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Norman Sperling
2625 Alcatraz Avenue #235
Berkeley, CA 94705-2702

cellphone 650 - 200 - 9211
eMail normsperling [at] gmail.com

Norm Sperling’s Great Science Trek: 2014

San Luis Obispo
Santa Barbara
Palm Springs
Death Valley
Tucson
El Paso
Corpus Christi
Baton Rouge
Tampa
Everglades
Key West
Winter Star Party, Scout Key
Miami

MARCH 2014:
up the Eastern seaboard
mid-South

APRIL 2014:
near I-40, I-30, and I-20 westbound

MAY 2014:
near US-101 northbound
May 17-18: Maker Faire, San Mateo
May 23-26: BayCon, Santa Clara

California till midJune

JUNE 2014:
Pacific Northwest

JULY 2014:
Western Canada, eastbound

AUGUST 2014:
near the US/Can border, westbound
August 22-on: UC Berkeley

Speaking engagements welcome!
2014 and 2015 itineraries will probably cross several times.

7 Spectral Types in 1 Big Loop

© Norman Sperling, April 15, 2012
Part of a series on Educational Star Parties:
Star Parties Designed for Students (July 7, 2012)
Trading Cards for Telescopes and Celestial Objects (September 20, 2012)
Telescope Triplets (November 25, 2011)

When I teach about stars, the 7 main spectral types usually seem rather abstract. I show their different spectra, but that's hard to relate to what students actually see in a starry sky. I show Planck curves and explain how surface temperature results in color differences that you can actually notice. Star colors aren't the sharp tones of advertising signs, but you can definitely notice the tinges.

Star tinges are less than impressive to the naked eye, because starlight is so dim that it mostly triggers the black-and-white-registering rod cells in your retina. Only the 20 or so brightest stars deliver so much light that they also trigger a few color-sensitive cone cells, and those only barely.

But even a small telescope collects enough light to trigger a whole lot more cones in your retina, making the colors appear appreciably bolder. So a star party that is deliberately planned for student education should use 7 small telescopes to point at a bright star of each of the 7 spectral types, to emphasize their different colors. Arrange the scopes so a single line of viewers looks through all 7 scopes in order, either OBAFGKM or MKGFABO. After everybody has seen that, re-aim those scopes to their next targets.

Yes, A and F stars really do look white, but now you appreciate how real that is, unlike an artifact of not triggering enough cone cells.

For each spectral type, at any position of the sky, you can find examples at third magnitude or brighter.

All 7 spectral types are blatant around the Great Winter Oval:
O: Mintaka and Alnitak
B: Rigel, Bellatrix, El Nath, Alnilam, and Saiph
A: Sirius
F: Procyon
G: Capella
K: Aldebaran and Pollux
M: Betelgeuse

The Great Winter Oval has many advantages. It's accessible late in the Fall semester, late in the evening; all winter long; and just after dusk well into Spring semester. Since it straddles the equator, it's easily seen from practically everywhere that people live. Only in May, June, and July is it not available - parts of it even then.

When part of the Great Winter Oval is hidden by the Sun's glare, here are some bright alternatives:
O: zeta Ophiuchi and zeta Puppis
B: Alpheratz, Algol, Regulus, Spica, and Alkaid
A: Denebola, Alioth, Mizar, Gemma, Vega, Deneb, Altair, and Fomalhaut
F: Polaris, Algenib, and Sadr
G: the Sun, beta Corvi, Vindemiatrix, eta Bootis, eta Draconis, and beta Herculis
K: Alphard, Dubhe, Arcturus, and Kochab
M: Antares, Mira, and beta Andromedae

Decrease the number of telescopes needed, and make the contrast more vivid, by showing wide, bright, color-contrast double stars:
Algieba: K + G
Albireo: K + B
gamma Andromedae: K + B
Cor Caroli: A + F

Bigger scopes show color contrast in:
32 Eridani: G + A
h3945 Canis Majoris: K + F

Don't try to add spectral class W unless you're far enough south to see the only bright one, gamma Velorum, -47 degrees. There are only about 150 Wolf-Rayet stars known in our galaxy. No others are close enough to look brighter than 6th magnitude. The biggest bunch is around the Summer Triangle.

I'll comment more on planning star parties for student education in later postings.

The Journal of Irreproducible Results
This Book Warps Space and Time
What Your Astronomy Textbook Won't Tell You

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