Shadow of Ganymede on Jupiter

Io and Ganymede, Shadow of Ganymede on Jupiter

July 1, 2010, 4am - simulated with Celestia software.

Ganymede is bigger than Io.

(p.s. I got up and looked at Jupiter this Thurs (July 1) with

the telescope and it wasn't this clear, but the moon's

shadow was clearly visible.)

Simulated view of Jupiter through a telescope

Click on this to see it bigger, then hit your back button to go back.
Callisto (4) , Ganymede (3), Jupiter, Europa (2), and Io (1) , from left to right.
Image made with Celestia software.
Ganymede is slightly larger than Mercury.
The Great Red Spot is in the South Equatorial Zone, centered.
Tilt your screen to see it more clearly, if it's not obvious.

Movement of Stars due to Rotation and Revolution, of the Earth

The earth's rotation rate is 15 degrees per hour.
This causes the stars to move left to right across
the southern sky.

The earth is also revolving in its orbit around the
sun, and this causes given stars to rise and set
4 minutes earlier each night.
This adds up to 28 minutes per week,
or two hours per month.
That is why we see different stars in the evening
at different seasons throughout the year. The night
sky faces outward from the sun in different directions
as the year progresses, at a given time of night.

Next Season's Preview in the Morning:

If you want to see what the stars will look like
three and a half months from now at 9pm in the evening,
then, just go out in the morning, at 4am, and there
they will be. The planets and moon will be different,
of course.
(The sidereal (star) time will be the same.)

List of Navigational Stars

Here is a list of the brightest and most famous stars.
Sailors have used these for a long time for determining
position at sea.
Since these are brighter, and easier to see, they
are often used by amateur astronomers to align
computerized telescopes, and otherwise find their
way around the sky.

http://www.saguaroastro.org/content/NAVIGATION-STARS-FOR-EQUINOX-2000.htm

Brighter stars along the ecliptic:
These often get blocked by the moon at times,
and they are good to know for positioning
at various seasons:

Regulus, in Leo, blue, late winter, early spring

Spica, in Virgo, blue, spring.

Antares, in Scorpius, red, early summer

Aldebaran, in Taurus, orange, late fall.

Some unusual things in the solar system, and Bode's Law

The following is a partial list of unexplained or partially explained
things of the solar system:

The planets come in similar but not identically sized pairs:

Venus and Earth
Jupiter and Saturn
Uranus and Neptune
Pluto and Eris, and others (dwarf planets)

Mercury, and Mars do not follow this pattern.

Bode's law is a simple mathematical formula.
Putting an integer from 0 to 9 accurately predicts the
orbital position of most of the planets , and is like a "harmonic"
which gets larger and larger, as follows:

a = orbital distance in astronomical units ( earth = 1)

a =( n +4 ) / 10
where n = 0, 3, 6, 12, 24, 48, 96, 192, 384

or

a = ( 3 * 2^m + 4 ) / 10

( 2 to the m power )

where m = 0, 1, 2, 3, 4, 5...

except:

There is a missing one between Mars and Jupiter.
Ceres the dwarf planet (580 miles in diameter)
lies in the spot where the missing planet would be.
Ceres is round but the other big asteroids are irregular.
if the planets didn't accrete from dust,
thiere could have been an exploded planet
at this position. Mars is slightly off, and Neptune
is closer than this would predict it to be.
Mercury's orbit is highly elliptical, so is Mars.
Venus hardly spins at all, very slowly. No magnetic
field to protect it from the sun.
Maybe it spun faster in the past.

The Earth's moon has many Maria (dark lava plains)
on the Earth-facing side, very few on the farside.

Mars has heavy cratering on one side,
and smooth on the other. Cracks and breaks look like it
had some planet wide catastrophe. 4 big volcanoes
all in the same region ( Tharsis).
Mars has evidence of running water in the past.
Water channels with erosion.
Jupiter's Great Red Spot never goes away. What lies under it?
Saturn's small inner moon Enceladus has ice fountains
Titan has big lakes and rivers of methane,
and a sizeable atmospheric pressure.
Uranus is tipped on its side, even more than 90 degrees,
so it really spins backwards.
and Neptune's Triton orbits in the opposite direction
of the other moons, and that the planet rotates in.
(it most likely is a captured dwarf planet like Pluto)

All Gas giants and ice giants except Uranus
give off more heat than they receive from the sun.
What is the source of the internal heat? Contraction?
Initial heat of formation?
Radioactive Decay? Chemical reactions?
They are far too small for nuclear fusion, like the sun.

