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February 2016 Volume 22 Number 8 Page 1
Star Gazer News
Newsletter of the Delmarva Stargazers www.delmarvastargazers.org
Upcoming Events: Meeting ! Feb 2
nd 7 PM Smyrna Church
Observing ! Feb 5,6th Dusk Eq. Cntr. or Blackbird
From the Prez...Finally Winter has arrived,
maybe, well at least it was cold last
night... With the colder weather hopefully
we will get some clear skies and dark
nights. I woke up about 2:30 this morning
and went out with my binoculars for about
30 minutes, the skies were nice and I en-
joyed spending a few minutes out in the
dark. Of course had I spent any more time
out, without dressing for it, I would have
risked freezing. Be sure that you dress ap-
propriately when you do go out this time of
year, and a warm drink would not hurt.
One thing I was specifically looking
for this morning, was comet C/2013 US10,
Catalina. After a few minutes to get my
eyes adjusted it was easy to find, it is
about magnitude +5.0 now and at about 85%
of what it should get to. Here is a sky
chart showing were it was now and it's
path.
Our last meeting was January 5th, we
had a small group for dinner and the bowl
turners meeting prior to the meeting- Don
and Dennis had a few bowls they are in the
process of making from some Ambrosia Maple,
i think it is from Lyles son's yard.
Lyle suggested a group trip out to
Nebraska to view the solar eclipse next
year, there seemed to be some interest so
he will be looking into it and more infor-
mation will be coming soon…
The Spring Star Party was discussed,
and a date has been set for May 5-8. We
also looked at the Mirror Making that is
coming up. We wrapped up with a video pres-
entation on the Southern Skies, which some
of will be enjoying a bit of at the WSP
down in the Florida Keys in February. One
of those going won their registration and
camping at our Star Party last spring.
Dark skies, nice park, good food and
great prizes; what more could you ask for
in a star party? We have a date set for May
5-8 at Trap Pond. From what I am hearing
there may have been some confusion about
fees, the only fee is registration; this
covers park entry fees, camping on the ob-
serving field, and all the Stargaze bene-
fits. The only fees not covered would be
camping in the park campground, use of the
dump station for RV sewage and beer money.
I am looking out the window at grey
winter skies, hoping it will clear up so I
can get the telescope out. Whether it is in
my driveway, at one of our observing sites
or at a world class location; I am looking
forward to getting out and seeing some-
thing. I hope I see some of you all
there…...Pete
February 2016 Volume 22 Number 8 Page 2
How to Join the Delmarva Stargazers: Anyone with an interest in any aspect of astronomy is welcome NAME_______________________________________________________________New_______Renew___________ ADDRESS_____________________________________________________________________________________ CITY, STATE & ZIP______________________________________________________________________________ E-MAIL ADDRESS (If any)_________________________________________________________________________ Please attach a check for $15 made payable to Delmarva Stargazers and mail to Kathy Sheldon, 20985 Fleatown Rd, Lincoln, DE 19960. Contact club President for more information.
Cepheus From Wikipedia
Cepheus is a constellation in the
northern sky. It is named after Cepheus,
King of Aethiopia in Greek mythology. It
was one of the 48 constellations listed by
the 2nd century astronomer Ptolemy, and re-
mains one of the 88 modern constellations.
Its brightest star is Alpha Cephei with an
apparent magnitude of 3.5. Delta Cephei is
the prototype of an important class of star
known as a Cepheid variable. RW Cephei, an
orange hypergiant, together with the red
supergiants Mu Cephei, VV Cephei and V354
Cephei are among the largest stars known.
In addition, Cepheus also has the hyperlu-
minous quasar S5 0014+81, hosting an ul-
tramassive black hole in its core at 40
billion solar masses, about 10,000 times
more massive than the central black hole of
the Milky Way, making it the most massive
black hole known in the universe.
History and mythology
Cepheus was the King of Aethiopia. He
was married to Cassiopeia and was the fa-
ther of Andromeda, both of whom are immor-
talized as modern day constellations along
with Cepheus.
Notable features
Delta Cephei is the prototype Cepheid
variable, a yellow-hued supergiant star 980
light-years from Earth. It was discovered
to be variable by John Goodricke in 1784.
