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^ 7 L A C H U A A S T R O N O M Y U B

—JANUARY 1989 — TtfE ALACHUA ASTRONOMY CLUB MEETS THE SECOND TUESDAY OF EACH MONTH AT THE DOYLE CONNER BUILDING, S.W. 34th STREET AND 20th AVENUE AT 7 PM. EVERYONE INTERESTED IN ASTRONOMY IS INVITED TO ATTEND. CALL CHARLES TARJAN AT 377-7403, FOR MORE INFORMATION ON MEETINGS AND OTHER ACTIVITIES.

H A P P Y N E W Y E A R ! ! !

GIVE A HEARTY WELCOME TO THE CLUB'S 1989 OFFICERS

CHARLIE TARJAN PRESIDENT JEFF MA JEW SKI VICE PRESIDENT

CHARLIE JARMAN SECRETARY DOUG RICHARDS TREASURER

and RANDY WARREN PROGRAM CHAIRMAN

CHUCK BROWARD FIRSTLIGHT EDITOR

BRING YOUR SCOPE TO THE JANUARY MEETING !!!

January's Meeting is DOUBLE-BARRELED.' Billy Cooke will kick off a year long discussion of our planets with a "Synopsis of the Planet Mercury", and members will then gather in the parking lot where Billy Dodd will direct a workshop on setting up YOUR telescope and its equatorial mount for a evening's viewing...so....

BRING YOUR TELESCOPE!!!

WIN A TELESCOPE! WIN A TELESCOPE!!! WIN A TELESCOPE!!!!

Of Course there a a couple of hitches!! First, you must have had paid your dues for the coming year, so bring your check book to the meeting!

Secondly, you must need the scope...e.g., you must presently not own a scope!

The RULES are simple...be a paid-up club member, appear at the next two meetings and place your names in the lens-cap. At the March meeting, a

DRAWING WILL BE HELD FOR THE FREE TELESCOPE! a winner will be selected

and you will be presented with the telescope...simple as that!

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $ $ $ PAY YOUR DUES AT THIS TUESDAY'S MEETING PLEASE $ $ $ $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

EDITORIAL COMMENT As some of you may have noticed, there was no December "FIRSTLIGHT".In part

because of the appearance of a small supernova in the Editor's household called Edith Virginia.' Carl Sagan, I think, said that we are all made of "starstuff", and if that is the case, Andi and I have indeed a bit of the universe awakening us at odd hours of the night. Please welcome our new daughter to our planet and our home (born 12-19 at 11:24P.M...I have no idea if the stars were visible or not!)

AN OPEN LETTER TO THE ALACHUA ASTRONOMY CLUB

FIRST AND FOREMOST, THANKS FOR THE OPPORTUNITY TO SERVE FOR ANOTHER YEAR AS PRESIDENT. MY NAME BEING THE ONLY ONE OFFERED IN NOMINATION CAN HAVE ITS NEGATIVE IMPLICATIONS WHICH I CHOOSE TO DISREGARD! INSTEAD I LOOK AHEAD TOWARD THE PROSPECT OF OUR CLUB CONTINUING "ON COURSE", GAINING NEW MEMBERS AS WE UNDERTAKE STILL MORE ACTIVITIES, AND HAVING AVAILABLE THE SAME EXCELLENT SUPPORT FROM SEVERAL MEMBERS.

WITHOUT RANDY WARREN, OUR PROGRAM CHAIRMAN, AND HIS TIRELESS PURSUIT OF SPEAKERS, WE COULD NOT HAVE HAD THE EXCELLENT PROGRAMS WE'VE ALL ENJOYED. RANDY'S ENTHUSIASM IS A GODSEND AND HIS WILLINGNESS TO COORDINATE SEVERAL OF OUR PAST ACTIVITIES IS REALLY APPRECIATED.

AN ORGANIZATION SUCH AS OURS IS ONLY AS GOOD AS ITS NEWSLETTER. AND WE ALL OWE ALOT TO CHUCK BROWARD FOR HIS ZEAL IN GETTING OUT A NEWSLETTER THAT CONTINUALLY HAS HAD INTERESTING ARTICLES AND CAN BE RECKONED AS THE MOST IMPORTANT CLUB ACTIVITY FOR MAINTAINING OUR AWARENESS OF THE ALACHUA ASTRONOMY CLUB AND WHAT IT'S DOING.

