From: Milton Aupperle <milton@outcastsoft.com>

Date: June 25, 2005 11:44:20 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: a couple of questions

Tim;

On 25-Jun-05, at 11:05 AM, Tim wrote:

Disadvantage of using a film can is that you're "stuck" with the IR blocking filter that came

with the camera. I can't remember whether it's easy to get off the fire-i or not.

The IR filter on the UniBrain and every other FireWire Web camera I've seen is on the back of the screw out lens. So once you remove the lens, you have lots of IR hitting the CCD. I showed the difference that this can make for color balance on page 37 of the manual.

For the Unibrain's, I bought a 15 mm square Glass IR filter for about $25 US (after customs, taxes shipping fees it was $65 CDN) form Edmund Optics and then have it mounted in my C-Mount to M42 adapter so I can use it with multiple cameras. For lunar or solar images, it's frankly necessary to get good color saturation and avoid loss of focus too.

I have a Lumicon focal reducer that I bought for DSO imaging with a Meade DSI Pro that I

also recently purchased. I don't use it with the webcams, though, as they're strictly for

planetary imaging (for me). I did experiment with the fire-i on M13 with the focal reducer

on my C9.25 at f/5, though, and couldn't see anything at all. But I didn't spend a lot of

time trying to refocus, and that may have been the problem.

I use a MOOG focal reducer and by increasing the distance from the CCD to the back of the Focal Reduce to about 100 mm, my MAK 127 mm aperture / 1540 mm focal length scope has an effective focal length of 550 mm. There is some vignetting and light fall off on the edges, but it does give me a decent FOV 0.49° x 0.37° with the Flea 1/3" CCD and 0.37° x 0.28° for the Unibrain type 1/4" CCD's. And the shorter the focal length, the less stringent you have to be for tracking too.

HTH..

Milton J. Aupperle

President

ASC - Aupperle Services and Contracting

Mac Software (Drivers, Components and Application) Specialist

#1005 - 815 14th Avenue. S.W.

Calgary Alberta Canada T2R0N5

1-(403)-229-9456

milton@outcastsoft.com