# Circumpolar Stars

1. Nov 16, 2007

### shaheen

If one is in the NH, then a circumpolar star must have a declination greater than 90 - observer's latitude.

But if one is in the SH, what is the corrected formula? do we just convert their latitude to -ve (e.g. 26 South becomes -26) and/or do we change the sign of the equation above....

if we were asked the question:

Q) If an observer's latitude is 26 degrees south, find the declination of stars that are circumpolar to this observer.

How would one solve such a question

2. Nov 16, 2007

### mgb_phys

Declination of the south pole is -90
so you could either take your southern latitide as -ve and use exactly the same equation

-90 - -26 = -64 or use positive values and flip the sign at the end, 90 - 26 = 64 => -64

3. Nov 16, 2007

### shaheen

so would that mean stars need to have a declination greater than/less than 64 degrees south.

i.e. would a star be circumpolar if its dec is -63 or -65?

4. Nov 16, 2007

### mgb_phys

Always confusing to talk about greater/less with negative numbers so lets say nearer -90, ie -65 is circumpolar