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 | My Current Eyepieces | Use of Magnifications | Exit Pupil | References | Links | Appendix: Simplified Tables

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 ... - in the meantime I bought the shortest version), and for the Celestron C8 (Schmidt-Cassegrain).

I also list a number of useful links.

Note: The appendix presents simplified tables that contain only the telescopes and eyepieces that I currently use.

Note: For definitions in a small glossary, see page Quick & Dirty Astronomy Glossary. For more information on the topic "exit pupil as a criterion for eyepiece selection" see page Eyepiece Selection (Focal Length).

 

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
220
195
260
20.00
18.57
32.5
35.0
3.3
2.5
Explorer PDS150/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 (Maksutov-Cassegrain)
1250
90
13.89
165
325
---
180
13.84
12.85
90.4
97.3
---
6.9
Skymax-102 (Maksutov-Cassegrain)
1300
102
12.75
212
---
204
15.69
14.57
82.9
89.3
---
6.4
Skymax-127 (Maksutov-Cassegrain)
1500
127
11.81
329
---
254
19.54
18.14
76.8
82.7
---
5.9
Celestron C8 (Schmidt-Cassegrain)
2032
203
10
841
---
406
31.26
29.03
65.0
70.0
---
5.0

*) Calculated for an exit pupil of 6.5 mm and 7 mm
+) Factor 1.5 or 2 for Dobsonian telescopes; in general, the lower value of 1.5 is used for Newtonian telescopes; if the manufacturer specified a different magnification, it is also listed (some manufacturer provide considerably higher numbers...).

 

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

Telescope
Further Data
Focal Length of Eyepiece (mm)
Magnification*
 
Focal Length of
Telescope (mm)
4
5
6
7
9
10
12
15
16
20
24
25
26
28
30
32
40
Heritage 76
300
75.00
60.00
50.00
42.86
33.33
30.00
25.00
20.00
18.75
15.00
12.50
12.00
11.54
10.71
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
16.67
16.00
15.38
14.29
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
20.83
20.00
19.23
17.86
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
27,08
26.00
25.00
23.21
21.67
20.31
16.25
PDS150/D. 6"
750
187.50
150.00
125.00
107.14
83.33
75.00
62.50
50.00
46.88
37.50
31.25
30.00
28.85
26.79
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
37.50
36.00
34.62
32.14
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
50.00
48.00
46.15
42.86
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
50.00
48.00
46.15
42.86
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
52.92
50.80
48.85
45.36
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
52.08
50.00
48.08
44.64
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
54.17
52.00
50.00
46.43
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
62.50
60.00
57.69
53.57
50.00
46.88
37.50
Celestron C8
2032
508.00
406.40
338.67
290.29
225.78
203.20
169.33
135.47
127.00
101.60
84.67
81.28
78.15
72.57
67.73
63.50
50.80
 
True Field of View (°)**
Apparent Field of View (°) >
82
68
60
82
52
42
70
52
52
82
52
65
42
70
56
70
52
52
 
Focal Length of
Telescope (mm)
4
5
6
7
9
10
10
12
15
16
20
24
25
26
28
30
32
40
Heritage 76
300
1.09
1.13
1.20
1.91
1.56
1.40
2.33
2.08
2.60
4.37
3.47
5.20
3.50
6.07
5.23
7.00
5.55
6.93
Heritage 100P
400
0.82
0.80
0.90
1.44
1.17
1.05
1.75
1.56
1.95
3.28
2.60
3.90
2.63
4.55
3.92
5.25
4.16
5.20
Heritage 114P
500
0.66
0.68
0.72
1.15
0.94
0.84
1.40
1.25
1.56
2.62
2.08
3.12
2.10
3.64
3.14
4.20
3.33
4.16
Heritage P130
650
0.50
0.52
0.55
0.88
0.72
0.65
1.08
0.96
1.20
2.02
1.60
2.40
1.62
2.80
2.41
3.23
2.56
3.20
PDS150/D. 6"
750
0.44
0.45
0.48
0.77
0.62
0.56
0.93
0.83
1.04
1.75
1.39
2.08
1.40
2.43
2.09
2.80
2.22
2.77
Dobson 6"
900
0.36
0.38
0.40
0.64
0.52
0.47
0.78
0.69
0.87
1.46
1.16
1.73
1.17
2.02
1.74
2.33
1.85
2.31
Dobson 6"
1200
0.27
0.28
0.30
0.48
0.39
0.35
0.58
0.52
0.65
1.09
0.87
1.30
0.88
1.52
1.31
1.75
1.39
1.73
Dobson 8"
1200
0.27
0.28
0.30
0.48
0.39
0.35
0.58
0.52
0.65
1.09
0.87
1.30
0.88
1.52
1.31
1.75
1.39
1.73
Dobson 10"
1270
0.26
0.27
0.28
0.45
0.37
0.33
0.55
0.49
0.61
1.03
0.83
1.23
0.83
1.43
1.23
1.65
1.31
1.64
ETX 90/EC
1250
0.26
0.27
0.29
0.46
0.37
0.34
0.56
0.50
0.62
1.05
0.84
1.25
0.84
1.46
1.25
1.68
1.33
1.66
Skymax-102
1300
0.25
0.26
0.28
0.44
0.36
0.32
0.54
0.48
0.60
1.01
0.80
1.20
0.81
1.40
1.21
1.62
1.28
1.60
Skymax-127
1500
0.22
0.23
0.24
0.38
0.31
0.28
0.47
0.42
0.52
0.87
0.69
1.04
0.70
1.21
1.05
1.40
1.11
1.39
Celestron C8
2032
0.16
0.17
0.18
0.28
0.23
0.21
0.34
0.31
0.38
0.65
0.51
0.77
0.52
0.90
0.77
1.03
0.82
1.02
 
