**HP Prime and Casio fx-9860GII/Prizm: Angular Distance Between Stars**

Given the right
ascension (α) and declination (δ) of two stars of the same epoch (J2000.0 is
the most current), the distance between the stars are:

d = acos( sin δ1
* sin δ2 + cos δ1 * cos δ2 * cos (α1 – α2) )

The distance is
usually given in decimal degrees.

Enter α in
terms of hours, minutes, seconds (standard notation) and δ in terms of degrees,
minutes, seconds (standard notation).

**HP Prime Program: ANGSTAR**

EXPORT ANGSTAR(α1,δ1,α2,δ2)

BEGIN

// 2017-06-08 EWS

// Angular Angle

// Degrees

HAngle:=1;

LOCAL d;

α1:=15*α1;

α2:=15*α2;

d:=ACOS(SIN(δ1)*SIN(δ2)+

COS(δ1)*COS(δ2)*COS(α1-α2));

RETURN →HMS(d);

END;

**Casio fx-9860GII/Prizm Program: ANGSTAR**

Deg

“RA 1: “?→A

“DEC1: “?→B

15A→A

“RA 2: “?→C

“DEC2: “?→D

15C→C

cos¯¹ (sin B * sin D
+ cos B * cos D * cos (A-C))→E

E>DMS

**Example**

Distance between
Regulus (A) in Leo and Sadalmelik in Aquarius:

(data via
Wikipedia)

Regulus: α = 10h8m23.11s, δ = +11°58’01.95”

Sadamelik: α = 22h5m47.03593s, δ = -0°19’11.4568”

Distance: 168°20’05.1793”

Source:

Meeus, Jean.

__Astronomical Algorithms__William-Bell, Inc. Richmond, VA 1991. ISBN 0-943396-35-2
Please stay
safe, happy, and sane. Happy computing,

Eddie

I hope to have
the new Casio Prizm FX-CG50 soon for review as I ordered one last Friday.

This blog is
property of Edward Shore, 2017.

For the HP, The line:

ReplyDeleted:=ACOS(SIN(δ1)*SIN(δ2)+

COS(δ1)*COS(δ2)*COS(α1-α2));

must be entered as one line:

d:=ACOS(SIN(δ1)*SIN(δ2)+COS(δ1)*COS(δ2)*COS(α1-α2));

To cut and paste your code from this page into the HP Connectivity kit, gives one the displayed text (with a line break).

Otherwise this code works. Stil trying to use from RPN.