STABILITY AND DEPENDABILITY DESCRIBES GEORGE RUSSELL (AND HIS TRUSTY OLD COFFEE MAKER WHICH BECOMES PROMINENT DURING OUR 10 MINUTE BREAKS) AND HIS WILLINGNESS TO CONDCT THE MEETINGS WHEN I WASN'T AROUND. NOW THAT JEFF MAJEWSKI HAS STEPPED IN AS VICE-PRESIDENT, HE WILL TAKE OVER THAT JOB. WE HOPE GEORGE WILL USE HIS ABILITIES IN OTHER CLUB PURSUITS.

SUSAN LUKE STEPPED IN TO PICK UP THE REINS OF THE SECRETARIAL OFFICE AT A TIME WHEN WE WERE HURTING. SHE HAS DONE AN EXCELLENT JOB IN GETTING OUR NOTICES OUT TO THE MEDIA, IN SENDING OUT THE XMAS PARTY NOTICE, AND IN MAINTAINING CLUB RECORDS. MANY THANKS FOR YOUR HELP, SUSAN, AND FOR CONVINCING CHARLIE JARMAN, YOUR REPLACEMENT, WHAT GREAT FUN IT IS TO THE SECRETARY OF OUR CLUB.

TO THE BEST OF MY KNOWLEDGE, DOUG RICHARDS HAS SUFFERED NO CHARGES OF MISAPPROPRIATION OF CLUB FUNDS, AND HAS NOT BEEN SEEN SECRETIVELY BUYING SHEETS OF LOTTERY TICKETS OR BOARDING PLANES DESTINED FOR LAS VEGAS AT GAINESVILLE AIRPORT. INSTEAD, HE'S MAINTAINED THE CLUB TREASURY MOST PROFESSIONALLY AS VERIFIED BY THE SCATHING AUDIT BILL WHARTON GAVE THE LEDGER LAST NOVEMBER. BEST OF ALL, HE DIDN'T GIVE US A HARD TIME WHEN WE WANTED TO HAVE A SUPER-DUPER XMAS PARTY WITH PLENTY TO EAT.

HOWARD COHEN, WITH HIS WILLINGNESS TO SHARE HIS PROFOUND KNOWLEDGE OF ASTRONOMY WITH ALL OF US IS MUCH APPRECIATED. THE PROGRAMS HE HAS GIVEN, SOME ON A MOMENT'S NOTICE, HAVE BEEN EXCELLENT. IT'S REASSURING TO KNOW THAT WE CAN ALWAYS COUNT ON HIS EXPERTISE AND THAT OF BILLY DODD, BILLY COOKE AND OTHERS WHO ARE NEVER RELUCTANT TO SPEAK UP AND THUS TO KEEP OUR MEETINGS ALIVE.

FOR THOSE OF YOU WHO MISSED THE XMAS PARTY

SHAME, SHAME, AND AGAIN SHAME ON YOU!! RANDY AND JANICE WARREN, WITH INPUT FROM BILLY COOKE, STAGED A MAGNIFICENT FEAST WHICH FOLLOWED THE INTERESTING PRESENTATION BY JOHN LEADER. WE HAD A NUMBER OF GUESTS AND THE ENTIRE EVENING WAS A FITTING WAY TO FESTIVELY END OUR YEAR OF ASTRONOMICAL TOGETHERNESS.

PA6<S 3

MANY THANKS, JANICE AND RANDY, FOR MAKING THE PARTY SUCH A SUCCESS! THEN TOO, IT HELPED TO REDUCE THE "FAT" IN OUR TREASURY WHICH NEATLY LEADS ME INTO THE PRONOUNCEMENT THAT —

IT'S TIME TO RENEW OUR MEMBERSHIPS!

PLEASE DON'T GIVE OUR TREASURER A HARD TIME AND HAVE YOUR CHECKBOOKS IN HAND FOR THE JANUARY MEETING!

WHAT LIES AHEAD FOR THE FUTURE?

