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* CAS *
Charlottesville
Astronomical Society
April 2013
Welcome Guests
Welcome New Members
&
Guests Larry, Josie and Aeriel Landress
&
Ned Yost
Club Business • 65 paid active members
• DUES ARE NOW DUE !!!
• Checking account and Cash on Hand: $4,011.32
• See Ed Preston for information on discounted subscriptions to Astronomy and Sky and Telescope
• Club Scopes available for use by members http://cvilleastro.com/club-telescopes-available-for-club-member-use/ – See Rich for information
Tonight’s Speaker
John Avellone
Mirror and Lens
An Inquiry Concerning Possible
16th Century Telescopes
BACKGROUND ● EILEEN REEVES (Prof. Of Comparative Literature)
MAKES THE FOLLOWING POINTS IN “GALILEO'S
GLASSWORKS”:
● EVIDENCE FOR 16th c. TELESCOPIC DEVICES BASED
ON MIRROR & LENS ARRANGEMENTS.
● GALILEO INITIALLY MISUNDERSTOOD REPORTS
DESCRIBING THE “DUTCH TELESCOPE”.
● “SIDERIUS NUNCIUS” IS REALLY TWO BOOKS -
● 1) OLDER DESCRIPTION REGARDING STARS IN ORION,
● 2) NEWER OVERLAY EMPHASISING DISCOVERIES
(SATELLITES OF JUPITER) VIA THE “DUTCH
TELESCOPE”.
TIMELINE / GALILEO
● FEB 1609: OBSERVE ORION & MOON - WITH WHAT?
● MAY 1609: NEWS RE “DUTCH TELESCOPE” FROM HOLLAND.
● AUG 1609: SHOW DOGE OF VENICE 8X DUTCH TELESCOPE.
● NOV 30-DEC 17 1609: LUNAR OBS, 20X DUTCH TELESCOPE.
● JAN 07-MAR 02 1610: JUPITER & SATELLITES, 20X TELESCOPE.
● JAN 30 1610: TAKE DRAFT OF “STARRY MESSENGER” TO VENICE.
● MAR 01 1610: CHURCH GRANTS LICENSE TO PRINT “SM”.
QUESTIONS:
1) WHAT WERE “MIRROR/LENS”
DEVICES?
2) HOW WELL DO THEY WORK?
3) COULD GALILEO HAVE USED ONE?
PROCEDURE
● CONSULT REFERENCES
● CONSTRUCT FUNCTIONAL REPLICAS
● TEST REPLICAS
REFERENCES:
● SIDERUS NUNCIAS/ GALILEO GALILEI/ 1610
● GALILEO'S GLASSWORKS/ EILEEN REEVES/ 2008
● THE INVENTION OF THE TELESCOPE/ ALBERT VAN HELDEN/
1977
● THE EMERGENCE OF THE TELESCOPE/ N. BARLOW PEPIN/
2004
● THE LONG ROUTE TO THE INVENTION OF THE TELESCOPE/
ROLF WILLACH/ 2008
● STARGAZER/ FRED WATSON/ 2004
● THE HISTORY OF THE TELESCOPE/ HENRY C. KING/ 1955
● WEB SEARCHES/ VARIOUS HISTORY OF ASTRONOMY SITES
● EMAIL/ JAMESTOWN GLASSWORKS
ITALIAN ACTORS (CONFUSING!)
● FRA PAOLO SARPI/ GALILEO'S COLLABORATOR/ LETTERS FROM
HOLLAND.
● GIOVANNI ANTONIO MAGINI & CESARE MARSILI (~1580-1600s??)
MIRROR + “TRAGUARDO”/ QUADRANTS.
● ETTORE AUSONIA (1550) LARGE CONCAVE MIRROR + CONVEX
LENS (UNPUBLISHED MANUSCRIPT)
● GIAMBATTISTA DELLA PORTA (~1589) LENS+MIRROR/ MULTIPLE
LENS/ MULTIPLE MIRROR TELESCOPE, CAMERA OBSCURA, 20
BOOKS ON “MAGIC”.
● GIROLAMO FRACATORE (~1550) CONVEX LENS AS ALTERNATIVE
TO MIRROR FOR ASTRONOMICAL OBSERVATION/ BIFOCALS.
USEFUL INFO:
● DISCUSSION OF MIRROR + EYELENS (“TRAGUARDO”)
ENGLISH ACTORS (PRACTICAL)
● FRA ROGER BACON/MIRRORS (1267) OPTICS-”CAUSE THE SUN,
MOON AND STARS IN APPEARANCE TO DESCEND HERE BELOW”.
● JOHN DEE (1570) ORIGINAL “AGENT 007”, LARGE MIRROR.
● LEONARD & THOMAS DIGGS (MILITARY
ENGINEERS)/”PANOMETRIA”/ MIRROR & LENS TELESCOPES ~ 1570
(“AN INFINITE UNIVERSE POPULATED WITH STARS”).
