Good focal reducers for Quark?

[Brett]

There are a couple of cheap brand focal reducers on the market to use with the Quark, but are there any reducers that will be better in terms of dispersion and spherical abberation that would go well with the Quark and a cmos camera? Also, would a 1.25 inch or 2 inch reducer be better fitted to the Quark?

[grimble_cornet]

This might be of interest: http://solarchat.natca.net/viewtopic.ph ... al+reducer

[Valery]

There are really no good reducers for Quark. Most of them are just a achromat doublet lenses with their own
sets of aberrations. The worst are field curvature, field astigmatism and spherical aberration.

I noticed that if I focus the system for the center, then field edges are softer and wise versa.

And the slower the telescope you do use with Quark, the better a given reducer works - as expected.



Valery.

[Astrograph]

As I have told many customers, the cheap reducers are not made for tele-centric beams like the Quarks. The only one I know of is the Baader 0.7x Tele-compressor. These are not cheap (£209) but work. They have 2" threads. Unfortunately they are very hard to get hold of

[marktownley]

I have and use the Baader Solar Telecompressor. It is great and shows none of the uneven field illumination, curvature and softness towards the edges like the cheapy 0.5x version I first tried. I whole heartedly recommend it.