Image of the day

Captured by
Alexander DiNota

IC5070 Pelican Nebula

My Account

New to Astromart?

Register an account...

Need Help?

FS102 Question...Color?

Started by glauria, 10/31/2003 02:11AM
Posted 10/31/2003 02:11AM Opening Post
In the past year, I purchased a used FS102. The first time I looked through a flourite doublet, (it was a home made 6" f/12) it had absolutely no color at all inside or outside of focus. It basically looked like a reflector telescope without the central obstruction.

When I bought the FS102, I was expecting the same performance. However, I notice that inside and outside of focus, there is a magenta color to the diffraction patterns, and when I look at the planets or a bright star, I can sometimes see a slight magenta halo around them. I emailed Texas Nautical about this problem, and the reply was that there was something wrong with the telescope and I should send it back for repair. However, I can't imagine what can be wrong with it except for an optics misalignment etc...

Does anyone who has (or had) a FS102 see the same thing? I was wondering if I was expecting too much from the telescope or perhaps there may definitely be something wrong (but I can't imagine what)?
Posted 10/31/2003 07:40PM #1
Hello Michael,

Thanks for the advice. I'm afraid that there is indeed something wrong then. I often see the magenta halo around vega when it is directly overhead. It is true that the color correction can be a function of the seeing, and the seeing where I live (in central Virginia) is typically pretty poor. Sometimes the halo is worse than other times. But for sure, you always see it when the the stars are inside/outside of focus. In my Newtonian, the stars are always white when they are out of focus. The only thing that I can think can be wrong is the spacing of the lenses, but that is pretty much fixed by the shims that are put between them. I'm wondering if somehow the spacing could have shifted during shipping or something like that.

Overall though, it is still a very fine refractor, and it gave me some very satisfying views of Mars this past summer. I wish I could look through another FS102 to do a comparison.