It varies between 3.5m and 4.4m over a pe-
riod of 5 days and 9 hours. The Cepheids
are a class of pulsating variable stars;
Delta Cephei has a minimum size of 40 solar
diameters and a maximum size of 46 solar
diameters. It is also a double star; the
yellow star also has a wide-set blue-hued
companion of magnitude 6.3.
There are several other prominent
variable stars in Cepheus. One, µ Cephei,
is also known as Herschel's Garnet Star due
to its deep red colour. It is a semiregular
variable star with a minimum magnitude of
5.1 and a maximum magnitude of 3.4. Its pe-
riod is approximately 2 years. The star is
around 11.8 AU in radius. If it were placed
at the center of the Solar System, it would
extend to the orbit of Saturn. Another, VV
Cephei A, like Mu Cephei, is a red super-
giant and a semiregular variable star, lo-
cated at least 5,000 light-years from
Earth. It has a minimum magnitude of 5.4
and a maximum magnitude of 4.8. One of the
largest stars in the galaxy, it has a di-
ameter of 1,300 solar diameters. VV Cephei
is also an unusually long-period eclipsing
binary, but the eclipses, which occur every
20.3 years, are too faint to be observed
with the unaided eye. T Cephei, also a red
giant, is a Mira variable with a minimum
magnitude of 11.3 and a maximum magnitude
of 5.2, 685 light-years from Earth. It has
a period of 13 months and a diameter of 500
solar diameters.
There are several prominent double
stars and binary stars in Cepheus. Omicron
Cephei is a binary star with a period of
800 years. The system, 211 light-years from
Earth, consists of an orange-hued giant
primary of magnitude 4.9 and a secondary of
magnitude 7.1. Xi Cephei is another binary
star, 102 light-years from Earth, with a
period of 4000 years. It has a blue-white
primary of magnitude 4.4 and a yellow sec-
ondary of magnitude 6.5.
(See Cepheus on page 6)
February 2016 Volume 22 Number 8 Page 3
Your 2015-2016 Officers Office Officer Phone email President Peter Graham President-elect Doug Towner Secretary Michael Lecuyer Treasurer Kathy Sheldon 302-422-4695 [email protected] Past President Lyle Jones 302-382-3764 [email protected]
Dental Stone
Volume Calculations
Michael Lecuyer
Dental stone tools are commonly used
in amateur telescope making simply because
they are far cheaper and more available
than glass and usually perform as well.
This is neither an article on making tools
nor using them however.
We will concentrate on the amount of
dental stone powder and water to mix for
the tool’s volume. This has not been
clearly addressed in the amateur telescope
making literature nor videos as sources add
water and powder during the mixing until it
“looks right.” This combined with bad math
can result in a mix that’s soupy and weak
or too thick and sets up too quickly and
contains voids.
There are three types of dental stone
that concern amateur telescope makers
(ATMs) Type 3, the normal cheap stuff com-
monly found; type 4 known as die stone
which has high strength, low expansion;
type 5 with high strength and high expan-
sion. Most of us will encounter Type 3 and
perhaps Type 4. This article is for Type 3.
The solution – provide the necessary
calculations to create the correct amount
of dental stone in the correct proportions.
We need to know the volume and the density
of the final product – the gypsum dihydrate
stone. The value I determined from test
blocks is a density of 2.3. The actual
value is said to be around 2.32, very
close to my value which is found in
[MSD]. This value is a good approxima-
tion since there are some variables in
the purity of the powder and water.
With fresh dry powder and distilled wa-
ter the simple calculations that follow
yield consistent results.
Density values manufacturers give
the dry are given in a range because
the contents may settle during shipping and these values can be ignored.
If you are lucky the distributor will
tell you the mix ratio which is always some
value of powder to water like 33 to 100
meaning thirty-three parts water to on hun-
dred parts of powder. Dismiss the tempta-
tion to use this as a percent. It’s a total
number of parts – 33 parts of powder to 100
parts of water which means there is a total
of 133 parts.
The calculation will be done in the
SI system using grams which measure mass
(not force) where a milligram of water has
a mass of 1 cm3 which conveniently lets us
weigh the powder against the water with no
conversions.
Constants
Density of dental stone Ds = 2.23
Powder Portion Pp = 100
Variables
r = Radius of tool
t = Thickness of tool
Wa = Water proportion: use 40 or manufac-
turers recommendation.
