zero cost DIY focal reducer

[nytecam]

Awhile back Comet Holmes expanded beyond the fov of my piggybacked ETX-70 and Starlight Xpress MX916 CCD. A quick focal reducer was made from a coated 20mm diam achromat of 120mm fl from a spare Meade finder!

Mounted in a 1-1/4" tube coupling scope and CCD it had a power x0.7 to nearly double the gross sky fov from 90' x 60' to ~120' x 90' with good stars images even to the corners as sample below ... and all at zero cost.

ps: the 'scope f/ratio 'speed' was doubled from native f/5 to f/3.5 for briefer exposures ! More DIY equip at WPO - Meade ETX-70AT with Autostar