                        THE ELECTRONIC JOURNAL OF 
                THE ASTRONOMICAL SOCIETY OF THE ATLANTIC

                    Volume 3, Number 3 - October 1991

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                            TABLE OF CONTENTS

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         * ASA Membership/Article Submission Information

         * An Introduction to Celestial Coordinates - Nils Turner

         * Astrophotography the Easy Way - Harry Taylor

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                       ASA MEMBERSHIP INFORMATION

        The Electronic Journal of the Astronomical Society of the 
    Atlantic (EJASA) is published monthly by the Astronomical Society 
    of the Atlantic, Incorporated.  The ASA is a non-profit organization 
    dedicated to the advancement of amateur and professional astronomy 
    and space exploration, as well as the social and educational needs 
    of its members. 

        ASA membership application is open to all with an interest in
    astronomy and space exploration.  Members receive the Journal of the
    ASA (Hardcopy sent through United States Mail - Not a duplicate of
    this Electronic Journal), and the Astronomical League's REFLECTOR 
    magazine.  Members may also purchase discount subscriptions to 
    ASTRONOMY, DEEP SKY, ODYSSEY, SKY & TELESCOPE, and TELESCOPE MAKING 
    magazines. 

        For information on membership, you may contact the Society at 
    any of the following addresses:

         Astronomical Society of the Atlantic (ASA)
         c/o Center for High Angular Resolution Astronomy (CHARA)
         Georgia State University (GSU)
         Atlanta, Georgia  30303  
         U.S.A.

         asa@chara.gsu.edu 

         ASA BBS: (404) 985-0408, 300/1200 Baud.

        or telephone the Society Recording at (404) 264-0451 to leave 
    your address and/or receive the latest Society news. 

        ASA Officers and Council -            

         President - Don Barry
         Vice President - Nils Turner
         Secretary - Ken Poshedly
         Treasurer - Alan Fleming
         Board of Advisors - Bill Bagnuolo, Jim Bitsko, Eric Greene 
         Council - Jim Bitsko, Bill Black, Bill Crane, Toni Douglas, 
	   Ruth Greene, Larry Klaes, Karla Poshedly, Tano Scigliano, 
           John Stauter, Gary Thompson, Bob Vickers


        ARTICLE SUBMISSIONS - 

        Article submissions to the EJASA on astronomy and space exploration 
    are most welcome.  Please send your on-line articles in ASCII format to 
    Larry Klaes, EJASA Editor, at the following net addresses or the above 
    Society addresses:  

        klaes@mtwain.enet.dec.com
        or - ...!decwrl!mtwain.enet.dec.com!klaes
        or - klaes%mtwain.dec@decwrl.enet.dec.com 
        or - klaes%mtwain.enet.dec.com@uunet.uu.net

        You may also use the above addresses for EJASA back issue requests, 
    letters to the editor, and ASA membership information.

        When sending your article submissions, please be certain to include 
    either a network or regular mail address where you can be reached, a 
    telephone number, and a brief biographical sketch.

        DISCLAIMER - 

        Submissions are welcome for consideration.  Articles submitted,
    unless otherwise stated, become the property of the Astronomical
    Society of the Atlantic, Inc.  Though the articles will not be used for 
    profit, they are subject to editing, abridgment, and other changes.  
    Copying or reprinting of the EJASA, in part or in whole, is encouraged, 
    provided clear attribution is made to the Astronomical Society of the 
    Atlantic, the Electronic Journal, and the author(s).  This Journal is 
    Copyright (c) 1991 by the Astronomical Society of the Atlantic, Inc.


                   AN INTRODUCTION TO CELESTIAL COORDINATES

                                by Nils Turner

        Earth-bound travelers know two things:  The locations of the
    beginning and end of their journey.  In the case of our planet Earth,
    these locations are given as longitude and latitude positions with
    respect to the prime meridian and equator.  The traveler wants to
    be able to determine position at any point along the way to their
    destination.  For that purpose as well as for astronomy, a similar
    structure named the celestial sphere has been created.

