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Pentax EDA PR-65 Meets The APM 12.5 mm Eyepiece (1 Viewer)

gcole

Well-known member
Pentax PR-65 EDA Meets The APM 12.5 mm Eyepiece

I thought this would be of interest to those of you who are always seeking to pushing the limits of your spotting scope. I love large eyepieces with outrageously large eye lens with corresponding super large eye relief. I waited over a year to get my hands on this beast. It’s the largest Astro 1.25 inch fixed power eyepiece I have ever tried in the little Pentax. This is the APM Hi-FW 12.5 mm eyepiece from APM Telescopes Germany. I anxiously waited .... would this come to focus in the little Pentax , would this eyepiece prove my little Pentax to be not up to the challenge ? ..... The Pentax passed with flying colors with the APM 12.5 mm eyepiece providing an extremely eeeee large FOV. with a 30x fixed power. It’s says 84 degrees on the eyepiece and when compared to my Pentax XW14/20 you really get a sense just how huge the view is. Optically when compared to the Pentax XW’s it is just as sharp/clear. It is a solid well built eyepiece, equal to the Pentax XW’s. I have provided a picture of the XW20 next to the APM to show the size difference.
 

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Boogieshrew

Well-known member
Looks like a great e/p. I always take notice of you posts. We have very similar taste in scopes and e/ps. Astro e/ps provide the wide bright fixed mag that I, like you, enjoy.
When I have some spare cash I’d like to try it on my older grey model Vortex Razor with Swarovski Astro adapter.
A very wide 30x is tempting.
As a spectacle wearer I’ve avoided the ultrawides but this claims 23mm eye-relief so should be good with glasses.
Thanks for the pointer.
 

gcole

Well-known member
Looks like a great e/p. I always take notice of you posts. We have very similar taste in scopes and e/ps. Astro e/ps provide the wide bright fixed mag that I, like you, enjoy.
When I have some spare cash I’d like to try it on my older grey model Vortex Razor with Swarovski Astro adapter.
A very wide 30x is tempting.
As a spectacle wearer I’ve avoided the ultrawides but this claims 23mm eye-relief so should be good with glasses.
Thanks for the pointer.[/QUOTE
I have no problems with the eye relief with my glasses on. The sweet spot is so huge I personally could not tell if I am taking in 65 degrees or all 84 because I tend to concentrate my wildlife viewing to the center of the view. The Docter 12.5 mm eyepiece is what drew my interest to this eyepiece. Ever since I saw the article with the Docter 12.5 being used on the Kowa 883 awhile back I looked for user reviews with most being found on the astronomy forums. There many discussions were the strong possibility that the APM was a clone of the Docter giving very similar views at one half the cost. I almost bought the Docter but the near $700 price tag at that time stoped me. The APM 12.5 can be had for around $300. and worth every penny.
 

JerryLogan

Well-known member
Gwen,

+1 for Boogieshrew. I too always take notice whenever you post. Lots of valuable information and insights over the years.

If anyone in the US is interested, APM has an outpost in Pennsylvania - Outdoor Sports Optics. The Docter clone is listed as available there for $295, as well as the other interesting APM products.

Best,
Jerry
 

gcole

Well-known member
Jerry ..... Thats what so great about this site, we all just by engaging with each other here on Birdforum see and learn so much. The same goes for all the Astronomy forums world wide that discuss all their equipment. Thanks to the worldwide internet we no longer need to rely on localized retailers to see and purchase our equipment. As for APM Telescopes I never would have known of their existence if I had not been trolling Cloudy Nights forum.
 

gcole

Well-known member
I thought this would be of interest to those of you who have been looking to use 2 inch size eyepieces in your spotting scopes. I have provided a picture of the XW20 next to the APM to show the size difference.
The APM just by its size alone looks like a 2 inch eyepiece. If it were not for its 1.25 inch size barrel one would think while in use you are actually experiencing the wide open view of a eyepiece of 2 inch or larger.
 

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billb9430

Well-known member
The APM just by its size alone looks like a 2 inch eyepiece. If it were not for its 1.25 inch size barrel one would think while in use you are actually experiencing the wide open view of a eyepiece of 2 inch or larger.

