Fixed EP recommendation for PF-65ED (II) (1 Viewer)

Hi,

I'm about to put in a order for my first scope: a PF-65ED II with a fixed WX series eyepiece. At the moment I'm leaning towards a 14mm/x28, based on the BVD review, and the fact that it seems to a pretty useful all-round magnification.

What I've found whilst searching around for info on EP's is that Astronomy users note that WX14's exhibit field curvature that isn't evident in other WX EP's. This seems - according to reviewers - to manifest as the edges of the image being slightly out of focus.

I'm quite unversed in the minutiae of optics, so I'm uncertain how significant this field curvature will be in birding usage. Would I be better off looking one of the other WX EP's? Any XW14 owners care to share their impressions?

cheers
Paul

I have the 10, 14, & 20 XW,S they are exellent .Definately my favorites.
After i read your post a few minutes ago i put the 14mm XW in my 80PF Seems ok to me , no curvature that i can see.I do prefer the 20 for most viewing though.
Nice feature of the XW,s is that you can unscrew the eye cup & use the thread on the EP to attache a camera with a suitable adapter.
You wont be dissapointed with a XW.
Brian.

Paul,

Each of the XW series focal lengths has its own particular mix of field curvature and astigmatism. Look at this Japanese Pentax data: http://www.pentax.co.jp/japan/tech/xo-xw/64.html

You can see that the field curvature (lines that curve away from the vertical line) is not much different in the 20mm and 14mm, but the 14mm has less astigmatism (difference between the dashed and solid curved lines). You may see more of both in the 65mm compared to the 80mm Pentax because the 65mm's focal ratio is lower. I have a 14mm XW. The field curvature is not bothersome to me. I wouldn't dismiss the smaller, lighter and cheaper Pentax 12mm XF. I just read an excellent review of it at Cloudy Nights.com

The field curvature issue really depends on the scope you're using -- I've read about those same issues over at the astro forums, but you have to realize that people are using many different types of telescopes with different focal lengths and optics systems.

Considering that the Pentax eyepieces were designed for Pentax scopes, I doubt you will see a problem. This field curvature is only apparent at the very edge of the field, if it's visible at all, and it's more of an issue for nightime astronomy use where people want to see a flat field of stars that's in focus all the way across. Most of the time with daytime birding use, you'll be looking at the middle of the field anyway. I highly doubt it will be an issue, or that you would even notice it considering this is your first scope.

The XW eyepieces are world-reknowned. I have a PF-65ED and I use a 14mm Pentax XL (the predecessor to the XW), and I would highly recommend that. The 28x fixed magnification is basically ideal, it hits the sweet spot of the 65mm scope, and you still get a huge, bright, wide field. You won't be disappointed with the XW14.

As to the XF 12mm, I would only get that if you are 1. concerned about the extra money or 2. concerned about a little extra weight. I had the XF 12mm originally, and sold it when I compared it to the XL 14. The XF is cheaper and smaller, and both eyepieces are equally sharp in the center of the field. However, I found the XL to be brighter, has a much wider field of view, and it holds the image quality to the edge much better than the XF 12.

Thanks for the replies. Nice to have some feedback from a PF65 owner on the EP selection.

I'd started digging about for info on scope optics and came across a great site with some good info on curvature here:

http://starizona.com/acb/basics/equip_optics101_curvature.aspx

There is also a fantastic site which despite focusing on camera lens is very useful:
http://www.vanwalree.com/optics.html

After reading the above I can see that the EP/Scope combination is going to have significant effect on curvature. eitanaltman, your points are well taken, and I think I'll stick with the XW14.

The XW14 on the 65 gives x28, while the XW20 on the 80 gives x26. So it seems a fixed magnification around that area is widely (from a sample of 2) preferred

Thanks henry I hadn't seen the technical information before. I'll have to run the text thru a translator.

Fortunately I'm getting the scope and EP through a contact who works for the local importer so that makes the XW's a bit more affordable, but still substantially more than the retail price of the XF's.

cheers
Paul

I have a pf-65 ed that I use with a xl14 (predicessor of the xw14) -- it works very nicley on that scope, and it is the one that "lives" on that scope. I also have a Pentax zoom (8-24mm) that is used on the pf65-ed. The fixed 14mm eyeice has a much greater field of view than the zoom.

