User's manual

Table of Contents

1. Introduction       
2. Description       
3. Instructions for Use      
3.1. Setting up the instrument     
3.2. Balancing the instrument     
3.2.1. Balancing about the declination axis
3.2.2. Balancing about the polar axis
3.3. Adjusting the instrument
3.3.1. Setting for the polar altitude
3.3.2. Adjusting in azimuth
3.3.3. Additional hints on adjustment
3.4. Object setting
3.5. Hints on the creation of a fixed erection place
3.6. Maintenance
3.7. Supplementary equipment
3.8. Solar observations
3.9. Cross-hair insets and ring micrometer
4. Specification
5. Standard equipment
6. List of illustrations

1. Introduction

The TELEMENTOR 63/840 School Telescope (Fig. 1) has been designed as combined observation and measuring instrument for particular use in lessons.

But due to its technical design the TELEMENTOR meets also the demands of the amateur astronomer the more so as a wide selection of astronomical supplementary units may be used.

Salient features of the telescope:

  • high-quality astronomical objective of outstanding imaging quality and resolving power
  • equatorial mount with setting facilities for the horizon and equatorial systems
  • large and clear graduated circles for object setting according to coordinates and for angle measurement
  • manually actuated fine motions in both axes
  • sighting device for coarse setting of objects
  •  cross-hair inset for the eyepiece as sighting mark for object setting in angle measurements
  • tripod with box level
  • easy operation due to the simple and rugged design
  • low weight, easy assembly and disassembly of the three main units telescope tube, mount and tripod, easy transport.
2. Description

The TELEMENTOR School Telescope consists of three principal constructional units:  the 63/840 telescope tube, the equatorial mount T and the tripod.

The 63/840 telescope tube (Fig. 2) is equipped with a high-quality astronomical objective of 63mm free aperture and 840mm focal length. The objective has a resolving power of 1.8" and ensures imaging without chromatic aberration.

The front side of the telescope tube (1) serves as sun shade in daytime observations or as dew-protection cap to protect the objective from damp in humid air. The opening of the tube may be closed by a protective cover (3), if required. Disturbing scattered light is eliminated by three stops inside the tube. A two-part sighting device (2) located on the tube faollitates the alignment of the telesoope with the object of observation. For focusing within a range of 100 mm knob (5) is used. Intermediate sleeve (6) which serves as an adapter to the different lengths of the supplementary devices, is connected to the telescope flange and can be easily screwed out, if necessary. This internemedíate sleeve carries a screwed-in eyepiece sleeve (7) taking the plug-in eyepiece (8) chosen.

As sighting mark for setting the telescope to an object a cross-hair insert is used which is pushed into the 16mm orthoscopic eyepiece from the side not facing the eye. Dovetail (4) located at the telescope serves as connector to the equatorial mount.

The equatorial mount T (Fig. 3) offers the possibility of a coordinate setting in the equatorial and horizon system. If the telesoope is to be used for observations in the horizon system, the polar altitude is set for 90°. The polar altitude scale (22) located at the polar head (9) permits direct  setting of the desired polar altitude. Hexagon-head screw (23) is used for clamping the housing of the polar axis (10) carrying the graduated hour circle (11) as well as the pivoted polar axis, to the polar head. The housing of the declination axis (17) carrying the graduated declination circle (16) and the pivoted declination axis is screwed to the flange of the polar axis. One side of the declination axis is expanded by a thread axis which carries the sliding weight (20) to balance the telesoope about the polar axis. This weight is clamped by clampscrew (21). On the opposite side the dovetail slide (15) is screwed to the flange of the declination axis by clampscrew (14) to accept the telescope tube. The housing of the declination axis and the fixture for the telescope tube accomodate clamping devices as well as fine motions for the polar and declination axes.

Clampscrew (18) for the polar axis and knob (19) for fine motion in hour as well as clampscrew (12) for the declination axis and knob (13) for fine motion in declination are conveniently arranged.

The fine motion range permits to follow a star for about 30 minutes without having to unlock the clamping.

When taking measurements in the horizon system, the graduated declination circle becomes the vertical circle and the graduated hour circle becomes the azimuth circle. The declination circle is divided into four parts from 0° to 90° with a graduation interval of 1°. The hour circle is divided from 0 h to 24 h with a graduation interval of 4 min. For azimuth reading it is additionally provided with a second graduation from 0° to 360° with a graduation interval of 1°.

The mount with polar head (9) is placed on the spigot of the tripod and fixed by clampsorew (24).

The portable tripod (Fig. 4) can be reliably placed on any ground. Each of its legs (29) can be drawn out seperately and clamped in any position by screw (28). The expansion of the legs is limited by a triangular plate. This plate is suspended behind the screws (30) on the inner side of the rigid tripod legs (25) and clamped with those. The plate can also be used as a rest for laying down accessory units. To check the spigot for its vertical position the tripod is provided with a box level (27).

3. Instructions for use

3.1. Setting up the instrument

- Loosen clampscrews (28) and bring tripod into the desired position. Draw out its legs (29) and tighten clanpscrews. Expand the tripod legs, hang triangular plate (31) behind clampscrews (30) and tighten them.

