Hirata, Ryuko

Imagawa, Fumihiko

Kawai, Seiichi

Ohtani, Hiroshi

Tsujimura, Tamiyuki

English

Kyoto University Research Information Repository

RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:The 40/70/120 cm SchmidtTelescopeImagawa, Fumihiko; Kawai, Seiichi; Tsujimura,Tamiyuki; Ohtani, Hiroshi; Hirata, RyukoImagawa, Fumihiko ...[et al]. The 40/70/120 cm Schmidt Telescope. Memoirs of theFaculty of Science, Kyoto University. Series of physics, astrophysics, geophysics andchemistry 1977, 35(1): 185-1951977-09http://hdl.handle.net/2433/257564Memoirs of the Faculty of ScieRce, Kyoto URiversity, Series of Physics, Astrophysics,       Geophysics and Chemistry, Vol. XXXV, No. 1, Article 11, 1977.THE40/70/l20 cm SCHMIDT TELESCOPEFumihike                   ByIMAGAWA*, Seiiehi KAWAI"sk•, Tamiyuki TSUJIMURA*•,   Hiroshi GHTANI*' and Ryuke HIRATA"Department of Astronomy, Faculty of Science, Kyoto University, Kyoto        (Received August 1, J976; reyised August 10, 1976)                         ABSTRACT   A 401701120 cm Schmidt telescope was constructed in May 1972. The telescopehas the followiflg two characteristics.(1) [lrhe vignetting free field is especially wide (7 O.1) cornpared with the usual Schmidttelescopes of the similar class to ours.(2) The telescope is designed to be used not only for the usual Schrnidt type, but alsofor a quasi-Cassegrain type.   We succeeded iR construction of a plate holder in which photographic plates arebent in contact with the spherical surface wkh the radius of curvature of l20 cm.   A short description on the optical aRd mechanical systems is presented with someresults of test observations.    A 401701120 cm Schmidt telescope of our institute was constructed in May 1972.A short description of the telescope and some results of test observations with itare presented here. The telescope was at first mounted in Fukuchiyama, seventykilometers north-west of Kyoto City, and is to be moved to Ouda, fifty kilometerssouth-east of Osaka City, in the near future.   This telescope is so designed as to be able to be used also for a quasi-Casse-grain type, to which we will mention briefiy in Appendix.1. 0ptical System    We designed our optical system in consideration of the next two points. Thefirst point is to make the vignetting free field as wide as possible rather than tomake F-ration small, in order to meet our observational demands for taking photo-graph of a large field object such as a cluster of galaxies on a single plate. Thesecond is to keep the size of aberration images within the grain size of photographicemulsion over the whole wavelength range 2R 3500-8500 A by a single correctingplate. Examinations of tlae image quality were carried out with the aid of spotdiagrams (Kawai and KogL}re 1968). The adopted system is shown in Figure l.The wide vignetting free field of 7Pl is a distiguished characteristic of our Schmidttelescope. '   Tlie surface profile of the correcting plate is shown in Figure 2. The e-line(5461A) was adopted as the basic wavelength. The choice of the wavelenegh is * Department of Astronomy, Faculty of Science, Kyoto University, Kyoto** Division of Applied Pliysics, Government lndustrial Research Institute, Osaka186 F. IMAGAWA,S. KAWAI, T. TSU3IMURA, H.OHTANIand R. HIRATAI==IT/foM==2o31442LOO,Og  -Corrector plate  lBK 7)- R=j203.144Fig. 1  s  6rmage' Surfaee. Optical system of the Schmidt telescope.119osss---  R=-240o.o             Main Misror              {Pyrex} Numerical values are in unit of mm.yLsseoutor-tsr/1t'too.o 'xjt..-.g'ge:..lgyg.seRcefgseE1ss9cotost'NY-xV-" 1.sHaxa tFCcrt-t) Rjcr1 = l,slB2S-  (fofractian itteLtec fitg-2t>nA.)R # 2+O O wt,n (RaoUtts of cavvatara of ml,ror)H = 200anrX CSaorti-af,ertar4 al C•R)       //////1// /oFjg. 2.        sD igoSurÅíace profile of the correcting plate.of the plate.XCMort)       Lse 2rjuThe origjn O jn the graph is the vertexdue to the fact that confusions of images caused by the chromac tic aberration aresimilar at both ends of the wavelength range 22 3500-8500 A, and is also due tothe easiness of optical tests in laboratory. Figure 3 shows the spot diagrams ef apoint source for various wavelengths and for semi-field angles OO, 20, and 30.5.   