What Magnitude is that star? Apparent magnitude:

An explanation of the stellar magnitude scale and how it works:
It is logarithmic and in dealing with light that is helpful for the large
ranges of values, just as decibels are in dealing with sound, which
has a large range of values, also.
The larger the number, the fainter the object.
If a star is one magnitude brighter than another one,
it is 2.512 times brighter. If a star is 5 magnitudes fainter,
it is 100 times fainter, in terms of how bright
(how much light it gives off.)
2.512 is approximately the fifth root of 100.
Here is a more detailed explanation of it:

http://en.wikipedia.org/wiki/Apparent_magnitude

The sun is -27, and the full moon is -12.
The full moon is about 1/450000 as bright as the sun.

Venus is -4.7 to -3.8
Jupiter is -2.9 to -1.6
Mars at opposition is -2.9 to -1.5
Saturn is 0.0 to 1.0
Uranus is 5.7 or so.
Neptune is 7.7
Pluto is 13.5 or fainter.

Sirius (the brightest star) is -1.5
Vega is about 0.0 magnitude, so is Arcturus,
and the faintest stars visible in a dark location
are about 6.5.

Orion's bright ones are 0.0 and 1st magnitude, some 2nd also,
and fainter.

The Big Dipper's stars, Polaris, and Kochab, Casseiopeia,
and Andromeda, have mostly 2nd magntude, with a few
third magnitude ones also.

In suburban America , the naked eye limit is usually 5.0 unless you
are standing near street lights, then it's 4 or 3, or worse.
To do any serious wide field photography of the Milky Way or
faint fuzzies, one needs to go away from city lights, especially in
urban metro areas. In the Northeast, Eastern Connecticut, the
Litchfield Hills, Massachusetts Quabbin area, Catskill Mountains,
Adirondacks, and parts of Northern New England mountain areas,
are good places to find dark skies.

Celestial Equator and Ecliptic, Declination

While the earth remaineth, seedtime and harvest
and cold and heat, and summer and winter
and day and night, shall not cease.
(Genesis 8:22)

In the northern hemisphere, as one looks to the south, one will see
the area of sky where the celestial equator and ecliptic are.

The Celestial Equator is the arc in the sky directly over the Earth's
equator. It is tilted, (90 minus your latitude) degrees
up in the south. Orion, Virgo, Ophiuchus, Aquila (Altair) and Cetus,
are all straddling the equator. It rises due east, arches over in the
south, and arcs down to due west, always.
It is at 0.0 degrees declination, and declination is the angle above
or below the equator, in sky coordinates, sort of like latitude on earth.
The North celestial pole is at 90.0 degrees declination, and the
South celestial pole is at minus 90.0 degrees.

In the southern hemisphere the celestial equator is up in
the north, and the south celestial pole is up in the south, and the
southern circumpolar constellations rotate around it.

The ecliptic is the path of the sun through the sky,
through the year. It is tilted 23.5 degrees from the
equator because the earth is tilted 23.5 degrees from the
plane of its orbit. This is what causes the seasons to
occur, as the sun shines on the ends of the earth at a
different angle throughout the year as it goes around the
orbit.

In the night sky, the ecliptic rides high in the winter, midway up in
the spring and fall, and low in the summer.
At night the part of the ecliptic one sees, due south at
midnight, is where the sun was 6 months ago.

The moon follows the ecliptic roughly, but is
inclined to it an additional 5.145 degrees, so it can
swing either above or below the ecliptic.
When the moon crosses the plane of the ecliptic,
twice a month, this is called a "node".
When the node lines up with the time of full moon,
a lunar eclipse occurs, and when the node
happens to occur at the time of new moon,
a solar eclipse occurs somewhere.

The ecliptic rides high in the west in the spring and this
makes it easier to see the waxing thin moon in the spring.
It rides high in the east before dawn in the fall,
and that makes it easier to see the waning thin moon at that time.
In the opposite seasons there is a disadvantage because
the ecliptic rides low and drags the horizon.

Lunar Eclipse photo - February 21, 2008

How to orient oneself under the night sky:

For middle latitude, in the Northern Hemisphere:

1. Look for the Big Dipper.

Around mid-evening, the Big Dipper, (seven stars, mostly second magnitude)
is in the following place:

Winter: Up in the northeast,standing on its handle
Spring: High in the north, spilling out
Summer: Up in the northwest, bowl below handle
Fall: Scraping the northern horizon


2. Look for Polaris , the North Star:

Look for the two stars at the end of the bowl of the Big Dipper.
These are the "Pointers" and they point toward Polaris. Up and out of the bowl.
Their names are Dubhe and Merak. Dubhe is orange.
Polaris is about 3/4 of a degree from north.