● WILLIAM BOURNE/ MATHEMATICIAN/ MANUSCRIPT DESCRIBES
OPTICS & DIGGS TELESCOPE TO LORD BURGHLEY.
● USEFUL INFO:
● 1) DESCRIPTION OF MIRROR/LENS TELESCOPE USED BY
DIGGS.
● 2) PROPOSED DESIGN OF A BIG REFRACTOR (BOURNE).
“REAL” MIRROR/LENS DEVICE (LEONARD DIGGS):
● REFLECTED IMAGE FROM CONCAVE MIRROR VIEWED THROUGH
AN OFFSET POSITIVE LENS.
● (BLOWN??) GLASS SPHERICAL SECOND-SURFACE MIRROR
COATED (“FOYLLED”) ON THE BACK (“HILLY”) SIDE.
● “SPECTACLE”-TYPE CONVEX THIN LENS GROUND AGAINST AN
IRON TOOL.
● THEORETICAL REFRACTOR PROPOSED BY
BOURNE: ● 1) OBJECTIVE: 1' DIA, FL~ 12'
● 2) EYE LENSE: NEGATIVE, LOCATED INSIDE FOCUS OF OBJECTIVE.
TECHNICAL CONSIDERATIONS for a “Diggs – type”
MIRROR/LENS Device:
● SHORT FOCUS LENSES:
● 1) THICK POSITIVE “READING STONE” (ROCK CRYSTAL) LENSES
AVAILABLE SINCE 7th c. BCE (“NIMRUD” LENS).
● 2) THIN POSITIVE AND NEGATIVE “SPECTACLE” LENSES
AVAILABLE AFTER ~ 1300 CE (IMPROVED VENETIAN “CRYSTAL”
GLASS).
● (LENSES ONLY NEEDED TO BE “GOOD” OVER CENTRAL 1cm)
● MEDIUM FOCUS GLASS SECOND-SURFACE SPHERICAL
MIRRORS:
● 1) BY MID 1400's, GLASS BLOWING ACHIVED CURVATURES
YIELDING FOCAL LENGTHS OF 4” to 10” WITH 12” POSSIBLE.
● (MIRROR SURFACE ONLY HAD TO BE OK OVER AN AREA OF AN
INCH OR TWO)
●
EXAMPLE OF 15th c
SPHERICAL MIRROR:
CONSTRUCT FUNCTIONAL REPLICA OF A
DIGGS - TYPE MIRROR/LENS DEVICE
● BASIC DESIGN:
● OFFSET SIMPLE SHORT-FOCUS EYE LENS
VIEWING A MEDIUM TO LONG FOCUS
SPHERICAL CONCAVE MIRROR.
● CONSTRAINT:
● USE OPTICAL COMPONENTS OF THE
APPROPRIATE (POOR) QUALITY.
OPTICAL ELEMENTS USED
● EYE LENS:
● +2” TO +4” FOCAL LENGTH (THICK AND THIN) DCX / PCX
● -2” TO -4” FOCAL LENGTH (THIN) DCV / PCV.
● (EYE LENS STOPPED DOWN TO ~ 1 cm DIAMETER.)
● MIRROR:
● +6” TO +12” FOCAL LENGTH SECOND-SURFACE
(DRUGSTORE) SPHERICAL “LOOKING GLASS” MIRRORS
SKETCH OF MIRROR/LENS GEOMETRY
EXPERIMENTAL RESULTS
● POSITIVE EYE LENSES GIVE BEST IMAGES (3X-6X).
● THIN LENSES WORK BETTER THAN “READING STONES”.
● NEGATIVE EYE LENSES BARELY WORK (DISTORT FOV).
● @ 3X, FOV=8*, @ 6X, FOV~4*.
● @ 3X, DEVICE GIVES 9-FOLD LIGHT GAIN OVER EYE (m=+9
VS m=+6)
● BEYOND 6X, COMA & OTHER DEFECTS DEGRADE IMAGE.
● IMAGE QUALITY OK FOR STAR FIELDS & MOON.
● COMA TOO BAD TO SHOW MUCH ON BRIGHT PLANETS (AT
BEST, ONLY CALLISTO COULD BE SEPARATED FROM
JUPITER'S BLAZE)
CONCLUSION
MIRROR & LENS DEVICES,
CONSISTENT WITH 16th CENTURY
DESCRIPTIONS & TECHNICAL
LIMITATIONS, ARE USABLE AS
LOW-POWER, WIDE FOV,
TELESCOPES FOR STUDY OF
STAR FIELDS & THE MOON.
BUT, WHAT ABOUT GALILEO's 6* X 6* SKETCH OF ORION?
