[Andrew C]

Hello All,

Some time back, I attended an astronomy presentation session locally at which the presenter illustrated his talk with a set of four star maps that he had developed himself showing the easily visible stars and constellations for that month and approximate time in the evening in the four cardinal directions (N,S,E,W), from the horizon up to about 60 degrees altitude – i.e. ALT AZ star charts. He had sketched the positions on the maps by eye, and had included just the right amount of detail. Each person was given copies.

This approach worked well with the audience (an average bunch of interested but non-experienced locals), who would have struggled to use a planisphere because of the inevitable associated distortions and the clutter (or lack) of detail that always seems to be a feature of those charts.

I decided to see what I could find on the web to do a similar thing in software, and was unable to locate anything that came close to being readily usable, so I decided to develop my own.

The result is shown by way of example in the attached set of Excel spreadsheets and XY scatter charts, which are configured for my home location (Alice Springs) for 9.30pm local time at mid January. As I have an interest in video astronomy, I have included objects that suit that as well as eyepiece observation.

I have one set for each month (which effectively gives object positions to the nearest hour throughout the year - which is ample for bright objects visible by eye), and apart from tweaking the position of fast moving planets (or omitting them), or adding new objects, these are good from year to year. Name labels for individual objects are generated from the spreadsheet using a freeware add-on for Excel called XYChartLabeler after each chart is generated and scaled in the Excel XY scatter chart function. Icons, lines and other information labels are added manually to suit personal taste, and all labels are repositioned or resized within the chart as necessary to improve readability.

Distortion of shapes and distances is largely confined to the higher altitudes (much like high latitude shapes and areas on typical maps that attempt to project most of the world on one map), and I have reduced the effect of that by copying some shapes from low altitude to high altitude in a few cases.

Without going into detail at this stage (I can do that later if people are interested to modify to suit their own needs), the charts work well, and can be customised for any location, time of day or set of objects. The spreadsheets could also be adapted for charting much smaller parts of the sky at an appropriately larger scale. In the example, I have included the underlying formulas for all the months, but derived the charts only for January. They make deciding what is worth looking at on a given night, and actually finding it, and conveying some sense of what is in the night sky to others, a whole lot easier.

Cheers,

Andrew