From: Ray Byrne <ray@in4media.co.uk>

Date: February 1, 2010 4:49:10 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Mars at Opposition

Hi Alan and all,

I don't know about imaging but I put a little helper into action tonight that was an eye-opener. I've been a bit off astronomy for a while I can't explain it maybe it's lack of good results, terrible weather, others doing better with the same gear, my other hobby luring me away? Anyway tonight I went out to my observatory (it's perverse that my interest waned when everything is now so easy) and turned to Mars. The visual image was quite detailed at almost 400x (I'd tweaked my collimation very well last time I'd used the scope) but was boiling away most of the time with very few moments of clarity. I'd bought a TeleVue Mars type II filter a couple of apparitions ago and not really reckoned it much. I attached it to my Baader 6mm Ortho and it was like magic I could see loads more detail over areas that were "glared-out" without it and what I had been observing was far more apparent.

I didn't attempt imaging as I knew that cloud was very close but I was really bouyed-up by this and the fact that my scope was fit for action and my mount kept Mars dead centre for over an hour in the 6mm EP (I had to leave it for family stuff hence the break).

I feel like I'm back in the groove now and I also had great views of M42 with a 32mm earlier

ATB

Ray

On 1 Feb 2010, at 17:32, Alan Friedman wrote:

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