Pentax SMC-XW 30mm

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Brand and Model:	Pentax SMC-XW 30mm
Price ($USD):	549
Type:	Ultra Wide Angle
Focal Length:	30 mm
Barrel Size:	2
Apparent FOV:	70.0 degrees
Field Stop Dia.:	36.2 mm
Eye Relief:	20 mm
Elements:	7
Weight (lbs):	26.1 oz
Description:

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Pentax SMC-XW 30mm

This ocular has been out for over a year and no one has written anything so I'll take the plunge. This is a pricey eyepiece but costs more at some places than others. Current low price is $489 at Highpoint Scientific but you can pay as much as $549 elsewhere.

I came to this eyepiece gradually. I have owned the Edmund 32mm Erfle, the UO 32mm Konig, and the Meade 32 SWA, in 2" format, and the TV 32mm plossl in 1.25" format. I became gradually more demanding of my eyepiece. At first I just wanted to get some "jee whiz" views of open clusters and didn't mind edge of field issues. But as I started chasing smaller planetaries in my f/11 C14 it became a problem because, in the Erfle, astigmatism made everything indistingishable at the edge. I purchased the UO 32mm Konig (do not confuse with the new MK 80 32mm by UO) with 60 degrees afov and the Meade 32mm SWA with 65 degrees afov. The Meade and UO were comparable quality but the Meade had the edge in fov. In addition, the UO had to be raised on its barrel to reach focus in a 14" f/4.8 T-scope, and the Meade did not. So I used the Meade 32mm SWA for about two more years but became frustrated by the field curvature, which made edge-of-field stars soft and continued to make for problems finding small planetaries in crowded star fields.

The Pentax 30XW solves these problems in both my f/6.5 102mm apo and my f/11 C14. That is to say, it exhibits no astigmatism that I can see and stars are equally tight with a unique focus point across the field, which means field curvature must be slight if present at all.

You won't get as much fov as in the Nagler 31. But what the eyepiece does offer is a crystalline sharp quality that seems to bring out extra definition. This is difficult to describe as something other than the way it "feels" at the eyepiece. I can see why someone might choose the Nagler 31 over the 30XW, because of the field diameter, but I also know people who consider the 30XW to have an optically sharper quality.

Is it worth it to spend this much on an eyepiece? Probably not for newcomers. When your observing agenda "pushes" you to seek performance improvements, and you keep finding that the less expensive alternatives "don't do it," that's when you may discover that this eyepiece really delivers everything the advertising copy says it will: sharp focus, extra brightness, and high contrast across the field of view. However, once one has a lot of observing experience and has tried alternatives, I think it is fairly easy to see that this is an excellent eyepiece that pays back in performance what it demands in price. You also have to be at a point in your observing agenda where having the widest possible field--the 82 to 84 degrees offered by competitors--is not as important as having a sparkling, high contrast field that is certainly wide enough to blow your mind.

Overall Rating: 10
Optics:10 Value:10
Weight: 5 (Veritable Vote)
Date: 11/01/2005 01:02:48 pm PST
By: gnowell
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=470679

Reply Replies: 0

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