Table of Contents
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:
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.
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 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.
- Place equatorial mount with polar head (9) on the spigot and fix it by clampscrew (2.4).
3.2. Balancing the Instrument
3.2.1. Balancing about the declination axis
- 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)
3.2.2. Balancing about the polar axis
- Clamp declination axis
by screw (12).
3.3. Adjusting the instrument
3.3.1. Setting for the polar altitude
- Use hexagon wrench to loosen hexagon-head screw (23).
- Tighten hexagon-head screw
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
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.
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)
micrometer eyepieces for eyepiece screw micrometer
- Wide-angle eyepiece f = 31 mm
- Intermediate tube 20 mm
- 42/150 finder telescope
- Motor-operated polar-axis
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.
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.
Huygens 25 mm eyepiece:
Diameter of exit pupil: 1.9mm
Orthoscopic 16 mm eyepiece:
Diameter of exit pupil: 1.2mm
Size of sun image (natural): 7.3mm dia.
Size of sun image on projection
5. Standard equipment
63/840 School Telescope
Telescope tube with
6. List of illustrations
2 63/840 telescope tube
3 Equatorial mount T
4 Portable tripod
|(c) 2001, Luis Argüelles. Oviedo, Spain|