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Everything posted by Merlin66

  1. Louise, Andrew beat me to it!
  2. Louise, A telescope is not necessary....basically what you’re doing is good to check the guiding on the slit... The next stage is to get the collimator focused on the rear of the slit plate. softly softly......
  3. Louise, Another step along the way......
  4. The cooler/ cold regions as recorded in an IR image of the Nebulae clearly shows the new star formation areas...... https://apod.nasa.gov/apod/ap160718.html
  5. Interesting the TO site mentions the "CE & ISO Certified" which only applies to solar sun glasses - not for telescopes or other optical systems. They compare with "mylar" which I think is bad marketing - The Baader solar film is definitely NOT maylar based, and Baader give details of the optical properties - something I can't find on the TO site. For the camera lens I would make a filter from the Baader solar film to fit the lens.
  6. Yes. I use AstroArt and the only time bias is mentioned is when you need to compensate your darks to another temperature....
  7. Yeah, I'm only doing spectroscopy.... I'm interested in the target star - not the whole field. In the spectroscope slit, normally 3-4 pixel wide and covering 90% of the FWHM image, it's the photons I can collect which makes the difference. I believe in this application, the "arrival times" are important.
  8. Derek, Hmmm I accept the arrival of the photons is random (shot noise) but they don't vary in position....I believe, based on our spectroscopy work, a combination of subs with some signal give a increased intensity and improved SNR. How else can I record the spectra of faint stars???
  9. If the sensor records say 10 photons in one minute, then over ten minutes it will receive and record 10 x 10 photons.
  10. Surplus Shed have all the amateur scientist articles available on one CD!!! It makes fascinating reading, something for everyone. https://www.surplusshed.com/pages/item/M2071.html
  11. 1. Has the lowest target signal and low SNR 2. Has an improved target signal, but similar to 1. due to the averaging, but an improved SNR (1 sigma) 3. Has a much higher target signal due to sum but similar SNR to 2. 4. Similar to 3.
  12. Dave, if you need help.....we're always here.
  13. Louise, Yes, I designed and built the Spectra-L200. I've also designed a FC 120 (folded Classical) and an MG80 (80mm collimator/ 300 l/mm/ Zuiko 50 mm ) using standard components. Details on the forum. I don't have access to 3D printing so I tend to skip these designs....I haven't looked at Christian's Uvex3 design. Paul G. and I communicated on his early design concepts. Ken
  14. Louise, Yes, it impacts on the spectral image. I use a hi res, narrow bandwidth, R=10000 Spectra-L200 and have to re-focus between the various target wavelength. It's very seldom that I add sections of the profile together...if you want a full spectrum spread, then a 300 l/mm grating or similar is used and set to the "average" focus. I have seen examples where the camera focal plane is tilted across the length of the spectral image, but when compared to the curve above, it's still a compromise.
  15. I use a Edmund Optics achromat in the Spectra-L200 (similar to the LHiresIII) it's a 30/200. The attached curve shows the required focus adjustment required over the visible spectrum. I use a Borg helical focuser.
  16. If you use the spectrograph on an f7 scope, the beam after the slit will emerge at f7 towards the collimator. This acts as an "aperture stop" - if the beam f ratio is > collimator f ratio then the illuminated part of the collimator will be smaller without adding a mask. I use a 30/200 (nominally f7) collimator which works (no masking) well on f8 to f12 scopes.
  17. I'm pretty sure there's a "freeware" spreadsheet program which reads Excel files... https://articles.bplans.com/4-free-alternatives-to-microsoft-excel/ For the Spectra-L200 which uses 30 x 30 mm gratings, I used Optometrics (Now Dynasil) https://www.dynasil.com/company/optometrics/ I made interchangeable holders to allow different gratings to be used - 300/ 600/ 1200/ 1800 l/mm.
  18. The SimSpec Spreadsheet will help you..... IMHO I'd go for a 30 x 30 mm grating. The grating will probably have to rotate to access the full spectrum, you'll need a holder and some means of fine adjustment. Ken
  19. The one you removed is a colour correction filter which reduces the red response. The front, remaining dust shake/ anti alias filter does a good job as a IR reject filter. I removed BOTH these filters to extend the Spectral response for spectroscopy.
  20. I agree with Robin! The Oly Zuiko lenses are pretty good. I still have some lenses from the ol' film days and use a 50mm f1.4 Zuiko on the MG80 spectrograph.....
  21. Robin, My bad.. I meant to say that the PH grism prism was glass and not acrylic.
  22. I use AstroArt for all my pre-processing, guiding and "tweaking" - sadly underrated - it punches well above it's weight. http://www.msb-astroart.com/ A good alternative to PS (layers, histogram. plug ins, etc. etc.) is Corel's PaintShopPro. No subscription.... https://www.paintshoppro.com/en/
  23. Dave, I'm pretty sure the PH spectroscope will use a glass prism. Fulvio "converted" a PH DV spectroscope to his Spec 600 http://www.lightfrominfinity.org/Spec 600/Spec 600.htm An Amici prism can be used successfully (the late Maurice Gavin's set-up is illustrated in "Astronomical Spectroscopy for Amateurs", p 170) using a barlow lens as a collimator. The available processing software (BASS Project etc.) can easily handle the prism non-linear spectral image.
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