gso rc8 focal reducer/corrector

[xcoupeb]

I have decided to step up from my ed80 to a gso rc8 with my imaging and have been trawling threads here and elsewhere on the net about flatteners and reducers for this scope.

It seems people are having varying degrees of success with different brands of flatteners etc however i havent found much info about what works with larger sensors. i have a 5d mark 2 which has the 24*36 sensor and am curious what other users with the same scope and large sensor cameras are using to avoid vignetting and getting flat field.

I have found a gso .75 reducer/corrector on Teleskop-express website which they say is for rc scopes-has anyone seen these or used one?
http://www.teleskop-express.de/shop/product_info.php?products_id=3823#z ubehoer

Camera side of the reducer they say has m48 thread is this the right thread for a wide t ring and not the usual t ring?


thanks
Gavin

[TrevorW]

I use a WO F2 .8 reducer works fine

[xcoupeb]

Thanks Trevor for responding, I see that reducer has been discontinued however the wo 4 looks like it would illuminate the whole chip anyone tried one of these with rc8? Alternatively are there any other suggestions?

[RickS]

The Astro-Physics reducers work well with the RC10, so I expect they'd work with the RC8 as well. I have the 27TVPH and I'm very happy with it. Others report good results with the CCDT67, but the image circle might be a bit small with your large sensor.

Cheers,
Rick.

[xcoupeb]

Thanks rick yes I have seen the ccdt67 supposedly only illuminates a field of 29mm which would be too small will have a look at the 27tvph. Also I enquired about the gso reducer at teleskop express they said they have no idea when it will be available. Guess a bit more research is in order

[JohnH]

I have the CCDT67 - and it works well with the RC10 and illuminates the APS size sensor on my Canon 20D.

BUT

It is a reducer only so you get field curvature in your image - quite normal for the RC design. With a full size sensor and an RC8 I expect you will see this issue. I think you will need a flattener more than a reducer - the HOTECH units get good reports.

Flatteners require exact CCD spacing to work well - reducers are not so sensitive (but you will not get the rated reduction if the sacing is not by the book).

The WO unit is a flattener/reducer and has adjutable spacing...but I do not think it works on the RC design - it is intended for refractors.

John.

[xcoupeb]

thanks John, the Hotech looks good and has the thread for bigger t ring which should help with vignetting. i have found another flattener which is stated to work well with rc8 and 10 and if i couple this with a wide t ring hopefully wouldnt get any vignetting

http://www.teleskop-express.de/shop/product_info.php/info/p4006_TS-2--corrector-for-GSO-Ritchey-Chr-tiens-w-o-focal-reduction.html

At least there are a few options out there for big sensors on these rc's