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   TAL-1 telescope's service manual
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TAL1

TAL-1

Contents


1. General directions
2. Specifications
3. Delivery set
4. Design of telescope
   4.1. Design and principle of operation
   4.2. Optical train
5. Preparation for operation
   5.1. Telescope assembling
   5.2. Telescope balancing
6. Order of operation
   6.1. Operation with telescope
   6.2. Photographic observations
   6.3. Telescope and atmospheric conditions
7. Maintenance
8. Possible derangements and methods of their elimination
9. Rules of storage
10. Acceptance certificate

 

The instrument is subject to continuous development and improvement, consequently it may incorporate minor changes in detail from the information contained herein.

ATTENTION!

The telescope forms the inverted image like any astronomical instrument does. The direct observations of the Sun through the black light filter are permitted only with the use of the solar diaphragm.

1. General directions

The telescope is designed for visual observation of the celestial objects.

The telescope can operate normally at the ambient temperature from 30C to minus 30C.

When buying the telescope one should pay attention to the package safety ensured by the seal of the manufacturing pliant. After unsealing the case one should check compliance of the complete set denoted in the list of enclosure. Prior to using the telescope one gets acquainted with its handling and order off operation,

Telescope is completed with additional reticle with cross for eyepiece F=25mm. User can adjust an optical axes parallelism of telescope tube and finderscope.

3. Delivery set

The composition of the telescope and its delivery set are shown in the table.

Telescope 5.803.040 1
Finderscope 6x 5.920.019 1
PlossI eyepiece of f'=25 mm. 1.25" 5.923.547 1
Equatorial mounting 6.063.306 1
Support 6.126.064 3
Pipe 6.452.062 1

Accessories and Parts

Kellner's eyepiece of f=1 5 mm, 1,25" 5.923.548 1
Barlow lens3" 5.932.671 1
Yellow light, filter 5.940.416 1
Black lightfilter (solar) -01 1
Blue light filter -02 1
Red lightfilter -03 1
Green light filter -04 1
Neutral (grey, lunar) lightfilter -05 1
Blind 7.006.415 1
Bracket 6.152.099 1
Stopper 8.632.379 1
Cap-diaphragm 8.057.126-01 1
Screwdriver 6.890.030-10 1
Napkin 8.890.001-01 1
Screen (for observation of the Sun) 6.430.431 1
Brush 1
Shipping Container
Shipping case 4-171.687 1
Service Documents
Service manual 3.807.005

4. Design of telescope

4.1. Design and principle of operation

The telescope consists of three basic units: the telescope tube, equatorial mounting and pier with supports.

Diagram of setting Barlow lens
Fig. 1a. Diagram of setting Barlow lens

The tube I (Fig. 1b) is the basic part of the telescope which embodies the optical parts: the primary mirror, diagonal mirror, finderscope 3 fixed in the locating rings 2, eyepiece's and Barlow lens which are inserted In the focusing mechanism 4.

The primary mirror (Fig. 2) is mounted in the cell and can be adjusted by means of the screws I and 2.

The diagonal mirror. (Fig. 3) is cemented to the cell and fixed in the telescope tube by means of a spider.

The inlet hole of the tube is covered with the cap 10 (Fig.4) after operation.

The focusing mechanism 4 (Fig. 1b) is composed of the mounting and barrels with thread for eyepiece allowing to achieve a sharp image of object to be observed.

Primary and diagonal mirrors
Fig. 2. Primary mirror
Fig. 3. Diagonal mirror

The finderscope 3 is the telescope with the magnification of 6" and viewfield of 8.

The equatorial mounting (Fig. 5) consists of two axesthe polar axis 2 and the declination axis 6 perpendicular to it.

Fastened on one end of the declination axis is the saddle with the hinged clips 4 in which the telescope tube is mounted; fastened on the other end of the axis is the counterweight 8 which can travel on thread for balancing the telescope. The screen I (Fig. 4) and the bracket for the camera 4 can be fastened on the same axis.

Accessories of TAL-1
Fig.4. Accessories and tools

The casing of the polar axis is fastened on the bracket 10 with the scale of latitudes (Fig. 5) by means of which the whole system is set to the latitude of the observer's site.

Equatorial mounting of telescope
Equatorial mounting

Each axis has a circle which shows an hour angle or declination of the object visible in the telescope viewfield. The position circle 7 on the declination axis which shows the declination of the object's figured from 0 to 90 with a division value of 2. The circle I on the polar axis (the circle lot hour angles) is figured from 0 to 24 hours with a division value of 10 minutes.

