Frequently Asked Questions
How do I read the sky map? What exactly does it display?
The sky map represents the entire visible celestial sphere. Zenith, i.e. the point directly overhead, is in the center of the map. The perimeter is the horizon. The point on the horizon right in front of you corresponds to the bottom of the display. So the lower half of the map represents the part of the sky you are facing.
Why are East and West reversed on the sky map?
Compared to a street map, on which we look down, on the sky map East and West seem "reversed", because the sky map shows what we see looking up to the sky.
I'd like to set my location, but I don't find my city in the list. What can I do?
To find your way in the night sky you don't need to set your location too precisely. Just choose the nearest city from the list or set your location on the world map (button "Location / City").
If you are missing an important city in the city list, please drop a hint on the Contact page.
How can I find out the names of the displayed constellations?
Activate "constellation names" in the control field "Auxiliary lines". The names of the bigger constellations are displayed. While zooming in, the names of smaller constellations appear also.
Alternative way: Activate "constellation pointer" in the control field "Auxiliary lines". Name and outlines of the constellation you move the mouse pointer into will turn green.
How many stars does AstroViewer's database of contain?
The star catalog of AstroViewer contains the 1,423 brightest fixed stars and Messier objects up to a magnitude of 5 mag. Sun, moon and the nine planets are shown as well.
What is that 6-digit HD number that appears when I click on a star?
The HD number is the reference number of that star in the "Henry-Draper-Catalog". This star catalog was published in 1918-24 and contains 225,300 stars up to a magnitude of 8 mag.
What is the "vernal equinox" in the Solar System?
The "vernal equinox" is a point in the constellation Fish where the celestial equator crosses the ecliptic and where the Sun is located on March 21 (the first day of spring in the northern hemisphere).
You can proof this definition in AstroViewer's solar system map when you set the date to March 21. At that date, the Sun is in the direction of the vernal equinox, seen from the Earth. Then switch to the sky map and activate the celestial equator and the ecliptic. You will find the Sun at the point where both lines cross each other in the constellation Fish.
The vernal equinox is generally accepted reference point for astronomical coordinates.
What is "mag: 1,25" in the detailed information of a star?
"mag: 1,25" is the "magnitude" or apparent brightness of a celestial body. Stars with a smaller (even negative) magnitude are the brighter ones. Sirius is the brightest star having -1,46m. AstroViewer displays stars up to +5,0m, i.e. all stars visible with the naked eye.
Does AstroViewer take into account daylight savings time?
Yes and no.
If you have selected a location from the city list, daylight savings time is considered when displaying local time, if applicable.
If you have chosen a location from the world map, the local time is derived from the longitude and no daylight savings time is assumed.
I have downloaded and installed AstroViewer. Why can't I set the time?
AstroViewer is shareware. The test version is restricted to the time range 1950 till 1959 (details...).
To enable the full time range a license key is needed. (How to obtain the license key...)
Anyway, you can use AstroViewer Online with the full functionality free of charge online.
The description looks nice, but where do I find the AstroViewer applet?
AstroViewer (a so-called JavaTM applet) should appear on the page "Interactive night sky map" at the upper left side. It is a grey area with a button saying "Start AstroViewer". Depending on the speed of your internet connection, it might take up to about a minute until it is loaded, as it is appr. 397 KBytes big.
Make sure that JavaTM is enabled in your browser.
If you are accessing this website from behind a firewall (e.g. from a corporate network), its setup may block JavaTM applets. Change the firewall setup or use another computer to access the internet (e.g. your home PC).
The status line of your browser (has to be enabled eventually) may also give you a hint why the applet does not work on your computer.
I have bought the license key. Where do I have to enter it?
When you have installed the AstroViewer test version and then start the program, an input field for the license key will pop up.
The best way to enter the key is to copy it from the e-mail that brought it to you into the clipboard (mark it and press <Crtl>c) and then insert it in the input field by clicking the button "Insert from clipboard".
Can I use the AstroViewer shareware also under Mac-OS or Linux?
Yes, you can, ...
... but unfortunately, I haven't tested it. On the other hand, there are many users who have, and they have told me that it works. So, if you would like to run the AstroViewer shareware under Mac-OS or Linux, please tell me by using the contact form. I will provide you with a special version of the AstroViewer shareware and installation instructions then.
I click on "Print version" in AstroViewer Online, but nothing happens. What can I do?
The print version of the sky map will be displayed in a new browser window. If you are using a popup blocker, it might prevent that window from being opened. Deactivate the popup blocker, maybe selectively for the AstroViewer website.
