From: Milton Aupperle <milton@outcastsoft.com>

Date: April 15, 2005 1:00:56 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] some pictures

Hi Neale;

The difference is that the Apple's or IOXperts drivers would leave the Auto color and Auto  brightness options enabled for the IIDC web cameras. That fine for talking heads and video conferencing, but pretty useless for scientific imaging especially when doing composites of multiple frames..

With Astro IIDC, those hardware options are always turned off so that they won't affect the image brightness or color balance and they stay constant.

Also, Apple and IOXPerts deliver YUV411 (every 4 luma pixels share a single red and blue color) video frames, so you get some very wicked color aliasing when you cross over a high contrast area like the moons limb. In Astro IIDC I extract the raw CCD Bayer camera data and convert it to RGB directly, so there is no color aliasing going on.

The reason Apple / IOXperts use YUV411 is because that is the only "normal" color format that can be delivered at 30 fps - but Astro IIDC rewrites part of the cameras firmware to force it to deliver bayer 8 bit color at 30 fps.

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

www.outcastsoft.com

On 15-Apr-05, at 12:08 PM, neale_monks wrote:

Milton,

Added a couple of pictures to the "Planetary" folder and one of the Moon to the "Files"

section.

What's interesting about this latter is that what you are looking at are unprocessed frames

stuck together in Photoshop. Usually, I have found that the brightness varies a great deal

between the limb of the Moon and the surface closer to the terminator. This seems to

throw the webcam off, and the colour balance is totally different in some frames compared

with others. Net result, I need to adjust each frame in Photoshop so that the joins can't be

seen. If I don't, I get this:

http://www.applelust.com/scitech/archives/graphics/m020405moonlg.jpg

Somehow, this didn't happen when used Astro IIDC. Brightness is very uniform, and each

frame blends with the next almost imperceptibly.

Cheers,

Neale

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