Jeepnut,

Thanks for your comments!

The PF65-EDa II's have apparently arrived in the country as of Thursday, so I'll hopeful be collecting mine on Monday :t: It does seem like the XW14 is the way to go. The distributor was waiting on stock of the XW14's last time I checked, but they hopefully have arrived too.

cheers
Paul

Pentax in hand...

I picked up the new PF65-EDa today. It's a nice looking unit, and very solidly put together. Unfortunately the xw14 wasn't in stock so, I've just done a quick trip to pick a up 9mm meade series 5000 5 element plössl. While I was in the shop I had the opportunity to look through a Meade UWA EP, which was really quite impressive.

I've only had a brief opportunity to use the scope in the park across the road but it seems to be bright and very sharp even with the "lesser" EP. It's pretty hot and windy, with lots of heat haze so hardly ideal conditions.

The guy at the scope shop (who sell Nikon & Swarovski plus astro scopes) was pretty impressed with the PF65 and felt that the top notch EP's like the Meade UWA really showed off it's abilities.

I don't have sufficient experience with scopes to proclaim a "highly recommended", however I'd suggest taking a look through one with a decent fixed eyepiece if you have the chance. I'm know that I'm a very happy camper, even before I get my xw14 EP.

cheers
Paul

I finally got hold of the XW14 on Friday, and have to say I'm blown away by the view through it.

I had a chance to head down to the local waterhole (adjacent to the 2006 Commonwealth Games athletes village fwiw) this morning, and found that the EP was a vast improvement over the Meade. I guess this shouldn't be too surprising given the dimmer image that results from greater magnification on the 9mm and the fact that the Pentax retails for close to 3x more $$.

The hot windy weather meant the pickings were slim on the big pond, but there was a solitary Australasian Grebe, Australian Wood Duck and a couple of Pacific Black Ducks to look at. The image was bright and razor sharp, and I didn't notice any obvious effects of field curvature. Across the road in the reedy pond there was a bit more action, Little Pied Cormorant, Purple Swamp Hen, Dusky Moor-hen, and a couple of male Red-rumped Parrot. Again the image with the WX14 was stunning even when looking at the Red-rumped Parrots feeding in the shadows at the base of a tree.

I can see why the BVD review rates the PF65/WX combination so highly. The WX EP is really quite stunning, and if your in the market for an EP from the PF65, I'd definitely recommend putting the WX14 on your short list.

cheers
Paul

Spent a few hours at Jawbone Nature Reserve (approx 10km south west of Melbourne CBD) with the scope and both EP's this afternoon. The weather is quite warm and very humid so less than perfect viewing conditions.

The XW14 was a pleasure to look thru, but I'm becoming increasingly disappointed with the performance of the Meade series 5000 9m plössl. I have to admit that heat haze was a factor, but in comparison with the XW14 the image it gave was rather soft. I felt I had more hope of identifying a group of what appeared to be sooty and pied oystercatchers sitting on a sandbar about 200-250m offshore using the XW14, as the added magnification was negated by the softness of the image.

I'm not sure how a XW10 or XW7 would have fared in the same conditions??

cheers
Paul

Paul,
I too have my doubts about the usefulness of higher magnifications for birding scopes but if you occasionally require around 45x the 8.5mm Pentax XF should be outstanding.
It is tested on this site:- http://www.astro-okulare.de/. Unfortunately, there is no English translation of the XF tests but once you have learned to interpret the results on the English site you can click on the + sign next to Pentax on the German site.
While sacrificing a little AFOV, the XF8.5 would appear to be at least as sharp as the XW7 and XW10 and at half the price!

John

John,

Thanks for the link.

