Re: Ultraviolet "Barlow" lens?

Dave Schaack wrote:
"Louis Boyd" <boyd@xxxxxxxxxxxxxxxxxxxx> wrote in message news:fcpdg7$e3m$1@xxxxxxxxxxxxxxxxxxxxxxxxx

I have a need for an achromatic "barlow" lens to effectively convert a 20" diameter F/4 Newtonian telescope (parabolic mirror) to F/8 and extend it's focal plane location a few inches. It needs to have reasonably low chromatic aberration and good transmission from 300 to 600nm. The Edmund 50.8mm x -500mm fl PCV fused silica lens would work were it not for the focal length shift versus wavelength. . Any ideas or sources for such a lens? I can afford up to about $1k. The lens also needs to act as an entrance window so it can't be a delicate material.


If you need 50.8 mm diameter, I doubt that you can do it within your budget. However, at smaller diameter, I think you could afford a custom Calcium Fluoride singlet and a catalog lens. You may be able to combine a CaF2 singlet with a catalog fused silica singlet to form an achromat that would do the job. If you need it to be robust on both sides, then perhaps you could use two fused silica singlets of half the power, that is, make a triplet.

Thank you for the help Dave. You've pretty well confirmed my suspicion that there isn't a simple or inexpensive solution to this problem.
.

Loading