From: Milton Aupperle <milton@outcastsoft.com>

Date: January 21, 2010 8:21:41 PM MST

To: Astro_IIDC@yahoogroups.com

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


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.