From: Mark Gaffney <markgaffney@me.com>

Date: January 21, 2010 8:45:40 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: New AstroIIDC user

Hi Milton, 

I thought I read that your Grasshopper is 4.4 microns too, is this the case? I guess there maybe other versions? I told the guy from Adelaide I`d get back to him with respect to the Astrodon`s but not at his exhorbitant price! Kurt`s just written with qualified praise for the Baader`s for their price. Do you think they`d be better than your run-of the -mill types like perhaps the Astonomicks, or any good at all?

Mark.

On 22/01/2010, at 2:21 PM, Milton Aupperle wrote:

Parfocal means you basically don't need to re-focus when you switch
filters, assuming of course they are properly seated in the filter
wheel.

http://www.astrodon.com/Orphan/parfocal_and_critical_focus_zone/

If you've used a cheap set of filters, you know what I'm talking
about, as you have to re-focus each time you change the filters. When
your brightest star in the FOV is mag 12, trying to focus on it nearly
impossible.

As to your Scorpion, it's not a great CCD for Deep Space Objects as it
has small 4.4 pixels which gather less light per pixel than other
CCD's. A 5.6 micron pixel CCD (like in the TIS mono camera) will
gather 1.6 times as much light as the 4.4 micron Scorpion pixels do
for the same exposure time. So to do the same density of exposure, you
need to expose the Scorpion 1.6 times as long as you would the TIS
camera would.

Milton Aupperle

On 21-Jan-10, at 8:04 PM, Mark Gaffney wrote:

>
>
> Well I`ve bookmarked the Astrodon link on the page below to the E
> series 2 filters to look at later-the Baader link is to Orion which
> is no good to me..The questions are; how important is the parfocal
> factor (the Baader link I found eleswhere dosen`t mention this
> factor.) & how compatible are either of the above with the Scorpion
> 20SO?
>
> Mark.