Аmateur astronomy and observing practice in Russia noticebly differs from that in, say, US or Italy. The climate of our northern country (Moscow lies as north as 56° ) is cold and cloudy. Because to see southern sky and to have comfortably observing, amateurs should to go to southern areas of Russia. The best places for it are mountains of Caucasus or Crimea. The 43° N position make this places good enough for viewing Scorpius or Sagittarius and the climate is warm and stable to have two or three weeks of warm (in comparison with Moscow, even on winter). So Moscow amateurs (mostly members of Club) establish a tradition to visit this places every year. To date twelve such “astro-adventures” were undertook in which partisipated to eight (usually 3-5) our Club members and our fellow amateurs from other cities at once. One of such adventures, 1996 Caucasus jorney, is described in this article. Article is placed here with kind permission of "Zemlya i Vselennaya" ("Earth and Universe") magazine, where it was printed originally (N 5, 1996), with the little changes and some shortenings.
The high heavens of Caucasus
...Train No.61 Moscow - Cherkessk arrived to the last station strictly under the timetable. Fifteen minutes later, we, a small group of Moscow amateur astronomers, loaded our backsackes and cases to a bus and went along the green streets out of this small town. We leave for Zelenchukskaya village. One and half hour-long trip is very picturesque: the road runs along rapid Kuban river and then meanders through the foothills along the bottom of Great Caucasus range. Every minute a new landscape opens in front of our eyes. Magnificent Elbrus, the highest mount of Europe (5633m), rise its mighty snow-covered head above the nearby peaks. Soon at the green background of the foothills a little white dot became visible. It is the giant dome of the 6-meter BTA telescope, not long ago the largest optical telescope of the world. It is the final goal of our travel and now only 30 kilometers remain between that point and us. Soon, changed one more bus, we are going from nice and quiet Zelencukskaya village along the Zelencuk river valley between mounts, covered with woods. Half of an hour later we entered town of Nizhny Arkhyz.
This tiny settlment located in picturesque small valley between the mountains on the Zelencuk riverside. The nice beeches, covered all the slopes around it, gives it the second (Russian) name - Bukovo (Russian word “buk” = beech). Here locates the centre of the SAO scientific complex (you can visit it on site http://www.sao.ru) with the laboratories, workshops, garages and apartment houses. From here astronomers going for observation up to the mountaintop where the optical telescopes locates or going down to giant radiotelescope RATAN-600, located below (halfway from Zelencukskaya to Bukovo). Joining new change of the serving staff which going “to the mount”, and sitting in a duty bus between vessels with a liquid nitrogen (for cooling the CCDs), we went up a 16-km-long serpentine road. As the road reaches the summit, a huge white dome comes into sight. It covers from daylight the 6-meter telescope BTA (Russian abbreviation for Large Azimutal Telescope). Soon other, smaller domes became visible. Besides of SAO there are two more observatories here.
One of them is the artifical salellites tracking and observation centre of Moscow “Astrophysics” Laboratory. Another is North-Caucasian astronomical station of the Kazan University (NCAS of КU). Here we’ll live for nearest time.
Now, the last part of a 1700 kilometer-long way is over. The time of implemention of the dreams is coming...
OUR HOME FOR THREE WEEKS
Small observatory of NCAS was the final point of almost all our Caucasian expeditions. This station located in about a half of kilometer from BTA and other scopes of SAO. We are aknoleged to their stuff for kind care and assistance. we were supplied with all necessary. For habitation we got few cabins, in which the university students usually lives. The Station has a laboratory house equipped with a computer, dark-room and which became a place of our day-time work, dining and rest.
The main instrument of the station is 40-cm Carl Zeiss lens astrograph. Its black dome ennobles above a small crest, on which it is located. Unfortunately, last time the Station, almost all work of which was based this high-quality instrument, is not so intensive, as earlier.
...The fuss of accommodation is over, the telescopes are taken from cases, assembled and adjusted. The first night coming. Southern sky, so long-dreamed, now above us, in all its glory. All the telescopes, cameras, binoculars in are aimed to Southern Milky Way and the air is full with excitement of people delightely staring into the sky. Soon, the excitemint is over, and the observing began...
