Sky & Telescope - December 2023 - 73
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pA simple spherometer will get you close
enough to the right curve. Look for how to build
this spherometer, based on Ed Jones's design,
in a future column.
small sunspots? If so, you're done. If
not, you can simply keep polishing until
both faces are adequately spherical.
The lens and mirror need a framework
to hold them in place. The Sun
moves across the sky, so unless you want
to keep running back and forth to adjust
the projector's angle, the mirror needs
to be moveable to track it. A picture is
worth a thousand words, so I'll just refer
you to the photo of Ed's projector on the
facing page. You can see that his mirror
can move on two axes for alignment,
and he's got a tracking mechanism that
keeps the sunlight aimed through the
lens at the distant screen.
The tracking mechanism is just a
short arc of Delrin with threads tapped
into it, with a threaded rod pulling the
arc along at the end of an arm. The
length of the arm determines the motor
speed. Perhaps surprisingly, the mount
isn't polar-aligned. Instead, since the
Sun only deviates slowly from a straight
line across the sky, Ed uses a tilting
tripod head to align the base of the
projector parallel to the Sun's path, and
the motor drive moves the mirror at
half the solar rate (because the reflection
doubles the effect of changing the
mirror's angle).
Ed's projector provides an excellent
view of the Sun, and, with a little care,
yours will too. During the upcoming
eclipse, you'll have the most popular
view at the party.
For more information, contact Ed
Jones at opticsed@gmail.com.
ยข Contributing Editor JERRY OLTION is
making a 4-inch version of this projector.
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Image: NGC 6891, a bright, asymmetrical planetary nebula in the constellation Delphinus, the Dolphin. (NASA)
STATEMENT OF OWNERSHIP, MANAGEMENT AND CIRCULATION (required by Act of August 12, 1970: Section 3685, Title 39, United States Code). 1. SKY & TELESCOPE 2.
(ISSN: 0037-6604) 3. Filing date: 10/1/23. 4. Issue frequency: MONTHLY. 5. Number of issues published annually: 12. 6. The annual subscription price is $57.75. 7. Complete
mailing address of known office of publication: AAS Sky Publishing, LLC, Washington, DC 20006. 8. Complete mailing address of headquarters or general business office of
publisher: AAS Sky Publishing, LLC, 1667 K Street, NW Suite 800, Washington, DC 20006. 9. Full names and complete mailing addresses of publisher, editor, and managing
editor. Publisher, Kevin B. Marvel, PhD, 1667 K Street, NW Suite 800, Washington, DC 20006, Editor, Peter Tyson, 1374 Massachusetts Ave., Cambridge, MA 02138, Managing
Editor, Peter Tyson, 1374 Massachusetts Ave., Cambridge, MA 02138. 10. Owner: American Astronomical Society; Kevin B. Marvel, Executive Officer, 1667 K Street NW,
Suite 800, Washington, DC 20006. 11. Known bondholders, mortgages, and other security holders owning or holding 1 percent of more of total amount of bonds, mortgages
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43,868. Actual number of copies of single issue published nearest to filing date: 42,678. B. Paid circulation. 1. Mailed outside-county paid subscriptions. Average number
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through dealers and carriers, street vendors and counter sales. Average number of copies each issue during the preceding 12 months: 3,380. Actual number of copies of single
issue published nearest to filing date: 2,894. 4. Paid distribution through other classes mailed through the USPS. Average number of copies each issue during the preceding
12 months: 0. Actual number of copies of single issue published nearest to filing date: 0. C. Total paid distribution. Average number of copies each issue during preceding 12
months: 35,082. Actual number of copies of single issue published nearest to filing date: 33,388. D. Free or nominal rate distribution (by mail and outside mail). 1. Free or
nominal Outside-County. Average number of copies each issue during the preceding 12 months: 0. Number of copies of single issue published nearest to filing date: 0. 2. Free
or nominal rate in-county copies. Average number of copies each issue during the preceding 12 months: 0. Number of copies of single issue published nearest to filing date:
0. 3. Free or nominal rate copies mailed at other Classes through the USPS. Average number of copies each issue during preceding 12 months: 0. Number of copies of single