Next, let us consider the confusions of the image due to malalignraents of theoptical parts and the error in the focal surface, Investigations by spot diagramsX=8500{1•50958)c CH g)7g = 6563".51384} e <Hg}7g "5461".51 825)g {H9}A= 4358(1,5261g}, X=3500{1.53903}Åë == eoÅë == 2eÅë=30.5,"tk.",.•`Si"/g/E  =               .:Si--:•,"k/itile ,/6"-/t/' -`ej,l•lilil,..",3stiv.'" " ' . . - K&k/t"•g g @O tOA$ {gii " . #. t}ii-g el   -- -t tt t- tast"'lv:-t- : : "-t:::::::.Zii'i :.:,::•t. t:s .:. .:. -1"-.es" -- -t --  t-'i"ii'li      "/i's.       ./l/:l    -- t. "" "  ttkS .:":. t" :t 'f1:. t.1ftt- . 1   N- "V-t       '.' iS..tfVCd#;S .,t..s.. ;... "e -- s-X   tt1ÅíFig. 3.Spot diagrams of the Schmidt system for various wave lengths. Numbers in parenthesis denote the refraction indicesfor each wavelength. Åë's are the semi-field angles. Basic wave length is 5461A (e-line).x188 F. IMAGAWA,S. KAWAI, T. TSUJIMURA, H.OHTANI and R.HIRATAled us to the following conclusions (Kawai and Imagawa 1972; Imagawa and Tsuji-mura 1976).    (1) The position of the focal surface should be adjusted within an accuracy of        10 pt.   (2) It is desirable to adjust the position of the correcting plate within Å}2 mm       froin the center of curvature of the mirror.   (3) It is necessary to adjust the discordance of optical axis of the correcting       plate with that of the main mirror within an accurayc of e.2 mm.   (4) The focal surface of the plate holder should be constructed within an       accracy of Å}20 mm around the theoretical radius of curvature.   The data of the optical system together with those of the objective prism areshown in Table 1.                     Table i. Data of the optical systemMain Mirror   Effective diameter   Thickness at the center   Radius of curvature   Weight   MaterialCorrecting Plate   Effective diameter   Thickness   Weiglit   MaÅíerialFocal Part   Radit}s of curvature of focal sLirface   Size of plate   VignettiRg free field   Scale on plateObjective prism   Effective diameter   Thickness Max.         Min.   Angle of vertex   Weight (including cell) ,   Material   Dispersion at Hr 70 cm 9 cm240 cm 7Z5 kg Pyrex 40 cm 1.8 cm 7 kgBK7l20.3 cm 16 Å~ 16 cm 7e.1=v149 cml72"/mm 40 cm 5.5 cm 2.0 cm 5o 30 kg LF5487Almm2. Meehanical system    A general view of the telescope is shown in the accompanying plate. Mount-ing is of the L}sual fork type. Particular attentions are paid on the following itemson the design and construction of the mechanical systena.    a) The supporting mechanism of the main mirror is similar to that used forthe Baker-Nunn Schmidt telescope, to give neither deformation nor displacementto the main mirror at any position of the telescope.   b) In order to compensate automatically changes in focal length due to changesin air temperature, three super-invar rods are provided between the main mirrorand the plate holder carriage.THE 4e1701120 cm SCHMIDTTELESCOPE 189    c) Bearing in mind tlae usage for quasi-Cassegrain type, the main tube ismade cylindrical instead of conical and the arms of the fork are made long enoughto be able to set a photometric or spectroscopic apparatus behind the main mirrorcell. Therefore, special cautions were paid on the stability of the fork.    d) The adjusting mechanisms of the optical system including that of the tilt-ing of the plate holder are made to satisfy the conclusions obtained in the previous   .sectlon.    The data of tlie rnechanical system are in Table 2.                     Table 2. Data of tke rnechanical systemTelescope Tube   Weight   Length (inciuding dew cap)   Diameter   Super-invar red       Diameter       Length       Expansion coeficientFork   Weight (including polar axis)   Length of arm   CIearance between maiR mirror cell and fork   on polar axis   Bendlng ef polar axis and armDriving Mechanism   Sidereal drive      Stability   Positional drive      Qtiick      Slow      FiRe I      Fine II      Trail  2t375 cmIOO cm  9mm120 cm 2 Å~ 10-7 per degree  3t23e cm80 cmWithin 10" at any hourangle and declination10-5 utiliziRg 60 Hz of citysource400!min 1 O/nlifi10"lsec 5"lsec OC'2-2"lsec (continuoGsly variable)3. Plate hglder    It is a matter of course that the Schmidt plate must be bent unless a fiattenerlens, which makes the image quality poorer, is inserted. Bending of thin glassplate in contact with a spherical surface, whose radius of curvat"re is 120 cm asin our case, is almost near the limit of elasticity. The critical point of rupture whichis different from plate to plate, depends on invisible cracl<s and defects in glasscaused by inhomogenities of the material, which are more serious in larger plates.    