From: Milton Aupperle <milton@outcastsoft.com>

Date: May 24, 2006 3:03:39 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Been a while!

Hi Duane;

On 24-May-06, at 2:28 PM, Duane wrote:

Those are the tips I am looking for.

As for the dark subtraction, it seems to help with a strange effect that fire-i board has.

There is a vertical seam right down the ccd, about 1/3 or more down. The color/density

on one side of this line is slightly different than the other. I haven't noticed it since I did

the dark subtract.

I think Alan also mentioned a fire-i he once had, did the same thing. I don't know if he

ever tried a dark subtraction. If anybody uses this camera, I'd like to know if yours has the

same problem.

That "vertical seam" is known as EM coupling noise. It shows up far more pronounced when you have the "CCD Over Drive option" enabled. As you change base CCD exposure or Camera Frame rate, the position of the "vertical seam" shifts horizontally. At faster frame rates it's closer to the center and at low rates it's closer to the left edge of the frame. Once your below 133 ms / 3.75 fps, it's pretty well gone. It's all dependent on how fast the frames are transmitted and slower rates have less noise.

Basically it's due to the layout of the camera electronics on the PCB and all the low cost cameras suffer from it, except for The Imaging Sources cameras (DMK DMM DFM DFK DBK DBM 21F04 series), but they aren't really "low cost" . The worse cameras were the iRez Stealth which also suffered from "random" diagonal interference noise too (see http://www.outcastsoft.com/AstroImages/MVMJS_04_03_28.jpg and notice the diagonal marks on Jupiter's limbs). That is the main reason we no longer officially support iRez.

And your solution to do a dark frame is a good choice and does help out quite a bit. I also use that when I'm guiding especially in Monochrome 2x2 binning modes with "CCD Over Drive option" enabled and the gains cranked up. It eliminates the edge noise a lot and helps Astro IIDC locate the star from the "noise".

I'll have to find some pure alcohol. I have a few motes and I think they are coming from

the filter.

Most Drug Stores should carry 99% Isopropyl alcohol, but you may have to ask them for it. They usually also have jugs of 99.9% pure distilled water too for medical purposes (i.e. treating burns, bathing wounds, eye wash etc.).

Drugstores are great place and is where I found a cordless gel pack heater / cooler at a drug store, which has been great for doing winter imaging. You toss it in a microwave, heat it up until it nearly burns your hands and then put it on the back of the LCD display to keep it from freezing solid and not updating anymore. It worked for a few hours at around -30°C to -40°C to keep the LCD above -20°C which is where it started freezing.

Sorry about posting. I'll refrain until I get something good :) or with more questions...

Not a problem. And if you had not posted it, we'd never have gotten into the discussion about what the "vertical seam" is or how to deal with it.

Hope That Helps..

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