The coarse focusing of the telescope tube, relative to both axes is performed by slackening the clamping screws 3 and by rotation of the tube relative to the respective axis with the further clamping of the axes. The fine focusing is performed by means of the micrometer screws 5 in the range of 4 relative to the declination and polar axes. The equatorial mounting is connected to the pier by thread.

The pier 6 (Fig. 1b) is composed of tube which is fixed on three supports 7.

Optical scheme of TAL-1 telescope
Optical train of telscope

The Newton system is used in the telescope. Observations are performed through the tube on which the finderscope is positioned. The tube axis is set in the required position with the help of the equatorial mounting.

4.2. Optical train

The reflecting telescope is provided with the Newton optical system (Fig. 6).The parallel beam of rays enters the telescope tube, falls on the primary mirror 1 with the focal length of 805 mm and, after reflecting from it in the diagonal mirror 2, refracts at 90 and is viewed with the help of the eyepiece 4.

The telescope gives the magnifications of 32; 54, 96; 162 When setting the eyepiece of f'=25 mm, one obtains the magnification of 32'; the eyepiece of f'=15 mm gives the magnification of 54; when setting the Barlow lens3with the 25 mm eyepiece, one obtains tile magnification of 96; when setting the Barlow lens and the 15 mm eyepiece together, one obtains the magnification of 162 (Fig. 1a).

Completed with the telescope are 6 light filters (Fig. 6, pos. 5): red, yellow, green, blue, grey (lunar), black (solar) ones.

Optical Train of Finderscope

The optical train of the finderscope is shown in Fig. 6. The finder-scope is composed of the objectives reticle 7 and eyepiece 8.

5. Preparation for Operation

5.1. Telescope Assembling

Before assembling the telescope the units and parts must be cleaned from the grease compound of the plant.

The telescope is assembled in the following way.

Three supports provided with captive screws are fixed to the pier through the holes on its lower end. The equatorial mounting is screwed on the upper end of the pier.

The polar axis is set by inclining the equatorial mounting by the scale of latitudes to the observing site and fixed by means of handle 9 (Fig.5).

The telescope tube is mounted on the supports of the saddle and fixed by means of two clips with the help of hinged screws.

The finderscope should be removed from the mortise of the case where the accessories are placed, then it should be mounted on the tube in two rings and fixed by means of six setting screws provided on the saddle.

For obtaining the required magnification of the telescoped the respective eyepiece or the eyepiece with Barlow lens 5 (Fig. 4) is inserted in the eyepiece tube.

5.2.Telescope balancing

For smooth motion of the telescope and reliable operation of the micrometer screws it is important to balance its movable parts on the axes of the equatorial mounting. With this purpose the telescope tube should be set in the horizontal position, the screw of the brake pos. 3 (Fig. 5) of the axis of declinations is unscrewed and, holding slightly the tube by hand, one sees to it whether the tube remains in the indifferent equilibrium or one of its ends overweights. If the tube is not in balance, one unscrews the screws of the clips which fix the tube and moves the tube along its axis until it will be in balance. After that one screw's in the screws of the clips.

It is required to set the axis of declinations in the horizontal position after unscrewing the brake screw pos. 3 (Fig. 5) of the polar axis and, holding the axis of declinations, to see to it whether the telescope is in balance about the polar axis. If it is not in balance, move the counterweight 8 (Fig. 5) along the axis of declinations by rotting it on thread.

When mounting the various devices on the telescope, for example, the camera, it is required to balance the telescope additionally.

6. Order of Operation

6.1. Operation with Telescope

Before mounting the telescope, it is required to choose the place and prepare the site. It must be even and solid. Mount the telescope on the site and check it for reliable stability.

The telescope has great magnifications and, hence, small viewfields; therefore, it is provided with a finderscope.

After mounting the telescope, it is required to set parallelism of the optical axes of the telescope tube and finderscope. Forthis purpose the telescope is pointed to the remote objected This position of the telescope is fixed by means of the screws of the brakes of the axes.

Then, by operating with; the setting screws of the rings 2 (Fig. 1b) of the finderscope, one brings the chosen remote object to the centre of the finderscope viewfield. This operation is performed only once. In the future, before observations only the parallelism of the optical axes of the telescope and finderscope is checked.

The celestial sphere together with the astronomical objects performs the visible motion about the celestial axis. Therefore, the telescope is provided with the equatorial mounting. Being set correctly, this mounting makes it possible to perform the celestial object tracking. After pointing the telescope to the object, the observer can keep the object in the viewfield centre for a half an hour by rotating slowly the micrometer screw of the polar axis.

