Calculating angular separation?

Where can I find the formula for calculating the angular separation
between two objects when given their respective R.A./dec?
--

Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
KG6RCR

"Mike Rocket J. Squirrel Elliott" m wrote in
message ...
Where can I find the formula for calculating the angular separation
between two objects when given their respective R.A./dec?


cos(d) = sin(d1)*sin(d2) + cos(d1)*cos(d2)*cos(a1-a2)

d is the angular separation
d1,d2 are the declinations
a1,a2 are the right ascentions

If the angular separation is close to 0 or 180 degrees,
the above formula is not great because cos(d) will be
very close to 1 and the cos function changes slowly near
those values. In such cases, use the approximation:

d = sqrt( ((a1-a2)*cos((d1+d2)/2))^2 + (d1-d2)^2 )

The above is from Meeus' "Astronomical Algorithms".

On 2/24/2006 7:53 AM Greg Neill wrote:

"Mike Rocket J. Squirrel Elliott" m wrote in
message ...
Where can I find the formula for calculating the angular separation
between two objects when given their respective R.A./dec?


cos(d) = sin(d1)*sin(d2) + cos(d1)*cos(d2)*cos(a1-a2)

d is the angular separation
d1,d2 are the declinations
a1,a2 are the right ascentions

If the angular separation is close to 0 or 180 degrees,
the above formula is not great because cos(d) will be
very close to 1 and the cos function changes slowly near
those values. In such cases, use the approximation:

d = sqrt( ((a1-a2)*cos((d1+d2)/2))^2 + (d1-d2)^2 )

The above is from Meeus' "Astronomical Algorithms".


Thank you!

--

Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
KG6RCR

Greg,

Is there a good Usenet newsgroup for astronomy?

--

Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
KG6RCR

On 2/24/2006 7:53 AM Greg Neill wrote:

"Mike Rocket J. Squirrel Elliott" m wrote in
message ...
Where can I find the formula for calculating the angular separation
between two objects when given their respective R.A./dec?


cos(d) = sin(d1)*sin(d2) + cos(d1)*cos(d2)*cos(a1-a2)

d is the angular separation
d1,d2 are the declinations
a1,a2 are the right ascentions

If the angular separation is close to 0 or 180 degrees,
the above formula is not great because cos(d) will be
very close to 1 and the cos function changes slowly near
those values. In such cases, use the approximation:

d = sqrt( ((a1-a2)*cos((d1+d2)/2))^2 + (d1-d2)^2 )

The above is from Meeus' "Astronomical Algorithms".

"Mike Rocket J. Squirrel Elliott" m wrote in
message .. .
Greg,

Is there a good Usenet newsgroup for astronomy?

Unfortunately, all the science newsgroups tend to
be infiltrated by crackpots and juveniles with
education envy. Sci.astro.amateur seems to have
a better signal to noise ratio than sci.astro or
alt.astronomy.

My strategy is to employ aggressive filtering
techniques that kill the unwanted crap before
I can look at it. It's not unusual for all but
two or three posts to make it through out of
a couple of hundred!

Greg Neill wrote:

snip

Unfortunately, all the science newsgroups tend to
be infiltrated by crackpots and juveniles with
education envy. Sci.astro.amateur seems to have
a better signal to noise ratio than sci.astro or
alt.astronomy.

Also much higher volume than either; if you're mainly interested in
cosmology or astronomical theory, lengthy discussions of the relative
merits of various makes or designs of telescopes & accessories, or of
the repute of one or another equipment vendor, can seem like noise
despite being perfectly topical there.

My strategy is to employ aggressive filtering
techniques that kill the unwanted crap before
I can look at it. It's not unusual for all but
two or three posts to make it through out of
a couple of hundred!

Yes; even this quite badly infested group is pretty tolerable once
the most prolific of the kooks and kook-baiters have been entered in
kill-filters, and the obviously off-topic threads ignored. OTOH a few
of the old regulars have apparently been driven away by the
comparatively recent spate of cross-posted drivel.

--
Odysseus