Overview of My Current Telescopes

Introduction | Sky-Watcher Skymax-127 OTA | Omegon Photography Scope 72/432 OTA | Celestron C8 OTA | Unistellar eVscope | TS-Optics Photoline 102/714 | Links | Appendix: Data of My Current Telescopes

On this page, I present some information about my current telescopes. Further below you will find a tabular overview of the basic data for the telescopes.

Note: Here you will find an overview of all telescopes that I own and owned. And here is my own little astronomy history.

 

Introduction

In the course of time, I have already tried a couple of telescopes and extended my "collection"several times, but also reduced again it at times. The reasons for the changes were of a different nature, and often the criteria "large aperture" and "weight/transportability" conflicted with each other. At the moment, my collection consists of the following devices, including a Sky-Watcher Star Discovery AZ GoTo mount, a Sky-Watcher AZ Pronto mount, and a Sky-Watcher AZ4 mount, on which I can use my telescopes more comfortably:

The following overview lists the various options offered by the individual telescopes:

Telescope Sky-Watcher Skymax-127 OTA Omegon Photography Scope 72/432 OTA Celestron C8 OTA Unistellar eVscope TS-Optics TLAPO1027
Type Maksutov-Cassegrain tube Refractor tube (doublet), also usable as a spotting scope and camera lens Schmidt-Cassegrain scope for maximum aperture that I can handle Newtonian scope with sensor chip, fully automated Refractor tube (triplet)
Data
Aperture, Focal Length, Focal Ratio 127 mm, 1500 mm, f/11.8 72 mm, 432 mm, f/6 203.2 mm, 2032 mm, f/10 114 mm, 450 mm, f/4 102 mm, 714/715 mm, f/7
Light Gathering Power, Limiting Visual Stellar Magnitude, Resolving Power 329, 13.2 mag, 0.91" 105.8, 11.1 mag, 1.61" 802.7, 14 mag, 0,57" 265.2, 16 mag, 1.02" 212.3, ca. 12 mag, 1.15"
Maximum Magnification approx. 250 x approx. 144 x approx. 406 x 150 x 204 x
Magnification with 32 mm / 4 mm Eyepiece 46.9 x / 375 x (too high) => 214.3 x (7 mm; 6 would be optimal) 13.5 x / 108 x 63,5 x / 508 x (too high) => 406 x (5 mm) --- 22.3 x / 178.5 x
Use
Used as... moon and planets telescope; travel scope (but already somewhat heavy...); telescope for a "quick look"; best suited to moon, sun, and planets, but also suited to brighter deep sky objects telescope for travel and home use; telescope for a "quick look"; for moon, planets, and brighter deep sky objects; rich-field telescope home telescope that still can be handled by me and offers maximum aperture; can be easily moved to observation locations in a car; for moon, sun, planets, and deep sky objects; aperture-weight optimum telescope for "video astronomy" (rich-field telescope) telescope home use for a "quick look"; for moon, planets, and brighter deep sky objects; rich-field telescope
Usable with My GoTo Mount? yes (but the finder is located poorly...) yes yes no, has its own GoTo mount yes
Usable with My AZ4 Mount? yes (but the finder is located poorly...) yes yes no, has its own AZ mount yes
Usable with My AZ Pronto Mount? yes, but already too heavy for this mount... yes no no, has its own AZ mount no
Observation
Sun yes (with solar filter size 6 that I own) yes (with solar filter size 4 - I do not own one)

yes (with solar filter - I do not own one)

no yes (with solar filter - I do not own one)
Moon yes (I own a gray filter for the moon) yes (I own a gray filter for the moon) yes (I own a gray filter for the moon; only for 1,25") no (but not well suited to observing the moon) yes (I own a gray filter for the moon; only for 1,25")
Planets yes, but the maximum usable magnification about is 250 x yes-and-no (planets are rather small...) yes no yes
Deep Sky Objects yes (the brighter ones; more magnification, but high focal ratio = slow) yes (the brighter ones; low magnification - rich-field observations) yes yes yes
Terrestrial Observations yes, with an Amici prism yes, with an Amici prism no (would be possible with an Amici prism, but too big and heavy, magnification too high) no yes, with an Amici prism

Further down, you will find a table with additional technical data for the telescopes.

