## 1815RE: [ccd-newastro] Re: Can someone let me use their M101 B channel?

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• Apr 1, 2001
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You can do the subtraction in Maxim. If you don't normalize the images first
(subtract using pixel math so all have the same background level), you can
compensate for color level differences using Color Balance on the color

Perform the subtractions in Maxim DL:

1. Open the L, G, R images.
2. Make the L image current.
3. Use the Process | Pixel math menu option.
4. Make the L image Image A.
5. Scale factor is 100%.
6. Make the operation Subtract.
7. Make the G image, Image B. Scale factor 100%.
8. Make sure add constant is set to zero.
9. Click OK to subtract the green image from the L image.
10. Repeat, subtracting the red image from the result of step 9.
11. Save as "M51_synth_B.fit" or use your own naming convention.
12. Color combine using original L, R, G, and synth_B images.

The New CCD Astronomy
http://www.newastro.com

-----Original Message-----
From: jeffh@... [mailto:jeffh@...]
Sent: Saturday, March 31, 2001 7:15 PM
To: ccd-newastro@yahoogroups.com
Subject: [ccd-newastro] Re: Can someone let me use their M101 B channel?

Yeah, I already thought of that--but I wasn't sure of how to do it
with the software I have available. Actually, I thought someone like
you would see this and tell me how <g>. I've got MaxImDL and PS
6.0...

Anyone know how to do this subtraction?

Jeff

--- In ccd-newastro@y..., "Eddie Trimarchi" <eddiet@b...> wrote:
> You could try synthesising a B image from what you have.
>
> Theoretically L = R + G + B
> so B = L - R - G
>
> The trick is matching the levels first so that the B data is
meaningful.
>
> It can be done though.
>
> Regards,
>
> Eddie Trimarchi
> ~~~~~~~~~~~~~~~
> http://users.fan.net.au/~eddiet
>
> >-----Original Message-----
> >From: jeffh@n... [mailto:jeffh@n...]
> >Sent: Sunday, April 01, 2001 9:43 AM
> >To: ccd-newastro@y...
> >Subject: [ccd-newastro] Can someone let me use their M101 B
channel?
> >
> >
> >It's snowing again here in WI, and I'm Jonesin' for some
astronomy.
> >A few weeks back I got 1 hour of L, and 30 minutes each of R and G
of
> >M101 at full resolution on my ST8E. I'd like to be able to stitch
> >together the whole image, but my blue image was lost when my mount
> >broke and stopped tracking (Ron W, if you're reading this you may
be
> >
> >Anyway, I would prefer a full-resolution image from an ST8E,
> >somewhere in the 30-45 minute range, but I'll take whatever. I
was
> >using a 5" refractor at f/8 if that gives any else any idea of
scale,
> >but again, that's less relevant.
> >
> >I'd just like to get some practice with my LRGB processing of
> >galaxies, and besides an M51 shot that I have whipped like a dead
> >horse, this is the only other I have.
> >
> >Anybody willing to help? I have broadband, so you can send me
large
> >files...you'll save me from the "snowy, cloudy skies blues."
> >
> >Feel free to email them to me.
> >
> >Jeff
> >
> >
> >
> >To unsubscribe from this group, send an email to:
> >ccd-newastro-unsubscribe@egroups.com
> >
> >
> >
> >Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> >
> >
> >

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