ONE THING I PERSONALLY WOULD LIKE TO SEE HAPPEN IS A NIGHT OUT EITHER AT BILLY DODD'S PLACE OR AT THE SPECIAL VIEWING AREA SEVERAL OF US USE IN THE HAILE PLANTATION (OFF SW 75TH ST, THE TOWER ROAD). IT WOULD BE A NIGHT OF "HANDS-ON" INSTRUCTION WHERE SEVERAL TELESCOPES WOULD BE SET UP AND THOSE OF US THAT NEED THE PRACTICE COULD BE PUT THROUGH THE STEPS OF FINDING CELESTIAL OBJECTS USING SETTING CIRCLES AND LISTED COORDINATES. IT SEEMS TO ME THAT SUCH KNOWLEDGE WOULD BE BASIC BEFORE WE COULD EVEN BEGIN TO CALL OURSELVES AMATEUR ASTRONOMERS!

ANOTHER ACTIVITY COULD BE PARTICIPATION, ONCE AGAIN, IN THE SPRING EQUINOX FESTIVAL THAT THE GARDEN CLUB HELD AT THE KANAPAHA GARDENS. A NUMBER OF PEOPLE STOPPED BY TO LOOK AT OUR TELESCOPES AND TO LOOK AT THE EXHIBITS WHICH GEORGE RUSSELL AND OTHERS PREPARED.

ALTHOUGH THERE WAS SOME TALK ABOUT IT, WE NEVER DID HAVE A CO-SPONSORED NIGHT OF VIEWING THE STARS FOR THE GENERAL PUBLIC, MUCH LIKE OCCURRED FOR THE MARS VIEWING AT THE UNIVERSITY OBSERVATORY SEVERAL MONTHS AGO.

SURELY SOME OF YOU DO HAVE OTHER IDEAS FOR CLUB ACTIVITIES. IF SO, PLEASE SPEAK UP. IN ORDER TO BE A VIABLE CLUB WE MUST BE AN ACTIVE CLUB AND ABOVE ALL WE MUST HAVE THE PARTICIPATION-PARTICIPATION-PARTICIPATION OF ALL OF YOU CLUB MEMBERS IN OUR ACTIVITIES.

THE BEST OF THE NEW YEAR TO ALL OF YOU!!!!

CHARLIE TARJAN, PRESIDENT

LAST CHANCE LAST CHANCE...YOU SHOULDN'T BE WITHOUT IT!!! Elsewhere in the FIRSTLIGHT is a page concerning "The Observer's

Handbook 1989". Gang, this handbook is worth purchasing!!! It is chock full of almost anything YOU would want to know, or dazzle your friends with. Your friendly editor purchased one, and reccomends it...friends now ask the silliest astronomical questions, and invaribly get the correct answer quickly and accurately. However, you have to purchase it to use it...its suggested that you who want it get together a bulk order and save some pennies.

FOR SALE FOR SALE CELESTRON C-8, CLASSIC ORANGE, CLOCK DRIVE (BYER'S DRIVE), 25, 7 MM EYE-

PIECES, DEWCAP...$750. LAPTOP COMPUTER, BATTERY DISC DRIVE, SOFTWARE... WANTED...CELESTRON C-5. CALL CHUCK 475-1014/392-1051

by Doug Richards

As anyone who has bought eyepieces for a telescope knows, this subject is surprisingly complex. You don't just walk into a store and say "I'd like a mid-priced, 40 power eyepiece, with a l l / 4 inch barrel". A salesman would likely reply that there is no such thing as a "40 power eyepiece" (or a mid-priced one either; the good ones are all expensive!). Although I am by no means an expert on eyepieces, I have bought a few, so I'll pass on a little of the knowlege I've acquired on the subject. A lot of this material is borrowed from the Tele Vue and Meade eyepiece catalogues* which include a pretty clear explanation of eyepiece selection.

