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100º AFOV eyepieces on birding scopes? (1 Viewer)

D

DRodrigues

Well-known member
I'm not the only one thinking on this as Can post http://www.birdforum.net/showthread.php?t=153877 shows.

After seeing the TMB 9mm 100º http://www.astronomics.com/main/pro.../4LTTSBRXCV069JKSSJ74CS9K41/product_id/TMB209 I was waiting for a 5mm to give a try (I need 1.25" size for my Optolyth 100).

Meanwhile TeleVue released the Ethos-SX 3.7mm 110° http://www.televue.com/engine/TV3_page.asp?id=20&Tab=EP_ETH-03.7 that went directly to my wish to test list at cr-telescopes at www.pt-ducks.com - if there was a 5mm version I might be tempted to ordered it but my bad experience with the Radian 4mm showed me that in a 630mm birding scope I'm pushing the limits too much...

Remembered to write this message because I just noticed the new Nikon NAV HW 12,5mm 102º http://www.apm-telescopes.com/nikon-nav-hw-125mm-okular_proinfo_52783.html that could be a new EDG eyepiece that would turn the Nikon EDG scopes more interesting, if the tag prices were not "astronomical" as the astro versions... Nikon don't have a wide field zoom as Leica or Swarosvky, neither a 20-75x zoom as Zeiss. A eyepiece of this sort would bring more "light" to the EDG scope line...o:D
 
that televue ep brought an image of john cleese into my head!

its a dead ringer for "an holy handgranade" !

Looks like a 2" fitting tho.....Could it be the Holy Grail of duck spotters??!
 
Greetings
David..You mentioned owing an Optolyth 10mm..It was a thread ,about Birding scopes that Use or advertise usni Fluorite in their Objectives...The Kowas 883 and 884 and all the top of their past Prominar lines use pure Fluorite Crystal in their Objectives...Optolyth uses the word Fluorite in their catalog,but also mixes some ambiguos terms,like" fluorite glass",or "glass containing Crystals ",this leaves all open to interpretation and it was a discussion to try to realize(a green laser test was mentioned)if pure fluorite crystal was used in these (optolyth scopes...excuse me for going away from your original post,but ,since You own one of the scopes,and ovbiously know Your glass,Can You briefly comment on this issue?...thanks
 
woodhornbirder

The Ethos 3.7mm might work with 500mm telescopes (i.e. 135x) but it's too much power for my 630mm scopes - at 170x light it's an issue, even in Portugal...


mayoayo

I read somewhere that Optolyth uses a rather rare glass - the FPL52. This means that is not a FPL53 (the best), but is better than the FPL51...
In terms of colours it's noticeable some yellow bias but doesn't bother me since in most situations increases contrast (using other brands EP also reduces the yellow bias). Not so innocuous is some CA visible but think that in the 80mm models it's not so visible (also the use of other brand EPs seems to reduce it...). As I say at cr-telescopes at www.pt-ducks.com - the Optolyth 100mm probably doesn't have the best image quality but the extra magnifications compensates it for cr-birding since has higher resolution.
 
TMB 9 mm

Since a long time ago I wanted to test one 100º eyepiece just to see what's the feeling...:-O
As still there isn't a 5mm model but noticed that the Ethos 6mm should work in spotting scopes I asked a friend to find me a used TMB 9mm - it's much cheaper than an Ethos and with the BS 1.6x Barlow element it would become a 5.6mm, eventually with better eye-relief. I received it today and didn't resisted to try it on the Optolyth just to see if it focused.
It focused and I managed to notice some details:
- it's big but shorter than a XW5 - in the enclosed photo the TMB has the BS cell (not visible since is covered by the dust cap);
- there is a design problem that prevents people like me, that use glasses, to view most field - besides the rubber eye cup, there is a metal "ring" over the eyepiece surface that induces 2-3mm lost of eye-relief, when using glasses. I suppose it's to prevent users without glasses to get closer to the lens (black-outs start to be visible), but a different design would allow glasses users to reach closer the lens (with the rubber eye cup twisted) and normal users to use it with the rubber eye cup in normal position - with this design a normal user has to twist down the rubber to see all field...;
- although I read bad reviews of the 16mm version, this one seems very good. In fact, the geometrical distortion is not visible unlike the TV Nagler 5mm and even the XW5 has a bit. Will have more to say at the end of next week, after some real field tests... Hope at that time I can update my 5 mm test at cr-telescopes on www.pt-ducks.com... ;)
 

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TMB 9 mm on the Pentax PF100

Still didn't have time to test the resolution and some other details but managed to confirm that it focus on the PF100, with and without barlow cell (as in the photo enclosed - it doesn't look bad, aesthetically at least...:-O).
As I told before is not an eyepiece for eye-glass users, but those that are happy with the eye-relief of the XF zoom will not complain about it...|:d|
 

