From: Alan Friedman <alan@greatarrow.com>

Date: April 22, 2005 1:23:34 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: saturn with five moons

Hi Neale -

I think you are absolutely correct on the role of aperture. In visual observing, issues (like central obstruction) that address producing the highest possible contrast at the eyepiece are important. For imaging, the issue is resolution which we will be a condition of aperture and focal length. Optics must be good and collimated and the instrument close to ambient temp. but you can always adjust the contrast in image processing - which is why many of the finest high resolution planetary images have come from production SCTs. 

It's interesting - 10" seems like a sweet spot for planetary subjects - not much additional detail has been captured with BIG (earthbound) scopes that is not seen in fine 10" images. But on the moon it is a different story - the bigger the scope, the smaller the craterlets that can be recorded. 

I hope you have checked out the Astromart CCD Imaging/ solar system forum - some very knowledgeable participants there - your skill level will advance quickly!!

Alan

On Apr 22, 2005, at 3:08 PM, neale_monks wrote:

Alan,

I'd agree with this wholeheartedly, though I admit I'm from the much less accomplished

end of the skill spectrum. Looking through what I've taken, it's not altogether obvious that 

the _theoretically_ best webcams have always been the ones I used to get my best 

pictures. Sometimes, but not always.

I think the telescope makes a big difference, though whether this is optics or additional 

factors like sensitivity to atmospheric conditions and thermal equilibrium is debatable. 

Aperture is also another factor that seems to get overlooked in the fuss over technology;

at least to me, a 10 inch / 250 mm aperture seems to be the threshold between "nice" and 

"awesome" shots of Saturn, for example. There may be some optical design constraints

here, so a good Mak-Newt or Apo with smaller aperture winning over bigger short focus

Newtonians or mass market SCTs.

Cheers,

Neale

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