[avandonk]

Mike it is a 150mm aperture Skywatcher achro and it is well corrected for spherical aberration. I have been warned about spherochromaticity but have not found any great sign of it. It is a native F5 but with a Hutech FR/FF #7887 it is an f/4.25. The field as you can see is flat over a full frame (36x24mm ). I have figured out a way to focus for each narrow band filter in situ. I then collect full colour data with my 100ED and merge the data with IP. So then I end up with dim nebula data and all the stars have colour! Actually this is not as onerous as it seems as you can get NB data with the Moon around and get full colour when it is not around.

Of course this does not beat a 152mm AP or TMB etc. But at least I can get data that is close. My greatest enjoyment is cutting up OTA's and modifying them and hopefully make them perform better. The 150mm skywatcher has an Astro Physics 2.7" focuser to minimise vignetting for a full frame sensor. I will put up some images tomorrow.

Bert