As one who enjoys adapted 2" eyepieces in the Pentax spotters, this appears to be a nice option for higher powers in those scopes. Thanks for your informative posts.

One additional question, could you please comment on edge distortion with the larger field of this eyepiece. Some time ago I tried a 24mm Panoptic that is praised by astro users, but did not like its rectilinear distortion for spotting scope use. Does the APM 12.5 have noticeable distortion, either RD (curvature of straight lines at the edge of the field) or AMD (rolling ball when panning)?
Thanks, Bill
 

gcole

Well-known member
As one who enjoys adapted 2" eyepieces in the Pentax spotters, this appears to be a nice option for higher powers in those scopes. Thanks for your informative posts.

One additional question, could you please comment on edge distortion with the larger field of this eyepiece. Some time ago I tried a 24mm Panoptic that is praised by astro users, but did not like its rectilinear distortion for spotting scope use. Does the APM 12.5 have noticeable distortion, either RD (curvature of straight lines at the edge of the field) or AMD (rolling ball when panning)?
Thanks, Bill

Bill ... I did not experience any noticeable edge distortion with the Pentax PR EDA. The view is so large, the viewing circle so big with such a huge sweet spot seemingly to take up the entire view. I am personally not affected by the rolling ball so I can not say. Any other noticeable type of distortion at the edge of field for me at least if it’s there I can not perceive it probably due to the pleasantly enjoyable view this eyepiece provides. On the CloudyNights forum many did have positive remarks regarding your concerns when compared to the Docter 12.5
 

gcole

Well-known member
The APM just by its size alone looks like a 2 inch eyepiece. If it were not for its 1.25 inch size barrel one would think while in use you are actually experiencing the wide open view of a eyepiece of 2 inch or larger.

Here next to a 15 oz can of clams
 

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Boogieshrew

Well-known member
Here next to a 15 oz can of clams

Yowzer! That's huge. It is also half the weight of my 65mm scope body.

If this e/p was around 18-20mm focal length but kept its other specs, it would be my all time favourite I suspect.
That fov, eye relief, large ocular and 20x mag would be fantastic.
 

gcole

Well-known member
From what I have read APM Telescopes is now designing an 18mm Hi FW to compliment the 12.5 mm eyepiece.
 

Boogieshrew

Well-known member
Now I am really eagerly awaiting the 18mm hi-fw. Today I lost my balder Morpheus 17.5mm. DOH!!! ��
 

gcole

Well-known member
Sorry to hear that but I tried all three Morpheus in my Pentax, sold all three they gave a yellow tint to the view. I really wanted to like the 12.5 mm but comparing it to the APM hands down the APM is a much better eyepiece in all respects from its quality of build to its true to color clear view.
 
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Tringa45

Well-known member
Europe
Some time ago I tried a 24mm Panoptic that is praised by astro users, but did not like its rectilinear distortion for spotting scope use.

I don't understand the Panoptic's reputation either. My 19 mm (AFIK they are all the same scaled design) has the highest amount of rectilinear distortion (pincussion) I have ever experienced and also considerable astigmatism.

John
 

Boogieshrew

Well-known member
Sorry to hear that but I tried all three Morpheus in my Pentax, sold all three they gave a yellow tint to the view. I really wanted to like the 12.5 mm but comparing it to the APM hands down the APM is a much better eyepiece in all respects from its quality of build to its true to color clear view.

I’m very surprised by the yellow tint. The 15.5 and 17.5mm on my old model Razor are very true to life. To my eye at least. The 12.5mm didn’t have enough e/r for me. But the 17.5 is superb. It is my favourite eyepiece of any scope I’ve ever owned. I can’t get enough of that wide view.
I hope the APM exceeds it 😀
 

giosblue

Well-known member
I’m very surprised by the yellow tint. The 15.5 and 17.5mm on my old model Razor are very true to life. To my eye at least. The 12.5mm didn’t have enough e/r for me. But the 17.5 is superb. It is my favourite eyepiece of any scope I’ve ever owned. I can’t get enough of that wide view.
I hope the APM exceeds it 😀


I tried a couple of Morpheus EP's a couple of years ago and I also thought they had a yellow tint. If you don't swap out and compare you get used to it.
The wide view is something else though.
 

