17mm 1.25" High Grade Plössl eyepiece

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This medium power Astro-Tech 17mm High Grade Plössl eyepiece is surprisingly affordable, yet gives up nothing in optical performance when compared with eyepieces more than twice its modest price.

The 55° field of view of this 17mm Astro-Tech is surprisingly wide when compared with other Plössls in this focal length range. It’s designed for detailed lunar observing, for getting up close and personal with emission and reflection nebulas, and for resolving globular clusters. It will work well with any telescope type, at any focal ratio, under virtually any seeing conditions.

From a fast Dob to a slow long focal length achro refractor, this Astro-Tech is a sensible choice for the discriminating observer on a budget. Its focal length nicely fills in the gap between the 25 or 26mm eyepiece that comes standard with most scopes and a high power planetary/binary star splitting eyepiece.

The useable eye relief is quite reasonable, but will somewhat vignette the field of view for eyeglass wearers. We can't whole-heartedly recommend this eyepiece for those who want to see the full field while wearing glasses while observing, but many observers will find the performance and price enticing enough to overlook some slight vignetting.

Field of view:
The field of view (FOV) is the amount of observable world one can see at any given moment.
55°
Eye Relief:
Eye relief is the distance from the last surface of the eye lens of an eyepiece to the plane behind the eyepiece where all the light rays of the exit pupil come to a focus and the circular image is formed, sometimes called the “Ramsden Disk.” This is where your eye should be positioned to see the full field of view of the eyepiece. If you must wear glasses because of astigmatism, you’ll usually need at least 15mm of eye relief or longer if you want to see the full field of view with your glasses on.

A note on our eye relief figures: Quite often, our eye relief figures will differ from those of the manufacturer. This is because we measure the “usable” eye relief, while the manufacturers specify their usually-longer (but technically correct) “designed” eye relief.

The eye lens of the eyepiece is normally recessed below the rubber eyeguard or rubber rim of the eyepiece to keep the lens from being scratched during use. An eyepiece might have a “designed” eye relief of 15mm (and the eye relief will truly measure 15mm from the eye lens to where the image forms). However, if the eye lens is recessed 3mm below the eye guard, the Ramsden Disk forms only 12mm above the eyepiece body (the 15mm “designed” eye relief, less the 3mm of eye relief made unusable by having the eye lens recessed into the body of the eyepiece). This “usable” eye relief of 12mm (measured from the rolled-down eyeguard – the closest point you can get your eye to the eye lens – to where the image forms) is the eye relief figure we would measure and list in this website.

Why is it important to list the “usable” eye relief? For those people who don’t wear eyeglasses while observing, a few mm difference between the eye relief they expect from the manufacturer’s literature and the shorter eye relief they actually get in real life doesn’t mean a lot. They can simply move a little closer to the eyepiece to see the full field, and never realize that the eye relief is a little shorter than they expected. However, some people must wear eyeglasses while observing, because of severe astigmatism. These observers can’t move closer to the eyepiece if the eye relief is shorter than expected because their glasses get in the way. For these people, the real life “usable” eye relief is more important than the technically correct but sometimes not fully usable “designed” eye relief. We measure and list the actual usable eye relief so that people in the real world can pick the eyepieces that will work best for them.

11mm
Focal Length:
This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

17mm
Number of optical elements:
4
Barrel Size:
The industry standard diameter, as of 2011, is 1.25" and is the most common.  Other sizes available are .965" and 2".
1.25"
Weight:
The weight of this product.
3.5 oz.
Warranty:
1 year
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1. Gregory on 4/30/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
I got the 17mm "high grade plossl" eight months ago. First, a few minor nits. For this one, my focuser has to be in about 5mm more than most of my other EPs -- it is very much not parfocal. Also, its funny-shaped barrel tends to be slightly harder to slide in and out of focusers and barlows than my smooth-barreled eyepieces. And this is very minor, but at first I found it really difficult to use because it doesn't have the simple rubber folding eyeguard that most inexpensive eyepieces have. Oh, and also I'm not convinced that it is truly any more "premium" than any other budget plossl. On the other hand, the price is still quite low!

But onto the good, it has actually become my go-to higher powered eyepiece. For my scope (StarBlast 6), I just find that 17mm is always a nice step up from 25mm "finder" EPs, and then the 17mm plus a 2x barlow is the perfect high power configuration. I find that I rarely use my 6mm or 10mm eyepieces anymore. The barlowed 17mm is really just a very easy to use combination for me, it is fairly high power, relaxed eye relief (I do not wear glasses at the scope, though), and no obnoxious distortions. I can't point to any optical flaws whatsoever in its behavior, no ghosting or anything, very easy to get it into focus. A very solid no-frills eyepiece.
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2. Jim on 9/27/2012, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
Work great in the WO binoviewers. The price is spot-on.
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52mm x 80mm eyepiece container
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Helpful Formulas
Telescope Eyepiece Formula
To calculate the magnification and approximate actual field of view of this eyepiece on your telescope, enter the focal length of your telescope below and press the "Calculate" button.

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Astro-Tech - 17mm 1.25" High Grade Plössl eyepiece

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Astro-Tech - 17mm 1.25" High Grade Plössl eyepiece
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 AstronomicsAstronomicsAstronomicsAstronomicsAstronomics (Average: 4.50 | Users: 2)  Only registered users can submit ratings - Register Here
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Compare the performance of this Astro-Tech 17mm High Grade Plössl eyepiece with other Plössls costing as much as twice its sensible price and you might find yourself very hard-pressed to see a difference . . .





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