Aids For Finding Stars

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Most people will long ago have picked their favorite star finding aids, but in case there are a few coming to AHSP who are just starting out, here's a partial list.

The modern winner is the one that fits in your pocket and does not require a flashlight. The free App Stellarium can be put in red display night view mode to preserve eye dark adaption. But start with setting your display brightness and turning off your screen's auto-lock setting so that you won't have to look at a bright screen to wake up your device. Laminated foldouts will also fit in a (large) pocket. They're 4.5"x8.5" folded, opening to 4.5"x19.25".

Ranking of Star Wheels and Charts:

Get and use Stellarium first, both versions, and do some web browsing. Part of modern amateur astronomy is just appreciating the awesome photography and astrophysics from Hubble class telescopes and maybe also learning where in the heavens these pictures came from.

It takes a year of occasionally going out in the evening to watch the stars go by and maybe two years to build a solid memory for how the celestial sphere fits together. We assume here that you are located at a northern latitude as in the US. Then there are two regions of the celestial sphere to keep in mind - 1) the northern view which is circular and rotates around Polaris, and 2) the southern view which is essentially a cylinder. It's the celestial sphere less cones around the polar directions and extends from a little north of your zenith down to Scorpio and Sagittarius. The mental map you build of time progression is essentially an x-y plot of this cylinder as in the next link.

Foldouts display these two views as distinctly separate. Star wheels and planispheres blend the two views together making a little confusion about how to hold the device. It's instructive to eventually learn how to use these wheels with the periphery cut off to make them smaller. The outer half of a trimmed-off wheel is similar to the x-y plot of a foldout, both giving the time progression of constellations and stars during the year.

Black background is better than white for maintaining eye dark adaption. Plastic or well laminated is needed for withstanding dew. Big can show more detail with some deep-space objects. You can write in and erase your own with felt pen on white plastic but not on the black star wheels.

After Stellarium, start with a red flashlight and the smaller Sky & Telescope star wheel, a KenPress monthly sky chart or maybe the foldout of stars. If you are beginning to use a telescope, you'll need to put things down on the wet grass, so though it opens to large size, the foldout that fits in a hip pocket is convenient.

To trim the size of a star wheel or planisphere start by using pliers to crimp shrink the central ring rivet so that it comes out without tearing anything. Then use scissors to trim off the outer periphery of month-day indicators on the star wheel. Get the hang of it, and you can throw away the holder part that bounds what you can see on the star wheel. Just look at the starry sky. The horizon boundary of what you can see is already there, and your star wheel is smaller without the cover.

Initialization of Stellarium on Computers:

To set the default time use the "Configuration window," go to subwindow "Navigation" and set "System Date" to 10:30 pm. Then to save this setting you must also go back to the "Main" subwindow and click "Save settings."

To set the default location use the "Location window." A very long list of locations is displayed. One and only one of them can have the check box selected to be "Use current location as default." (Better wording would be "Use this location as default.") You can scroll through the list or do a text search to find the location nearest to you. Then check the box for "Use current location as default." Now closing the window saves your setting. This won't be exactly your location, but it's good enough, especially in suburbs where you can't see much near the horizon anyhow.

Representing the Celestial Sphere:

A star wheel for use at northern latitudes like the US is made by opening up and flattening the celestial sphere less a 40° cone in the southern direction that can not be seen. See you-make star wheel above.

A planisphere is formed similarly but by doing less flattening, twice. The northern celestial hemisphere plus 20° below the equator is flattened and put on the front side of the wheel. The southern celestial hemisphere plus 20° above the equator is flattened and put on the back side of the wheel. This reduces distortion at the price of the user having to get used to flipping the planisphere when viewing stars below the equator.

A monthly sky chart uses the least flattening - of just the half of the celestial sphere that is overhead at about 10:30 in the evening.

Simplest in principle is the Cartesian x-y display for a foldout. This leaves out two cones, around both the northern and southern directions, flattens the remaining part of the celestial sphere onto a cylinder and then displays that with latitude for the y axis and right ascension for the x axis. Unlike a star wheel, the foldout does not cover the part of the sky that you can't see at a particular time. This EZStars.info is a tutorial interactive version of the Cartesian display.

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