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man thats a sexy looking scope/ep combo! (shame i wear glasses)

BEt its not very light tho......I used to have an pentax 80mm and i thought it was too heavy.
 
updated 5mm ep test

Finally I updated the info on the 5mm eyepieces adding the TMB100 evaluation - see it at http://www.pt-ducks.com/cr-telescopes.htm#Test of 5mm eyepieces
The experience with the TMB was not the best but was good enough to wish to try again with a TV Ethos. The ES100 are no longer in my wish to test list since don't have 1.25" barrel, so not possible to use on spotting scopes. Even so I tested a 14mm in the TMB92+NikonFSA-L2 combo and the result shows that ES is also forgetting eye-glass users since the top the lens and the rubber eye-guard design induce a great loss of eye-relief.
Meanwhile I noticed that the Naglers type 4 have good eye-relief and tested a 17mm with the TMB92+NikonFSA-L2 combo. Unfortunately this version have problems with blackouts / kidney bean on day light use and the eye-relief (17mm) is not good enough to see all field (the same should happen with the 12mm version). The 22mm version has 19mm ER and no black out problems so I'm looking to test one...;)
Also noticed that the Meade 5000 UWA 18mm might be a good solution for birding. Does any one use it in a spotting scope?
Besides this last one (being discontinued - is being replaced by a 19mm version that has 2"barrel size...), the only other UWA eyepiece useful for birding, for eye-glass users, is the Docter 12.5 UWA http://www.apm-telescopes.de/docter-astro-eyepiece-uwa-125mm_proinfo_37366.html that might focus on spotting scopes - will not try to test it since is out of the magnifications range I want. However might be interesting for fanatics of wide angles.
 

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woodhornbirder

That is only useful for astro-telescopes like your WO. On spotting scopes the 2" will not reach focus with this. To reach focus with my 30mm UWA 2", I have to take out the 2" barrel piece and hand old it on the scope... With the Nagler 17 that isn't possible since it has lens in the 2" barrel.
I don't know if there is any spotting scope that can receive 2" eyepieces. Another detail is to know the maximum field stop of the scope. On the Optolyth 100 and the PF100 they are >= to the 27mm, the maximum of the 1.25" eyepieces. On the 2" eps the maximum is 46mm.
 
Largest true field

Though different from having the largest apparent field eyepiece, many birders and wildlife watchers might appreciate a scope-eyepiece combination that gives the largest TRUE field. There seems to be a gap between the highest power handheld binoculars and the lowest power, wide field spotting scope views. As an incremental improvement to satisfy this view, the Pentax PF spotting scopes (100, 80, and 65 mm apertures) can be modified to accept some 2" eyepieces. As David correctly points out, the maximum field is still limited by the 1.25" opening, so only 2" eyepieces with field stops smaller than 1.25" can be fully used here. The PF-80 and PF-100 can be modified by replacing the eyepiece collet-turning ring with a thicker one having a nylon screw to hold an adapted 2" eyepiece. A relatively low cost 26mm 70 degree apparent field SWA eyepiece used without its bottom 2" part provides maximum true field for these scopes. The PF-65 can use the same eyepiece, but here only modification to the eyepiece is necessary. Since there is no 1.25" tube projecting into the scope collet, the full 1.25" or 31.75mm aperture is available, rather than the usual 27mm.

I realize you may want more details but since this is my first post on this forum, it looks like I cannot post photos. I will refer anyone interested to a thread on the astro-site, Cloudy Nights in the "Cloudy Days & Microsopes" section (Spotting scopes) entitled "Pentax Spotter using 2" eyp. optics". Photos of my adapted scopes there should make the modifications clear. This url should get you there:http://www.cloudynights.com/ubbthre...7344/page/2/view/collapsed/sb/5/o/all/fpart/1

I made these modifications to my scopes last spring and used the scopes to watch birds, bears, and other wildlife this past summer in the northern Rockies. I think the low-powered, wide field views are worthwhile, especially for finding birds in thick cover and watching larger animals.
Bill
DRodrigues said:
woodhornbirder

. . . I don't know if there is any spotting scope that can receive 2" eyepieces. Another detail is to know the maximum field stop of the scope. On the Optolyth 100 and the PF100 they are >= to the 27mm, the maximum of the 1.25" eyepieces. On the 2" eps the maximum is 46mm.
Click to expand...
 
Last edited:
Thanks Bill. I just read your link and it's very interesting - you might consider putting it also on the Pentax forum. Your link also helped me to remove the Meade 5000 UWA 18mm from my wish to test list...
By the way what do you think of the quality of the SWA 20mm for terrestrial use? Have it much pincushion?
 
