A new 290 mm F/2.5 Astrograph!
Posted 03 October 2012 - 12:42 PM
This instrument looks like a very short Newtonian with an optical window, but it is a bit more complicated than that. It uses an aspherical window and a field corrector and this specific combo provides a diffraction limited flat field of more than 50 mm diameter for a wide spectral range, see the accompanied matrix spot diagram below. The small black circles represent the airy disc. The visual and photographic tests confirm the total absence of chromatic errors and preliminary observations with a 13 mm Ethos convinced me that this instrument is not just a photographic instrument but it will also be a first class Wide-field telescope with coma-free images!
In the coming months the final (Carbon) housing will be made together with a brand-new focuser, specially developed for this instrument. At the end of this year we expect to have first light on the sky, untill then I'll post some updates so once in a while....
Posted 03 October 2012 - 12:51 PM
Posted 03 October 2012 - 02:01 PM
Posted 03 October 2012 - 02:50 PM
Ziet er zeer interesant uit!
Very interesting spot-diagrams, I hope to see more on this
project, especially images taken with it!
If it is only 1/10th as good as your 16", this will be
an absolute killer optic!!
Keep them coming Rik!!
Posted 03 October 2012 - 03:10 PM
As it will also be used as a visual instrument it needs to be very well corrected.
This front view shows the temporarily pole on which the flat secondary is attached. In the final instrument the flat mirror is directly attached to window by means of a mechanical solution.
Posted 03 October 2012 - 03:31 PM
Posted 03 October 2012 - 03:59 PM
All refractive elements will have a broad band AR coating for maximum transmission. I‘ll still have to find a reliable company who can make these AR coatings, so suggestions are welcome!
Posted 03 October 2012 - 04:23 PM
Posted 03 October 2012 - 04:43 PM
Posted 03 October 2012 - 07:05 PM
I want one... Comets are coming.
Posted 04 October 2012 - 02:11 AM
Mike and Jim, thanks a lot for the AR-coating companies! 15 years ago I had a disastrous experience here in Europe with one company that succeeded in destroying three finished 260 mm diameter Schmidt-correctors at once during cool-down after coating, so it is for that I look for experienced companies even if they are outside Europe.
Posted 04 October 2012 - 02:40 AM
Could we ask for an optical prescription or Zemax file?
Posted 04 October 2012 - 08:53 AM
I'm sorry for not being able to publish all the design details (yet). A detailed publication is foreseen somewhere next year, so I hope you can wait that long ;-)