The sky here (altitude 2050m) is very dark, and the observation often carries out on a theoretical limit of instruments, and sometimes outside it. Some nights has unique transparency. It is due to the place is practically free of light pollution (The closest noticeble source of it is Zelencukskaya, 25 km away from a observation cite). М33 galaxy (6,3m) in Triangulum, often using in other cites as the indicator of sky darkness, was easily seen here with unaided eye every moonless night, and some sharp-eyed observers sometimes catched M81 galaxy (7,9m) only with eye. A 15-cm telescope easily shows the stars fainter than 14,5m, while 35-cm one - the galaxies up to 15,7-16m! But unfortunately, early in summer the weather here is quite unstable and due to often clouds and dew some expeditions had only about 60 % of total observing time. But autumn and winter time is very good period for long observation sessions.
Each participant of expeditions usually had own observational program, but, of course, no one did deny itself in pleasure to admire the sky splendors, which in the clear and dark Caucasian sky looked absolutely in a new fashion. During first expedition on SCAS a nice 35-cm Dobsonian, constructed by Andrei Ostapenko - chairman of Club, was left there and all people had coming to SCAS used it. Many guests of us, including SAO astronomers used it. All of them will remember the amazing views, given by this instrument for a long time. For example, the galaxiy М51 and M104 or Ring nebula, М57, look just as in the photos! And it is difficult to find words to tell the impressions of even from a quick sight on Orion nebula, М42 or Hercules globular cluster, M13. By the way, using this reflector even unexperienced observers found such difficult object, as Horsehead nebula.
Very dark sky allows to get very interesting result even with small instruments. It was one of favorite kind of observarions of autors. We found that the sky conditions difference is better noted just with such instruments. An 80-mm f/10 reflector was found as a surprisingly powerful scope. After some practice we had glimpsed with it galaxies and star clusters as faint as 11,5. One of our favorite telescopes, 110 mm f/7.3 Newtonian, Mizar (Russia-made, named TAL for export), surpassed all expectations. For example, autor Andy Ostapenko with it observed faint (13m) galaxies in Cetus, i.e. not high above horizon (NGC 255, NGC 470, NGC 474, NGC 532, NGC 533). Also we used two large army binoculars TZK and, of course, smaller ones (20x60, 10x50 and 7х50). With it we usually observed large and faint nebulae (North America (NGC 7000), Pelikan (IС 5067, 5068, 5070) and Cirrus (NGC 6960, 6992-5) in Cignus, NGC 2174 in the Cemini and Helix (NGC 7293) in Aquarius). California nebula (NGC 1499) with pair of 50mm binoculars is not bad result. Using other very good Russian telescope, 150-mm INTES (f/10 Maksutov-Cassegrain) Leonid Alikhashkin found galaxies not brighter than 13,5-14m! This telescope easily resolved the doubles with 0,8” separation and allowed to find Pluto (13,7m - we don’t know other case of Russian amateurs observed Pluto visually with so small scope).
A lot of time we spent observing Solar System objects. Now we especially recall one night of summer expedition (on July 4-5). The moon has gone before midnight and we could pick Mars, Jupiter, Saturn, Uran, Neptune and Pluto, and also the periodic comets D’Arrest, Jackson-Neujmin (when was found it’s magnitude was 14m) and Clark (it’s declination was -35° !). Some days later Venus became visible. On orange disk of Mars, despite of its small size (that time its diameter was only 4,5”), the 35cm telescope easily show a large bluish polar cap and some dark greenish “seas”. A phase of a planet was well-definite too. It is necessary to note, that due to atmospheric turbulence near Pastukhov Mt., especially just after sunset, the observation of weak details on planets is a problem, but at the moment of good seeng very impressing show opened. Jupiter amazed with an abundance of details and variety of colours (it was especially good with 15-cm long-focus guiding refractor of Zeiss astrograph, while this type of a telescope always has the greater contrast of the image, than reflector). Equatorial zone of the planet had distinct bluish color, equatorial belts was- brown with reddish hints, temperate belts - grey and brown; the numerous fine details could differ from grey-bluish and greenish up to dark brown. Leo Alikhashkin in INTES at 300x could consider disks two largest of four Galilean of the satellites of Jupiter - Ganimed and Callisto. It became possible due to high quality of optics of the instrument, as the diameter of disks of them is small, 1.1? and 1.2? , accordingly.