- Adjust tripod legs (29) until the bubble of box level (27) is centred within the ring mark. Tighten clampscrews (28). The spigot (26) is now vertical to the horizontal plane.

- Place equatorial mount with polar head (9) on the spigot and fix it by clampscrew (2.4).

- Introduce telescope tube (1) with dovetail (4) into dovetail slide (15) of the mount and clamp it by screw.

3.2. Balancing the Instrument

3.2.1. Balancing about the declination axis

- Bring declination axis into horizontal position by loosening clampsorew (18) of the polar axis. Then turn the instrument around the polar axis and tighten clampscrew (18).

- Unlock clampscrew (12) of declination axis

- Slacken slampscrew (14) and slide the telescope along the dovetail slide until it is balanced about the declination axis. Tighten clampscrew (14). Now the telescope must stay in any position when turned around the declination axis, even with clampsorew (12) slackened.

3.2.2. Balancing about the polar axis

- Clamp declination axis by screw (12).
- Unlock clampscrew (18) of polar axis and hold telescope in place.
- loosen clampscrew (21) and slide weight (20) until the telescope is balanced about the polar axis.
- Tighten clampscrews (21) and (18). The telescope must stay in any position when turned around the polar axis, even with clampscrew (18) slackened.

3.3. Adjusting the instrument

3.3.1. Setting for the polar altitude

- Use hexagon wrench to loosen hexagon-head screw (23).

- Rotate housing of polar axis around the axis of screw (23) until the polar altitude (geographic latitude) of the erection site is indicated at the polar altitude scale (22)

- Tighten hexagon-head screw (23).

3.3.2. Adjusting in azimuth

- Set declination and hour angle of a celestial object on the respective graduated circle by turning the telescope around the declination or polar axis, respectively. The hour angle of the object to be observed has to be calculated for the Instant of observation.

- loosen clampscrew (24) and rotate the telescope in azimuth around the spigot until the object appears within the visual field.

- Tighten clampsorew (24). Now the telescope is ready for astronomical observation.

3.3.3. Additional hints on adjustment

Especially suitable for azimuth setting is the pole star, since an error in sidereal time in the pole region causes only a slight position error (an error of 40 min in sidereal time causes a position error of 0.15° in the case of the pole star). The hour angle may be taken from a nomogram consisting of two concentric circles rotatable against each other. One circle is provided with the 365 days of the year evenly spaced within 360°, arranged in clockwise direction. This circle is additionally provided with a marking for the geographic longitude of the observation site. The marking for the geographic longitude of 15° is at the date of "October 23.8", markings for other longitudes are distant by respective angles, their values increasing in counterclockwise direction.

The second cirole is provided with an hour graduation in clockwise direction.

These circles have to be turned such that the time of observation coincides with the geographic longitude of the observation place; the hour angle of the pole star can be directly read from the circle at the date of the day of observation.

In daytime observations the sun may be used for adjustment. The hour angle of the sun equals the difference between the sun's culmination at the observation site and the moment of adjustment.

A very simple method may be applied if the erection site of the School Telescope is not changed. After a first precise adjustment a distant terrestrial object is sighted (e.g. a spire, chimney or another prominent terrain point still visible in the dawn, by twilight or even at night). Its coordinates are read from the hour and declination circles and noted down. A re-erection at the same place requires only to set the telescope for the coordinates noted down and to rotate it around the spigot until the distant target appears in the visual field. After having tightened clampscrew (24) the telescope is ready for use.

3.4 Object setting

It is recommended to set the telescope to an object with the screws (12) and (18) clamped only slightly. If the object is within the visual field, tighten the clampscrews and correct the position, if necessary, by means of the fine motion knobs. In this way the fine motion range is not restricted quite from the beginning and setting is facilitated since the observer's hands must not always handle the clampsorews.

In order to make full use of the fine motion range in hour (abt. 7.5° at a following-up time of 30 min) when following a celestial object, fine motion knob (19) should at the beginning of observation be screwed out so far that one rotation of the motion range is left. In the case of angle measurements push the cross-hair insert, serving as sighting mark, into the 16mm  eyepiece until the cross-hair appears sharply depicted within the visual field of the eyepiece.

3.5 Hints on the creation of a fixed erection place

The School Telescope should have a fixed place. This could be achieved in the following way: Fasten a steel gudgeon having the same dimensions as the spigot of the tripod (dia. 20h8, 70 mm long) to a steel tube of abt. 50mm diameter by using an intermediate piece. Concrete this steel tube in at a suitable place such that the spigot of the tripod is vertical. This method ensures a vibration-free erection of the School-Telescope as well as a quick azimuth adjustment.

3.6 Maintenance

Like all other high-quality precision Instruments this telescope requires a careful  maintenance and has to be protected against contamination or damage of any kind.

Remove the dust deposited on the optical parts with a soft brush at first and if this will not do wipe with a soft cloth. Do never use the cloth prior to the brush. Otherwise the tiny but often hard and sharp-edged dust particles would scratch and damage the sentitive optical surfaces.

