Data of All My Telescopes and Eyepieces

Data that Is Independent of a Specific Eyepiece | Visual Power (Magnification) and other Data for Different Focal Lengths of Eyepieces | Use of Magnifications | Exit Pupil | References

On this page, I present data for my all telescopes and eyepieces (including the sold ones). In addition, I list data for three variants of 6" telescopes, which lie "between" my telescopes and appear interesting to me for use on the GoTo mount (if they were not so heavy ...), and the Skymax-127.

Note: For definitions in a small glossary, see page Quick & Dirty Astronomy Glossary.

 

Data that Is Independent of a Specific Eyepiece

Telescope

Focal
Length
(mm)

Aperture
(mm)
Focal
Ratio
Light
Gathering
Power
Maximum+
Minimum*
Maximum*
Minimum+
Usable Magnification
Usable Focal Length
of Eyepiece (mm)
Factor/Exit Pupil (mm) >
Manuf.
1.5
2
6.5
7
6.5
7
1.5
2
Heritage 76
300
76
3.95
118
114
152
11.68
10.85
25.7
27.7
2.6
2.0
Heritage 100P
400
100
4
204
150
200
15.38
14.29
26.0
28.0
2.7
2.0
Heritage 114P
500
114
4.4
265
171
228
17.52
16.27
28.5
30.7
2.9
2.2
Heritage P130
650
130
5
345
195
260
20.00
18.57
32.5
35.0
3.3
2.5
Dobson 6"
750
150
5
459
225
300
23.08
21.43
32.5
35.0
3.3
2.5
Dobson 6"
900
150
6
459
225
300
23.08
21.43
39.0
42.0
4.0
3.0
Dobson 6"
1200
150
8
459
225
300
23.08
21.43
52.0
56.0
5.3
4.0
Dobson 8"
1200
200
6
816
300
400
30.77
28.57
39.0
42.0
4.0
3.0
Dobson 10"
1270
254
5
1317
600
381
500
39.08
36.29
32.5
35.0
3.3
2.5
ETX 90/EC
1250
90
13.89
165
325
---
180
13.84
12.85
90.4
97.3
---
6.9
Skymax-102
1300
102
12.75
212
---
204
15.69
14.57
82.9
89.3
---
6.4
Skymax-127
1500
127
11.81
329
---
254
19.54
18.14
76.8
82.7
---
5.9

*) For an exit pupil of 6.5 mm and 7 mm
+) Factor 1.5 or 2 for Dobsonian telescopes; Teleskop-Service uses the lower value of 1.5 for Newtonian telescopes in general; if the manufacturer specified a different magnification, it is also listed

 

Visual Power (Magnification) and other Data for Different Focal Lengths of Eyepieces

Characteristic Telescope
Further Data
Focal Length of Eyepiece (mm)
   
Focal Length of
Telescope (mm)
4
5
6
7
9
10
12
15
16
20
25
26
30
32
40
Magnification* Heritage 76
300
75.00
60.00
50.00
42.86
33.33
30.00
25.00
20.00
18.75
15.00
12.00
11.54
10.00
9.38
7.50
Heritage 100P
400
100.00
80.00
66.67
57.14
44.44
40.00
33.33
26.67
25.00
20.00
16.00
15.38
13.33
12.50
10.00
Heritage 114P
500
125.00
100.00
83.33
71.43
55.56
50.00
41.67
33.33
31.25
25.00
20.00
19.23
16.67
15.63
12.50
Heritage P130
650
162.50
130.00
108.33
92.86
72.22
65.00
54.17
43.33
40.63
32.50
26.00
25.00
21.67
20.31
16.25
Dobson 6"
750
187.50
150.00
125.00
107.14
83.33
75.00
62.50
50.00
46.88
37.50
30.00
28.85
25.00
23.44
18.75
Dobson 6"
900
225.00
180.00
150.00
128.57
100.00
90.00
75.00
60.00
56.25
45.00
36.00
34.62
30.00
28.13
22.50
Dobson 6"
1200
300.00
240.00
200.00
171.43
133.33
120.00
100.00
80.00
75.00
60.00
48.00
46.15
40.00
37.50
30.00
Dobson 8"
1200
300.00
240.00
200.00
171.43
133.33
120.00
100.00
80.00
75.00
60.00
48.00
46.15
40.00
37.50
30.00
Dobson 10"
1270
317.50
254.00
211.67
181.43
141.11
127.00
105.83
84.67
79.38
63.50
50.80
48.85
42.33
39.69
31.75
ETX 90/EC
1250
312.50
250.00
208.33
178.57
138.89
125.00
104.17
83.33
78.13
62.50
50.00
48.08
41.67
39.06
31.25
Skymax-102
1300
325.00
260.00
216.67
185.71
144.44
130.00
108.33
86.67
81.25
65.00
52.00
50.00
43.33
40.63
32.50
Skymax-127
1500
375.00
300.00
250.00
214.29
166.67
150.00
125.00
100.00
93.75
75.00
60.00
57.69
50.00
46.88
37.50
                                 