        The celestial sphere has analogs of latitude declination (Dec.)
    and longitude right ascension (R.A.).  Dec. is measured in hours (h)
    rather than degrees, where 24 hours corresponds to 360 degrees.
    Imagine now the gridwork one can find on an Earth globe and project 
    it onto the sky above.  There are now two gridwork systems which 
    rotate about one another:  One stays fixed with respect to the 
    stars, while the other stays fixed with respect to Earth.  

        The main benefit of such a system is that a star remains at a
    given R.A. and Dec., just as a mountain on Earth remains at a given
    longitude and latitude.  These two gridwork system rotate with res-
    pect to one another at a period of time known as the sidereal rate.

        The zenith is the sky point directly over an observer.  The
    horizon is the line at which the ground appears to meet the sky.  
    Note that there are horizons in all directions.  The observer's local
    meridian is the great circle on the celestial sphere which passes
    through the northern and southern points on the horizon and the
    zenith.  The time that it takes for a star on the local meridian to
    return to that local meridian on the next night (assuming that the
    observer has not moved) is one sidereal day.  To determine the solar
    day, replace the example star with the Sun. 

        Note that the sidereal and solar days do not correspond to the
    same length of time.  The differences between the sidereal and solar
    rates suggest two separate ways of timekeeping.  Local Sidereal Time 
    (LST) is the R.A. hour coordinate passing overhead on the local meri-
    dian.  Universal Time (UT) is the local solar time at the point of 
    zero degrees longitude on Earth.  The relevant event in local solar 
    time is noon, when the Sun is on the local meridian.  The relevant 
    event in sidereal time is 0h, when this star coordinate line passes 
    the local meridian.  These two clocks coincide at the vernal equinox 
    each spring season.

        When our traveler knows the UT and date of the zero degree longi-    
    tude position, tables can give the LST at zero degrees longitude.
    The traveler can determine LST by observing the stars.  By properly
    comparing the two times, the traveler's longitude is revealed.  The
    elevation of the pole star (Polaris of the Ursa Minor (Little Bear)
    constellation in the case of the Northern Hemisphere) measured from
    the horizon completes the traveler's position determination, giving 
    them their latitude on Earth.

        About the Author -

        Nils Turner, ASA Vice President, is a Ph.D. student and resear-
    cher with CHARA at GSU.  Nils' interests include infrared astronomy, 
    speckle interferometry, and astronomical instrumentation.


                          ASTROPHOTOGRAPHY THE EASY WAY

                                 by Harry Taylor

        Beside my desk at home, I have a framed photograph of the Horsehead 
    Nebula in the constellation Orion that was a gift to me from my parents 
    many years ago, when I was still in elementary school and showed an 
    early interest in astronomy.  It is one of those Harvard Observatory 
    photos dating from the early part of the Twentieth Century and is not 
    of the best quality. 

        On the afternoon of Sunday, November 13, 1990, I carefully took
    down the photo and placed it aside.  I had just taken a better photo
    of the Horsehead region with the Schmidt Camera (twenty-centimeter 
    (eight-inch) f/1.5 Celestron Schmidt camera with Kodak Tech Pan 2415 
    film) SBIG-ST4 combination at Georgia's Hard Labor Creek Observatory 
    (HLCO) the previous night! 

        After numerous encouraging but frustrating attempts to use this
    system in the very hazy sky conditions of the September, 1990 observing 
    sessions, it was great to see the clear and dry fall weather that set 
    in after the Georgia Star Party.  The sky conditions on Friday, November 
    11, were great, but the next night was simply awesome.  It was the best 
    I have yet seen at HLCO.  You could tell by around noon on Saturday - 
    with the rich, dark blue background sky - that it was going to be 
    something special.  The seeing and transparency were super, which was 
    certainly an important factor when comparing our astrophoto results 
    with our previous efforts in September. 

