Monochrome CCDs and Achromats

[Lee]

Here is a question..... imaging with a monochrome CCD and filters and a fast achromat scope. Colour fringing is due to colours focusing at different points isn't it.... so if you refocused in between colour filters you'd have a non-fringed image? no???? Luminance frames is where it would fall over I suppose.....

[astroboy]

Hi Lee
Even with doublet apos you need to refocus for RGB but with a fast achromat I think the stars in each colour would be a bit bloated.
I think it would work with the narrow band stuff though ( Ha O111 S11 etc ) but if you have a good CCD and the expensive filters a decent telescope is the cheapest bit.

Zane

[Lee]

Tell me about it! Even without the "good CCD" the scope is still cheap in comparison. I think my scope will be cheap in comparison to the aluminium mounting gear for it and the guidescope!