Saturn attracts a special attention: this was time of a series of passages of the Earth through a plane of planet’s rings. Almost all this period the planet seemed ringless the Earth observer. During June trip the plane of rings had an inclination from 2 up to 3° and to line of sight, making a ring practically indiscernible even in 15 or 25cm reflector. Their presence could be defined only by of thin black strip of shadow on the planet’s disk. Only 35-cm telescope at magnification 160x and higher allowed to catch a thin black thread, stretched to both sides from a planet. Sometimes on extensions of this line outside of disk were suspected three tiny light spots in each side - three main rings of a planet showed itself in such manner. The observers have fixed interesting, though known, fact: when the observer look on the ring side, not lit by the Sun, the rings (just at this time and the observation), looks as a negative image: their parts which are usually looks lighter, became darker, and countrary.
Due to small opening of Saturn’s rings it was possible to catch some rare phenomena in it’s satellites system. One this events, Titan, the largest satellite, passage in front of planet’s disk, remembers now as a good luck. Titan looked a dark round when slowly entering on a bright planet’s disk. But as it completely came there, it became visible, that in comparison with the coal-black ring’s shadow, Titan has distinct reddish-brown color. Some observers noticed the hints of irregularities of the Titan’s disk albedo. When Titan has left the disk and went to the black background, it became a usual yellowish star again.
The traditional interest of the Moscow amateurs to comets has determined the special attention to these objects. Result of this work - a lot of visual brightness estimations of three above mentioned comets, and also comets deVico and Bradfield. The nice comet deVico, shining as 5m, has a tail of few degrees in length, became the perfect award for everyone, who saw it.
all expeditions always had two main tasks. If the visual ones is th first, the photographic is the other. It always is interesting to take the astrophotos of the real dark sky and, by the way to test of new emulsions, of lenses and cameras quality. Except for the 40-cm Zeiss astrograph we used 155-mm Wright camera, designed and made by Anatoli Sankovich and Russian-made telephoto lenses Rubinar 500/5,6, ZМ-6А (both F = 500 mm), Jupiter-21 (200mm f/4) and Jupiter-37 (135mm f/3,5). Usually the lenses were piggyback mounted on the astrograph tube, that allowed to have the guaranteed high quality of guiding is and made the unnecessity to carry one more heavy mount.
Usually, for astrophotography we used the color negative films Fujicolor HG400, Fujicolor HG800, Kodak ProFoto 400, Fuji Sensia 1600, and also on black-and-white Kodak Т-Мах 400 and Kodak Т-Мах 3200. Also we tested some of domestic black-and-white emulsion. With fine-grain of them the impressing results were received. For example, the Wright camera, despite of modest focus of 690 mm allowed on a film N-400, Kodak Т-Мах 400 to register galaxies up to 17,5m! The measured star images size usually was no more than 15 micrometers. Perfect results showed and Rubinar. Its resolvation usually find within the limits of 15-20 micrometers, that allow to make about tens of remarkable shots with it.
...AND NOT ONLY OBSERVING
Keenness by favourite business did not prevent us to delight with wonderful and majestic surroundings landscapes. A panorama of mountain chains lit with the first rays of the sun, noise of the mountain river, the grass and the branches of trees covered with причудливым patterns of the hoarfrost, rich greens of a wood and blossoming alpine meadows, unusual silence around and hot sun. All this was absolutely unusual for eyes and ears of moscovites.
Walking around on a mountain slopes one can meet variety of wild animals: not only usual wild boars and hares and even a rare red deer. Such walks with binoculars and camera brought us a pleasant variety of impressions and helps to relax after everyday “night works”. The earby forests is full of of fine small birds, and often low above a domes hungs eagles of many kinds: huge vultures with two-meter wing-span and it is a lot of others, is smaller. Sometimes ТZК allowed to examine the rare white-head bald-eagle. During the winter expeditions we often catch serene days to go brown.
