* 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LENS (UNPUBLISHED MANUSCRIPT)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