products/SkyMapPro/samples/.

SkyMap Pro Sample 4

 

Comparison Between SkyMap Pro and the "Real" Sky

The "ultimate test" of any star charting program is how well it compares with the actual sky. To give an idea of this, we first of all present a photograph showing the area around the galaxies M65 and M66:

 

Photograph of the area of sky around M65 and M66

 

This picture is taken from the large collection of astronomical pictures supplied with SkyMap Pro. Here, for speed of loading, it's been considerably reduced in size from the supplied original.

Several things are obvious when looking at this photograph - it shows three galaxies, one pretty bright star, and a lot of fainter stars. Although we know that this picture shows the region of M65 and M66 there are lots of questions we might ask. Which galaxy is which (and what is the third one)? What's the "scale" of the picture? How is the picture oriented - ie which way is north? Just how bright is that bright star, and what is it? How faint is the faintest star shown?

A few minutes work with SkyMap Pro easily answers all these questions. First we search for "M65" (or M66) to go to the right general area of the sky, then we change the field of view so the two pictures look roughly the same "size", and finally we rotate the map to match the orientation of the image. The end result is a SkyMap Pro screen looking like this:

 

SkyMap Pro chart showing the area of M65 and M66

 

Compare this picture with the one above. Looking at the "star patterns" it's easy to see that SkyMap Pro shows almost every star in the original photograph. Moreover, we can now easily answer all our questions: the three galaxies are M65, M66, and NGC 3628. The scale line at the lower right of the picture immediately shows us the scale of the map (it's easy to estimate, for example, that M65 and M66 are roughly 20 arc minutes apart), and the compass rose at the upper left shows us the map orientation. Right clicking on the bright star quickly reveals it to be the star TYC 861-1162-1, or BD +14 2374 with a visual magnitude of 7.12 - an F8V star 156 light years away. The faintest star shown on the SkyMap Pro map is around mag 15; we can say that the photograph probably shows stars to around magnitude 15-16.