I noticed in pics for the Coronado SolarMax II 40/ RichView Tuner Package for Double-Stacking SM40, there is a centered disk in the filter of the double stack unit. What is this center disk for?
Coronado SolarMax II 40/ RichView Tuner Package for Double-Stacking SM40
Posted 29 May 2020 - 09:00 PM
It's a spacer. Most larger etalons have these, and bigger ones have several. And yes, they are just like having little obstructions in there, but they don't bother much as they're front mounted and out of focus. You'll only find them in front mounted etalons for that reason. Lunt has them too. Only some of the smaller etalons like the 50mm series Lunt and 40mm series PST are unobstructed. The rest designed for front mounts that are larger pretty much all have spacers like that (some up to 3 of them in a triangle pattern, all obstructions). Central-etalon designs (like some double stack modules) and rear-mount-etalon designs are smaller clear apertures and do not have these central spacers due to their smaller size.