Do starcharts need updating sometimes?

Question

Do starcharts,planitariums,moonmaps that sort of thing need updating sometimes or do they never really change so i dont have to buy new ones?

Answer 1

Every star in the sky has what is called 'proper motion'. This is the apparent movement of that star across the sky in relation to other stars. Each star's movement is different. Every star chart has a date called the epoch that it is correct for. 1950 and 2000 are popular epochs for star charts.

The good news is that the proper motion for most stars is very, very small for time periods of a few dozen years. So for most purposes, using a 1950 starchart in 2007 won't cause any major problems.

The biggest problem with an old star chart will be in predicting planetary positions. Star charts usually have a table of planet positions that only covers a limited time period. So an old chart might not help you to find where the planets are today.

Planitarium software for your computer doesn't have any of these problems. It knows about the proper motions of all the stars and automatically shows the right position for any epoch you'd like to display.

Answer 2

In general, NO.

Star charts do not show "all" the stars. So, as new ones are discovered and nuimbered, time marches on. The general star charts you see published in the magazines and books are good for at least 25 years or more. Stars, as a rule, are there for the long term. Our star, the Sun, has been where it is, for example, for at least 4 1/2 Billion Years.

Now, that is not to say stars are not moving steadily. They are all moving. However, in relation to a dot on a piece of paper, they have not moved enough for someone to notice in 25 years. The scale of reality to an 8 1/2 x 11 Inch page is so huge that one light years distance would not matter at differences such as 60 or 100 light years.

Going back 500 years or so, there would be significant differences. But there would not be significant differences every year or so.

Answer 3

Hi super -

Well, the stars, galaxies, clusters themselves usually don't move enough in a lifetime to justify updates. But I generally get updates online to see where the planets are , to check moon phases etc. This comes in very handy for planetary observing, or just to identify that weird thing that showed up in Leo where it doesn't belong. Here's a good site that has good charts that can be downloaded daily using Cartes du Ciel software (not terribly user friendly, but very versatile - and it's free)!

http://www.stargazing.net/astropc/

Answer 4

The Earth's exact orientation in space is constantly changing (precession of the equinoxes) so the coordinate system used to define star positions also changes. For really precise purposes, the coordiates need to be calculated for the current "epoch" (2007.7 or so), but normally star atlases are updated every 50 years. For example, current atlases ae all for epoch 2000.0, but when I started in amateur astronomy in 1957, they were all epoch 1950.0. In addition, the stars themselves are moving slightly. The Sun, Moon and planets move more quickly, and must be calculated for the present date. New asteroids and comets are discovered, stars go nova, all of this needs to be updated. My software program Starry Night automatically downloads updated data files every 24 hours.

Answer 5

yes.

way back when dinosaurs roamed the earth, and I was doing some work in an observatory, we had to make charts of the area of the sky (usually a very small square of sky) which included all the 'proper motions' for the stars in the telescopes view.

that meant we had to update every chart every time we observed.

Answer 6

They might do them on new media (like DVDs) but the data remains good for millennia. Unless some planets or stars collide their paths are unchanged.

Researchers who are always checking about the star of Bethlehem usually look though the history of the star charts for that era to try to find which of the modern stars correlate with that event.

Answer 7

When I work for NASA the star chart originated in the 1800. They changed very little in man's time.