Calculate the combined mass (Density of
dental stone times the tool volume)
M = Ds * (PI * r2 * t)
The final two calculations use the total
mass and break it into the weight of each
component.
Grams of water:
w = Wa / (Wa + Pp)
or
w = Wa / (Wa + 100)
Grams of powder:
p = Pp / (Pp + Wa)
or
p = 100 / (100 + Wa)
For our example the tool will be 8
inches across (20cm) and 1 ½ inches thick
(3cm).
The volume of the tool will be it’s
radius (1/2 diameter) times it’s thickness.
The given diameter is 20 cm therefore the
radius r = 10 cm so r2 = 100.
PI need be no more accurate than our
February 2016 Volume 22 Number 8 Page 4
measurements at 3.14
M = 2.23 * (3.14 * 100 * 3)
M = 2,101 g
The tool, when mixed will weigh 2.101
kg which will change as the excess water
(water not required for the chemical reac-
tion) evaporates or is added by rinsing.
The mix we're using uses a 40 : 100
proportion of water to powder therefore the
total parts will be 140.
From the manufacture's proportions
above we will calculate the fractional pro-
portions of materials.
Wa is the proportion of water which
100 is the constant proportion of powder.
The calculation of amount of water to use
in grams (milliliters) is:
w = Wa / (Wa + 100)
w = 40 / (40 + 100)
w = 0.29
The proportion of powder will be:
p = 100 / (100 + Wa)
p = 100 / (100 + 40)
p = 0.71
Checking our work: the two amounts (p
and w) are 0.29 + 0.71 = 1.00 (or 100% of
the ingredients).
Now we calculate the mass of each in-
gredient.
The total mass is 2,101 from the cal-
culation above using our proportions w and
p.
Calculate our water in grams.
W = 0.29 * 2,101
W = 609 grams of water
Powder in grams:
P = 0.71 * 2,101
P = 1,492 grams of dental stone
Checking our work again 1,492g + 609g =
2,101g which is correct.
That's the mix! The amounts measured
should be within a few grams of the calcu-
lated amounts.
Naturally there's an app for that so
you don't have to go through all those
steps each time.
<Where is this magical application?>
Speeding up setting and drying times:
Microwave ovens have been demon-
strated to cut setting times from 48 hours
to just 5 to 15 minutes [MD1] [MD2]. These
values were for small expansion studies
samples in research on dental stone so we
have to be careful when using them for much
larger tools. Instead of 400 watts for 5 to
15 minutes we will use no more than a ½
power setting (for a microwave this trans-
lates into duty cycle of 50%, half the time
on, half the time off, and only for short
periods of two or three minutes with rest
times outside the oven until cooled pre-
venting steam from building up cracking the
tool.
Careful heating and cooling cycles
can also be used to dry and heat the tool
so pitch will stick to the tool.
References:
[MSD] "Material Science for Dentistry Ninth
Edition" by B.W.Darvell published by the
CRC Press published in 2009.
[MD1] Microwave drying of high strength
dental stone: effects on dimensional accu-
racy.
Yap AU1, Yap SH, Teo JC, Tay CM, Ng KL,
Thean HP.
[MD2] The effects of drying techniques on
the compressive strength of gypsum products
Radhwan H Hasan, Kasim A Mohammad (College
of Dentistry, University of Mosul)
ISSN: 1812-1217
February 2016 Volume 22 Number 8 Page 5
This article is provided by �ASA Space Place. With articles, activities, crafts, games, and lesson plans, NASA Space Place encourages
everyone to get excited about science and technology. Visit spaceplace.nasa.gov to explore space and Earth science!
The Loneliest Galaxy In The Universe
By Ethan Siegel Our greatest, largest-scale surveys of the universe have given us an unprecedented view of cosmic structure extending for
tens of billions of light years. With the combined effects of normal matter, dark matter, dark energy, neutrinos and radiation all af-
fecting how matter clumps, collapses and separates over time, the great cosmic web we see is in tremendous agreement with our best
theories: the Big Bang and General Relativity. Yet this understanding was only possible because of the pioneering work of Edwin
Hubble, who identified a large number of galaxies outside of our own, correctly measured their distance (following the work of
Vesto Slipher's work measuring their redshifts), and discovered the expanding universe. But what if the Milky Way weren't located in one of the "strands" of the great cosmic web, where galaxies are plentiful and
ubiquitous in many different directions? What if, instead, we were located in one of the great "voids" separating the vast majority of
galaxies? It would've taken telescopes and imaging technology far more advanced than Hubble had at his disposal to even detect a
single galaxy beyond our own, much less dozens, hundreds or millions, like we have today. While the nearest galaxies to us are only
a few million light years distant, there are voids so large that a galaxy located at the center of one might not see another for a hundred
times that distance. While we've readily learned about our place in the universe from observing what's around us, not everyone is as fortunate.
