Eyepieces for the 80mm Pentax (1 Viewer)

[JBT]

I just found out that the Pentax scopes can use all kinds of different astronomical eyepieces which has got me very interested in getting a Pentax spotter instead of the Nikon Fieldscope. I've done some research but having trouble finding what I'm looking for I'm hoping someone can help before I make my decision. I'm looking for a fixed wide view eyepiece that is between 15 and 20 power when used on the 80mm scope. If anyone know if they make one or give me some ideas on where I could look please let me know.

Thanks,
Joe

 

[Kevin Conville]

You're going to have a tough time getting that low a power with wide angle.
The PF80 has a focal length of 504 mm. Magnification = scope's FL / EP FL.
The best quality eyepiece that I know of that gets you in the neighborhood AND is 1 1/4" would be the 24mm Panoptic which yields 21x. I haven't used one on the PF80 and won't vouch for it's performance with this scope.

A Pentax XW20 will give a 70 degree AFOV and 25x and in my opinion is the best wide angle setup for that scope. That same EP on a PF65 will give 19.5x.

For very low power and wide angle look at small scopes. With their shorter focal lengths there are more options.

 

[FrankD]

JBT,

What price/performance range are we talking about here? I have been doing alot of tinkering with a variety of 20-25 mm eyepieces lately. As Kevin mentioned above you would need at least a 25 mm to get in the ballpark, magnification-wise, for what you are looking for. As I recently found out there are alot of eyepieces out there with alot of different designs.

There are also alot of individuals on here that have alot more experience with eyepieces than I do. If you are looking at the relatively inexpensive route (under $150) then I can offer alot of suggestions. Above that my only experience is with the XW 20 and that binocular speaks for itself.

Just to give you a little something to chew on, I am currently using the SWAN 20 mm wide angle eyepiece (72 degrees). I find its optical performance to be very good. Good apparent resolution, good color rendition and good edge sharpness. It isn't the equal of the XW 20 in terms of the latter characteristic but it most certainly would satisfy all but the most discriminating user. I definitely prefer it to the Stratus 21 mm (see my Pentax 20 mm eyepiece thread in this forum).

Hope this helps somewhat.

 

[JBT]

Thanks for the info guys I guess I might need to bump up my desired magnification a bit. I've done some more research and found quite a bit more info most of it came from here http://birdforum.net/showthread.php?t=77678&page=2 . What I'm hoping to achieve is a view similar to what I got with my Nikon 50ed using the Nikon 16x/24x/30x wide eyepiece. At 16x I believe I got a FOV around 226 @ 1000 yards which to me looked very binocular like it was great but it didn't work to well in low light. I was thinking if I could find an eyepiece with similar results but in a 80mm it would be the ultimate for me. My goal is to find the right combo of EP and 80mm scope to achieve a view similar to a top of the line binocular like the Swaro 15x56s but in 80mm. So I'm hoping to get way better results in low light than any bino ever made.

My reasoning behind all this madness is that I'm blind in one eye and I'm way more comfortable behind a scope than a binocular as far as the ergonomics go. I also feel like I'm wasting my money buying bins because I only use half of the optics.

 

[Kevin Conville]

If you don't mind spending the money, a Swarovski 80mm HD with their 20XW EP should give an amazing view. 180' at 1000 yards.

I don't think a top cabin view will be available below 20x with an 80mm spotting scope. If you're amenable to toting a short focal length 80mm (or so) astronomical scope that accepts 2" EPs, then you can probably have your very low power view. For me the "price" of that view is too high however in weight, fragility, and non-waterproofness. I'm also not aware of a 2" erecting prism, though I could be wrong. Without the prism (and just using a diagonal), you'll get a mirror image view.

 

[mmdnje]

my 2 cents: get the pentax XW20.

 

[RJM]

Problem with trying to use a 24mm widefield eyepiece in the PF-80ED (or any fieldscope I think) is the prism clear aperture is only about 23mm while a widefield eyepiece like the 24 Panoptic has a fieldstop of 27mm. This means you will get some vignetting of the outer field edge, probably equal to the same FOV as a 20mm XW.

If you want a low power largest exit pupil/brightest view, then a 24/25mm plossl will give you that and with good eyerelief. But the FOV will be about the same as 20mm XW.

HOWEVER, the PF-80ED seems to suffer from some mechanical vignetting when focusing so it may not be a true 80mm aperture scope anyway. I think my sample tested out at ~77mm at infinity all the way down to ~65mm at close focus. This was first detected by Henry Link and search of this forum for posts under his name will give more details.

cheers,
Rick

 

[medinabrit]

Ive had dozens of EPs but ended up with the Pentax XW & XF EPs as i found them to be the best in my modest opinion.
When looking for EPs go to the Astromart site where you will find hundreds of great used EP deals . I must have purchased at least 15 on there & never had a bad experience .
Brian.

 

[John Dracon]

Joe - As the other fellows have recommended, the XW 20 is the way to go. When I purchased my Pentax 80 mm ED, it came with a zoom which I really didn't like. So XW 20,14,& 10 EPs were purchased, and they work just fine. Also have the Pentax 65 ED which I use outside and find the XW20 to be excellent.