CONSTRAINTS
● THE ORION STAR FIELD SKETCHED BY GALILEO IS ~ 6* X 6*
● STARS DOWN TO m~8.8 ARE SHOWN
● FIELD OF VIEW & LIMITING MAGNITUDE ARE CONSISTENT
WITH CAPABILITIES OF A MIRROR & LENS DEVICE OF 3X TO
6X
● IN CONTRAST:
● A GALILEAN REFRACTOR (“DUTCH TELESCOPE”) OF ~ 11X
HAS A FOV ~ 20' OF ARC (2/3RDS OF A FULL MOON) AND A
LIMITING MAGNITUDE < m=8 (REMEMBER, TITAN IS @ m~8
AND WAS NOT DETECTED BY GALILEO).
April is Global Astronomy Month
http://www.astronomerswithoutborders.org/global-
astronomy-month-2013.html
Check Out the Site and Get Involved
Club Events
Fan Mountain Open House
Friday, April 12
Bring your scope to show the visitors
you favorite object
Be on top of the mountain by
Club Events
Our Contribution to the Global Star Party
At
Ivy Creek Natural Area
Friday, April 19
7:30 – 10:00 pm
https://maps.google.com/maps?f=q&hl=en&q=1776+earlysville+road,+charlot
tesville+va
Member of the Month
My Favorite Object At least for this month.
April, 3 2013
Wesley Epperly
CAS
Look Southeast at about 10 PM
30 Degrees from Horizon
Spica
Algorab Gienah
Kraz
Minkar
Achiba
10 x 50
FOV
Image Credit: Jerry Lodriguss, “A Beginner’s Guide to
Astrophotography”
M104, The Sombrero Galaxy
8” Telescope provides fair
visual image
Astronomical League Awards
Have you participated in any of the following?
• Fall Fan Mountain
• Hollymead Star Party
• Ivy Creek
• Rockfish Valley Star Gaze
• Open Doors session
• McCormick Group Nights
If so…………..
Astronomical League Awards
The Astronomical League
Outreach Award
5 two hour outreach sessions
Document using an AL spreadsheet
Confirm with club officer
Science Fair Wrap-Up
Science Fair Wednesday, March 13
CAS Prizes
CAS
Membership
• Junior Winner
• Matthew Harmon – Dixon Smith MS,
Stafford County
• EFFECTS OF THE MOON ON STAR
GAZING
• Senior Winner
• Meredith Hooper – AHS
• CORRELATIVE STUDIES OF SOLAR
FLUX, GEOMAGNETIC INDICES AND
VAN ALLEN RADIATION BELT
STRUCTURE
Library Project
Library – Jim Wilson, Michael Rein, Steve Layman
We already cataloged more than 60 video
Presentations (VHS, CD, DVD) that members
are willing to lend to members.
The list will be posted on our Yahoo Site
Files Section
Do You have Library Books Out ?
McCormick History Project
Susan Bender
Wes Epperly
Michael Hegadus
Fred Repich
Steve Layman
Met with Ed Murphy this afternoon
to get project outline.
Parallax Display Project
Rich Drum
Larry Landress
Fred Repich
Steve Layman
Met with Ed Murphy this afternoon
to get project outline.
Astronomical Events for April
http://hubblesite.org/explore_astronomy/tonights_sk
y/
Our Solar System
http://www.cfa.harvard.edu/pao/skyreport/solar_syst
em.html
Upcoming Speakers May
• Bill Phillips, CAS Member
• Optics 101 for the Amateur Astronomer
Saturday, June 2
Special Meeting at the John C. Wells
Planetarium at James Madison University,
Harrisonburg, VA
Tour and Planetarium Show
Upcoming Speakers
July
• The Early History of the McCormick Observatory as
Recorded in the News
• CAS Member Wes Epperly
August
* Star Formation through Radio Eyes: Probing
Magnetic Fields with CARMA
• Chat Hull, Uva Alum, PhD candidate UC Berkley
• Video Lecture from Berkley
Upcoming Speakers
September
* UVA Microfabrication Lab and ALMA
* Dr. Arthur Lichtenberger, UVA
October
* Ed Preston
Upcoming Speakers
November
• Tom Field
• Real Time Spectroscopy (Rspec)
• Video Lecture from Seattle
NEAIC and NEAF • North East Astro Imaging Conference
• April 18 – 19
• North East Astronomy Forum
• April 20 – 21
• Suffern, NY • http://www.rocklandastronomy.com/NEAIC/schedule.html
• http://www.rocklandastronomy.com/NEAF/index.html
Field Trip
Monday, July 22
Tour includes satellite ground
ops and clean room http://www.jhuapl.edu/aboutapl/organization/default.asp
Fan Mountain Retreat
• Friday, August 2 and 3 (rain date 9/6 – 7)
• Ed Murphy Sky Tour
• Rapid Robotic Telescope Demo
• ?????
Web Site of the Month
Udemy
Welcome to Asstronomy – State of the Art
https://www.udemy.com/lectures/welcome-to-
astronomy-state-of-the-art-239552
Next Meeting
Wednesday
May 1, 2013
Door Prize Drawing
Recommended