Sometimes we get questions about the accuracy of our star charts. Most of our customers are not astronomers by profession, so it might be hard to verify if the constellations of a custom-made star map really represent the sky above you at the moment you selected.
Below, there is a detailed explanation of a real-life example, but you will also be happy to know that our star maps are indeed verified audited, you can read more here: Astronomically Verified Star Maps
Lengthy, practical example:
It might seem like the stars do not change as you change the time or location. In order to explain why, we think it’s best if we give you a practical example:
We created 2 maps, one from Winnipeg, the other from Yellowknife (about 1600 miles from W), for the exact same time.
Then we compared them with an image comparing software, here are the differences and the originals below:
As you can see, there are differences between the images, but these are not very significant. The explanation simply put is that while Winnipeg and Yellowknife are relatively far from each other on the map, on a global scale they are pretty close and so they both look up to a very similar sky. Here's a picture of both locations on the globe to get an idea:
This is called parallax. You can observe it when driving in the night and look at the moon - it seems to move with you. It's because it's far from Earth and so distances on Earth don't make a big difference in the perceived location on the sky. The same thing happens with the stars, except that the closest star to us (that is not the Sun), Proxima Centauri is approximately 104,430,223 (~hundred million) times farther from us than the Moon. Here's a demonstration (naturally not-to-scale):
So are all star maps the same?
No. Even with huge stellar distances like this, there are differences between the maps as you have seen in the picture above because you see a slightly different portion of the sky. Real big differences occur in time or between the Southern and Northern hemisphere, simply because of how to Earth moves and where it's located in the galaxy.
For example, here are two maps, both from Winnipeg, same day, different hour - 12pm and 12am:
If you look at the individual images you'll see that they look quite different.
Here's another example, same day and time but one is from Winnipeg, the other one is from Buenos Aires:
It gets even more exciting when the difference is not only North-South but also West-East (e.g. Canada vs New Zealand).
As you can see, there are vast differences in how maps look in different times and places. Winnipeg and Yellowknife in the exact same time just don't do justice for our algorithms.
We encourage you to check it yourself by generating a map on our website from the location where you are and the current time, and then look at the stars in the sky and see if they are the same. Obviously, this is a bit easier to do in the night, but if you do it, we would love to hear from you as we are sure it would be quite special. ⭐️