issue published nearest to filing date: 0. 4. Free or nominal rate distribution outside the mail. Average number of copies each issue during preceding 12 months: 0. Number of
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number of copies of single issue published nearest to filing date: 0. F. Total free distribution (sum of 15c and 15e). Average number of copies each issue during preceding
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preceding 12 months: 8,786. Actual number of copies of single issue published nearest to filing date: 9,290. H. Total (sum of 15f and 15g). Average number of copies each
issue during preceding 12 months: 43,868. Actual number of copies of single issue published nearest to filing: 42,678. I. Percent paid. Average percent of copies paid for the
preceding 12 months: 100.0% Actual percent of copies paid for the preceding 12 months: 100.0% 16. Electronic Copy Circulation: A. Paid Electronic Copies. Average number
of copies each issue during preceding 12 months: 14,105. Actual number of copies of single issue published nearest to filing date: 14,627. B. Total Paid Print Copies (Line 15c)
+ Paid Electronic Copies (Line 16a). Average number of copies each issue during preceding 12 months: 49,186. Actual number of copies of single issue published nearest to
filing date: 48,015. C. Total Print Distribution (Line 15f) + Paid Electronic Copies (Line 16a). Average number of copies each issue during preceding 12 months: 49,186. Actual
number of copies of single issue published nearest to filing date: 48,015. D. Percent Paid (Both Print & Electronic Copies) (16b divided by 16c x 100). Average number of copies
each issue during preceding 12 months: 100.0%. Actual number of copies of single issue published nearest to filing date: 100.0%. I certify that 50% of all distributed copies
(electronic and print) are paid above nominal price: Yes. Report circulation on PS Form 3526-X worksheet. 17. Publication of statement of ownership will be printed in the Dec
'23 issue of the publication. 18. Signature and title of editor, publisher, business manager, or owner: Peter Tyson, Editor-in-Chief. I certify that all information furnished on this
form is true and complete. I understand that anyone who furnishes false or misleading information on this form or who omits material or information requested on the form
may be subject to criminal sanction and civil actions.
sk yand tele scope .o r g * DECEMBER 2023 73
JERRY OLTION
http://www.aas.org/join
Sky & Telescope - December 2023
Table of Contents for the Digital Edition of Sky & Telescope - December 2023
Contents
Sky & Telescope - December 2023 - Cover1
Sky & Telescope - December 2023 - Cover2
Sky & Telescope - December 2023 - 1
Sky & Telescope - December 2023 - Contents
Sky & Telescope - December 2023 - 3
Sky & Telescope - December 2023 - 4
Sky & Telescope - December 2023 - 5
Sky & Telescope - December 2023 - 6
Sky & Telescope - December 2023 - 7
Sky & Telescope - December 2023 - 8
Sky & Telescope - December 2023 - 9
Sky & Telescope - December 2023 - 10
Sky & Telescope - December 2023 - 11
Sky & Telescope - December 2023 - 12
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Sky & Telescope - December 2023 - 14
Sky & Telescope - December 2023 - 15
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Sky & Telescope - December 2023 - 22
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Sky & Telescope - December 2023 - 30
Sky & Telescope - December 2023 - 31
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Sky & Telescope - December 2023 - 33
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Sky & Telescope - December 2023 - 37
Sky & Telescope - December 2023 - 38
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Sky & Telescope - December 2023 - 40
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Sky & Telescope - December 2023 - 42
Sky & Telescope - December 2023 - 43
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Sky & Telescope - December 2023 - 45
Sky & Telescope - December 2023 - 46
Sky & Telescope - December 2023 - 47
Sky & Telescope - December 2023 - 48
Sky & Telescope - December 2023 - 49
Sky & Telescope - December 2023 - 50
Sky & Telescope - December 2023 - 51
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Sky & Telescope - December 2023 - Cover3
Sky & Telescope - December 2023 - Cover4
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