Loading ...
Sorry, an error occurred while loading the content.

1823RE: [ccd-newastro] Re: Can someone let me use their M101 B channel?

Expand Messages
  • Ron Wodaski
    Apr 1 12:34 PM
    • 0 Attachment
      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
      menu.

      Perform the subtractions in Maxim DL:

      0. Perform image calibration (darks and flats) and normalize.
      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.

      To normalize, perform pixel math setting the operation to None and the "add
      constant" to a negative number equal to the average background value - 50.
      This is not terribly effective if there is a gradient, however; in that
      case, normalize to the same location in all of the image, since there isn't
      really an average background due to the gradient. For example, use the value
      at the upper left of each image.


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

      -----Original Message-----
      From: jeffh@... [mailto:jeffh@...]
      Sent: Sunday, April 01, 2001 11:28 AM
      To: ccd-newastro@yahoogroups.com
      Subject: [ccd-newastro] Re: Can someone let me use their M101 B channel?


      Ron,

      I did have the L-channels IR blocked, probably doubly so, since I had
      the SBIG/Custom Scientific IR-blocking filter and the IDAS LPS filter
      in place (and I know that blocks a good bit of IR).

      However, I didn't get the instructions from you on to use MaxIm to do
      this subtraction. Email error?

      Can you post here or try again?

      Thanks,

      Jeff

      --- In ccd-newastro@y..., "Ron Wodaski" <ronw@n...> wrote:
      > This won't work well unless the L image was done with IR blocking.
      > Otherwise, you have IR + R + B + G in the original image, and
      performing
      > just L - R - G will leave you with B + IR.
      >
      > I've sent instructions for how to do this in Maxim separately. Be
      sure to do
      > darks and flats before you perform the math.
      >
      > Ron Wodaski
      > The New CCD Astronomy
      > http://www.newastro.com
      >
      > -----Original Message-----
      > From: jeffh@n... [mailto:jeffh@n...]
      > Sent: Saturday, March 31, 2001 7:15 PM
      > To: ccd-newastro@y...
      > 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
      > > >pleased to know that I traded up to an NJP).
      > > >
      > > >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/
      > > >
      > > >
      > > >
      >
      >
      >
      > 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/



      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/
    • Show all 14 messages in this topic