Exit Pupil (mm)
 
Focal Ratio
4
5
6
7
9
10
12
15
16
20
24
25
26
28
30
32
40
Heritage 76
3.95
1.01
1.27
1.52
1.77
2.28
2.53
3.04
3.80
4.05
5.07
6.08
6.33
6.59
7.09
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
6.00
6.25
6.50
7.00
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
5.47
5.70
5.93
6.38
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
4.80
5.00
5.20
5.60
6.00
6.40
8.00
PDS150/D. 6"
5
0.80
1.00
1.20
1.40
1.80
2.00
2.40
3.00
3.20
4.00
4.80
5.00
5.20
5.60
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
4.00
4.17
4.33
4.67
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
3.00
3.13
3.25
3.50
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
4.00
4.17
4.33
4.67
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
4.80
5.00
5.20
5.60
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
1.73
1.80
1.87
2.02
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
1.88
1.96
2.04
2.20
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
2.03
2.12
2.20
2.37
2.54
2.71
3.39
Celestron C8
10
0.40
0.50
0.60
0.70
0.90
1.00
1.20
1.50
1.60
2.00
2.40
2.50
2.60
2.80
3.00
3.20
4.00

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 as a general information in case that you own similar eyepieces and/or telescopes...

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.

Field of View: Allows to predict whether an extended object can be fully captured or whether adjacent objects can be observed together.

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

See below for photos of the current eyepieces.

2" eyepieces:

All other eyepieces are 1.25" eyepieces:

Italic: No longer in my possession

 

My Current Eypieces

As of May 2017, I own the following eyepieces (the crosshair and the 28 mm eyepiece for 2" are missing):

    
     
 

Photos: Top row (from left to right): 4 mm and 7 mm UWA, 10 mm Sky-Watcher eyepiece, 10 mm Explore Scientific eyepiece; bottom row (from left to right): 16 mm UWA, 25 mm Sky-Watcher eyepiece, 24 mm TeleVue eyepiece, 32 mm Plössl eyepiece

The 12.5 mm crosshair Plössl eyepiece is not shown, as well as the 28 mm eyepiece for my 6" Newton tube (2").

 

Use of Magnifications

I found (and added to... source regrettably unknown...) 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 Selection).

 

Exit Pupil

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

General rules:

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

 

References

 

Appendix: Simplified Tables

The following simplified tables apply only to the telescopes and eyepieces that I currently use. This way, they are clearer and easier to use for me.

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 100P
400
100
4
204
150
200
15.38
14.29
26.0
28.0
2.7
2.0
Explorer PDS150
750
150
5
459
225
300
23.08
21.43
32.5
35.0
3.3
2.5
Skymax-102 (Maksutov-Cassegrain)
1300
102
12.75
212
---
204
15.69
14.57
82.9
89.3
---
6.4
Skymax-127 (Maksutov-Cassegrain)
1500
127
11.81
329
---
254
19.54
18.14
76.8
82.7
---
5.9

*) Calculated for an exit pupil of 6.5 mm and 7 mm
+) Factor 1.5 or 2 for Dobsonian telescopes; in general, the lower value of 1.5 is used for Newtonian telescopes; if the manufacturer specified a different magnification, it is also listed (some manufacturer provide considerably higher numbers...).

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

Telescope
Further Data
Focal Length of Eyepiece (mm)
Magnification
 
Focal Length of
Telescope (mm)
4
7
10
16
24
28
32
Heritage 100P
400
100.00
57.14
40.00
25.00
16.67
---
12.50
PDS150
750
187.50
107.14
75.00
46.88
31.25
26.79
23.44
Skymax-102
1300
325.00
185.71
130.00
81.25
54.17
---
40.63
Skymax-127
1500
375.00
214.29
150.00
93.75
62.50
---
46.88
 
True Field of View (°)
Apparent Field of View (°) >
82
82
70
82
65
56
52
 
Focal Length of
Telescope (mm)
4
7
10
16
24
28
32
Heritage 100P
400
0.82
1.44
1.75
3.28
3.90
---
4.16
PDS150
750
0.44
0.77
0.93
1.75
2.08
2.09
2.22
Skymax-102
1300
0.25
0.44
0.54
1.01
1.20
---
1.28
Skymax-127
1500
0.22
0.38
0.47
0.87
1.04
---
1.11
 
Exit Pupil (mm)
 
Focal Ratio
4
7
10
16
24
28
32
Heritage 100P
4
1.00
1.75
2.50
4.00
6.00
---
8.00
PDS150
5
0.80
1.40
2.00
3.20
4.80
5.60
6.40
Skymax-102
12.75
0.31
0.55
0.78
1.26
1.88
---
2.51
Skymax-127
11.81
0.34
0.59
0.85
1.35
2.03
---
2.71

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 above.

Field of View: Allows to predict whether an extended object can be fully captured or whether adjacent objects can be observed together.

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 above.

 

An den Anfang   Homepage  

gerd (at) waloszek (dot) de

About me
made by walodesign on a mac!
18.11.2017