I was comparing a GPC to three Barlows, using them to find a way to extend my focal point away from the scope.
I noticed that they had very different clear apertures (comparing diameters of the glass), but more importantly my FOV seemed twice as big in the GPC vs the Barlows.
Many of these devices are oriented to using Binoviewers, many are for astrophotography, but I’m looking at visual for single eyepiece views… to extend that focal length.
Why is the FOV of the GPC twice that of a Barlow of similar magnification? How would a focal extender or reducer compare for FOV? Is there anything I should watch out for with regards to the clear aperture?