Filter Slides, Flip holders

For filter slides or a flip holder similar to the moonlite CR3/CR4 design, since these mount id, do they interfere with the view?

* How much obstruction does this add?

* Do you notice any diffraction spikes?

I have a truss dob so the secondary cage is designed a bit tight. Does this make a difference?

Ed

[QUOTE]Ed York said:

For filter slides or a flip holder similar to the moonlite CR3/CR4 design, since these mount id, do they interfere with the view?

** I use an Astrocrumb filter slide on my 12.5" truss dob. The inside diameter of my UTA is about 13.75" and I can see a slight indentation in the "roundness" of my primary mirror when I am collimating. If I remove the slide, I notice no such indentation. I simply use the filter slide to make comparisons of filters or when I am wide field cruising with a few different filters. I used the slide a lot when I first installed it. I compared filters and selected the OIII that works best for me. I also placed both the UHC and the OIII in to find which worked best - I still do this but much less than before. I don't use the slide a lot anymore, but it's nice to have and it makes comparing filters a snap.

I have one filter that I generally use for Jupiter and Saturn. When planetary viewing, I remove the filter slide and mount the filter on my 1.25" adaptor.

How much obstruction does this add?

** Obviously some, but it is very little in my experience.

Do you notice any diffraction spikes?

** I have never noticed any diffraction pattern coming from the rails. When viewing planets, I have the slide removed.

I have a truss dob so the secondary cage is designed a bit tight. Does this make a difference?

** Sure, if the circumference is tight, the slide will intrude further into the light path. You'll have to determine if your circumstances are such that the slide is too much of a compromise. I am pretty sure that if I acquired another telescope, I would install a filter slide again.

Gary Weber