Boogieshrew

Well-known member
There’s no accounting for eyeballs I guess. I used to swap Morpheus, celestron xl ans Swarovski e/ps and never saw the yellow. ��
 

billb9430

Well-known member
I'm a little late with my contribution, but I bought this eyepiece in June, soon after gcole started this interesting thread. The APM 12.5 is indeed a nice, higher power eyepiece for use with all sizes of the Pentax PF spotters and I especially enjoy the wide field in the PF100 at 50x.

I have noticed a couple of things not yet mentioned in this thread. The APM 12.5 does show a bit of the "ring of fire" aberration (red or orange shading) at the field edge IF you get your eye pupil slightly off axis when looking directly at objects near the field stop. When normally viewing a bird or animal in the center of the field and taking in the field edge with peripheral vision, this is NOT evident at all. This "ring of fire" effect is not so pronounced as with some astronomy eyepieces (for example, the ES 30mm 82˚ "hand grenade" size astro eyepiece).

The other item is that my APM 12.5 eyepiece shows a bit of angular magnification distortion (AMD) or "rolling ball effect" when panning. This is interesting, as I PM'ed Starman1 (Don Pensack) who is an eyepiece vendor over on the Cloudy Nights astronomy forum and he noted that with the APM 12.5 he tested, he saw rectilinear distortion (RD) also called "pincushion" distortion. He mentioned that he is very sensitive to AMD and, indeed, did not like the Docter eyepiece version similar to the APM 12.5 because of its strong AMD. I have great confidence that Don, who has vast eyepiece experience, saw this in his eyepiece but equally feel that MY particular APM 12.5 does have AMD with little or no RD, at least when used in the Pentax spotters. I suspect that either APM changed the optical perscription for this eyepiece at some point, OR perhaps the scope in which the eyepiece is used has more effect on edge-of-field distortion than most of us realize. Perhaps other APM 12.5 users can look for these edge-of-field distortions and chime in on this?

On another related topic, since this thread was started for those who enjoy wide field eyepieces with big eye lenses, have any of you tried the Masuyama 85˚ eyepieces in a Pentax spotter? I've been enjoying using 26mm adapted 2" barrel SWA 70˚ Afov eyepieces with all apertures of PF spotters for years (see very old thread in this forum) but recently acquired a Masuyama 26 mm 85˚ Afov 2" barrel ocular that shows promise of giving an even better view when similarly adapted. I still have to machine an adapter to hold the upper section of the Mas 26 on my Pentax adapted spotters, but handholding it there seems to give a superior view. I'll post more once I get the adapter made, but wondered is others have looked at this. - Bill
 

henry link

Well-known member
The other item is that my APM 12.5 eyepiece shows a bit of angular magnification distortion (AMD) or "rolling ball effect" when panning. This is interesting, as I PM'ed Starman1 (Don Pensack) who is an eyepiece vendor over on the Cloudy Nights astronomy forum and he noted that with the APM 12.5 he tested, he saw rectilinear distortion (RD) also called "pincushion" distortion. He mentioned that he is very sensitive to AMD and, indeed, did not like the Docter eyepiece version similar to the APM 12.5 because of its strong AMD. I have great confidence that Don, who has vast eyepiece experience, saw this in his eyepiece but equally feel that MY particular APM 12.5 does have AMD with little or no RD, at least when used in the Pentax spotters. I suspect that either APM changed the optical perscription for this eyepiece at some point, OR perhaps the scope in which the eyepiece is used has more effect on edge-of-field distortion than most of us realize. Perhaps other APM 12.5 users can look for these edge-of-field distortions and chime in on this?

There are at least two other possible explanations for your differing impressions of the distortion. One is that there may be enough pincushion to be visible to someone who is looking for it, but not enough to completely correct the AMD for someone who is looking for that. The other is that the eyepiece may use "mustache" distortion wherein there is a moderate or even large amount of pincushion in the inner 1/2-2/3 of the field which then reverses in the outer 1/3, reaching zero pincushion or even mild barrel distortion at the very edge of the field. That causes AMD, sometimes quite strong, but just at the very edge of the field.
 

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