Focal reducer for 204-6 ?

[dd]

I've just ordered a 204-6, and I was told it will take 9-12 weeks.  Very excited for the big day.   My question is, will there be a focal reducer for it ?  I'm assuming that's what a Raycorr lens is, but I really don't know.  There isn't much information on Raycorr or reducers for this scope.  Can you please enlighten me ?

thanks,
Dave 

[mikey cee]

Dave you struck out on both counts. At F/6 you don't want a focal reducer you want a barlow lens. No the Raycorr was a piece of pie in the sky. It was for color correction of the achromatic doublets.......it wouldn't have affected your magnification or FOV. Mike

[astromanuk]

Hi dd,

Congratulations on your new telescope. I am sure you will enjoy it immensely.

I have the same model and have nearly finished putting together a mount for it - just in time for the spring galaxy season.

I cannot see a reducer ever being marketed for such a short focus achromat, nor a chromatic aberration corrector. These big, short focus achromats are built to do one thing extremely well and at a reasonable price. That is low power wide fields where the chromatic error can be tamed with modern narrow band filters.

I will be posting some pictures of mine as soon as it is complete. Keep us In touch with the progress on your new 'scope!

[dd]

Hi Ian,

Thanks for the reply. My goal is narrowband imaging, but occasionally I might try visual viewing. So what do people do about the terrible CA of these scopes ? Fringe killers ? Moon and Skyglow filters ? Minus V filters ?

Is there some kind of field flattener I can use on the scope for imaging ?

Dave

[astromanuk]

Mar 23, 2014 8:42:18 GMT -5 dd said:

Hi Ian,

Thanks for the reply. My goal is narrowband imaging, but occasionally I might try visual viewing. So what do people do about the terrible CA of these scopes ? Fringe killers ? Moon and Skyglow filters ? Minus V filters ?

Is there some kind of field flattener I can use on the scope for imaging ?

Dave

Dave,

With the amount of CA this 'scope generates filtering needs to be quite aggressive. Baader in Germany do several good filters. My favourites in short achromats have always been narrowband such as Olll or Hb. Also for general work the Televue nebustar filter is excellent.

As I have purchased my 204/1200 solely for visual work on a narrow selection of objects including comets, galaxies and nebulae. I am principally going to be using powers of under 100x and no bright objects so CA will not be noticeably disruptive.

I do not know what your previous instruments have been but have a look at the work of JP and his 9" Istar which is optimised for Ha. His exceptional images show what an experienced imager can achieve with an achromatic telescope. Although JP' s telescope is optimised for solar work his images of Jupiter and the Orion nebulae have to be seen to be believed.