Pentax SMC-XW 3.5mm

 Info  Votes  Messages  More Stats  Up One Level
Brand and Model:Pentax SMC-XW 3.5mm
Price ($USD):339
Type:Ultra Wide Angle
Focal Length:3.5 mm
Barrel Size:1.25
Apparent FOV:70.0 degrees
Field Stop Dia.:4.3 mm
Eye Relief:20 mm
Weight (lbs):14.3 oz

Vote Highlights Vote
Pentax SMC-XW 3.5mm
Eyepiece: Pentax 3.5 XW sale price $399 cdn
Test scope: William Opics 80mm riplet ED f7 560mm fl
Comparison oculars: 7mm ortho barlowed with 2X TV, barlowed Speers Waler 5-8 zoom, Orion Epic ED 3.7mm.

Test objects: Moon, Mars Oct/Nov 05, M45,42,43,57 Double cluster

On axis the Pentax 3.5mm and barlowed ortho produced nearly identical results. One time the Pentax would win out the other the ortho, depended on the seeing.
Off axis the Pentax showed less color and a crisper image then the barlowed ortho or the other oculars. The other oculars displayed more color and had more field curature requiring slightly different focus with objects on the field edge. I don't really find the twist up / down eyeguards to be such a great feature on any eyepiece I've ever tried. I always wear my glasses for astigmatism, but even when I do take them off I never find this particular feature ever to be much use.

Negatives: size = 14.3 oz and it's a big eyepiece, you can get it to kidney bean over 20% of the field on the Moon but you really have to work at it and place your eye in a strange off axis position.

Positives: 70 degree AFOV is about the largest field I find useful anyway and they created a large flat beautiful field with this eyepiece. Eye relief is very forgiving, it feels like 20mm and eye placement is not critical unless you go way off center. Build quality is 10/10, you can buy this eyepiece and know it'll always be there for you unless someone steals it!

Recommendation: the Pentax is a VERY comfortable eyepiece which allows extended viewing compared to any other eyepiece I own. At 160X you are just under .5 TFOV which allows nearly the entire lunar surface to be viewed. When swapped with the ortho at the same power you feel as though you are looking through a straw. IF I was observing planets with a tracking mount in a wind sheltered observatory I would not buy this eyepiece, you could get along fine with the ortho and barlow. But for those of us who observe at high power with alt/az scopes AND with glasses this eyepiece is the way to go.

I should add that I had previously viewed many objects with the Nagler 3.5mm and I think that's also an excellent ocular but not as comfortable to look through with glasses on. If I didn't wear glasses I'd get that eyepiece, it's smaller.


PS I still stick by my remark that if pressed to keep one eyepiece out of all that I've ever looked through my med-high power would be the Speers Zoom, It's not better then any Pentax/Nagler at a particular focal length but it's so close and you get 5-8mm to play with.

Overall Rating: 9
Optics:10 Value:10
Weight: 5 (Veritable Vote)
Link to this vote:

Pentax SMC-XW 3.5mm
Expensive EP with excellent eye relief, idiosyncratic eye guard that cannot be rapidly adjusted and Pentax' multicoatings that seem to have a strong circular dichroism (making "floaters" appear in the eye.)

In my very subjective evaluation (Orion 80ED/f7.5, TeleVue 101NP/f5.4 and, just for the heck of it, Celestron 9.25 SCT), this eyepiece was less impressive than Nagler type 6 3.5 (although the outer 10-20% of the field in the Pentax seemed sharper than the outer 20-30% of the Nagler t6; both were perfect on-axis). It also seemed to be somewhat inferior to Nagler's 3-6 zoom (obviously, the Pentax had a wider field and better eye relief, but the little zoom "felt" better on Jupiter and Saturn. Also, the zoom was very "warm", while the Pentax was "cold". I prefer "warm" but many people like the blue tint more.)

This "holy hand grenade" is very impressive at star parties (kids and novices seem to be in awe of it, hence I am keeping mine but I will not be using it much myself); not the best EP around; try before you buy: floaters may be very annoying (just one look through this eyepiece will tell you whether your eyes are too old for this EP...)

Overall Rating: 7
Optics:7 Value:7
Weight: 1 (Unreliable Vote)
Link to this vote:

Pentax SMC-XW 3.5mm
This ep gives 137x in my TV-76, and was purchased 6 months ago as a widefield option to my short fl orthos. It is large and heavy, but wow...what a view. The image is clean and crisp. No blackouts and very little, if any, ghosting. The top lens is huge (almost as large as my 35mm panoptic!) The threaded eyecup works great. I can't imagine a more comfortable view in a short fl ep. The only negative is the price. A keeper.

Overall Rating: No Vote
Weight: 1 (Unreliable Vote)
Link to this vote:

[Click Here to Login]
Don't have a login? Register!