As far as we know from communications with many observatiories, the filmis used or the fiattener is inserted without exception when the focal length is shorterthan l20 cm. The telescope at Bosscha Observatory has the shortest focal length(127 cm) among the Schmidts where the plate is used without a flattener.    After several experiments and improvements of pressing mechanism of plates,190 F. IMAGAWA, S.KAWAI, T. TSU3IMURA,H. OKTANIand R. HIRATAwe succeeded in construction of the plate hloder now used. Its diagram is shownin Figure 4. The pressure strength by the spring @ in the figure is 2e kg. Thepercentage of rupture of plates within two or three hours after loading is about 10,when Kodak plates with•thickness ofO.030 inches are used. We intend to decreasethe rate of rupture further by future improvements.lock."--Ht..- ---- h!l"wu4ne-y.-'xxN71/'I/lt(xxNÅ~xsh.sxiÅ~-XxxN'1,x1lwwwrt---in-th'ti'me-lt;•. - ...."1-- s.--.-- --"..-lL@-Å~21(iii)5Fig. 4. Design diagram of the plate holder.   1) Concave surface 5) Slide schutter   2) Convex surface 6) Rear lid   3) Locking plate 7) Photographic plate   4) SpringOne presses down the locking plate and turRs it in the direc-tion of arrows to lock.                   THE 4017e/120 cm SCKMIDT TELESCOPE 191    We had also made a film holder, but it was found diMcult to load the filmclosely to the curved surface of the holder by means of a simple mechanical presser.In addition, there js another dithculty in using the film, that the minimum quantityof order for Kodak films is too much.4. Test Observations    Examinations of the optical system were carried out mainly by the HartmanRmethod by stars. The Hartmann constant js 1.4. The minjmum star image is assmall as 25 pt in diameter, on l03 a-E plates without filter. .    We performed some test observations for detecting the field error and plateerror in stellar photometry. We adopted a method by widely extended open clusterssuch as Hyades or Coma Berenices, which include many photoelectric standardstars. In this method, no ocnsiderations are necessary concerning changes of skycondition during exposures and differences of photographic processings. Caljbra-tion curves for the standard magnitude V against the iris-photometer reading ofstar image are obtained for 1) all standard stars contained in the field, 2) the stand-ards within semi-field angle 20 and 3) between 20 and 3P5 from the plate center.Supposing the calibration curve to be a second order polynornial within a six mag-nitudes interval, we get the least square solutions, one of which is illustrated inTable 3. The Ietters a, b and c denote coeMicents of the polynomial.                               Table 3}i    aO.020thO.OOIIO.020thO.OO15O.020drO.OO16     b-1.497Å}O.064-1.502Å}O.086-1.501Å}O.089    c31.56Å}O.8831.62th1.231.61 ,l,1.2m.e.of VÅ}O.18Å}O.19,l,O.I5    Three curves almost coincide with one another. Field errors are at mostO.03-O.04 magnitudes, which are very satisfactory.    The above observations were performed by films when the plate holder wasnot yet accomplished. Films used are Kodak XXX and the filter is Fuji SC 50which sharply cuts the wavelength region shorter than 5000 A. Therefore, oursystem does not rigorously correspond to the standard V. If a suitable combina-tion of emulsion and filter is adopted, photometric errors are expected to be reduced.    Next, we took photographs of the Virgo cluster of galaxies as a preliminaryobservation utilizing the wide unvignetted field, and performed microphotometertracings along the major and minor axes of some member galaxies, one of whichis illustrated in Figure 5. The figure shows the density distribution along the majoraxis of NGC 4486 (M87) photographed on a Kodak 103 a-E plate with a Fujifilter SC58 which sharply cuts the shorter wavelengths than 580eA. Numbersin parentheses shown on the mean density curve denote the surface brightnessexpressed in magnitude estimated by comparing the results of Markaryan et al.