        ASA President and Vice President Don Barry and Nils Turner used the
    setup that Friday night at the monthly ASA observing session.  There
    was a large crowd at HLCO, thanks to ASA Executive Board Officer Eric
    Greene's announcements and telephone canvas.  I was there for several
    hours but had an early Saturday commitment and reluctantly had to
    leave.  During the evening, they shot two series of exposures with the
    Kodak 2415 film.  Unfortunately, an improvised roll-film adapter used
    in the first series did not work well. 

        This setup had been devised after the September efforts in an
    attempt to make developing the little chips of 35-millimeter film
    easier.  They went back to cutting individual film chips, but instead
    of doing it the old way in the changing bag, they simply did it in the
    light-tight HLCO darkroom.  This worked nicely.  Only a few emulsion
    defects showed up in a couple of the resulting negatives.  With the
    changing bag it was just too easy to inadvertently damage the emulsion. 

        During the remainder of Friday night Don and Nils took a beautiful
    shot of the Andromeda galaxy and an image of the Pleiades star group
    in Taurus which showed a lot of nebulosity.  It looked encouraging! 

        On Saturday, Don and Nils had remained at the observatory to
    participate in the construction of the Multi-Telescope Telescope (MMT)
    shelter.  Don, Nils, and I, along with Chris Lee and his Coulter 44-
    centimeter (17.5-inch) instrument, were the only people at HLCO that 
    night.  After the Moon had "set" at 10:20 p.m., we "attacked" the con-
    stellation Cygnus with a run of three exposures and developed them.

        The results were excellent:  The best guide star was not chosen,
    but we got the lower half of the North American Nebula (the Gulf of
    Mexico region).  We also had great frames of the dense star clouds 
    and nebulosity around Gamma Cygni and the Veil Nebula region about 52
    Cygni.  The tracking was close to perfect:  Very tiny star images
    across the entire six-degree field! 

        After their long day of construction labor on the MTT shelter with
    Harry Gelblat and Bill Bagnuolo, Don and Nils hit the HLCO bunks at 1
    a.m..  I managed six additional exposures alone:  Double clusters,
    M33, Zeta Orionis, M42, the Cone Nebula, and the Rosette Nebula. 

        I learned something about exposure times in the process.  The
    bright Orion Nebula (M42) was badly overexposed in the ten-minute
    exposure.  We should use no more than five minutes with 2415 film 
    on the next attempt.  Also, given good sky conditions, a fifteen 
    or twenty-minute exposure of M33 or a faint object like the Cone
    Nebula region would definitely give better results.  The spiral
    arms of M33 were clearly visible, along with a dense core, but the
    outer branches and H-II regions were indistinct.  Sadly, I found out
    that the film orientation in the camera (6 x 3.5 degrees) can matter
    given the guide star selected.  I managed to split the Rosette along
    the cluster in the center of the nebula.  Well, maybe half a rose is
    better than none at all! 

        It was 5:30 a.m. on Sunday when I finished developing the negatives.  
    Upon seeing the results, I suddenly did not feel the least bit sleepy!  
    It really was quite a thrill to see IC-434 streaking down the negative 
    of Zeta Orionis with the obvious impression of something dark in it.  
    Actually, I did manage a few hours of sleep on the sofa at HLCO, but I 
    just had to get back to the darkroom to see what the negatives would 
    reveal.  The Kodak 2415 held up very well under the high magnification 
    needed to print enlargements of the small Schmidt images. 

        I have had my turn and now someone else can have their shot with
    this wonderful equipment at the next HLCO observing session.  That is
    assuming, of course, that they are physically able to pry me away from
    it!  Actually, two or three people working together would be more
    productive than a single person working alone.  I encourage anyone
    interested to jump in and help.  If I can do it, anybody can. 

        About the Author -

        Harry Taylor is the Chairman of the ASA Amateur Telescope Making 
    Committee.


     THE ELECTRONIC JOURNAL OF THE ASTRONOMICAL SOCIETY OF THE ATLANTIC 

                        October 1991 - Vol. 3, No. 3

                          Copyright (c) 1991 - ASA
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