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About Merlin66

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    Bright Giant

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  • Interests
    Spectroscopy, Solar observing,- and my wife!
  • Location
    St Leonards, Vic, Australia
  1. Vlaiv, The grating dispersion is non-linear with wavelength, but usually so small it can be ignored. Robin's given you some useful answers. I'd just use what you have and see how the results pan out.
  2. Merlin66

    Julian Shaw's sombrero - with a surprise!

    My rule of thumb for solar imaging is focal ratio =x5 pixel size. Usually work around f25.
  3. Merlin66

    Julian Shaw's sombrero - with a surprise!

    Note also that the Meade Series 5000 x3 Extender is very similar to the ES and is telecentric design.
  4. The Herschel wedge with a ND3 filter is considered safe for all apertures. Addition filters - Continuum may improve the contrast.
  5. Merlin66

    SW 80ED - convert to 10:1?

    Hmmm... OK, I think your saying the end of the drawtube has a 56mm thread. This is where the 2" adaptor screws onto the drawtube? All the 10:1 focusers I have came from "other" ED scopes, so I'm not sure what the thread is on a generic GSO type focuser......
  6. Merlin66

    SW 80ED - convert to 10:1?

    What about this: https://www.ebay.com.au/i/123328294840?chn=ps
  7. Merlin66

    100mm APO scope

    John, Thanks for that. Always good to be corrected! Bang per buck I find it hard to go past a good ED doublet.....
  8. Merlin66

    100mm APO scope

    John, My SW ED80's are the older "Champagne" ED80 pro model. I think the newer "Black Diamond" versions us the Schott FPL 53 glass.
  9. Merlin66

    100mm APO scope

    Vlaiv, I use three ED80 scopes, I believe using FPL-51 glass. I don't see purple fringing and I'm not sure what the FPL-53 adds other than smart marketing. To achieve "APO" performance you need the corrections applied to three optical elements, a doublet can only be a compromise.
  10. Merlin66

    SW 80ED - convert to 10:1?

    Michael, I use three ED80's and I've converted them all to 10:1 focusers plus added a SW motor using a timing belt drive. I assume if the reducer screws onto the extisting focuser then it would also screw onto the replacement. ( I don't use one so can't confirm) Look for a 96mm fitment 10:1 Crayford.
  11. Merlin66

    Starting out in Spectroscopy?

    Robin's put you on the right path..... Check out our website for additional detail: http://www.astronomicalspectroscopy.com/
  12. Merlin66

    sun filter

    Peter, Based on my twenty odd years of solar observing and the extensive use of the Baader solar film, it's most unusual to get pinholes - the material is coated on both sides so the pinhole would have to be on both and align. (I keep my filters in a dust proof container when not in use) If a pinhole is found, it's not the end of the world. The increase in light reduces contrast and causes glare, certainly not a cause of eye damage. The pinhole can be covered by Typex or black marking pen - and life continues. It's of more concern to always have the filter securely fastened to the scope. Check, check again then do a final check.......
  13. Merlin66

    sun filter

    Many of us on numerous occasions have pointed out the unsafe nature of these filters....and still they continue.
  14. Merlin66

    M42, Second attempt.

    Interesting... I can't seem to find any reviews/ experience with this new Celestron focuser - or any vendor offering them. I used the Vegemite lid, larger knob option on the C9.25/ C11 for many years then adapted a SW motor as a belt drive...changed to the micro focuser on the C9.25 - absolutely great! On the C11 I now use the JMI focus motor and the computer control. Works very well for me and meets my spectroscopic needs.

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