The first thing you need to decide upon is the magnification that you want to achieve with a particular eyepiece. The novice may think that more magnification is always better, but because the brightness of objects and field of view are decreased at higher powers, low powers are best for many types of viewing. Tele Vue suggests a range of 5 desired magnifications, expressed in terms of magnification per inch of aperture:

A (4X per inch) For widest possible field; large galaxies, open clusters, diffuse nebulae

B. (7X per inch) Clusters, nebulae, general viewing C. (12X per inch) Planets, moon, globular clusters, double stars, planetary

nebulae D. (20X per inch) Maximum planetary detail, close double stars E. (35X per inch) Closest doubles on best nights

Power should never exceed 50 or 60 per inch of aperture, since this is the theoretical limit of resolution. Because of atmospheric turbulence, even large telescopes can rarely use more than 300X to 400X.

Once you decide how much magnification you are after in an eyepiece, you need to decide on the focal length of the eyepiece that wil l give you that magnification. To do this use the following formula:

Magnification = Focal length of the Objective Focal length of the eyepiece

This equation can be rearranged, and the focal length of the objective can be divided by the desired magnification to derive the desired focal length for the eyepiece. Remember to convert the focal length of the objective, commonly expressed in inches, into millimeters, which is the unit commonly used for eyepieces (25.4 mm/tn).

Have you ever noticed how beginners have a harder time finding the image in the telescope eyepiece when high powers are used? This is because the exit pupil, the disk of light which contains the image, is smaller at higher magnifications. The size of the exit pupil is also something to consider when choosing an eyepiece.

This can be calculated for a given telescope by this formula: Exit Pupil (mm) = focal length of the eyepiece

f number of the telescope My six inch reflector is an f/8 instrument, so a 32 mm eyepiece has

an exit pupil of 4 mm. With an f/4.5 instrument, the exit pupil would be greater than 7 mm using the same eyepiece, obviously giving a much brighter image. If the exit pupil is greater than the pupil of the eye at maximal dilation (7 mm), this extra illumination cannot reach the retina, and is useless.

An important feature of eyepieces, especially for eyeglass wearers, is the "eye relief" of an eyepiece. This term refers to the distance from the eyepiece your eye must be placed to see the entire field of view. Lower power eyepieces have longer eye relief. I can easily observe with my glasses on when I'm using my 32 mm eypiece (38X in my telescope), but when I switch to my 13.8 mm eyepiece (88X) my eye can't get close enough to the eypiece with my glasses on. If I use my 2X Barlow lens with the 32 mm, the magnification is almost the same, but I can leave my glasses on, because the eye relief is better with the Barlow combination.

The next topic with regard to eyepieces is the "field of view". Here it is very important to distinguish "true field" from "apparent field" of view. You wil l often see eyepieces advertized as having an apparent field of up to 82 degrees. This doesn't mean that you can see 82 degrees worth of the sky (this is close to what you can see with no telescope at all!), but that as you gaze into the eyepiece the image makes up 82 degrees of your field of view. This is determined by the design of the eyepiece, not necessarily by the focal length or magnification per se. The true field of view is the actual angular width of sky that you see. This can be calculated by the formula:

True field = Apparent field Magnification

Even though the 2X Barlow/32 mm eypiece combination I described above gives the same magnification as my 13.8 mm eyepiece, I usually prefer to use the latter, because it is a wide angle eyepiece, with a wider field of view, (apparent field 65 vs 50 degrees, true field 0.74 vs 0.65 degrees). Even if I am looking at a planet which could easily f i t into the narrower field of view, I enjoy the feeling of seeing the planet with a l itt le more space around it.

In addition to considering these factors when buying eyepieces, its a good idea to keep them in mind when buying a telescope as well. Consider what would happen if I built a 17.5 inch f /4.5 reflector. If I used the same eyepieces I now own, my 32 mm eypiece would now have a power or 62 X (objective f.l. of 2000 mm divided eypiece f.l. of 32 mm). The apparent field would be unchanged, but the true field would decrease from 1.3 degrees to 0.8 degrees. With larger aperture telescopes now becoming available to amateurs, its easy to see why long focal length eyepieces with wider apparent fields of view are also becoming more popular!

One important subject which I won't get into is that of vignetting (when the base of the eypiece holder or the barrel of the eyepiece itself block light which would otherwise help make a brighter image at the focal plane). This is mainly a problem with telescopes with short focal lengths

(low f ratio), used with eypieces of long focal lengths. If you ever buy or build such a telescope, you wil l probably want to familiarize yourself with this subject.

