Frequently Asked Questions
Astronomy
1.1 What is that 6-digit HD number that appears when I click on a star?
1.2 What is the "vernal equinox" in the Solar System?
1.3 What is "mag: 1,25" in the detailed information of a star?
How to use AstroViewer
2.1 How do I read the sky map? What exactly does it display?
2.2 Why are East and West reversed on the sky map?
2.3 I'd like to set my location, but I don't find my city in the list. What can I do?
2.4 How can I find out the names of the displayed constellations?
2.5 How many stars does AstroViewer's database of contain?
2.6 Does AstroViewer take into account daylight savings time?
Installation and operation of AstroViewer
3.1 I have downloaded and installed AstroViewer. Why can't I set the time?
3.2 I have bought the license key. Where do I have to enter it?
3.3 I have downloaded and installed the AstroViewer software again, but my license key seems not to work. What's wrong?
3.4 Can I use the AstroViewer shareware also under Mac-OS or Linux?
Astronomy
1.1 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.
1.2 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.
1.3 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 with a magnitude of -1.46m. AstroViewer displays stars up to +5.0m, i.e. all stars visible with the naked eye.
How to use AstroViewer
2.1 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 center of the display is the direction you are facing. You can change the viewing direction with the sliders "Rotation" (at the bottom) and "Inclination" (at the right). Moreover, you can use the zoom slider (at the left) to enlarge the viewing section.
2.2 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.
Imagine you are lying on the ground in a starry night and you are looking vertically up to the sky. Your feet are pointing to the south. West is at your right then and east at your left hand side, exactly like it is displayed on the sky map.
2.3 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 a city in the city list, you can enter it yourself by clicking the button "Enter coordinates" in the dialog "Location / City". A new dialog pops up, where you can enter name and coordinates of the desired location.
2.4 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.
2.5 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 +5.0 mag. Sun, moon and the nine planets are shown as well.
2.6 Does AstroViewer take into account daylight savings time?
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 may be derived from the longitude, applying no daylight savings time. In this case the time is marked with a * symbol.
Installation and operation of AstroViewer
3.1 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 almost the full functionality free of charge online.
3.2 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 pressing <Ctrl>v.
3.3 I have downloaded and installed the AstroViewer software again, but my license key seems not to work. What's wrong?
If you have bought your license key before August 27, 2009, it is valid for the AstroViewer versions 2.10.x or 2.11.x. The current version is 3.1.2. For that version another license key is required, that can be obtained here.
The " old" AstroViewer versions 2.10.8 and 2.11.5 can still be downloaded (av2-10-8-setup.exe, av2-11-5-setup.exe). Your "old" license key will do with one of these versions.
3.4 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, download the jar file "av3-1-2.jar". Save it to a directory of your choice and execute it.
Please download the jar file and test it to make sure it runs on your Mac or Linux system, BEFORE you buy the license key.
