8mm Brandon

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The 8mm Vernonscope Brandon eyepiece is designed for high power use with any telescope type, at focal ratios f/7 and above. It provides highly detailed/high contrast close-up lunar, planetary, star cluster, and binary star observing. With shorter focal length scopes, down to f/4, it is still exceptionally sharp at the center of the field (although somewhat less so at the edges).

While the designed and technically correct eye relief is considerably longer at 6mm, because of the recessed location of the eye lens, the measured usable eye relief of 1mm is too short for unvignetted use with eyeglasses. However, most of the objects being observed at the magnification this eyepiece provides are small. They are typically placed at the center of the field, where vision is sharpest and vignetting of the edge of the field due to eyeglasses should not be an issue. As a personal aside, your author uses this eyepiece in both his 3.5” and 7” Questars and has never had a problem with the eye relief, even when wearing glasses.

For a brief discussion of how we define and measure usable eye relief and its importance to you, an explanatory text box will pop up when you move your cursor over the term “Eye Relief” in the "Tech Details" pull-down tab above. Removing the eyepiece’s rubber eyecup will provide several mm of additional usable eye relief, but at the expense of exposing your eyeglass lenses to the metal top of the eyepiece.

The Brandon is the sharpest design currently available for very high magnification eyepiece projection photography. The body of the 8mm is considerably narrower than most similar focal length Plössl eyepieces, allowing its use in an eyepiece projection adapter much more readily than a wider Plössl. Its rolldown rubber eyecup can be removed, should the eyepiece/eyecup combination still be too wide to fit easily into your eyepiece projection adapter.

Field of view:
The field of view (FOV) is the amount of observable world one can see at any given moment.
42°
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.

1mm
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.

8mm
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.
2 oz
Warranty:
Limited Lifetime
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1. Chuck on 9/10/2012, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
These eyepieces are the Best. And made in America.
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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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Vernonscope - 8mm Brandon

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Vernonscope - 8mm Brandon
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The 8mm Vernonscope Brandon eyepiece is designed for unsurpassed high power lunar, planetary, star cluster, and binary star observing, particularly with telescopes having a focal ratio of f/7 and above . . .





. . . our 34th year