(Markaryan et al. 1965).   The authors wish to express their hearty thanks to the retired Professor T.Shimizu and Professor I. Kawaguchi for their constant encouragement. Their192'''t-lIil.p:H-lI  -  :ewJ:ew-ttF18)-IMAGAWA,s:R8/k'/k"/gttlx/•le4"------ ;----I,AWAKs.t eS-t- -A-.'---iL .Tl8{+t-     -lr :-"l i'- iÅ} -lll---Jpt -:H:--.-.rt+ -1--•i----+Hr;INATHoH.A,RUMJIUsTli,?1-  tl'i-Fttl---:l H--Tx1-- --"LItt{ f2.  `=f .:'L---'lE 1'lilk      I   ili   -1J,:]z''--sLt?lhtttr g- xot,   ' -t   s}).-.K-- },JstI----1I,ll        {           l        1,      IIt      }"Itnynti                     i       tl                     li                           :        -II                           1             T                     tli                     iV           .. " -v- .-. oeoe e'o et wts .J ti sc ̀                          l                  ;                             L  are also due to Dr. B. Hidayat,        hisK. Tomita and M. Shimizu of TokyoSome parts of this research were carried              , the chief of the research group                       REFERENCES    F. and Tsujimura, T. (1976): Technica; Repoit No. 1Japanese)11ltl--- r -.-'iiH'•11e11t.t          t-          l          -t 9          l             t          BosschaAstronomical         a research tio e   ..s -    It       L '    I       1    s l. Å};    +F i    l       l    l    li    : tl     l clc r"s    isDirector fsystem.out undercl9-•,,,>-ts.h ..j.$ [,--,,-etleS:X'l?` llg'-'   )iikig/'-"l-l,-"ti     --     "-l-tATARAHIR.Rda-iiiiaiiiilllL-FIr:.tÅ}               sl}llii +i•y"'/i'   6ltlii'l"-it,4g:';+t.-tln--'ksny+   -   "-   l/i•g,ih,tovaerbsoahcssoB  fot ?  orkedh se?•vd areO tt lla ote bethmofruiZmhistn T.a1'ghcraeserorssferoPg1thanksLembang, for valuable comments on the design of the plate holder, andsers. Observatory,useful advice  to the design of the mechanicalMinistry of Education being Professor Ir.imagawa, ,Dept Astron., Kyeto Univ. (m                 THE 40!701120 cm SCHMIDT TELESCOPE 193Kawai, S. and Imagawa, F. (1972): Reports of Meeting on Measuring Apparatus of Astronomical   Plates, p. 45 (in Japanese)Kawai, S. and Kogure, T. (1968): Mem. Fac. Sci., Kyoto Univ., Ser. A, 33, 95.Markaryan, B. E.; Oganesyan, E. Ya. and Arakelyan, S. N. (1965): Astrofizika, 1, 38.ag#:The 40/70/120 cm Schmidt telescope194 F. IMAGAWA, S.KAWAI, T. TSUJIMURA,H. OHTANIand R. HIRATAAPPENDIX   Our telescope is planRed to be used also for a quasi-Cassegrain telescope whose effectiveaperture is 70 cm by removing the correcting plate and attaching a secondary mirror of aspheric ofhigher orders. For this purpose, a hole is made through the central part of the main mirror asseen in Figure 1. The secondary mirror aspheric of tenth order is novv uRder construction. Thesurface profile of it is shown in Table Al. Figures Al and A2 show the spot diagrams and opticalsystem (FllO). It is a fatal defect of a quasi-Cassegrain system that extremeiy asymmetric aberra-tions appear even for slightly off-axis rays.Table Al. Surface profile of the aspheric mireror.spheric surface is 647 mmRedius of curvature of the reference'i'li Z2-Zl o.-o.oooo-o.oooo-O.OOOI-O.OO04-O.OOII-O.O022-O.O042-O.O071-O.Ol15-O.O177-O.0261-O.0373-O.0519-O.0707-O.0943-O.1239zcwtpm)Ptmu  zt  Å~(anpt)Z4 kSarimcst sfiT2vic SKVf"C4  Agkeric surfaca.      ttRLPHF= Q.O       ttRLPHP= S.e       t/PLPHR=10.ee  "";• r;./.`.tr•.•.#s:.'}.t..ttsl'gi'cil,}',s"t.cQrS'.`'XZ rf"tes",k2),.iii{ii?i L'O. O.GI H" e. G,02"HFig. Al. Spot diagrams ofthe quasi-Cassegrain system       rays with the optical axis.        -        e. e.,os HH. a's are the angles ofincident/ E\  THE 40170f120 cmKpt 9St.SCHMIDT TELESCOPE    !Lr/U.)LJ" - gsn. )X 1195S, `'-R•   Z4rv-7liHe--'RX--Il,Fig. A2.  Stterdarif Mrrrcfl.Optical system of thein unit of mm.quasi-CassegrainMaln MÅ}'ryevtelescope.       Cctssfsral"• Fe`"sNumerical values are

The 40/70/120 cm Schmidt Telescope

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The 40/70/120 cm Schmidt Telescope

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