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First Look: Astro-Tech Paradigm Eyepieces


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paradigm
First Look: AT Paradigm Eyepiece
Tom Trusock
1/09


A gripe on the boards has always been the lack of decent eye relief, short focal length eyepieces in the under $100 arena.   Astro-Tech has hopped on board with an option – one that they specify is a totally new design never before offered in the US.  It's comprised of six elements, a group of one, a group of two, another group of one and then another group of two.  The AFOV is (factory stated) 60 deg, eye relief varies from 13 to 15 mm, and the eyepiece is available in focal lengths of: 5, 8, 12, 15 , 18 and 25 mm.  The price is $79.95 across the board.

I was shipped the entire set, but due to a (shipping) problem with the 5 mm I was unable to evaluate it at this time and therefore have not included it in this quick peek.   The  5mm and 8mm were prototypes.  I was told the only difference was that the barrel undercut was moved to a more traditional style for the production versions - the optics remain the same.

This has probably been my worst winter on record for observing.   This is the first opportunity to observe since late October, and I just had time for a couple of quick sessions (both during the day and night) with these in the TV85 before the skin froze.  This is hardly a definitive report, and  I expect to put the entire series  (including a 5 mm) to a more stringent test in my NP101 at a later date.  However, since these are a new eyepiece, I figured somebody might at least like to see some (perhaps sketchy) data.



Mechanically these are well designed and attractive eyepieces.  They all sport large eyelenses, and have spin up eye cups.  The overall look is somewhat reminiscent of the Pentax line of XW eyepieces with a large knurled plastic grip - a nice touch for winter observing.  One well thought out bit is the identifying color ring on the side that assists you in determining which focal length you're grabbing.  Surprisingly however, the 8mm and 25mm have nearly identical color rings.   I wouldn't be surprised if this was addressed in the next run.  The eyepieces come with endcaps and a soft cleaning cloth.    They sport the popular (shallow) undercut common to eyepieces today.  The coatings look good, and the eyepieces appear to be internally well blackened.   Nighttime observing was a treat.

In general I thought they performed fairly well at f7 with no obvious killer aberrations.   I found them to be (for the most part) parfocal. A nice bit, if you appreciate that sort of thing.  In general I also found them to be pretty free from astigmatism.  This is particularly nice to see.   A problem inherent in budget widefields, it's the one I despise most.    

Probably my least favorite of the set is the 25mm, as that tends to get slightly mushy towards the edge.  Overall, I found them well constructed, nice to look at and comfortable to view with.  It's nice to have some longer eye relief options in the short focal length.    I did note that I had some minor problems with eye placement in the daytime, nothing major and definitely of less concern at night when the pupil is fully dilated and the eyeguard properly employed.

Specific focal length notes follow:




25 mm

Although pretty good at f7, this is probably the worst of the bunch.   The field is curved and requires a slight refocusing at the edges for the sharpest focus.  There is some very minor pincusion.  There's no on axis color detectable, but there is a little bit of lateral color seen (although part of that could be the telescope).  Eye relief is adequate, and quite nice at night although in the daytime I found this eyepiece a bit prone to blackouts.  Glare and scatter were not an issue.  Even though I felt the other eyepieces outperformed it, overall I found this a nice eyepiece (again, note I was operating at f7).  If you can overcome the tendency to blackout, this is a good daytime eyepiece as well. 

18 mm

Optically, this was the best focal length of the group.  Images were crisp and well defined, the field looked good and fairly flat with just a tiny tiny hint of pincushion and I that suspect will go completely undetected in normal use.   I saw no on axis or lateral color with this eyepiece.   This is an excellent eyepiece for daytime observation.  I'd also like to note that I was very pleased with its color rendition.

15mm

To my eye and this scope, this was the second best focal length.   Again the edge correction was pretty good, but there was a little more pincusion in the 15 than in the 18 although still not an objectionable amount.   There were some minor hints of lateral color, but the center of the image had excellent rendition and good definition.   The field was, again, fairly flat.


12 mm

This is the region where the increased eye relief made itself evident as compared to a typical plossl.  Pincusion was clearly evident, slightly worse than in the 15 mm, but again it wasn't a major factor for nighttime observing.

8 mm

Pincushion was most obvious in this focal length, and there were some minor problems with eyeball reflections, although not nearly as drastic as what I've seen in other eyepieces over the years.   The eye relief was very nice and most users would find it quite comfortable.   Like a couple of the other eyepieces, I did notice a bit of lateral color during the day, but it was non-existent at night.  This was an extremely nice eyepiece for lunar observation in the TV85, the globe of the moon fitting just within the field of view, but providing enough magnification for some fairly detailed study.

If you're looking for something with a bit apparent field than a traditional plossl, I found these a good value for the money. In fact I'd go so far as to say that the longer focal lengths make excellent partners for the Burgess / TMB planetary eyepieces if you're fond of those.  To make some quick comparisons to a standard plossls, (which are somewhat in a similar category), and I think the a good plossl is perhaps in general just a bit cleaner for purists, but at 60 deg the  Paradigms field is definitely wider and the greater eye relief makes them noticeably more comfortable in the shorter focal lengths.    In short, these are a well constructed, attractive addition to the eyepieces available to todays amateur astronomer, and a very good bang for the buck.





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