 

Sky-Watcher Skymax-127 OTA (November 2017)

Side view on AZ Pronto mount with extension tube

Ditto (detail)

Other side, on AZ Pronto mount without extension tube

Ditto (detail)

Purchased used in November 2017. The Sky-Watcher Skymax-127 OTA (focal length 1500 mm) is a Maksutov-Cassegrain tube, which allows higher magnifications than Newton telescopes of the same aperture. Therefore, it is useful for observing the sun, the moon, and the planets. Most of the time, I use the tube on the Sky-Watcher AZ Pronto mount, but I also use it on the Sky-Watcher Star Discovery AZ GoTo mount. If I use the AZ Pronto mount for my refractor, I can now manually use the Skymax-127 in parallel on a Sky-Watcher AZ4 mount.

For details see page Sky-Watcher Skymax-127 OTA Information (5" Maksutov-Cassegrain). For technical data see below.

 

Omegon Photography Scope 72/432 (September 2018)

Side view on AZ Pronto mount with extension tube

Ditto (detail)

Other side, on AZ Pronto mount with extension tube

Ditto (detail)

Purchased in September 2018 at the AME2018 astronomy fair and delivered soon after. The Omegon Apochromatic Refractor Pro APO AP Photography Scope 72/432 ED OTA is a refractor tube, which is useful for observing the sun, the moon, and maybe the planets, but also for wide-field DSO observations. It can also be used as a spotting scope (with an Amici prism) and as a camera lens. Most of the time, I use the tube on the Sky-Watcher AZ Pronto mount, but I will also use it on the Sky-Watcher Star Discovery AZ GoTo mount.

For details see page Omegon Photography Scope 72/432 ED OTA Information (2.8" Refractor). For technical data see below.

 

Celestron C8 OTA (November 2019)

Side view on Star Discovery mount

Ditto, front view

Ditto, rear view

The Celestron C8 is a Schmidt-Cassegrain telescope which, like Maksutov-Cassegrains, is a reflector with a "folded" light path and therefore very compact for its large aperture. Accordingly, it has a long focal length, which makes it particularly suitable to observing the moon and the planets. However, the C8 is also suitable as a "universal telescope" for DSO, as long as they are not too extended. As such, it can do everything, but nothing really outstanding... I bought the C8 in November 2019 in order to have a telescope with as much aperture as possible (8", more is no longer possible) for me. Telescopes with an aperture of 8" are often referred to as the "aperture-weight-optimum". I use the C8 on my Sky-Watcher Star Discovery AZ GoTo and on my Sky-Watcher AZ4 mounts.

For details see page Celestron C8 OTA Information (8" Schmidt-Cassegrain). For technical data see below.

 

Unistellar eVscope (January 2020)

The eVscope is a 4.5" Newtonian telescope (aperture 114mm, focal length 450mm, aperture ratio f/4) on an Alt-AZ GoTo mount. Its special feature is, however, that it is designed to produce images of celestial objects that are reminiscent of photos taken with large or space telescopes (of course, in a lower resolution, but at least, it can...) and that can even show colors. The telescope is announced as working simply and more or less fully automatically. I took part in a Unistellar Kickstarter campaign in November 2017, and received the eVscope on January 27, 2020. The next day, it quit its service after the first observation session. The internal microSD card from which the control program is loaded was identified as the source of the error. I replaced it in the meantime, but I have not yet been able to gain any experience as to how reliably my eVscope now is working.

For details see page Unistellar eVscope. For technical data see below.

 

TS-Optics Photoline 102/714 (July 2020)

The TS-Optics Photoline 102 mm f/7 FPL53 Triplet Apo with 2.5" RPA focuser is regarded as exhibiting very little color fringing with respect to its price. That is why I bought it in July 2020 on the advice of my astronomy dealer - unfortunately not from him, because the unit was hard to get. I will operate the refractor on the Sky-Watcher AZ4 mount manually and on the Sky-Watcher Star Discovery AZ GoTo mount with GoTo. In a first comparison day and night (M 3) the refractor showed itself clearly superior to my Omegon refractor PS 72/432.

For details see page TS Optics Photoline 102/715 Information (4" Refractor). For technical data see below.

 

Links

 

