rc6 visual ?

[omegacrux (David)]

Hi all
I am thinking of getting a gso rc6
I like the idea of the long focal length , compact body and no mirror flop
And I was wondering if they are any good as a visual scope.
Or are they just for AP
I have sent a pm to a member but collective wisdom is appreciated aswell

Thanks for any info Dave

[Amaranthus (Barry)]

Why do you care about mirror flop for visual?

[omegacrux (David)]

Its a pet hate when focusing

David

[Tinderboxsky (Steve)]

David, I am more a refractor user, however, I recall reading a number of comments on this forum that RC scopes are not considered highly for visual use. These comments have been driven by the RC design having a quite large secondary mirror in relation to the main mirror. This results in a central obstruction in the 40-50% range. Such a large obstruction adversely impacts the visual image, such as lowered contrast. Such a large obstruction is immaterial for astro photography.

Perhaps someone with actual visual experience using an RC can chime in on this.

Cheers

Steve.

[omegacrux (David)]

Yeah your probably right Steve
Might look at an 8in newt instead
I'm the same I like refractors aswell but the one I'd like is a bit out of budget.

Thanks David

[Regulus (Trevor)]

This interests me too and I would like to know if the image optimised fast GSO newt is ok for visual use?
Or is it projecting a flat field for camera film/sensors that would mean that some of the field will always be out of focus visually? And is this the same thing a RC does?

Trev

[Tinderboxsky (Steve)]

I think the fast imaging optimized newtonians (usually F4) are ok for visual but are not the best. Short focal lengths mean a steeper light gradient needing a larger secondary mirror (more obstruction and less contrasty images), higher coma distortion (needing a corrector), are more sensitive to focus, generally need better quality eyepieces to get reasonable results and need to be accurately collimated.

Slightly longer focal length newtonians (eg F5 or F6) are better suited to visual work - they have a smaller secondary mirror (better contrast), have less problems with coma, are much easier to focus, are more tolerant of lower quality eyepieces and are more tolerant of slight errors in collimation. Of course these will have a longer focal length, so a longer tube and a narrower field of view. I am thinking of a newt in time and am looking at an F6.3 focal ratio for visual work.

Having said that, many use short focal length newtonians for visual - most of the large aperture newtonians (set up as dobs) have focal ratios well under F5 to keep the length down and make them manageable.

Just come in from a session outside - a glorious clear night down here and have managed to track down Comet Linear in Horologium.

Cheers

Steve.

[Regulus (Trevor)]

Thx Steve.
Getting Linear is a nice reward.
Cloudy here but no rain (yet) :-(

[omegacrux (David)]

Looks like an 8in newt is the go
They are good value per inch
Thanks for the input

Ps Steve Linear good catch it must be very small

David

[pluto (Hugh)]

I viewed Jupiter through my RC6 a while back and I was amazed at how much less contrast there was between that and the views I was used to with my ED80 at the time.

[omegacrux (David)]

Thanks Hugh
I am chopping and changing my mind at the moment
Something will turn up that I think I desperately need !

David

[MattT]

Hi David,
My 10" f4.8 Newt is an imaging one, with a CO of 25% and I find my 6" f12 refractor gives more detail on solar system objects, Mars in particular. The Newt is miles ahead on DSO's. The only RC I looked through was a 12"...not that good as a visual scope, compact...yes.
Matt

[Paul Haese]

RC design is not good for visual work, simply because the secondary is so large it reduces contrast severely. By comparison a Newtonian of say around f4.5 will have a small secondary and will be nice for visually viewing faint and diffuse objects. My recommendation is to look at either a refractor or an 8" Newtonian. Either will be much better than an RC.

[alistairsam]

hi

are Mak-Cas's any good for visual? main attraction would be the compact size and smaller obstruction than an RC.

Newt is the way to go but if you want compact, the 6inch F5 newt is also decent for wide views. less light gathering, but if you have dark skies it might be ok. not sure though.

I've used an 8inchF4 for visual with an mpcc and eyepiece and although the mpcc is not designed for visual, it did reduce coma with an average eyepiece and 60 to 70% of the FOV was acceptable. nice wide field though.

the Paracorr type 1 is supposedly very good for coma correction with visual use. I had a view through an 18inch F4.5 SDM with a paracorr and nagler and was blown away with the stars, pinpoint right to the edge.

Cheers
Alistair

[omegacrux (David)]

Thanks for the input fellas
Yeah I'm leaning towards the 8in newt in f4-5 range
Or I just might get an eq3pro for the Ed80
Decisions decisions

David

[dannat (Daniel)]

an SCT is compact -is it just for visual?

[omegacrux (David)]

Yes it is Daniel

David