From: Phil Houston <pkh111@knology.net>

Date: April 14, 2008 8:16:58 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Lines of Saturn

Hi Milton,

Today I ran a few more tests with the DMK camera.  Here is what I found.

1 Using various firewire cables, 6 ft. and a 3 ft., no reduction in banding was observed. 

2 The banding was seen only when capturing at 15 FPS.  None at 30 or 7.5 using the same shutter speeds.

3 Histogram stretch showed wide vertical bands originating from the left side of the frame and fading towards the center of the frame.

4 The upper portion of the frame was lighter than the lower half when the shutter speed was set at 33 ms. and moved as the shutter speed was varied.

5 There was no difference if the laptop was using battery power or used with the power adapter.

Here is a link to a single frame, daytime image.  This image has not been processed and the banding is harder to see but I'd guess if a stack were aligned and processed the effect would be quite noticeable.

http://www.knology.net/~pkh111/camera_test.jpg

I can't believe this is normal and that I did not notice this before now.  Tomorrow I will contact the nice folks at The Imaging Source and see what they say.

Thank you Milton and Alan for jumping in to help me with this issue.

Phil

On Apr 14, 2008, at 12:00 AM, Milton Aupperle wrote:

Hi Phil;

A 5 meter FireWire cable could be the problem too.

FireWire 400 is technically only only rated for 1.5 meters without a repeater, although if it's very good quality cable (well insulated) and has Ferrite beads on it, it may be okay that long. FireWire 800 is rated out to 100 meters at FW400 speeds (I might be wrong on the speed though -  would need to re-read the spec).

My longest cable here is 3 meters and it has ferrite beads on it. I use a hub repeater if I need more.

The other thing is making sure the cable is not picking up EM noise from some power source or powered device.

When I worked for Vitana / PixelLink, we had an awful time getting some cameras passed for CE EM emissions because of cable issues. Once we swapped out the standard cable for a "Granite" one with Ferrite beads we passes with flying colors.

Possibly the reason you didn't see the noise at longer exposures or 2x2 mode is because it shifts over time and gets blended in.

HTH..

Milton Aupperle