Well, >70 degrees AFOV is a challenge, but can be achieved with Pentax XW eyepieces without modifications.
Same goes for the Nikon Wide MC for the Fieldscope series (they are listed as 63 degrees AFOV by Nikon, but that figure comes from ISO calculation).

Just the other day, a newest Celestron C90 Mak arrived my home. The best eyepiece for it at the moment is a GSO Superview 20 mm (61x magnification)
I've ordered a William Optics SWAN 15 mm with 72 degrees AFOV. (83x)
Using the 12 mm BST Explorer (104x) craves a lot of light and the TFOV is very small.
Hopefully, the SWAN will be brighter and a bit easier to locate the birds with.
Of course I will try it with the Pentax 65mm too.
 
David, if you can find a 100 degree apparent field eyepiece of focal length 18 mm, THAT would also give the maximum field with a 1.25" diameter eyepiece scope - with significantly more magnification than my 26 mm SWA. I do not know if those are available, however. Any longer focal length 100 degree eyepiece would be vignetted in a 1.25" scope.

To answer your questions, the 20 mm SWA is a 72 degree Afov 1.25" barrel eyepiece and gives surprisingly good views, considering it costs less than $50 US. Both it and the adapted 2" 26 mm SWA ($70 US) show only a little pincushion. They do not have the "tack sharp to the edge" and "NO pincushion" features of the Pentax XW 20 mm, but are close. The 26 SWA has a larger true field and is also very comfortable and easy to use. I like it especially for public use. When grizzlies are visible on the slopes in Glacier National Park (USA), putting up a tripod with spotting scope gathers a crowd pretty quickly! The 26 SWA in the Pentax spotters, with its large exit pupil and wide field, makes it simple for even little kids to view.

I look forward to your continued testing of ultra widefield eyepieces. Thanks! -Bill

DRodrigues said:
Thanks Bill. I just read your link and it's very interesting - you might consider putting it also on the Pentax forum. Your link also helped me to remove the Meade 5000 UWA 18mm from my wish to test list...
By the way what do you think of the quality of the SWA 20mm for terrestrial use? Have it much pincushion?
Click to expand...
 
`This url should get you there:http://www.cloudynights.com/ubbthrea.../o/all/fpart/1`


We cannot proceed.
Access Denied.

If the post you are trying to find is an old post... you may be able to access it here: Archive Link

not working for me(
 
Woodhornbirder - Sorry the connection did not work. Try going to the Cloudy nights site here: http://www.cloudynights.com/ Then click on "Forums" and scroll down to "Cloudy Days & Microscopes" It is near the bottom. In that forum, the "Pentax Spotter using 2" eyp. optics" thread should be about 3 pages down. It is from January 11, 2011. I hope this will get you there.
Best regards,
Bill

woodhornbirder said:
`This url should get you there:http://www.cloudynights.com/ubbthrea.../o/all/fpart/1`


We cannot proceed.
Access Denied.

If the post you are trying to find is an old post... you may be able to access it here: Archive Link

not working for me(
Click to expand...
 
looksharp65
I think you missed the good idea of Bill - more than the AFOV he was looking and found more true FOV!!!
By the way don't know what image erector you are using on the C90 but you might be interested in having a look at http://www.pt-ducks.com/cr-telescopes.htm#Test of image erectors

Bill
The more complex 2" eyepieces have lens in the 2" barrel so should not be possible to focus on spotting scopes. I remembered that is possible to do something similar to your adaptation with the Optolyth (but needs screw thread) and I remembered that would be interesting to know the maximum prism exit field stop of top birding scopes. The Kowa 88 is probably the easiest to do this sort of adaptation since has a large screw thread besides the bayonet system for the normal birding eps...
 
Hi guys,

the SWAN has landed yesterday. Being a tiny, well-built and very elegant eyepiece, it is apparently not made for the Pentax PF-65EDAII. (More on that later)

I ordered it for the C90 Mak and it seems to fit this slow (f/13.9) scope very well. The view is relaxed and very wide, though not tack sharp close to the edge. With 83x magnification it seems to touch the realistic limit of magnification with the C90.

On the fast (f/6) Pentax scope, however, it is a disappointment. It feels like the eye relief is less than with the C90 (?!), but above all it shows way too much curvature of field. With a giant AFOV, some edge deterioration could be acceptable, but the SWAN and the Pentax don't really make a happy marriage.

//L
 
DRodrigues said:
looksharp65
I think you missed the good idea of Bill - more than the AFOV he was looking and found more true FOV!!!
By the way don't know what image erector you are using on the C90 but you might be interested in having a look at http://www.pt-ducks.com/cr-telescopes.htm#Test of image erectors
Click to expand...

Thanks, I'll have a closer look tomorrow. Now I'm using the supplied cheap 45 degrees that comes with the C90 Mak.
It's barely acceptable, and for planetary watching purpose it's definitely no good.

//L
 
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