From: Alan Friedman <alan@greatarrow.com>

Date: February 1, 2010 10:32:53 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Mars at Opposition

Damian's article is a good reference for the myriad factors that play on the contrast a telescope system can deliver... and quite the tease with that fine saturn image! 

There are many great debates on which telescope is best for visual planetary observing. It tends to be a free wheeling subject... fun, but subjective and dependent on the eye and bias of the observer. 

For imaging, I believe that central obstruction in and of itself is a minimal factor. The first thing we do in processing planetary images is apply a BIG boost to image contrast with unsharp mask or other similar routines. In fact, potential resolution is increased by an obstruction as the size of the airy disk is reduced by the introduction of a central obstruction into the optical path. 

Factors most important to planetary image quality are aperture, thermal stability, collimation, optical quality and, or course, seeing. This is evidenced in the wealth of superb planetary images being made by users of off the shelf SCTs with a central obstruction of 35-40% and large newtonians on tracking platforms. The C14 is probably responsible for more superb images than any other single telescope model.

If I could buy any one thing to improve my planetary imaging results, it would be a house in southern Florida.

cheers,

Alan

On Feb 1, 2010, at 11:31 AM, Ray Byrne wrote:

Hi Jim and All,

Here's a link that may be of interest:

<http://www.damianpeach.com/simulation.htm>

ATB

Ray

On 1 Feb 2010, at 16:13, Jim Chung wrote:

Hi Milton,

I've been following the CN thread about this scope design. Until I 
see it in person it almost seems like magic. I too always thought
that any central obstruction reduces contrast.

Jim