All observatories are located on northeast spur of a Pastukhov mount (2700 м), and its summit often was the aim of the hike of many people coming to Bukovo. This 3-4 hour-long rise is not hard and the way to there is very nice, so many members of Club could try it. Nearby of Bukovo there are ruins f ancient Alan settlement and of the early (Х a.c.) christian monastery. It one of first christian churhes in territory of Russia.
The SAO is the main centre of ground astrophysical and astronomical researches in Russia. So it was very intereting to visit BTA and RATAN-600 telescopes. A diameter of the primary mirror BTA 6,05 м, and Ciclopean size truss tube and mount make unforgettable impression. Some of us has fortune to even to sit in a observer’s cabin in the main focus of a telescope, on 25-meter to height above the primary mirror. The special emotions were caused by spectrographs of the telescope occupying a four-storeyed room in one of racks azimutal fork. During excursion on RATAN-600 we saw how the Sun observation and spectra processing made.
Now in Club the while new, interesting plans are preparing, the new telescopes are made and we dreams about new asstro-adventures under magnificient, high Caucasian sky.
Star casket: January — February
The clear March evening has opened wide for mysterious nature's casket - a star night. All southern part of sky is covered by bright winter stars. In their round dance the naked eye easily finds well-known figures: Gemini (the Twins), Auriga, Canis Minor (the Lesser Dog), Taurus(the Bull) ... But at the centre of attention, certainly, Orion...
This constellation occupies the specific status in a mind of observers but not only it rather beautifu or personifies winter. A variety and beauty that disappears in star depths of Orion is comparable to its splendour and glory only. What the intense program of seeing had not been planned for night it's skarcely to find thought one amateur, who would be kept from a fluent sight into a telescope to the Great Nebula in Orion - M42.
The Great Nebula in Orion(М 42) - one of the main pearls of amateur astronomy. Probably there is no book on astronomy, where would not appear its photo. This glory was quite deserved: М 42 - the brightest dim nebula of the winter sky, and even in the most modest telescope it represents impressing object. The nebula is appreciable even by a unaided eye, is especial by lateral sight, as strange light environmental an average asterisk “ Orion's Sword ”. In the binoculars here already it is possible to consider large, about 1° in a diameter, slightly oval luminous area environmental beautiful double star q (Theta) Orionis.
Большая Туманность Ориона (М 42) - одна из главных жемчужин любительской астрономии. Наверное нет ни одной книги по астрономии, где бы не красовалась ее фотография. Слава эта вполне заслуженна: М 42 - ярчайшая диффузная туманность зимнего неба, и даже в самый скромный телескоп она представляет собой впечатляющий объект. Туманность заметна даже невооруженным глазом, особенно боковым зрением, как странное сияние, окружающее среднюю звездочку <меча Ориона>. В бинокль здесь уже можно рассмотреть большую, около 1° в поперечнике, слегка овальную светящуюся область, окружающую красивую двойную звезду q Ori.
Guide there telescope, let even small, and you will see a remarkable picture: each of a component of this double system, in turn has broken up - q 1(Theta1) on two, and q 2(Theta2) - on whole four! These last, grouping closely at the centre of nebula, formed tiny a trapeze. And itself nebula? Now, two light “wings” departing in the different parties from its bright central area, distinctly are visible, which already attracts attention with the outlines: its two edges seem cut off on to a ruler and converge precisely under a direct corner. It is difficult to believe, that only game of a case, fancifully twirled a huge cloud of a dust and gas. With increase of a diameter of a telescope the eye notices ever more and more thin details in structure the nebula. Black “failure” between “wings” not so seems completely dark, on a background of the bright centre now distinguishing tens dark spots and strips, and like the simple task - to sketch the nebula - seems impracticable. When the diameter of a telescope reaches 20-30 см, the central area of the nebula reminds a piece of old wood, damaged by insects, so intricate and distinct the dark fibres on its background seem. “Wings” break up to separate jets, and nebula М 43, the small fragment of a complex separated dusty(dark) strip from М 42, now under the form reminds a point. It is difficult to expess impression, arising at a sight on М 42 in 35-см (or greater) telescope, words. In such tool nebula it not so seems by sulfur, as well as the majority of heavenly objects, and gets the distinctly expressed greenish colour.
