Visit the Cellar!

The Cellar Image of the Day is just a section of a larger web community: bright folks talking about everything. The Cellar is the original coffeeshop with no coffee and no shop. Founded in 1990, The Cellar is one of the oldest communities on the net. Join us at the table if you like!

 
What's IotD?

The interesting, amazing, or mind-boggling images of our days.

IotD Stuff

ARCHIVES - over 13 years of IotD!
About IotD
RSS2
XML

Permalink Latest Image

Dec 12th, 2017: Sierra Railway No. 3

Recent Images

Dec 11th, 2017: Halszka
Dec 10th, 2017: Tuturumuri School
Dec 9th, 2017: Stretchers
Dec 8th, 2017: Wounded Warrior
Dec 7th, 2017: Infamy
Dec 6th, 2017: MAREA
Dec 4th, 2017: Sad Reindeer

The CELLAR Tip Mug
Some folks who have noticed IotD

Neatorama
Worth1000
Mental Floss
Boing Boing
Switched
W3streams
GruntDoc's Blog
No Quarters
Making Light
darrenbarefoot.com
GromBlog
b3ta
Church of the Whale Penis
UniqueDaily.com
Sailor Coruscant
Projectionist

Link to us and we will try to find you after many months!

Common image haunts

Astro Pic of the Day
Earth Sci Pic of the Day
We Make Money Not Art
Spluch
ochevidec.net
Strange New Products
Geisha Asobi Blog
Cute animals blog (in Russian)
20minutos.es
Yahoo Most Emailed

Please avoid copyrighted images (or get permission) when posting!

Advertising

Philadelphia Pawn Shop
The best real estate agent in Montgomery County
The best T.38 Fax provider
Epps Beverages and Beer, Limerick, PA
Sal's Pizza, Elkins Park
Burholme Auto Body, Philadelphia
Coles Tobacco, Pottstown
ERM Auto Service, Glenside
Glenside Collision
Moorehead Catering, Trappe
Salon 153, Bala
Dominicks Auto Body, Phoenixville

   Undertoad  Wednesday Sep 26 10:11 AM

September 26, 2007: Geostationary satellites



This was an Earth Science Pic of the Day a few days ago.

This is 8 and a half hours of an open shutter pointed at the sky. Now,
that makes clear what the trails are - stars, captured as they move
across the sky while the earth rotates. But then, the dots that don't
have any trail are geostationary satellites, in geostationary orbit.

They don't have any trail because they move along with the rotation
of the Earth. They orbit at exactly the equator. That means stationary
dishes on Earth can "see" them at all times, which is why there are so
many of them. People don't want to move their dishes!

So if you follow: the camera is stationary on Earth, except that it's not
stationary at all; it's moving with the rotation of the Earth. The
satellites appear to be stationary in the picture, but that's only
because they are moving in exact harmony with the motion of the
camera. And the things that appear to move completely across the
image are stars, entirely stationary.

Well, except that they probably aren't -- but with our short span of
attention, our 70 years, we can't sit around long enough to notice
that motion... we can't perceive it.

So why does XM Radio have three satellites while Sirius appears to
have none? Sirius' satellites use a different type of orbit, a Tundra orbit.
This allows two of their three satellites to be visible to all of North
America at any given time.



theotherguy  Wednesday Sep 26 10:43 AM

We need more Directv satellites.



barefoot serpent  Wednesday Sep 26 12:27 PM

Now I know why XM radio is always playing ZZ Tops LaGrange.



Trilby  Wednesday Sep 26 01:04 PM

This is too complicated and 'boy' looking for me to know or care what it is. It's some kind of "graph" that employs the ugliest green color in the world so it is not worth my attention.

How come there are no GIRL-focused IotD stuff like shoes or diamond rings or self-tanning products on the Cellar? Ever ask yourself that, UT?



Flint  Wednesday Sep 26 01:08 PM

Actually, Brianna, that's a close-up of the skidmarks you left when you dragged your butt across the carpet.

The labels pinpoint different things you've had for dinner recently.



Trilby  Wednesday Sep 26 01:30 PM

Oh! Thanks, Flint! I knew it was something you'd know about!



