Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.


andrew s

Advanced Members
  • Content Count

  • Joined

  • Last visited

Community Reputation

1,150 Excellent


About andrew s

  • Rank
    Sub Dwarf

Profile Information

  • Location
  1. Yes I study star spectra with a home built echelle spectrograph. I have a guide head on a telescope which feeds the starlight into a fibre optic which guides the light to the spectrograph. This allows the spectrograph to be stable as it does not move as the telescope tracks the star. Regards Andrew
  2. The reflective version should be ok with any camera. A prism adds aberrations when off axis. I use mine as the input to a spectrograph. Regards Andrew
  3. @vlaiv yes I agree with your comments. Do you have a view on quantisation noise with current CMOS cameras and very short exposures, gain settings etc. This is not an issue with true photon counting if I remember correctly but it was 40 yrs ago when I did it. Regards Andrew
  4. Looking at yours it must have a reflective coating on the 45 deg face. This is mine https://www.teleskop-express.de/shop/product_info.php/info/p641_TS-Optics-Off-Axis-Guider-TSOAG9---Baulaenge-nur-9-mm.html it uses the prism with total internal reflection. You can see they are quite different. It is probably that yours uses reflection as yours is for an EOS camera with a large field. Regards Andrew
  5. Then the 45 deg face is reflecting about 5% of the light to the guide port? It looks nothing like my teleskop services OAG prism. You live and learn. Regards Andrew
  6. That prism looks slivered and is acting as a mirror. Is that correct? Regards Andrew
  7. Hi Alan, I don't follow the logic in this. If shot noise from the sky background dominates the read noise then taking longer exposures will improve the S/N ratio of both the background and the "target". A good thing or am I missing something? I know stacking can do this but less efficiently. Regards Andrew
  8. The second coloured diagram is not correct. The blue prism is the wrong way round. No known material could deviate the light at a right angle in this configuration. Regards Andrew
  9. Using a star give a combined instrument response and that of the atmosphere who's response is not insignificant. Even reflective optics will have an effect as will the grating. It is not easy. Buil is a very respected and careful worker I this area, I would trust his results. Regards Andrew
  10. I think the first was correct. The light undergoes total internal reflection at the 45 deg face. The light path in the coloured diagram is impossible. Regards Andrew
  11. You still do better, even with CMOS, with the longest exposure your system can manage without saturation. Regards Andrew
  12. I am sure many still exist and are treasured possessions why not appeal for photos via this and other astro sites. I could ask on the BAA site if you are not a member. Regards Andrew
  13. You should get an ISBN and publish it then I can go to a copywriter library an see if for free. Only kidding but I am sure you could sell a few copies if you wanted to but I understand you might not want to. Regards Andrew
  14. I would dip my toes in and ask what a moon river is? Regards Andrew
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.