Do never wipe the anti-reflection coated lens surfaces with a cloth in case of major contaminations. To avoid any damages to the coating, first use a soft brush to remove the dust and afterwards a tampon impregnated with alcohol to wipe carefully over the lens surfaces.

Keep brush and optics cloth in a dust-proof container.

To avoid rusting and to maintain their functional reliability not varnished metal faces, exterior support and contact points as well as threads should be provided with a thin layer of non-corrosive grease. Varnished surfaces should be carefully wiped from time to time with a soft cloth impregnated with oil or grease.

To protect the objective against unnecessary contamination, slip the protective cover over the dew-protection cap when the telescope is not in-use.

Depending upon the climatic conditions check the state of the instrument every 3 to 6 months.

3.7. Supplementary equipment

The School Telescope has been designed such that most of the supplementary devices of our make may be attached to it. The most important devices are shown in the schematic drawings in the Annex of illustrations of this instruction manual.

Further accessories not contained therein may also be used:

- Adapter ring for the connection of a miniature reflex camera of type Exa or Exakta (bayonet)

- Adapter ring for the connection of a miniature reflex camera with Praktica M 42 x 1 thread

- 1.3x Barlow lens

- Eyepiece spectroscope

- Sun filter (to be inserted into the dew cap of the telescope tube)

- Orthoscopic micrometer eyepieces for eyepiece screw micrometer
f =  6 mm
f = 16 mm
f = 25 mm

- Wide-angle eyepiece f = 31 mm

- Intermediate tube 20 mm 
30 mm
40 mm
60 mm
70 mm

- 42/150 finder telescope

- Motor-operated polar-axis drive

3.7.1. Solar observations 

In solar observations where large quantities of light and heat enter Into the objective and are concentrated in the focal plane, care has to be taken that these rays do not harm the astronomer and are not damaging the instrument. A direct visual or photographic observation of the sun without any auxiliary means is therefore not allowed. For observations a sun filter (set of neutral grey filters) or a sun projection screen has to be taken.

If the sun projection screen is used for observations use eyepieces with uncemented lenses only, i.e. Huygens eyepieces.

3.7.2. Cross-hair insets and ring micrometer

Cross-hair insets and ring micrometer listed under No. 5 in Fig. 8 are supplied with especially prepared orthoscopic eyepieces of the corresponding focal length. Such an eyepiece is the f = 16 mm orthoscopic eyepiece included in the TELEMENTOR standard outfit.

On special request of the customer standard-type eyepieces already available can be retrofitted with a cross-hair inset or ring micrometer. For fitting these insets into your eyepieces send them to our works.

Cross-hair Insets and ring micrometer designed for the same eyepiece focal length can be exchanged against each other in the corresponding eyepiece.

4. Specifications

Free aperture: 63mm
Focal length: 840mm
Resolving power: 1.8”

Huygens 25 mm eyepiece:

Diameter of exit pupil: 1.9mm
Geometric light Intensity: 3.6
Magnification: 34x
Field angle: 1º 9’

Orthoscopic 16 mm eyepiece:

Diameter of exit pupil: 1.2mm
Geometric light intensity: 1.44
Magnification: 53x
Field angle: 48’

Size of sun image (natural): 7.3mm dia.

Size of sun image on projection screen
(when using the Huygens 25 mm eyepiece): 100mm dia., approx.

Telescope tube: 3.4 kg
Equatorial mount T: 5.6 kg.
Tripod: 5.0 kg.
Container: 2.3 kg.

5. Standard equipment

63/840 School Telescope

consisting of:

Telescope tube with
63/840 objective
80mm intermediate sleeve
Eyepiece sleeve
Orthoscopic 16mm eyepiece
Cross-hair inset for 16 mm eyepiece
Huygens f = 25mm eyepiece
Equatorial mount T
Tripod with triangular plate
Hexagon wrench
Dust brush
Polishing cloth
Container for school telescope
Container for accessories
Instruction manual

6. List of illustrations

Fig. 1  TELEMENTOR  School Telescope 

Fig. 2  63/840 telescope tube
1  telescope tube
2  sighting device
3  protective cover
4  dovetail
5  focussing knob
6  intermediate sleeve
7  eyepiece sleeve
8  eyepiece

Fig. 3 Equatorial mount T 
9    polar head
10  housing of polar axis
11  graduated hour circle
12  clampscrew for declination axis
13  fine motion knob for declination
14  clampscrew for tube clamping
15  dovetail slide
16  graduated declination circle
17  housing of declination axis
18  clampscrew for polar axis
19  fine motion knob for hour motion
20  sliding weight
21  clampscrew on sliding weight
22  polar altitude scale
23  hexagon-head screw for polar altitude variation
24 clampscrew for fastening the polar head to the spigot

Fig. 4   Portable tripod
25  rigid tripod leg
26  spigot
27  box level
28  clampscrew
29  extending tripod leg
30  clampscrew for triangular plate
31  triangular plate

Fig. 5   Placing the equatorial mount on the spigot 

Fig. 6   Inserting the telescope into the dovetail slide of the equatorial mount 

Fig. 7   Set-up of the school telescope for measurements in the horizon system



(c) 2001, Luis Argüelles. Oviedo, Spain