In the same constellation, near М 42 one more object certainly familiar to everyone is located who is interested in astronomy - dark nebula “ Horsehead ”. Its portrait also decorates almost all popular astronomical books, but in contrast the Great Nebula in Orion, it is very difficult for supervision, and few can brag, that saw it. Two difficulties trap those who has decided nevertheless to find a famous cloud of an interstar dust. First - a little who imagines, as it should look actually. The one who expected to see the large beautiful black failure precisely allocated on a bright background, the disappointment waits. First of all, nebula is rather small, only about 5 ', and as the light background, so obvious in photos, appears at all not bright, and faster, absolutely weak, slightly brighter than environmental sky, “ Horsehead ” the observer almost for certain at once will not notice. Only after adaptation of an eye it is possible to notice, on neat expression of one American astronomer, “ a small slice of darkness, even more black, than gloom, environmental it”. The form of the nebula, if nevertheless it managed to be noticed, is guessed almost at once. The second difficulty follows from first: do not try to begin searches, if the sky though is slightly lighted. In end it is necessary to note, that the diameter of a telescope for successful “ hunts behind heads ” should not be less than 150 mm.
In general, nearby with z (Zeta)Ori very many different interesting objects (actually speaking are located to name as their different not absolutely correctly, you see all of them - only bright parts one huge complex, consists from gas and dust, which enter and М 42 and “Horsehead”). One of them - bright and large, 30 х 30 ', dim nebula NGC 2024. It is well visible in 10-см reflector. Even at small increase the eye distinguishes a precise dark strip of a dust dividing the nebula in two. In conditions especially of transparent sky the nebula becomes visible even in 5-см the binoculars, that the author had an opportunity once again to to make sure the last autumn. NGC 2023, that in half-degree to the south of it, is quite accessible for “Мizar”. From NGC 2024 it is distinguished with appreciable increase of brightness to the centre, where the star 7,8m sparkles. It is more difficult to notice IС 434, on which background and visible “ Horsehead ”, but sharply outlined east edge of this weak transparent tape nevertheless quite we shall distinguish, is especial if to shake a telescope in a direction, perpendicular to it, that is to say, from east on west.
Dim nebula М 78 in 2,5° north-east of z Ori - bright and compact and it very simply to find. It has shine about 8,5m and sizes 8 ' х 6 '. Surprises its external similarity to a comet: a bright nucleus, gradually “ descending on is not present ” an elliptic environment. Spoils a kind only “ extraneous ” a star near to “ by a nucleus ”. The similarity here is deceptive: the nebula is a cloud of an interstar dust illuminated from within by a star (that is closer to the centre). Its one edge has precise border: it is as though cut off. For the first time observing М 78 in Moscow with “ Мizar ” there are a lot of years back, I unexpectedly have found out, that in one a field of sight with it another is visible a nebula, up to strangeness reminding neighbour: same round little spot, unless by the size hardly is smaller, and the star at the centre is weaker, about 10m. The star atlas has shown, that “ open ” nebula carries a designation NGC 2071, and nearby two are marked — NGC 2067 and NGC 2064. To find them with “Мizar” then it was not possible, and some more years have passed, until I had to the good luck to find them (with the large work) in 35-centimetric “Newton”.
In star depths of Gemini(the Twins) many remarkable objects accessible even to small amateur tools disappear. Planetary nebula NGC 2392 - one of most accessible in the sky, and is easy to distinguish it from stars even in small school refractor, “Мizar” allows confidently to observe small bright oval by the size 13 " х 43 " with an appreciable central star 10m . This nebula around of a bright internal part has a wider and weak external environment. In conditions of a very high transparency of an atmosphere it could be noticed in refractor АVR-1 (D = 200 mm, 1: 15) of Shtrenberg's Astronomical Institute observatory, Moscow, with increase 216x. Thus, on a background of a bright central part dark structures distinctly were visible. The nebula is beautiful and carries the name “ the Eskimo ” for really appreciable similarity to a physiognomy of the eskimo (or ours Chukchi), dressed in their national clothes. Nearby from NGC 2392 the rather nice absent-minded cluster NGC 2420 is located. It has shine 10,2m , the size 7 ' and totals about 20 stars. To find it is not very difficult.