I've had a dig around on cloudynights and came up with a couple of semi-relevant reviews:

http://cloudynights.com/item.php?item_id=1438
http://cloudynights.com/documents/pentax.pdf

There is also an interesting post comparing 7xw and 8.5xf on this site:
http://www.birdforum.net/showthread.php?t=72778

One thing that keeps coming to mind when I read these astro reviews is question "just how relevant is this??". I keep reading comments on how such-and-such EP is good for planetary observation but bad for Deep Space Objects. The criteria being used for judging the EP's - an illuminated or light emitting object on a black ground - is quite alien to the conditions under which EP's are used for birding, so just how applicable are the reviews?

cheers
Paul

PaulJacobson said:

One thing that keeps coming to mind when I read these astro reviews is question "just how relevant is this??". I keep reading comments on how such-and-such EP is good for planetary observation but bad for Deep Space Objects. The criteria being used for judging the EP's - an illuminated or light emitting object on a black ground - is quite alien to the conditions under which EP's are used for birding, so just how applicable are the reviews?

Click to expand...

Paul,
I'm not an astronomer so I really wouldn't know. Perhaps Henry Link could chime in on this one.
However, the TV Radian/Pentax XF comparison was very thorough and the results fairly conclusively in favour of the XF. I wonder if some other comparisons are prejudiced by the expectations, i.e. eyepiece A is twice as expensive as eyepiece B so it's got to be brighter, sharper etc.
BTW, your first obsevations with the scope brought back fond memories of birding in Oz a couple of years ago. There are so many more species there and, of course, everything was new to me anyway.

John

I'm quite surprised by the "hard limit" that atmospheric conditions put on resolution (obviously I'm a scope newbie!).

I decided to try some very basic testing on my 2 EP's, as I've had some disappointing experiences with the Meade EP.

I located a pretty basic copy of the USAF1951 optical test chart that was scaled for A4, which I printed thru a 1200dpi laser printer on standard bond. I mounted this to a scrap bit of 1" MDF. I placed the target leaning against a post at ground level approximately 100M away from the scope. All this is very non-optimal, but quite adequate for purposes of comparison.

First try was mid afternoon, temp about 29C, 54% humidity and killer heat haze.
On the target I was able to resolve element 2 in group -2 using the XW14. Switching to the Meade 9mm gave me a larger image but was unable to resolve any further detail on the chart.

I decided to make a second try at about 7.30 pm, which is pretty late afternoon so light is less than optimal. The key thing was that the temp had dropped to about 22C (78% humidity) and the heat haze had gone. There was a moderate breeze which caused some minor scope shake. Using the same setup, I was now able to resolve
to element 2 in group -1 with the XW14. I'm pretty sure I could have resolved even more detail if the scope was better damped. Switching to the Meade 9mm I was able to resolve to element 6 in group -1, and at times element 1 of group 0.

Anyway this was a stark illustration of the effect of atmospheric conditions, and I was quite staggered at the difference the cooler conditions made. This went a long way to explaining why I'd had issues a few days ago in similar conditions.

Hi Paul,

I've had similar experiences with extra magnification vs. extra resolution. As I mentioned, I use the XL 14 as my "all-purpose" eyepiece for the PF-65, and I love it. I've been searching for a high-magnification eyepiece for those times when I need to get a little closer.

My experience is quite parallel, as for quite some time I had the XL 14 and the TMB/BO 9mm, which is similar to the 9mm Meade plossl. In extensive comparisons, I find that, while the image is slightly larger, I really can't *resolve* anything extra with the higher mag. I found that I wouldn't ever really reach for the 9mm after a while, perhaps because the difference between 28x and 43x isn't that dramatic. Mostly, however, I've found what you have -- the limiting factor is really the air between the scope and the target bird!

Under ideal conditions -- indoors, no heat haze, with a target only 50mm away -- the PF-65 can resolve additional detail up to 60-70x I would bet. But, in practical usage, 30x is really the sweet spot.

I've since tried a few others, including the Scopetronix 7-21mm zoom and a Celestron Deluxe Zoom 6.5-18mm. I also traded my 9mm TMB/BO for a 7mm of the same line, hoping the extra magnification separation (28x to 55x) would tempt me to use it more. Unfortunately, there's only occasional situations where 55x is even feasible in real-life birding conditions. I still find that I rarely am tempted to switch out from the XL 14 -- and the TMB/BO's are about as clear of a high-power eyepiece as you can find.

So, basically, if you want to study a close-up bird (i.e. within 100m) in exquisite detail, when there isn't heat haze, you can go higher power. But if you're trying to see a bird that's 1/4 mile away in bright sun with shimmering heat haze, there is no eyepiece that can allow you to do that, because the scope/eyepiece isn't the limiting factor in that optical chain.