In order to avoid guiding: correction in declination, the polar axis of the telescope should be set parallel to the celestial axis. In this case the north (upper) end of the polar axis faces the celestial pole positioned near Polaris (a Ursae Minoris). For visual observations it is enough to tilt the polar axis at an angle equal to the latitude of the observing site and to direct it approximately along the line the South the North.

With such coarse setting of the telescope the object will "deviate" step by step in declination (it is lifted or lowered in the viewfield). This error is corrected at times by means of the micrometer screw of the declination axis.

For photographic operations and in the cases when the telescope can be set stationary, the polar axis of the telescope should be set precisely. For this purpose one observes any bright star in the East, then in the South and makes notice to what direction the star is displaced.

If in observation of the star in the East, it is displaced in the telescope viewfield so that in its tracking the upper end of the telescope tube sinks slowly, the north end of the polar axis should be somewhat lifted.

If the upper end of the tube is lifted step by step, the north (upper) end of the polar axis should be lowered.

For precise setting of the axis by azimuth one observes the star near the meridian circle (above the South point) in the same way. If in the star tracking one should lower slowly the upper end of the telescope tube, the north end of the polar axis should be displaced to the West.

If in the process of the star tracking the upper end of the telescope tube is lifted, the north end of the polar axis should be displaced to the East.

In 20-30 minutes of such observations one can set the polar axis so that the star will remain on the cross-hairs for 10-15 minutes without correction in declination.

After precise setting of, the polar axis one can set the declination and hour circles which must help to search the objects invisible with a naked eye or even through the finderscope.

First of all, one should set the hour circle which is fixed on the polar axis. For this purpose after the fine setting of the polar axis one unscrews the screw of the brake of the polar axis and sets the declination axis horizontally. The horizontal setting should be checked with the aid of a level. After setting of the axis, one sets the hour circle so that "0" is found against the index. The circle is fixed with screws and tightened with a nut.

For setting the declination circle fixed on the declination axis one should find the declination of two-three bright stars in the star catalogue or make use of the declinations of the planets given in the astronomical calendar. With thee help of the finder scope one brings the star or the planet to the viewfield centre of the telescope at maximum magnification. After that one sets the declination of the required star against the index. The circle is fastened by means of a screw. Then one makes attempt to find the second star by its declination. For this purpose one slackens the screws of the brakes of tile axes and checks the telescope so that the declination of the sought star is set on the declination circle. The .declination axis is fixed and, by rotating the telescope tube slowly clockwise and counter-clockwise around the polar axis, one brings tile star to the telescope viewfield centre. After checking of tile circle setting, one tightens it with a nut.

In order to avoid resetting of tile polar axis and circles one should choose the solid horizontal site. Best of all, it is a concrete section of 1.51.5 m size. The position of three supports of the telescope pier should be marked on this site. The telescope is mounted according to the marks on the concrete.

6.2. Photographic Observations

The complete set of the telescope includes the bracket for a camera with the help of which one can mount a miniature camera.

For this purpose the bracket is mounted on the axis of declinations from the counterweight side and the camera is fixed to it with the help of a captive screw.

The exposures witch are required for photographing the starfields are tenths of minutes without hindrance of the street lighting, Therefore, for this period of time one should see to it that the camera follows the sky precisely in its diurnal rotation. With this purpose the Barlow lens and the eyepiece with the reticle possessing great magnification are inserted in the eye piece tube. Near the viewfield centre of the camera one chooses the bright star to which the telescope is pointed. To keep the star on the reticle cross-hairs is the problem for an observer for the whole period of exposure. As the cross-hairs of the telescope is not illuminated, the image of the guide star should be slightly defocu-sed in order to cross a light circle of the unsharp image of the star by the cross-hairs and to keep the star in this position for the period of exposure. For the whole period of exposure one rotates carefully a micrometer screw of the polar axis. One corrects the position of the guide star by means of the micrometer screw of the declination axis as well in case of necessity. To obtain the minimum corrections in declination the polar axis should be set as precisely as possible to the celestial pole. One should remember that, if the polar axis is set incorrectly, the images of the stars at the viewfield edges appear as dashes even in the case when the star image is kept on the crosshairs.

The bracket makes it possible to use the camera with tile remo vable objectives, if their mass is not so great.

6.3. Telescope and Atmospheric Conditions

At great magnifications together with the increase of the visible dimensions of the object the disturbances due to atmosphere are increased. It is expressed in great blurring of the images of the distant objects, in scintillation of the star images.