Appendix: Data

Technical Data of My Current Telescopes

Telescope
Sky-Watcher Skymax
Omegon Celestron Unistellar TS-Optics
Skymax-127 PS 72/432 C8 eVscope  TLAPO1027
Optical Design Maksutov-Cassegrain Refractor (Doublet) Schmidt-Cassegrain Newton (Parabolic) Refractor (Triplet)
Primary Mirror Diameter 127 mm (5") 72 mm (2.8") 203.2 (8") 112 mm (4.5") 102 mm (4")
Focal Length, Focal Ratio 1500 mm
f/11.8
432 mm
f/6
2032 mm
f/10
450 mm
f/4
714/715 mm
f/7
Resolving Power (arc secs) 0.91" 1.61" ** 0,57" 1.02" 1.15"
Limiting Visual Stellar Magnitude 13.2 mag 11.1 mag ** 14 mag 16 mag about 12 mag
Light Gathering Power 329.2 105.8 ** 842.7*/841/843 265.2 212.3
Maximum Practical Visual Power 254 x 144 x 406 x 150 x 204 x
Optical Tube Dimensions
(diam. x length)
14.4 x 33 cm 10 cm x 39.4 cm 23.8 x 43.2 cm n.a. 10.5/12.6 cm x 61.5 cm (transport size)
Net Weight Basis --- --- --- 7 kg in total ---
Net Weight Optical Tube 3.4 kg 2.06 kg 5.67 kg 5.6 kg

*) My own measurement; **) corrected values

Observation-Relevant Data

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
PS 72 (Refractor, Doublet)
432
72
6
106
144
108
144
11.08
10.29
39.0
42.0
4.0
3.0
TLAPO1027 (Refractor, Triplet)
714
102
7
212.3
153
204
15.69
14.57
45.5
49.0
4.7
3.5
Skymax-127 (Maksutov-Cassegrain)
1500
127
11.81
329
191
254
19.54
18.14
76.8
82.7
7.9
5.9
Celestron C8 (Schmidt-Cassegrain)
2032
203
10
841
305
406
31.26
29.03
65.0
70.0
6.7
5.0
Celestron C8R (Schmidt-Cassegrain)
1280
203
6.3
841
305
406
31.26
29.03
41.0
44.1
4.2
3.2

*) 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), True Field of View, and Exit Pupil for Different Focal Lengths of Eyepieces

Blue: borrowed eyepieces; italic 2" eyepiece; gray: sold

Telescope
Further Data
Focal Length of Eyepiece (mm)
Magnification
 
Focal Length of
Telescope (mm)
4
7
10
16
18
24
26
28
32
32
35
38
40
56
PS 72/432
432
108.00
61.71
43.20
27.00
24.00
18.00
16.62
15.43
13.50
13.50
12.34
11.37
10.80
7.71
TLAPO1027
714
178.50
102.00
71.40
44.63
39.67
29.75
27.46
25.50
22.31
22.31
20.40
18.79
17.85
12.75
Skymax-127
1500
375.00
214.29
150.00
93.75
---
62.50
---
---
46.88
---
---
---
---
---
C8
2032
508.00
290.29
203.20
127.00
112.89
84.67
78.15
72.57
63.50
63.50
58.06
53.47
50.80
36.29
C8 (Red.)
1280
320.00
182.86
128.00
80.00
---
53.33
---
---
40.00
---
---
---
---
---
 
True Field of View (°)
Apparent Field of View (°) >
82
82
72
82
82
65
70
56
52
70
69
70
68
52
 
Focal Length of
Telescope (mm)
4
7
10
16
18
24
26
28
32
32
35
38
40
56
PS 72/432
432
0.76
1.33
1.67
3.04
3.42
3.61
4.21
3.63
3.85
5.19
5.59
6.16
6.30
6.74
TLAPO1027
714
0.46
0.80
0.91
1.84
2.07
2.18
2.55
2.20
2.33
3.14
3.38
3.73
3.92
4.08
Skymax-127
1500
0.22
0.38
0.48
0.87
---
1.04
---
---
1.11
---
---
---
---
---
C8
2032
0.16
0.28
0.35
0.65
0.73
0.77
0.90
0.77
0.82
1.10
1.19
1.31
1.34
1.43
C8 (Red.)
1280
0.26
0.45
0.63
1.03
---
1.22
---
---
1.30
---
---
---
---
---
 
Exit Pupil (mm)
 
Focal Ratio
4
7
10
16
18
24
26
28
32
32
35
38
40
56
PS 72/432
6
0.67
1.17
1.67
2.67
3.00
4.00
4.33
4.67
5.33
5.33
5.83
6.33
6.67
9.33
TLAPO1027
7
0.57
1.00
1.43
2.29
2.57
3.43
3.71
4.00
4.57
4.57
5.00
5.43
5.71
8.00
Skymax-127
11.81
0.34
0.59
0.85
1.35
---
2.03
---
---
2.71
---
---
---
---
---
C8
10
0.40
0.70
1.00
1.60
1.80
2.40
2.60
2.80
3.20
3.20
3.50
3.80
4.00
5.60
C8 (Red.)
6.3
0.63
1.11
1.59
2.54
---
3.81
---
---
5.08
---
---
---
---
---

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.

 

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16.07.2020