Gemini has “own” galaxy - NGC 2339 with shine 11,5m . The seen sizes 1,9 ' X 1,5 ' and to find it it is possible even in a 10-centimetric telescope, however this case, though is interesting (galaxy is at edge of the Milky Way), but nevertheless is not unique, that will not tell about our last object.
In 7° to the north of a star Castor (a (Alpha)Gemini) there is an object completely untypical of this area of the sky. The globular star cluster, as is known, concentrate to the centre of our Galaxy, and it is possible to see that one of them, NGC 2419, in a direction almost strictly opposite to it (galactic longitude of a cluster almost 180°), fact rather conspicuous. The cluster is in constellation of a Lynx and deserves the special attention also because of its remoteness from us. Up to it 300 thousand lights years, that is to say, it is located from the Sun twice further, than the Greater Magellanic Cloud - present intergalactic wanderer! However, even being so far, the cluster shines as a star 10,3m . Its seen diameter — 1,7 ' (class — II). It was opened it by W. Hershel in December, 1788.
А. Yu. Оstapenko.
This material - reduced and a little bit changed variant of an article from a cycle “ Star casket”, published in a magazine “ the Earth and Universe".
FORGOTTEN PAGES OF
This article dedicated to forgotten facts, events and peoples of Russian astronomy.
First Soviet Reflector
At the turn of XX century Russia had no possibilities to manifactury high-quality mechanical and optical instuments. All kinds of them being delivered to Russia from other contries, mainly Germany's Carl Zeiss.Only in 1930 year in various fields of science and technique precision manufacturing was started in our country, in particulary astronomy instruments. This new point was arisen in 1928 in Astronomy Institute by pressing initiative of its Director, prof. B. Numerov. New Desing Department was created under Astronomy Institute, which objective was to desing various types of astronomical, survey instruments and gravimeters. Experimental models of above mentioned had been produced in Institute's mechanical workroom.
One of such instruments was 13" reflector, fully engeneered and completed in the end of October 1932, and intended for mounting at the Institute's Mountain Astronomical Observatory in Abastuman.
- OPTICAL SCHEMATIC -
13" reflector was mounted on similair scheme like the 60" Mount Wilson telescope. It's mount was designed to install instrument at the latutude 42њ30'. It works in the following 4 optical schemes, each of them has special splinted demountable part.
-- optic making--
Main mirror of the telescope had diameter 33 sm and focal lenght 1655mm light-gathering power 1:5. Preliminary grinding was done with the coarse abrasive till curvature was reached. Final grinding was done with the smaller abrasive fractions and levigationed in the water (1,5,10 and 30 minutes) fractions. Polishing had been done with special polishing pad made of wood pitch and using rouge as the polishing matirial. During polishing was started to inspect optical quality of the main mirror by using Fuco method of measuring longitudinal aberrations. For this object star simulator device with fine adjustment screw was manufactured in Institute's mechanical workroom. Main mirror was exanimed from the center of curvature and by the shadows seen on the mirror surface and measuring it's longitudinal aberrations it could be estimated about quality. After main mirror was examined in the autocillimation scheme with a big flat mirror with light source in the focus of paraboloid. In the final tests founded aberrations not exeeds 0,1 mm. Thus quality of the main mirror was quite good. Theoretical quality is 0.05 of qreenwave , i.e 1:40000 mm. The last phase was silver coating and mounting mirror in the tube.
MECHANICAL PARTS OF THE TELESCOPE
Ocular unit consists of rack mechanism and mounting plate on which can be mounted eyepiece or photographic plate (6x6 sm) covered 30 sq.min of the sky.
Worm gear. Right accession movement of the reflector does by means of series worm gears. By this it is difficulty to make worm teeth pitch constant, i.e. to do periodical error minimal. Fabrication of the parts of the worm gear was done by following procedures: on the screw-cutting lathe (Boley&Leylen) worm had been toothed with the tooth step 1.5 mm, diameter 20 mm and lenght 80mm. Checking of step persistence done by чйну ( All-Union Intitut of Metrology and Standardization, at last Chamber of Mesurements and Weighting) on the Carl Zeiss comparator with accuracy 0.1 mkm. Checking results that worm has step persistence 0.2 mkm. As calculations shown to reduce whole reduction ratio needs to insert additional worm gear with the triple spiral worm of 9 mm step and diameter 22 mm. Checking of step persistence also done by чйну Checking results that worm has step persistence +3 mkm. It's twice over needed for this worm gear.