3. Find Kochab, the End of the Little Dipper.
This is an orange star, about as bright as Polaris (2nd Magnitude)

It's in the direction of the handle of the Big Dipper - out from Polaris.

The exact north pole is on a line between Polaris and Kochab, 3/4 of a degree from Polaris.


4. Seasonal Constellations: Check with a planisphere, seasonal star chart, or

astronomy software for nice maps. Try Starry Night, Stellarium(free) or Software Bisque.

Winter:

Taurus in the southeast, Pleiades up first:
Orion in the east-souteast.
Gemini in the northeast
Cygnus in the northwest ( in early winter)


Spring:

Leo, (star Regulus) high in the south:
Virgo (Spica) up in the southeast
Bootes up in the east. (Arcturus)
Hydra - under Leo and Virgo

Summer:

Ophiuchus in the South
Scorpius low in the south (Antares - Red )
Sagittarius low in the souheast
Cygnus - in the northeast, then high overhead
Lyra - up in the northeast (Vega)

Vega, Deneb, and Altair are the Summer Triangle

Fall:

Piscis Austrinus - Low in the South (Fomalhaut )
Pegasus - Great Square.
Andromeda
Perseus - over in the northeast - left of Pleaides
Casseopeia - high in the north
Taurus - Low in the northeast Pleaides come out in October.
Summer Triangle still visible, but over in the western half of the sky.

Pole star, and history thereof:

History of the pole star, and how to find it.

Also, path that the south polar axis traces out in the starry background.

http://en.wikipedia.org/wiki/Pole_star

http://en.wikipedia.org/wiki/Polaris

Double Cluster in Perseus

This beautiful object is easily seen in binoculars or a small telescope.

Better in low power - needs a wide field. It is fairly far north on the

celestial sphere, so although it is an autumn object, it is also visible

in winter and spring, and also late summer before dawn.

Located between the top of Perseus and Casseiopeia.

Orion's Sword

This is one of the brightest

diffuse nebulae in the

nght sky. Messier 42,

in the sword of Orion

5 minute exposure on

a Canon 6.3MP

EOS 300D

and 300mm lens.

Earth and Moon (with Celestia software)

The Celestia program gives a realistic view of many objects in the solar system.

Here is a view of the Earth and moon.

It shows the relative size of them compared

to each other.

The specular reflection off the ocean is real.

In the Holy Scriptures:

Job 26:7 He stretcheth out the north over the empty place, and hangeth the earth upon nothing.

View of Jupiter with a Celestron 8

Contrast enhanced so the Great Red Spot shows up better
This one taken a few years back.

Waning Crescent Moon ( in the morning before sunrise)

Crater Copernicus on the terminator.

This phase is visible best before dawn, and in the late summer or fall, because of the angle of the ecliptic.

Photo with a Canon G2 camera, Celestron 8 SCT telescope, 40mm Plossl eyepiece

Scale of Distance - Pluto, (Now) versus Alpha Centauri

Is not God in the height of heaven? and behold the height of the stars, how high they are! (Job 22:12)

Someone asked me how much further the nearest star is,
compared to the outer planets in our solar system.
(approximately)
The following is a simple calculation about that:

Takes light 4.30 hours to go to Pluto (4.30 light-hours) at 186000 miles /sec.
assuming 31 AU's away. (This in May 2010, sometimes less, will get greater as the next few years go by, for quite a while, because it's going outward on its elliptical orbit)

It just so happens this year that Pluto is the same number of light-hours away, as the
nearest star is in light-years.

1 AU is 92.9 Million Miles. - The radius of the Earth's orbit around the sun.

Takes light 4.3 years to come from Alpha Centauri
There are 24 hours in a day and 365.25 days in a year.
that makes:
8766 hours per year (average of regular years and leap years)

8766 X 4.3 / 4.3 = 8766

Alpha Centauri is 8766 times further away than Pluto is (on average).
1/8766 is .0001141 or .01141 percent.

A light year is 5.879 x 10 to the 12th power miles, or
5.879 thousand billion, or trillion miles.

Guided photography with a 50mm lens

A short (5 minute) time exposure on Fujicolor 800 film,

of Cygnus and the North America Nebula.

Olympus OM-2, with 50mm lens at f/2 attached to the back of a driven Celestron 8.

Welcome to JohnC SkyWatcher

Waning Gibbous Moon with a Meade ETX-125 telescope.

2 days after full,

crater Langrenus.

This blog will usually contain the following kinds of posts:

1. Basic information to help a beginner get started
with amateur astronomy.

2. Highlights of current events in the astronomical world.

3. Links to interesting articles I find.

4. Other science and math related stuff.

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