 
Apparent Field of View (°) >
82
68
60
82
52
42
52
52
82
52
42
70
70
52
52
 
Focal Length of
Telescope (mm)
4
5
6
7
9
10
12
15
16
20
25
26
30
32
40
True Field of View (°)** Heritage 76
300
1.09
1.13
1.20
1.91
1.56
1.40
2.08
2.60
4.37
3.47
3.50
6.07
7.00
5.55
6.93
Heritage 100P
400
0.82
0.80
0.90
1.44
1.17
1.05
1.56
1.95
3.28
2.60
2.63
4.55
5.25
4.16
5.20
Heritage 114P  
0.66
0.68
0.72
1.15
0.94
0.84
1.25
1.56
2.62
2.08
2.10
3.64
4.20
3.33
4.16
Heritage P130
650
0.50
0.52
0.55
0.88
0.72
0.65
0.96
1.20
2.02
1.60
1.62
2.80
3.23
2.56
3.20
Dobson 6"
750
0.44
0.45
0.48
0.77
0.62
0.56
0.83
1.04
1.75
1.39
1.40
2.43
2.80
2.22
2.77
Dobson 6"
900
0.36
0.38
0.40
0.64
0.52
0.47
0.69
0.87
1.46
1.16
1.17
2.02
2.33
1.85
2.31
Dobson 6"
1200
0.27
0.28
0.30
0.48
0.39
0.35
0.52
0.65
1.09
0.87
0.88
1.52
1.75
1.39
1.73
Dobson 8"
1200
0.27
0.28
0.30
0.48
0.39
0.35
0.52
0.65
1.09
0.87
0.88
1.52
1.75
1.39
1.73
Dobson 10"
1270
0.26
0.27
0.28
0.45
0.37
0.33
0.49
0.61
1.03
0.83
0.83
1.43
1.65
1.31
1.64
ETX 90/EC
1250
0.26
0.27
0.29
0.46
0.37
0.34
0.50
0.62
1.05
0.84
0.84
1.46
1.68
1.33
1.66
Skymax-102
1300
0.25
0.26
0.28
0.44
0.36
0.32
0.48
0.60
1.01
0.80
0.81
1.40
1.62
1.28
1.60
Skymax-127
1500
0.22
0.23
0.24
0.38
0.31
0.28
0.42
0.52
0.87
0.69
0.70
1.21
1.40
1.11
1.39
                                   
   
Focal Ratio
4
5
6
7
9
10
12
15
16
20
25
26
30
32
40
Exit Pupil (mm) Heritage 76
3.95
1.01
1.27
1.52
1.77
2.28
2.53
3.04
3.80
4.05
5.07
6.33
6.59
7.60
8.11
10.13
Heritage 100P
4
1.00
1.25
1.50
1.75
2.25
2.50
3.00
3.75
4.00
5.00
6.25
6.50
7.50
8.00
10.00
Heritage 114P
4.4
0.91
1.14
1.37
1.60
2.05
2.28
2.74
3.42
3.65
4.56
5.70
5.93
6.84
7.30
9.12
Heritage P130
5
0.80
1.00
1.20
1.40
1.80
2.00
2.40
3.00
3.20
4.00
5.00
5.20
6.00
6.40
8.00
Dobson 6"
5
0.80
1.00
1.20
1.40
1.80
2.00
2.40
3.00
3.20
4.00
5.00
5.20
6.00
6.40
8.00
Dobson 6"
6
0.67
0.83
1.00
1.17
1.50
1.67
2.00
2.50
2.67
3.33
4.17
4.33
5.00
5.33
6.67
Dobson 6"
8
0.50
0.63
0.75
0.88
1.13
1.25
1.50
1.88
2.00
2.50
3.13
3.25
3.75
4.00
5.00
Dobson 8"
6
0.67
0.83
1.00
1.17
1.50
1.67
2.00
2.50
2.67
3.33
4.17
4.33
5.00
5.33
6.67
Dobson 10"
5
0.80
1.00
1.20
1.40
1.80
2.00
2.40
3.00
3.20
4.00
5.00
5.20
6.00
6.40
8.00
ETX 90/EC
13.89
0.29
0.36
0.43
0.50
0.65
0.72
0.86
1.08
1.15
1.44
1.80
1.87
2.16
2.30
2.88
Skymax-102
12.75
0.31
0.39
0.47
0.55
0.71
0.78
0.94
1.18
1.26
1.57
1.96
2.04
2.35
2.51
3.14
Skymax-127
11.81
0.34
0.42
0.51
0.59
0.76
0.85
1.02
1.27
1.35
1.69
2.12
2.20
2.54
2.71
3.39

Italic: I do no longer own this telescope/eyepiece; italic: added for comparison purposes; 2" eyepieces (see below) are not usable at most of my telescopes, but the tables are only meant for general information...

Magnification: Yellow: low (30-50 x); magenta: medium (80-100 x); violet: high (150-200 x - and more); red: beyond maximum usable magnification.
For use of magnifications, see below.

Exit pupil: Values in magenta cells are either too small (< 1 mm) or too large (> 6.4/7 mm); yellow background: best for galaxies (about 2-3 mm).
For more information on the exit pupil, see below.

*) Can be doubled with a 2 x Barlow lens.
**) The full moon is almost exactly 0.5° (= 30') in diameter.
?) Sky-Watcher lists a field of view of 42° as default value for typical amateur eyepieces (please, replace by the actual values if known).

About My Eyepieces

2" eyepieces:

All other eyepieces are 1.25" eyepieces:

 

Use of Magnifications

I found the following recommendations for the use of magnifications:

Note that similar recommendations are given in the literature as well as on the Internet based on the size of the exit pupil. For more information on the topic "exit pupil as a criterion for eyepiece selection" see page Eyepiece Selection (Focal Length).

 

Exit Pupil

The definition of the exit pupil can be found in the glossary.

General rules:

For more information on the topic "exit pupil as a criterion for eyepiece selection" see page Eyepiece Selection (Focal Length).

 

References

 

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gerd (at) waloszek (dot) de

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made by walodesign on a mac!
28.02.2017