The observations in the cold seasons are possible when all telescope parts acquire the ambient temperature. For air circulation inside the telescope tube there is a hole plugged, with a stopper in the cell of the primary mirror. In operation the stopper should be unscrewed from the cell.

But in observations the great disturbance of atmosphere may take place at nights, that leads to bad images of the celestial objects. It is quite possible that at those nights the observations of the fine details of the planets and of the Moon are unsuccessful.

7. Maintenance

For faultless operation the telescope should be kept in cleanness and protected against mechanical damage. The metal surfaces are periodically dusted by using clean soft napkins, then wiped with a napkin impregnated with acidless vaseline, after that with a dry napkin.

.The aluminized mirrors require particular care. The accumulated dust is removed only with the use of a soft brush or cotton wool tampon. .Cleaning should be carried out without excessive effort to avoid formation of thin scratches on the mirrors surface which deteriorate the image. If some fat spots are found on the mirrors, never wipe them. In this case the mirrors are washed. The primary mirror (Fig. 2) is taken out of the tube after unscrewing the screws which fix the cell to the tube. Without removing the mirror from the cell, the mirror surface is wetted considerably with pure medical alcohol with the help of a cotton wool tampon. By using the came tampon, one wipes slightly the wet mirror without excessive effort and puts it at once under the stream of pure water. After removing alcohol in this way, one puts the mirror on its edge until it is dried. The drops of water are removed with a blotter by slight touching them with a blotter corner.

The diagonal mirror is cleaned in the same way. After cleaning the mirrors are put in their places.

The lenses of the eyepieces are wiped with a dry linen napkin. The fat spots are removed with a cotton wool piece impregnated with alcohol.

One should dismantle the optics only in case of necessity. In non-operating position the telescope tube must be constantly covered with a cap and the eyepiece one - with stopper 8:632.379.

8. Possible derangements and methods of their elimination

When manufacturing the telescope at the plant, the optical parts are carefully set (adjusted) relative to each other. However, in case of transportation or considerable impacts of the telescope the optical parts may be displaced (the adjustment is disturbed). In this case it is required to readjust the telescope. Prior to this operation one should remove the eyepiece from the eyepiece tube and check whether the mirrors are displaced from the given places. For this purpose, it is necessary to look through the eyepiece tube from which the eyepiece and the Barlow lens are removed. If the telescope is adjusted, the plane diagonal mirror mast be concentric relative to the brim of the focusing mount. The reflection of the primary mirror in the diagonal one is non-concentric it is necessary to reflection of the diagonal mirror with the spider system is seen in the primary mirror. The image of the diagonal mirror must be positioned precisely in the middle of the primary. The reflection of an observer's eye (see Fig. 7) must be seen at the centre of the diagonal mirror reflection.


Fig. 7
1-tinner diameter of focusing mount;
2-diagonal mirror; 3-reflection of primery mirror in the diagonal mirror;
4-reflection of diagonal mirror in the primary one; 5-observe's eye.

In adjustment it is required to correct the position of the diagonal mirror or primary one. If the image of the primary mirror in the diagonal one must be concentric as well. The change the position of the diagonal mirror. For this purpose one unscrews the screw 2 of tile cell of the diagonal mirror Fig. 3) and, operating with one of three screws 1, brings the reflection of the primary mirror in the diagonal one to the centre of the diagonal mirror.

It the position of the primary mirror is disturbed, the reflection of the diagonal mirror with the spider in it is seen not at the centre, in this case one unscrews the screws 2 of the cell of the primary mirror and, by operating with three screws 1 (Fig. 2), sets the primary mirror so that the reflection of the diagonal mirror in it is found at the centre 20 (becomes concentric). After setting the mirror in the correct position, one fixes the cell in portion by means of the screws 2. The adjustment of the telescope is delicate and is carried out only in case of emergency, when it is clear that tile telescope Is misadjusted and its mirrors and reflections from them are not concentric.

9. Rules of storage

It is recommended practice to store the telescope in tile casein the hearted premises with relative humidity of maximum 80%, at air temperature from 5 to 40 .

The impacts and sharp shaking should be avoided.

It is forbidden to store the telescope together with acids, alkalies, materials which liberate moisture or chemically-active gases and vapours.

10. Acceptance certificate

The amateur astronomer telescope, serial No____ is found fit for service, slushed and packed in accordance with the established requirements.

Grease compound is effective for one year. Signatures

Date of manufacture and grease.

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