June 2005
Beginner
412 pages
13h 45m
English
Content preview from Astronomy Hacks
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Chart Your Eyepiece Characteristics
Knowing the capabilities of your eyepieces makes it easier to choose the right one. Paste a reference chart to your scope to keep this information at your fingertips.
If you have only one scope and a few eyepieces, it’s easy enough to remember the magnification, field of view, and other characteristics of each eyepiece. But if you have multiple scopes and many eyepieces, it can be difficult to remember all the details.
For example, assume you have three telescopes, an 80mm f/5 [Hack #9] short-tube refractor with a focal length of 400mm, a 10” f/5 Dob with a focal length of 1,255mm, and an 8” f/10 SCT with a focal length of 2,032mm. You also have a very nice selection of Tele Vue eyepieces—41mm, 27mm, and 19mm Panoptics; and Radians in 14mm, 12mm, 10mm, 8mm, and 6mm focal lengths—and a 2.5X Powermate, which effectively multiplies the power of any eyepiece it is used with by 2.5X.
Your first attempt at an eyepiece chart for the 400mm short-tube refractor might look something like Table 4-3.
Table 4-3. An eyepiece chart for a 400mm f/5 refractor
|
Alone |
w/ Powermate | ||||||||
|---|---|---|---|---|---|---|---|---|---|
|
Eyepiece |
Mag |
Field (°) |
Field (') |
Pupil(mm) |
EFL(mm) |
Mag |
Field (°) |
Field (') |
Pupil(mm) |
|
41mm Panoptic |
10X |
6.6 |
395.3 |
8.2 |
16.4 |
24X |
2.6 |
158.1 |
3.3 |
|
27mm Panoptic |
15X |
4.4 |
262.1 |
5.4 |
10.8 |
37X |
1.7 |
104.9 |
2.2 |
|
19mm Panoptic |
21X |
3.1 |
183.1 |
3.8 |
7.6 |
53X |
1.2 |
73.2 |
1.5 |
|
14mm Radian |
29X |
2.1 |
123.8 |
2.8 |
5.6 |
71X |
0.8 |
49.5 |
1.1 |
|
12mm Radian |
33X |
1.8 |
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