Pentax SMC-XW 40mm

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Brand and Model:Pentax SMC-XW 40mm
Price ($USD):549
Type:Ultra Wide Angle
Focal Length:40 mm
Barrel Size:2
Apparent FOV:70.0 degrees
Field Stop Dia.:46.5 mm
Eye Relief:20 mm
Weight (lbs):24.7

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Pentax SMC-XW 40mm
I never used to use my C14 with my 40mm eyepiece unless it was absolutely necessary. Now I *like* viewing w/the 40mm because the XW is so contrasty. It is difficult for me to evaluate edge of field astigmatism because of my own astigmatism. I did have the opportunity to compare the eyepiece to a Nagler 31mm and frankly I prefer the greater contrast and wider fov of the 40XW. Like another reviewer in this section, I found the 40XW to have greater contrast than the 31 Nagler even though ordinarily the advantage lies with the shorter fl eyepiece. In the C14 I had to work to see serious field curvature effects, which was surprising.

I also evaluated it in my f/6.5 102mm apo and a friend's f/4.8 dob. It was a winner at all focal lengths. I don't usually observe with glasses but I found that I could keep them on and easily take in the entire fov. With my glasses on the edge of field performance was quite good. In the 102mm apo I viewed the N America nebula in OIII and found the view in the 40XW offering "darker darks," "whiter whites," and wider fov than the 31 Nagler.

Prices on the 40 and 30 XWs vary considerably: as I post, $540 at Anacortes, $500 at Astronomics, $489 at Highpoint Scientific.

After I got the 40XW I felt that I had a new telescope. The eyepiece it replaced, a UO 40 MK 70, is well reputed and no slouch. But Pentax definitely delivers high value for the money. Opinions will differ concerning the Naglers vs. the Pentax widefields, but I think the Pentax designers achieved what they wanted: by keeping the apparent field of view tighter they bought extra clarity and sharp contrast. The view of M42 in the C14 is never anything short of marvelous, but in the Pentax XW 40mm I felt like I was seeing it for the first time.

Overall Rating: 10
Optics:10 Value:10
Weight: 5 (Veritable Vote)
By: gnowell
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Pentax SMC-XW 40mm
Wow. What a great EP. The contrast in this EP was striking when I compared it to my Nagler 31mm. That is a surprise considering the lower F.L. and higher power of the Nagler should have given it the edge. I am awaiting a Panoptic 41 to compare them side by side. However, I am very impressed after having used Panoptics and Naglers almost exclusively.

Paul Atkinson

Overall Rating: 10
Optics:10 Value:10
Weight: 1 (Unreliable Vote)
By: Anonymous (
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