Gear had been toothed in Russia for the first time. It had diameter 480mm and 960 toothes, i.e. during each 90 sec. gear rotated on 1 tooth and it corresponds to one worm revolution with 1.5 mm step. With the help of additional worm gears main gear does one revolution per sideral day. Gear had been toothed on the milling machine (Schuchsrdt&Schutte). Ball bearing mounted gear was preliminary grooved and after toothed gear-milled cutter with mudulus 0.5. Final toothing done with precision hobbing cutter (made by Sestroretsky toolmaker factory) basing breacking-in technique.
Usually process of manufacturing of worm gear is as follows: the screw is preparing with the precisely same step, diameter and length, what are necessary for worm hob. After that on miller machine longitudinal grooves are slotting for formation cutting edges and the worm hobl is ready. Now it is only necessary to do thermal processing in the special bake oven. These operations are most dangerous, since the hob exposed by its internal tension able to cause of a crack and buckling. To avoid it and achieve of the maximal accuracy Sestroretsky toolmaker factory made a worm hob not on the screw-cutting latche but on grinding machine, i.e. spiral groove and longtitudal groove were milled on the hardened surface with the special flute-grinding wheel. Only such way of manufacturing of a worm hob has enabled to achieve step quality nearly 1 micron. After hob the wheel was attached on the top part of a polar axis and matched with worm gear located on an arm. The hour wheel together with worm gear was very precisely adjusted and by means of especially mounted from the motor belt transmission was started and regrinded with levegated from ribber brick abrasive dust. The operation of regrinding proceeded about two weeks, i.e. before reception of a regular and smooth movement.
Limbs. Rather serious and crucial work was a division of the right ascention and declination limbs. The difficulties were increased because the workshop of Institute had no special machine to do these work and consequently all work should be executed on universal - milling machine with a special tool. Limb was made for RA axis had a diameter of 350 mm and accuracy within 1 minute, i.e. was divided on 1440 partitions. Limb for declination axis had the diameter of 300 mm and also was divided to achieve accuracy within 15 ' arc min, i.e. was divided on 1440 partitions.
Clock drive and guide. The
clock drive mechanism is an unique and only one serious part received for reflector from
Carl Zeiss in 1930. The guide was acquired from private hands and is a 2.5" small
viewfinder given the quite good images. Micrometer was also adapted to the guide.
Tests. The first attempts to perform star tests of the reflector were made on 3 September, 1933. But then still nothing could be told about quality of the instrument since the mirror was not aligment yet. It was only possible to ascertain of the reflector quality on September 14, during a lunar eclipse. This evening it was possible practically to define resolution appeared equal about 0.7". The theoretically required power for the intrument is equal 0.5". The definition of the resolution power was made by observing of double stars. In particular were observed double е1 and е2 Lira, which were very precisely resolved into pairs. Star clusters located and globular ones in Hercules, Andromeda Galaxy, various objects of a lunar surface etc. very well were visible also.
TASKS OF THE REFLECTOR
Through photo-electric photometer the regular study of change of brightnesses variable stars such as Algol and also definition of their colour was supposed; study of change of brightnesses of the companions of planets and asteroids, on advantage of objects with weak amplitude in change of brightnesses. With the help of the chinkless spectrographic quartz camera the study UV- part of spectrum and study of a physical structure of comets was supposed. Reflector was also been intended for use at various researches of a Solar surface. Moreover the task of an establishment of homogeneous system of photographic and visual magnitudes, study of a nature of a dark nebulaes were done by study of their colour, and also there distribution in space. Tasks of spectrographic research of separate stars with the quartz spectrographic camera & photo-electric photometer, study of brightness of spectral-double systems also were put.
Article is prepared by Oleg Sankin on basis of the materials of Russian Astronomical Calendar (XXXVI, 1933)