The Burgess Optical / TMB Planetary eyepieces offer a 60 degree field of view with a tack
sharp view and lots of eyerelief. Just what is needed for extended gazing at our close
neighbors. And, just what you would expect from a Thomas Back designed eyepiece.
Check out our construction and features:

Designed by Thomas Back of TMB Optics
Fully internally baffled
Every Air to Glass surface has Multi Broadband coatings!
Internal spacers have flat anodizing to reduce reflections.
Twist-up eyecups with flexible eyecups on top.
The designer, Thomas Back, has posted a message to the Yahoo BurgessRefractors group
describing the path he has taken designing these eyepieces. Read that message here.

These eyepieces feature twist-up eyecups topped with a flexible eyecup. The right eyepiece
below shows the twist-up eyecup in the screwed down (retracted) position and the eyepiece
on the left shows the extended position. The eyecup is easily adjusted up or down, and the
eyepiece accomodates eyeglass wearers as easily as those who observe naked eye.

What makes an eyepiece a planetary EP?
The typical eyepiece today is designed for wide-field views of deep space objects (DSO).
They offer a portal to the sky, where the DSO of interest is nicely framed. To achieve these
nice, wide field of views, design choices have to be made, such as using a large number of
elements and groupings of elements. These design choices sometimes result in lateral color.
Lateral color is an abberation where different colors intercept the focal plane at different points
and can be seen when viewing bright objects off-axis. When observing dim DSO, lateral color
in the typical eyepiece is rarely seen. Also, these design choices sometimes result in light
scatter, seen as a halo or glow around bright objects. Again, light scatter is rarely seen when
observing dim DSO. If there is a bright star near the edge of the field, then lateral color and
light scatter might be seen when observing dim DSOs. But, the lateral color and light scatter
would be associated with the bright star, not the DSO.

The design choices for typical wide-field eyepieces are different than the design choices for a
planetary eyepiece. The typical eyepiece is optimized for wide-field views of DSO and suffers
when viewing very bright objects, particularly off-axis.

A planetary eyepiece is optimized to view bright objects while showing maximum detail and
definition. It is an eyepiece with very high light transmission, very high contrast, minimal
lateral color, and minimal light scatter. For Dobsonian users and others without tracking
drives, lateral color and other abberations are minimized to allow the planet to drift across the
field of view while still being sharp and having high contrast. Also, because lunar and
planetary observers seek to see as much detail as possible, planetary eyepieces typically
have a short focal length for high magnification.

The Planetary eyepieces have a twist-up eyecup for adjusting desired the eye relief from the
top of the eyepiece. A light coating of lubricant has been applied to the threads in the twist-up
eyecup. If any lubricant is visible on the inner eyepiece body with the twist-up eyecup in the
extended position, remove the excess lubricant with a clean wipe, such as a tissue. Operate
the twist-up eyecup several times, cleaning the body as necessary until no more lubricant is
visible on the eyepiece body when the twist-up eyecup is fully extended.

Specifications:
2.5mm 1-1/4" 60 degree FOV, 20mm Eye Relief
3.2mm 1-1/4" 60 degree FOV, 20mm Eye Relief
4mm 1-1/4" 60 degree FOV, 20mm Eye Relief
5mm 1-1/4" 60 degree FOV, 20mm Eye Relief
6mm 1-1/4" 60 degree FOV, 20mm Eye Relief
7mm 1-1/4" 60 degree FOV, 20mm Eye Relief
8mm 1-1/4" 60 degree FOV, 20mm Eye Relief
9mm 1-1/4" 60 degree FOV, 20mm Eye Relief

Prices:
2.5mm - £49.95
3.2mm - £49.95 - Out of Stock
4mm - £49.95
5mm - £49.95
6mm - £69.00 - Out of Stock
7mm - £49.95
8mm - £49.95 - Out of Stock
9mm - £69.00 - Out of Stock

Sky & Telescope Hot Product 2007.

The Astronomy Shop

1 Tone Hill. Wellington

Somerset TA21 0AU

United Kingdom

Telephone: +44 (0)1823 665510