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21569Re: [ccd-newastro] A DIFFERENT CONCLUSION ABOUT 4" refractorRe: What would you buy with $10-12,000?

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  • Bill Bradford
    Jan 2, 2004
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      Hi Richard,
      Thanks a lot for the comparisons. I liked the way you used the filters on the Crab. It seems that I would be better of starting with a 9nm or 10nm filter.
      Regards and Happy New Year!
      ----- Original Message -----
      From: rdcrisp
      To: ccd-newastro@yahoogroups.com
      Sent: Thursday, January 01, 2004 11:41 PM
      Subject: [ccd-newastro] A DIFFERENT CONCLUSION ABOUT 4" refractorRe: What would you buy with $10-12,000?

      --- In ccd-newastro@yahoogroups.com, "Bill Bradford"
      <bcbradford@a...> wrote:
      > Richard,
      > Great example of images. What is your opinion as to the Ha filter
      that would enable you to image the greater number of targets. I saw
      that you used the 3nm a lot in your photos.

      I have two different Ha filters: a 3nm Custom Scientific and a 9nm
      Schuler. The Schuler really is an Ha + [NII] filter though: the two
      [NII] lines are just either side of the Ha line and are only about
      2nm separated. So the Schuler picks them all up. The Cust Sci doesn't

      The Cust Sci also doesn't let as much light through so it will not
      expose the detector as fast as the Schuler.

      I ended up putting my Schuler in my LRGB filter wheel as my 5th
      filter. My Cust Sci is in my Emission Line Filter wheel along with my
      other Cust Sci filters: [SII], [NII], [OIII] and Hbeta.

      I have obtained good results with both filters. For the ST10XME, it
      is nice to have a bit of a speedup so the Schuler is a good choice
      and particularly so if you want to self-guide because the Ha really
      socks the stars.

      I mostly use the Cust Sci with my FLI Dream Machine. With the higher
      quantum efficiency in the TK1024 back-illuminated detector and the
      huge 24 x 24 micron pixels, the camera is very very fast compared to
      my ST10XME. Just the geometry alone accounts for about a 9:1 speedup.
      So the greater attenuation going through the Cust Sci doesn't seem
      too bad with the DM. Some folks have been using the newer 4.5nm Cust
      Sci filters with good success, but I cannot speak to any first hand
      experiences with them.

      I did a comparsion shot of the Schuler versus Cust Sci filters back
      in mid 2002. I shot the Pelican: 6 x 10 minutes with each filter.
      Here's the comparision result:


      Because I was concerned about whether or not the 3nm Cust Sci filters
      really would separate [NII] from Ha, I shot a "tricolor" image of the
      Crab using Ha for Red and [NII] for both Green and Blue. If the data
      were the same in both filters, the color image would be greyscale
      basically. But it is not:


      Happy New Year!

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