The final consideration I wil l mention is the design of the eyepiece and quality of construction. Many of the newer designs are made specifically to allow extremely wide apparent fields of view (e.g. Meade Ultra Wide Angle). These eyepieces are very expensive. Several of the older designs (e.g. Othoscopic) are said to give very clear crisp images, but do not give the same field of view as newer designs (Plossl, Konig). I have not read any comprehensive review comparing eyepieces for clarity of image, sharpness at the edge of the field, etc., but I would assume that the popular designs being marketed are those which have the best compromise of performance and cost. It has been said that in buying eyepieces you get what you pay for, and I assume this is true. My modestly priced B&L 32 mm Plossl eyepiece (about $50) performs adequately, but my more expensive Meade 13.8 mm Plossl wide angle eyepiece (about $120) gives appreciably sharper images. If you have the money to spend, you wil l probably be glad you bought the better eyepiece; if not, there are many adequate eyepieces available for a lot less money.

*Tele Vue 20 Dexter Plaza Pearl River, NY 10965 Meade Instruments 1675 Toronto Way Costa Mesa, Ca 92626

Home Brew Amateur Astronomy George Russell I suspect that sometimes I go overboard in my enthusiasm when I see

an item of great usefulness that has been hand crafted by a fellow amateur. This comes probably from my great interest in my other hobby, ham radio, where a tremendous amount of self satisfaction occurs when I can build some-thing and use it to whatever purpose I desire.

Case in point was Doug Richard's " Poncet " platform, table or mount which was brought to last months meeting for a little " show and tell ". Unfortunately, by the time the meeting ended, not enough time had been spent on this unique item. The Poncet mount is a combination of mechanical ideas devised in a structure to provide tracking and photographic opportunities.

The Poncet mounting has a North pivot point and on the South end two Teflon bearings riding on a smooth incline plane. The inclined plane forms an angle equal to 90 degrees less the local latitude. Precise alignment at the North end is thus automatic. The Poncet mount is usually made to track starsby using a threaded rod driving a nut attached to the platform. Doug attached a flywheel and cord arrangement that turns the threaded rod. Ideally, an electric motor is used and usually the motor rpm and the thread-ed turns per inch will be limiting factors. By providing a means to con-trol the motor speed, precise tracking can be obtained. Such a device, to control the motor speed, was described in the January issue of FirstLight, 1988, the premier issue! Their is great beauty in simple things. I hope we can again see your Poncet mount, Doug.

~

2? * 82

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THE OBSERVER'S HANDBOOK 1 QflQ

81st Year of Publication Editor: Dr. Roy L. Bishop

The Observer's Handbook is a 200-page guide published annually by The Royal Astronomical Society of Canada. Through its long tradition and the expertise of some two dozen contributors, the Observer's Handbook has come to be regarded as the standard North American reference for data on the sky. The material in the Handbook is of interest to professional astronomers and other scientists, amateur astronomers, teachers at all levels, students, science writers, campers, scout leaders, as well as interested general readers. The Observer's Handbook is an integral part of many astronomy courses at the secondary and university levels, and it should be on the reference shelf of every library in North America.

The various sections in the Observer's Handbook are of two kinds:

(1) Sections dealing with astronomical events which occur during the current year. e.g. Times of sunrise and sunset, moonrise and moonset (for latitudes 20° to 60° N), eclipses, location of the planets and bright asteroids, returns of periodic comets, times of meteor showers, predictions of occupations by the Moon and by asteroids, the orbital positions of the brighter satellites of both Jupiter and Saturn, predictions of the cycles of many variable stars. There is a special 24-page section called "The Sky Month By Month" which gives an extensive listing of events.

(2) Sections dealing with astronomical data and other information which do not vary from year-to-year (although revisions are made annually to ensure that the information is the best available), eg. Orbital and physical data on the planets and their satellites, astronomical and physical constants, information regarding some optical properties of telescopes, a description of the various systems of specifying time, information on the Sun including sunspots and aurorae, a list of meteorite craters in Canada and the United States (of special interest to geologists and other travellers), information on the Gegenschein and zodiacal light, 40 pages of authoritative tables dealing with stars, star clusters, nebulae and galaxies, maps of the Moon and the entire stellar sky.