As an aside, I had the XL 10mm as well -- also an exceptional eyepiece. But I sold it for the same reasons; it just didn't allow me to see anything extra over the XL 14mm, and I didn't want to lug around an extra "grenade" that didn't even show me that much extra.

I would bet that the best combination is to use a fixed, ~30x ep for almost all situations, and carry around a high-quality zoom like the Vixen for those occasional times you'd like extra mag. The advantage of the zoom is that you can dial it up and down to find the sweet spot for magnification given the seeing conditions of that moment.

I use the 65ED with both 14XW and 20XW. They are both great. My only comment is don't rule out the 20XW ... the huge field of view makes it a joy to use.

eitanaltman,

it does sound like you've tread the path I'm on at the moment, and the suggestion of a zoom as a backup/alternative to the XW14 does seem to have a lot of merit.

The local distributor has stock of the XW7 but I'm pretty hesitant to spend the money on that given the consensus on high mag EP's. The XF 8.5 is on back order and will be at least 4 weeks before they have stock. Both the XF and 8mm-24mm zoom's are also available.

I guess I better do some serious research before I splash the cash.

cheers
Paul

pf65 zoom?

gentlemen, ma'ams:

In my humble opinion the 14mm ep (especially the Pentax XL or XW series) are the dead-center, best of bread, good choice, eyepeice a very broad range of conditions. Don't get me wrong, I would love to be able to report on the entire line of ep's. The 10mm for the power, the 20mm for the exit pupil, but in all honesty I have used the zoom ep at 24mm (26x) on the pf100-ep, after dark in YNP, it was quite adequate for observation of coyotes on the ridge behind the Yellowstone Institute in the Lamar Valley.

I currently own a pf65-ED and a pf100-ED, two Pentax zoom eyepeices and one fixed xl14m eyepeice, the pf100-ed always has a zoom eyepiece attached to it, the pf 65-ed always has the xl-14 attached to it, the second zoom ep is almost always in an armoured case.

The zoom eyepice is great for flexibility, the xl14mm delivers a great field of view and incredible clarity (resolution), as it should, it is right in the mid-range of magnification of refractor scopes. In any case the second zoom ep is rarely used.

I almost forgot to mention my first Pentax scope was p0f80-ed -- it was sold to buy the pf100-ed that I do not leave home without. Within a few months, I had to have a pf65-ed, not a bad choice, I would do it again.

For matter of fact, I have never seen referrence to, or about Pentax scopes that would cause me to seek other brands.



The pf65-ed is simply more scope than the money -- spend what you save on a quality ep -- remember, Pentax invented and created the market for high quality ep's.

Jeepnut,

I don't think you'll get (m)any dissenting opinions on the PF65/XW14 match up. :brains:

Are you using the SMC 8mm-24mm on the PF65? I'm curious how well that works out as the 8-24 seems like it would be huge on the smaller scope.

Anyway from the thread so far it looks like the recommendations for primary fixed EP for the PF65 ED[a] [II] in order of preference are:

i) XW14 or XL14 (x28)
ii) XF 12 (X32.5)

cheers
Paul

PaulJacobson said:

Jeepnut,

I don't think you'll get (m)any dissenting opinions on the PF65/XW14 match up. :brains:

Are you using the SMC 8mm-24mm on the PF65? I'm curious how well that works out as the 8-24 seems like it would be huge on the smaller scope.

Anyway from the thread so far it looks like the recommendations for primary fixed EP for the PF65 ED[a] [II] in order of preference is:

i) XW14 or XL14 (x28)
ii) XF 12 (X32.5)

cheers
Paul

Click to expand...

I have the XF12 and use it mainly for digiscoping. I use a 8-24 zoom for general birding................but I'll be getting a Pentax XW14 later this year (hopefully as my primary eyepiece if it's as good as everyone is saying)

Others on this forum recommended the Baader Hyperion 13 and 17 eyepieces and I admit they look a good option. If you live in Europe or the US these are attractively priced but for me with the weak yen are almost as much as the Pentax XW once you include postage. Baader wanted a shocking 58 Euros (!) to post ONE eyepiece to Japan...........