Humboldt Jim
Well-known member
A View From a Room
I recently compared all my eyepieces in my new Pentax PF-65 ED AN scope. My primary objective (pun intended) was to determine which of the eyepieces worked best for the widest real field of view (RFOV). I also wanted to get an impression of any other variations in optical characteristics of the various eyepieces with this scope.
Test conditions consisted of viewing through an unobstructed window at a utility pole some 30 meters distant. I wanted to avoid haze and atmospheric effects as much as practical. The sun position was to the right and behind me through very light high clouds. The weathered wood, cables, clamps nut and bolts provided good target for evaluation purposes.
Following are my impressions:
Pentax XF-12, 32.5x: This is my basic eyepiece for the scope. Sharp and flat field edge to edge and a typical spotting scope RFOV
Vixen 10-mm lanthanum, 39x: The image is as good as the XF-12 but has a typically narrower field as expected with the higher power. The 20-mm eye relief makes it easy to use for eyeglass wearers.
GSO 20-mm wideview, 19.5x: A good apparent FOV and a RFOV consistent with the power. A bargain at US $40.
Celestron 26-mm Plossl, 15x: Not as quite good overall as the XF-12 or Vixen but quite nice to look through, bright throughout the whole field under these conditions. The expansive RFOV and ease of viewing make for an impressive combination.
Celestron Ultima 30-mm, 13x: A very wide view and very good overall image but with distortion and darkening around the edge of the field. Also tended to “black out.”
My conclusions:
The Celestron 26-mm Plossl is my choice for maximum RFOV and when the scope is on my Bushmaster shoulder pod. This seems to provide the maximum RFOV, as suggested to me by the Pentax field rep who initiated the concept of the PF-65 ED.
The wide apparent FOVs of the 30-mm Celestron and 20-mm GSO can be problematic for eyeglass wearers. I prefer to see the view comfortably presented as a moderately wide AFOV.
I am now on the lookout for a Zoom eyepiece. If the 10-mm Vixen is any indication of what the zoom is like that is a viable choice.
For those wanting maximum RFOV “wow factor,” go for a 26-mm. The Plossl that I tested is a fairly good eyepiece but there are probably better ones for terrestrial viewing.
I look forward to reading other's reviews of some long eye relief zooms.
I recently compared all my eyepieces in my new Pentax PF-65 ED AN scope. My primary objective (pun intended) was to determine which of the eyepieces worked best for the widest real field of view (RFOV). I also wanted to get an impression of any other variations in optical characteristics of the various eyepieces with this scope.
Test conditions consisted of viewing through an unobstructed window at a utility pole some 30 meters distant. I wanted to avoid haze and atmospheric effects as much as practical. The sun position was to the right and behind me through very light high clouds. The weathered wood, cables, clamps nut and bolts provided good target for evaluation purposes.
Following are my impressions:
Pentax XF-12, 32.5x: This is my basic eyepiece for the scope. Sharp and flat field edge to edge and a typical spotting scope RFOV
Vixen 10-mm lanthanum, 39x: The image is as good as the XF-12 but has a typically narrower field as expected with the higher power. The 20-mm eye relief makes it easy to use for eyeglass wearers.
GSO 20-mm wideview, 19.5x: A good apparent FOV and a RFOV consistent with the power. A bargain at US $40.
Celestron 26-mm Plossl, 15x: Not as quite good overall as the XF-12 or Vixen but quite nice to look through, bright throughout the whole field under these conditions. The expansive RFOV and ease of viewing make for an impressive combination.
Celestron Ultima 30-mm, 13x: A very wide view and very good overall image but with distortion and darkening around the edge of the field. Also tended to “black out.”
My conclusions:
The Celestron 26-mm Plossl is my choice for maximum RFOV and when the scope is on my Bushmaster shoulder pod. This seems to provide the maximum RFOV, as suggested to me by the Pentax field rep who initiated the concept of the PF-65 ED.
The wide apparent FOVs of the 30-mm Celestron and 20-mm GSO can be problematic for eyeglass wearers. I prefer to see the view comfortably presented as a moderately wide AFOV.
I am now on the lookout for a Zoom eyepiece. If the 10-mm Vixen is any indication of what the zoom is like that is a viable choice.
For those wanting maximum RFOV “wow factor,” go for a 26-mm. The Plossl that I tested is a fairly good eyepiece but there are probably better ones for terrestrial viewing.
I look forward to reading other's reviews of some long eye relief zooms.
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