The 1989 edition of the Observer's Handbook will be available in November 1988. For ordering information, please see the reverse side of this sheet.

Price schedule

Single copy (and recommended retail price) $10.00* postpaid

" " (airmail overseas) $12.50*

10 - 29 copies $6.90*

30 - 99 copies $6.70*

100 + copies $6.50*

*In order to cover higher costs, outside of Canada these prices are to be read as U.S. dollars.

The Royal Astronomical Society of Canada 136 Dupont Street Toronto, ON Canada M5R 1V2

Please send copies of the 1989 Observer's Handbook

Name

Address

Payment Enclosed $ Please invoice**

**Only for orders received on institution letterhead. Accounts must be paid in full within 30 days; overdue accounts will be charged interest at 15% per month.

Note: (1) No Handbooks will be accepted for credit refund. (2) RASC Centres should not. use this form for ordering Handbooks.

A special order form is sent to each Centre in August, and additional copies are available from the National Office.

A'Afie 5

SO YOU WANT TO BUY A TELESCOPE 11 Recently, I received a phone call concerning the value of a 'scope.

Upon observation, it was obvious that the C-8 needed a lot of TLC..and the previous owner had become disenchanted with the almost portable 8 inch.

Sadly, many scopes end up on the block, covered with dust and cobwebs. Their previous owners have tired of the hauling from closet to backyard, of the fuzzy confused images, of not seeing what the splashy magazine ads promise.

Today, for several thousand dollars, one is told they can see a hundred objects a hour. One is told they can have perfect astro-photos in minutes. One is told they will receive endless hours of enjoyment.

BULL!!!! Unless you are unique, you vill soon tire of the splendid gizmo that demanded the cost of a trip to Mexico to see, in person, a unique solar eclipse (by the way, a 8 inch scope will not fit under a aircraft seat!). Unless you are unique, images of fuzzy creame and mauve blobs will become boring. And, unless you are unique, one session of guiding a scope for a hour, in a attempt to make a decent photo of some obscure cotton visp will send you growling back to the livingroom!

The solution is simple. Curb your appitite for highpriced techy optics until you are absolutely sure of what you want! Go to star parties and check every scope on site. Be a pest and touch and handle every scope you can lay your hands on! But wait before you buy! There are bargains to be found among the ones who did not wait and are now disenchanted (the C-8, by the way, was a bargain, but not a steal...it needed work!)

Wanted: 12" X 6' Songtube --George Russell If you have read Richard Berry's book: Build Your Own Telescope",

you would have come across an article entitled: "Build a 10" Dobsonian Reflector". My interest in the It) " developed about this time last year but was soon lessened when I had some difficulty in locating a suitable tube for an enclosure.

A concrete-form tube is not the best possible tube material but it is by far the least expensive — about $10.00 for a 6' length — so they say. Phenolic plastic or Fiberglass runs around $100.00.

So my plan is to build the 10" if I can get all of my materials to-gether within a reasonable time and cost. The tube appears to be the stumbling block at the moment. I would appreciate any leads anyone might have on such a tube; telephone: 376-7633.

WANTED WANTED WANTED... YOUR KNOWLEDGE. IDEAS. AND EVENTS! This Newsletter is not just a exercise, it is a tool to reach other

amateur astronomers with info and knowledge. That knowledge comes from you. The Editor needs people to provide others with data on up-coming events, new ideas and local happenings. Call me, send me copy, upload stuff...PLEASE!!!

DON'T FORGET BAJA CALIFORNIA AND THE ECLIPSE! Dr. Howard Cohen has said that available reservations are filling up for

the forthcoming solar eclipse.. .So, contact him for latest info and plans... this is indeed a event of a lifetime!

WELCOME TO NEW MEMBER RICHARD RUSSIN... Richard is a Gainesville resident, owns a Meade refractor...

BRING A FRIEND TO THE MEETING... INTRODUCE SOMEONE TO ASTRONOMY...

AND HELP BUILD A STRONGER CLUB!

f . ^ - o w r see y0^ AUTICLB ? zs FATIBNT... ,r W U A P P I T A R . /