From: Milton Aupperle <milton@outcastsoft.com>

Date: October 28, 2009 5:07:23 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] IR/UV-Cut filters....

On 28-Oct-09, at 4:47 PM, Mark Gaffney wrote:

P.S. I understand the IR-Cut filter on the PGR cameras is a feature of  

just the colour cameras & that it can be removed from them only by  

dismantling the camera..?

It depends on which camera and the generation your talking about. The Flea I have (about 4 years old now) required dismantling the camera to remove it, which was doable but voided the warranty. Later model cameras (Flea 2, Grasshopper etc.) may have the filter removed by undoing some screws to loosen a front plate, which means the camera doesn't require disassembly.

And the only reason I removed the filter was because the IR cut filter that PGR used had cut off into the red band Hydrogen Alpha (about 656 angstroms) to about 50%. Perhaps the filters they use now don't do that now. I use a IDAS UV/IR cut filter now for imaging with the Flea now. For guiding,  I have the CCD naked so I can pick up every photon of light especially at 9th magnitude and the small pick off prism.

The filter helps keep the CCD clean too, as the electrical  charge on it may draw in dust. If your in a dusty environment and are swapping camera parts a lot, you'll likely need to clean the CCD a lot.

HTH..

Milton J. Aupperle