Pentax 10 - Manual (Page 14)

14
Eyepieces
The Teleport’s 2” focuser and 1.25” adapter allow the use of many
different eyepieces. Many types are available with a wide range of
features, quality and price. Over the past several years I have evalu-
ated many of the better types for use with the Teleport. As a group, I
have found none as good overall as the Pentax XL series.
Pentax Eyepieces
Desirable attributes of the Pentax XL series include:
1. Ideal selection of focal lengths in logical steps throughout the range.
2. Full 20mm eye relief in all focal lengths
3. Wide 65
°
apparent field of view—which I find ideal (the 28mm is 55
°
)
4. High brightness, contrast, and sharpness.
5. Weights closely matched throughout the entire set.
6. Parfocal to a very close tolerance.
7. Very effective, adjustable rubber eye cups.
Tradeoffs are cost and slight edge astigmatism, which I find acceptable.
The following table lists the focal lengths available, with their magnifi-
cations and fields with the Teleport:
Focal Eye Apparent Magni- True
Length Relief Field fication Field
40.0 mm 20 mm 65
°
32 x 2.04
°
28.0 mm 20 mm 55
°
45 x 1.22
°
21.0 mm 20 mm 65
°
60 x 1.08
°
14.0 mm 20 mm 65
°
91 x 0.72
°
10.5 mm 20 mm 65
°
121 x 0.54
°
7.0 mm 20 mm 65
°
181 x 0.36
°
5.2 mm 20 mm 65
°
244 x 0.27
°
My usual set (Fig 23) includes the 40, 21, 10.5, and 5.2. For certain
objects, however, the 14 and
the 7 are ideal. Seeing condi-
tions often preclude the use of
the 5.2, so I sometimes substi-
tute the 7. It can be used a bit
more often, but doesn’t provide
quite the detail of the 5.2 when
seeing is really good. The view
through the 40mm is spectacu-
lar on extended objects. Its 2
°
field is almost half that of
many finder scopes, making a
finder scope unneccessary.
Fig 23: My Accessories Drawer
Pentax XL
Eyepieces
Red LED
Flashlight
Eyepiece
Heater
Laser
Collimator