Why are RC scopes so special?

Tandum (Robin) · #1 22-09-2009, 12:18 AM

I don't understand why RC scopes are so special. To me they look like a Vixen VC200L with the correction being done in the mirrors rather than lenses in the focus tube. It seems there is a flaring problem from off axis stars with all of them, regardless of the manufacturer or cost. I've never heard of these issues with any other type of scope. Why buy one?

Gama · #2 22-09-2009, 12:35 AM

Nothing really so special, just another telescope design.
It does have a flatter and better imaging field then most.
Due to its mirrors only design, it introduces much less abberations than many others too.
The VC200L is another great design, again with a flat field, etc etc, as is the CDK, the corrected Newtonian etc..
Up to your individual needs/purpose i suppose.

Theo.

Tandum (Robin) · #3 22-09-2009, 12:50 AM

Theo, you own a monster RC, do you get this flaring problem that others have? Here's an example : http://www.iceinspace.com.au/forum/a...se.php?a=64300

And another :
http://www.atscope.com.au/BRO/gallery10.html

I'm thinking they make huge scopes as RC scopes as it's cheaper to make corrected mirrors than make corrected lenses.

Peter Ward · #4 22-09-2009, 10:39 AM

Quote:

Originally Posted by Tandum

Theo, you own a monster RC, do you get this flaring problem that others have? Here's an example : http://www.iceinspace.com.au/forum/a...se.php?a=64300

And another :
http://www.atscope.com.au/BRO/gallery10.html

I'm thinking they make huge scopes as RC scopes as it's cheaper to make corrected mirrors than make corrected lenses.

Put a bright star just outside a camera's FOV and all telescopes will show similar diffraction effect....its a basic property of light, not RC's .

Gama · #5 23-09-2009, 01:15 AM

Quote:

Originally Posted by Tandum

Theo, you own a monster RC, do you get this flaring problem that others have? Here's an example : http://www.iceinspace.com.au/forum/a...se.php?a=64300

And another :
http://www.atscope.com.au/BRO/gallery10.html

I'm thinking they make huge scopes as RC scopes as it's cheaper to make corrected mirrors than make corrected lenses.

Well, its not a monster RC, its a CDK, and just something i threw together from bits laying around for simple star gazing

.
But as Peter said, basically you have to live with it. You can reduce it for some types of off axis, but others, well..

I will put a bright star off axis and take a 5 minute sub and see how bad mine is. But, as of yet, i havent noticed any.

Theo

renormalised (Carl) · #6 23-09-2009, 10:24 AM

Quote:

Well, its not a monster RC, its a CDK

Which can be just as large...Planewave made a 40" CDK for an University in the US.

Any telescope can get flares in the optic train caused by off axis stars. Most abberations just get photoshopped out, or aren't as noticeable in the pics as they otherwise might be.

AlexN · #7 23-09-2009, 06:15 PM

For imaging in general, as Peter and Theo have mentioned, the RC design has a few upsides, the coma free design is a big plus. the lack of lenses of any description mean less abberations, the field is fairly flat, they do show some curvature on larger sensors though.. The CDK is another fine example of an astrograph designed with similar ideas, the CDK actually offers a flatter field, and better off-axis performance than the RC..

The RC comes into its own when doing Photometry/astrometry work.. the lack of coma across the field is a big upside in measuring stars for brightness/movement etc.

As Carl says, any optical design will show flares when you put a bright star just off axis... My newt did, my C11 did, all my refractors have (including the TMB) the RC did...

VISAC vs RC of equal build quality and accuracy, RC > VISAC