BigV  Wednesday Sep 26 01:45 PM

Quote:
Originally Posted by Brianna View Post
This is too complicated and 'boy' looking for me to know or care what it is. It's some kind of "graph" that employs the ugliest green color in the world so it is not worth my attention.

How come there are no GIRL-focused IotD stuff like shoes or diamond rings or self-tanning products on the Cellar? Ever ask yourself that, UT?
Did you just volunteer for IotD-er of the month duty? Cause we're looking for one.


spudcon  Wednesday Sep 26 01:52 PM

Has anyone noticed several of the star tracks suddenly winked out? Is the sky falling?



hampor  Wednesday Sep 26 05:19 PM

End of the Star

Quote:
Originally Posted by spudcon View Post
Has anyone noticed several of the star tracks suddenly winked out? Is the sky falling?
That's just where the star happened to be when the exposure started or stopped.


BeltNah  Wednesday Sep 26 05:49 PM

Help

Where do you put suggestions for IotD?



Undertoad  Wednesday Sep 26 06:18 PM

Send as links or attachments with all relevant info to undertoad @ cellar dot org.



BeltNah  Wednesday Sep 26 06:46 PM

Thanks



Sarasvati48  Wednesday Sep 26 08:47 PM

Damn...there are still women who play that "I'm too dumb to understand because I'm a girl..." game? I truly hope that was sarcasm...



Trilby  Wednesday Sep 26 08:51 PM

Quote:
Originally Posted by Sarasvati48 View Post
Damn...there are still women who play that "I'm too dumb to understand because I'm a girl..." game? I truly hope that was sarcasm...
um...what do you mean by that?


aero geek  Wednesday Sep 26 11:09 PM

Where are the GPS satellites?



tulzscha  Wednesday Sep 26 11:29 PM

Quote:
Originally Posted by aero geek View Post
Where are the GPS satellites?
Not geostationary, so not visible in the picture.


CharlieG  Thursday Sep 27 10:04 AM

Quote:
Originally Posted by aero geek View Post
Where are the GPS satellites?
They are not geosyc!


Anton  Thursday Sep 27 11:05 AM

Quote:
Originally Posted by Undertoad View Post
But then, the dots that don't have any trail are geostationary satellites, in geostationary orbit.
Nah, they are just specs of dust on the camera's sensor! Space objects? Whatever next! :p


TheMercenary  Thursday Sep 27 02:24 PM

Cool beans.



HungLikeJesus  Thursday Sep 27 02:30 PM

Quote:
Originally Posted by CharlieG View Post
They are not geosyc!
Geosycamore?


BigV  Thursday Sep 27 03:34 PM

neither are they geodesic.



Saphyre  Thursday Sep 27 04:19 PM

Orbits

GPS Satellites operate in a Mid-Earth Orbit, approximately 1/2 of the height of the satellites shown in UT's pic. This type of orbit allows for better GPS service near the polar regions of the Earth.

<-- doesn't play the "dumb" game



predatormc  Thursday Sep 27 05:28 PM

8.5 hours; the photographer must have steady hands.



glatt  Thursday Sep 27 05:53 PM

Undertoad, I didn't mention this before, but this IotD is a great one. Good job!

It has slowly grown on me over the last couple days. I was mulling over the possibility of taking a similar image myself. I wonder what sort of equipment you need? The link says it was taken at Kitt Peak, but not which instrument was used. I wonder if it was one of the big telescopes there, or just a camera on a tripod with a long exposure? The satellites are +10 to +14 magnitude in brightness, but I don't know exactly what that means in camera exposure speak. Eight hours is a long exposure.

Looking at the link again, it says the view spans about 10% of the arc. That's roughly like a 50mm lens. You should be able to reproduce this shot in your back yard with a 35 mm camera on a tripod! (assuming a clear night.)

Cool.



dar512  Thursday Sep 27 05:55 PM

Wouldn't you get too much light pollution there in Arlington?



glatt  Thursday Sep 27 05:58 PM

Yeah, way too much here. I can see the planets and the moon though.

But you know, when you travel to someplace nice and have a clear night, you can do this.



Your reply here?

The Cellar Image of the Day is just a section of a larger web community: a bunch of interesting folks talking about everything. Add your two cents to IotD by joining the Cellar.