View Full Version here: : Pentax XF12 Users query (Steve H - Janoskiss?)

25-06-2007, 10:33 AM
I'm looking at the 12-13mm eyepiece range and am drawn to the Pentax XF 12mm and Hyperion 13mm as they are both $215. I already have the hyperion 8mm and love it. Quite a few people, like our own Steve H, rave about the Pentax and report that it has an excellent light throughput with 6 elements to the Hyperion's 8 elements.

My main concern about the XF range is that Pentax state that this a bird watching eyepiece for spotting scopes, yet Frontier Optics tout it as a Planetary Eyepiece. Is this also OK for Deep Sky, Nebulae, Clusters and dare I ask Galaxies?

Am I correct in treating the XF as an XW with only a 60 degree Apparent Field of View, with an excellent bank to buck ratio compared to the more expensive wider angled Pentax sibling?

The scope will be an F4.72 SkyWatcher/Saxon 10" dob, which is why I picked on Steve.

25-06-2007, 12:32 PM
It will be awesome on galaxies and nebulae. The XWs are also marketed by Pentax mainly as spotting scope EPs.

The XW is also better i.t.o. comfort but the XF is pretty good already. The 10mm XW has no visible field curvature the 14mm XW has more than the 12mm XF. I don't find the FC of the 12mm XF bothersome except perhaps on the moon which comes close to filling the FOV in a 1200mm FL scope.

Hey! Stop picking on me! :P
If you can afford the 10mm XW, go for it - it's the best DSO and whole-moon-in-fov lunar EP for that scope IMO - but if not the 12mm would be a great general purpose DSO EP also. Leaves the 13mm Hyperion well behind IMO. OTOH the Vixen LVW is worth considering as an alternative. Different characteristics and style of EP. I like both the XFs and LVWs for different reasons. Could not pick a winner but for my purposes the XF suits better. Best if you try compare taking your time with each EP.

25-06-2007, 12:47 PM
Hi Steve
Thanks for your advice:thumbsup: . I did note that OPT are doing LVW's at good prices, but unfortunately my budget is limited, so it looks like an XF 12 at some point in the near future;) .

25-06-2007, 05:04 PM

Forget about what manufacturers/sellers claim as to what purposes specific eyepieces are suited to. Two of the most widely used "planetary" telescope eyepiece designs of all time, the plossl and the orthoscopic were originally designed for use in microscopes. It just so happened they worked very well in telescopes.

It's worth noting that Pentax produce very little in the way of "specialist" astronomical equipment. Four of the Pentax XW series are sold as "spotting scope" eyepieces and the other four are sold as "astronomical eyepieces". A pure marketing ploy as they are all essentially designed with similar design objectives and they all work equally as well for both purposes.

I own the 8.5mm Pentax XF. It is an excellent lunar/ planetary eyepiece. Of course it works equally as well in a spotting scope. It would also work very well in a microscope.

CS-John B

25-06-2007, 11:28 PM
G'day there Pete,

I bought an XF12 from Frontier Optics about a month ago; what with the weather, I've not been able to give it extensive use.

There have been a couple of reasonable nights viewing however and certainly no glaring shortcomings have been obvious. With an F5 Newt it gave a very respectable view and only at the very edge did I detect some minor abberation which I've seen that in more expensive EPs as well. I note that you use an F4.72 Newt which is more demanding.

It's an aesthetically pleasing EP with its light weight and compact dimensions. Coupled with more than competitive performance and its hard to fault or beat at its price.


26-06-2007, 11:30 AM
John, thanks for the update on Pentax. It's just that their website seemed to be worded defensively as if being cautious about making specific claims, whereas everyone else seems to be bragging about how tack sharp and contrasty their eyepieces are. I didn't know that Plossls were originally designed for microscopes. Then again I've seen similar scenarios within the audio industry where a microphone like the AKG D12 was marketed as a "warm" vocal mic, yet because it emphasised frequencies around 80 Hz ended up being the industry standard mic for Bass Guitar and Bass Drum instead.

Mark thanks for your update as it confirms my hunch that there's more to the XF range than meets the eye. I'm not too bothered about the edge, and know that a 60 degree XF will show less edge abberation than a 68 degree Hyperion in a fast scope.


26-06-2007, 11:39 AM
Steve, John, Mark
I've decided to go for the Denkmeier D21 and the Pentax XF12 to cover the 20-22mm and 12-14mm ranges. The light throughput, good eye relief and reasonable 60-65 degree apparent field of view are the main deciding factors. I know that I won't be disappointed.
Thanks again for sharing your experiences with the Pentax eyepieces.

27-06-2007, 12:16 AM
The Denk 21 is a nice eyepiece...I use a pair in the Denk "Big Easy" binoviewer...

While I love my 24 Pan (and will never part with it)...they are every bit as good (some might give them a slight edge besides difference in magnification)

I hope you enjoy it!

27-06-2007, 10:04 AM
Thanks Wavelandscott, I got the impression that Denks were good eyepieces, but I was initially hesitant as they are often sold as a pair and designed mainly for Binoviewing. John of Ausastronomer fame put me straight on them. I know that I can get both eyepieces from Frontier Optics, so may be able to wangle something with Daniel.

Whilst I am ready to order a SkyWatcher/Saxon 10" dob the skies have been rubbish lately in Perth, so I may get the eyepieces first. The problem is someone always sells a tempting eyepiece here on IIS and I've bought 3 already, so maybe I had better not look on the For Sale section until I've got the scope. :rofl: