
Location: Geeveston, Tasmania
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Not sure if there is a 2" visual back for the C8, nothing on the Celestron website, only for 9.25" and larger.
A quick web search also failed to turn up a 2" to 1.25" diagonal i.e. to connect to a 1.25" visual back and allow the use of 2" eyepieces. (Any details on these welcome)
Being impatient, I've just ordered a couple of 1.25" UO eyepieces from Frontier Optics. Should keep me going...
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11-05-2006, 04:00 PM
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Moderator
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Join Date: Apr 2005
Location: NEWCASTLE NSW Australia
Posts: 33,369
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Quote:
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Originally Posted by snowyskiesau
Not sure if there is a 2" visual back for the C8, nothing on the Celestron website, only for 9.25" and larger.
A quick web search also failed to turn up a 2" to 1.25" diagonal i.e. to connect to a 1.25" visual back and allow the use of 2" eyepieces. (Any details on these welcome)
Being impatient, I've just ordered a couple of 1.25" UO eyepieces from Frontier Optics. Should keep me going...
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Mate, a standard SCT is the C8, get a SCT threaded 2" diagonal, even the Bintel or andrews Dielectric one for 149 dollars will do. 
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11-05-2006, 04:01 PM
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Moderator
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Join Date: Apr 2005
Location: NEWCASTLE NSW Australia
Posts: 33,369
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that was you will not need the visual Back unless you want to do astrophotography, then you will need a refracter type 2" diagonal
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11-05-2006, 04:48 PM
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Registered User
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Join Date: Mar 2006
Location: Geeveston, Tasmania
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My education continues 
More web research is obviously required into this.
I might have to tell Daniel to hold that 1.25" order and replace it with bigger shiny things...
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11-05-2006, 08:14 PM
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Looking Down From Above
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Join Date: Dec 2005
Location: Cootamundra, NSW
Posts: 1,711
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You are going to need a 2" SCT adapter if you intend using a refractor type diagonal otherwise as already stated a screw on 2" SCT diagonal, bear in mind that any SCT under 10" will not give you a full 2" opening and, as such, the full potential of a 2" eyepiece is not reached, however, having said that, and having used an 8" SCT for a long time, you will definately get the wow effect with a good diagonal and a 35mm Panoptic.
JohnG
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11-05-2006, 08:17 PM
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Join Date: Jul 2005
Location: Wentworth Falls NSW
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One example
https://www.bintelshop.com.au/welcome.htm
Telescope accessories page 2
Bintel Star Diagonal 2" 99% (SCT) $95.00
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12-05-2006, 11:47 AM
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Join Date: Jun 2005
Location: Mornington Peninsula Victoria Australia
Posts: 337
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2" eyepieces are very nice for their expansive views.
Just need to remember that the 8" SCT's have a 38mm diameter exit from the baffle tube, upon which the primary mirror slides. This 38mm aperture may result in vignetting (seen as a gradual darkening of the view towards the edge of the field) if the field stop of the eyepiece exceeds 38mm. A 27mm Panoptic has a 30.5mm field stop so no vignetting, the 35mm Panoptic has a field stop of 38.7 mm, this is very close to 38mm so vignetting would barely be noticed, however, wide view eyepieces like the Konig Mk70 with a field stop of 46mm, or Nagler 31mm (42mm stop), are likely to show darkening towards the edge of the view.
Regards Mark
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12-05-2006, 02:30 PM
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Join Date: Mar 2006
Location: Geeveston, Tasmania
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I've stuck with the 1.25 eyepieces I've already ordered (16mm Konig, 12mm and 18mm HD Ortho). Perhaps the 2" option next time.
Thanks to everyone for the advice.
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