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 memomsheldon@comcast.net Past President Lyle Jones 302-382-3764 worm1647@comcast.net

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