In particular, the galaxy MCG+01-02-015 has not a single known galaxy around it for a hundred million light years in all directions.
Were you to draw a sphere around the Milky Way with a radius of 100 million light years, we'd find hundreds of thousands of galax-
ies. But not MCG+01-02-015; it's the loneliest galaxy ever discovered. Our Milky Way, like most galaxies, has been built up by
mergers and accretions of many other galaxies over billions of years, having acquired stars and gas from a slew of our former
neighbors. But an isolated galaxy like this one has only the matter it was born with to call its own. Edwin Hubble made his universe-changing discovery using telescope technology from 1917, yet he would have found abso-
lutely zero other galaxies at all were we situated at MCG+01-02-015's location. The first visible galaxy wouldn't have shown up until
we had 1960s-level technology, and who knows if we'd have continued looking? If we were such a lonely galaxy, would we have
given up the search, and concluded that our galaxy encompassed all of existence? Or would we have continued peering deeper into
the void, eventually discovering our unusual location in a vast, expanding universe? For the inhabitants of the loneliest galaxy, we
can only hope that they didn't give up the search, and discovered the entire universe.
Image credit: ESA/Hubble & �ASA and �. Gorin (STScI); Acknowledgement: Judy Schmidt, of the loneliest void galaxy in the
known: MCG+01-02-015.
February 2016 Volume 22 Number 8 Page 6
Kruger 60 is an 11th magnitude binary
star consisting of two red dwarfs. The star
system is one of the nearest, being only 13
light years away from Earth.
Deep-sky objects
NGC 7354 is a planetary nebula lo-
cated in the constellation Cepheus. NGC
188 is an open cluster that has the dis-
tinction of being the closest open cluster
to the north celestial pole, as well as one
of the oldest known open clusters.
The Fireworks Galaxy (NGC 6946) is a
spiral galaxy in which nine supernovae have
been observed, more than in any other gal-
axy.
IC 469 is another spiral galaxy,
characterized by a compact nucleus, of oval
shape, with perceptible side arms.
The nebula NGC 7538 is home to the
largest yet discovered protostar.
NGC 7023 is a reflection nebula with
an associated star cluster (Collinder 429);
it has an overall magnitude of 7.7 and is
1400 light-years from Earth. The nebula and
cluster are located near Beta Cephei and T
Cephei.
The quasar 6C B0014+8120 is one of
the most powerful objects in the universe,
powered by a supermassive black hole
equivalent to 40 billion Suns.
Visualizations
Cepheus as depicted in Urania's Mir-
ror, a set of constellation cards published
in London c. 1825.
Cepheus is most commonly depicted as
holding his arms aloft, praying for the
gods to spare the life of Andromeda. He is
also depicted as a more regal monarch sit-
ting on his throne.
Equivalents
In Chinese astronomy, the stars of
the constellation Cepheus are found in two
areas: the Purple Forbidden enclosure (紫微垣, Zǐ Wēi Yuán) and the Black Tortoise of
the North (北方玄武, Běi Fāng Xuán Wǔ).
In popular culture
In the TV sitcom 3rd Rock from the
Sun, the aliens' home planet is stated to
be located in a barred spiral galaxy on the
Cepheus-Draco border.
The performer Deadmau5 named his
song, "HR 8938 Cephei" after a star in the
constellation.
Namesakes
USS Cepheus (AKA-18) and USS Cepheus (AK-
265), United States navy ships.
(Cepheus from page 2)
February 2016 Volume 22 Number 8 Page 7
February 2016 Volume 22 Number 8 Page 8
Astrophotos from members and friends
Lunar eclipse 8-28-2007…waiting for the 301 bus at Smyrna Rest Area…about 6:30 AM— Don Surles