You mention that you are blind in one eye. One of my nephews recently lost his vision completely in one eye. I had on hand a Kern IF binocular (now a monocular because the other half went to a man with sight only in one eye), and so I gave that to my nephew who really uses it. Zeiss made an excellent 8 power monocular back in the 1960s as a telephoto lens for cameras. They occasionally come on ebay and go for around $150.
Of course Zeiss and other make monoculars today. You may find a monocular will help supplement your use of your spotting scope. John

 

[JBT]

Thanks for all the info guys its been very helpfully. So far I'm leaning toward the 80MM with the pentax 20xw but the 20xw in the 65mm is also very tempting because I tend to like views from lower mags. But I also find myself looking to the Nikon 82mm because I already have 2 eyepieces for it a fixed and the zoom.

Here's alittle of my scoping history. I started out with the Zeiss 85mm with the zoom eyepiece which is considered one of the best wide zooms on the market. I loved this scope but even with the wide view I wasn't getting the view I wanted out of it. So I sold it and switched to a Nikon Fieldscope III 60mm non ED with a 24x ds ep. I loved the view I got from that scope and ep combo. Well then the little Nikon 50ed came out and caught my attention especially after I found out that my 24x for the FS III would work on the 50ed and give it 16x with a fov over 220 @ 1000 after finding this out I had to give it a try.

I bought and tried every eyepiece available for it and ended up keeping the 16x(my ep of choice), 20x and the 13x-40x zoom. I liked the 27x but it was too dark for my eyes and I never used it so I sold it. I really enjoyed the view I got from the 16x I could look through it for hours at a time with no eye fatigue whatsoever. I ended up selling my 60mm FS III non ED and keeping the 50ed. The only complaint I had with the 50ed was the lack of higher power and the low light performance but for me the view from 16x made up for it.

A year latter my 50ed and 16x ep has come up missing and I need a new scope. If I still had the 16x ep I would probably get the 50ed again but this isn't the case. Sorry for the rambling but I thought if I gave this info it might help give a better example of what I'm looking for. After writing all this the more I think the Pentax 65mm w/ the 20XW might give me the results I'm looking for. Unfortunately I don't having anywhere close by to test one out first so I'm going to have to do the buy then try and hope I like it.

Thanks again everyone,
Joe

 

[John Russell]

Joe,
Just a thought. Have you considered the Fujinon 16x70 FMT-SX2? It enjoys an excellent reputation amongst astronomers and has a wide 4° FOV. One drawback from your point of view might be a close focus of 16m.

John

 

[RJM]

I've owned the Pentax 65ED v1 and 80ED with XWs, as well as the Nikon ED50, EDIII, and ED82 and a Kowa 663 Prominar all at the same time have done some extensive comparisons as to their dslr digiscoping capability. A digital camera's sensor takes no prisoners and reveals many issues the casual visual observer may not notice.

The Nikon's with their excellent DS eyepieces CLEARLY have better optics than the Pentax samples I had. This was shown in daylight pics and during star testing. So while the Pentax's may be good enough for the typical visual observer, they weren't suitable for me and were sent off to new homes.

FWIW, the Kowa 663 Prominar probably has the best optics of the bunch. But my Nikon dslrs play nicer with Nikon fieldscopes. Decided to compromise and keep the ED50 for hiking and ED82 for super-telephoto lens and sold the EDIII (too big/heavy for its aperture).

The Kowa sits in the closet waiting to be joined by its larger 884 sibling (when I can get a good deal!) for a faceoff with the Nikons.

Rick

 

[FrankD]

Joe,

I think you would love the 65 ED/XW 20 combination. I used it almost exclusively for two years to hawkwatch. A wonderful combination as it produces a wide field of view with little to no distortion and very low levels of color fringing.

 

[DRodrigues]

Problem with trying to use a 24mm widefield eyepiece in the PF-80ED (or any fieldscope I think) is the prism clear aperture is only about 23mm while a widefield eyepiece like the 24 Panoptic has a fieldstop of 27mm. This means you will get some vignetting of the outer field edge, probably equal to the same FOV as a 20mm XW.

Rick,
I was surprised by this and did a small test with a PF100 and a Optolyth 100mm, that seemed to have a bigger prism fieldstop than the PF100. For the test I used a Vixen NLV40mm (it has the maximum fieldstop possible from a 1,25" eyepiece), and a 2" 30mm UWA (without the 2" barrel, hand hold to allow focus).
The results were that the Vixen didn't vignetted in both scopes, and the UWA showed bigger FOV than the Vixen (+9% on the Optolyth and 18% on the PF100, at close focus), and even the UWA didn't vignetted in the PF100...
This show that prism fieldstop is not a limit factor for the use of big FOV eyepieces (at least in these 2 scopes...). In this way I could suggest Joe other eyepieces:
- there is a Baader Hyperion 24mm that has a FOV similar to the TV Panoptic, has better eyerelief and is much less expensive. Does any one tested/use it in a Pentax scope? By the way, does anyone tested the 31 and 35mm 2"versions in a scope? They have a 1.25" adapter that is supposed to give the widest FOV possible from a 1.25" attachment.
- if Joe want low power he could also use 32mm (16x) or 40mm (13x) Plossls, with the same FOV. These are usually cheap and the new Vixens NLV and NPL have twist-up eye-cups that are very useful for birding - 40mm problem is usually their very long eyerelief that makes observation tiring after a bit of time (difficult to hold head still). In the NLV that I have that problem doesn't exist since with the twist-up system we reach a comfortable stable position.
David