From 886aaeb489ccd61c707d2a5ac6660e5170d00503 Mon Sep 17 00:00:00 2001
From: rongmon <rongmon.bordoloi@gmail.com>
Date: Mon, 14 Feb 2022 12:38:03 -0500
Subject: [PATCH] Added cone search functionality

---
 catalog/rb_search.py | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 catalog/rb_search.py

diff --git a/catalog/rb_search.py b/catalog/rb_search.py
new file mode 100644
index 0000000..5b92e97
--- /dev/null
+++ b/catalog/rb_search.py
@@ -0,0 +1,36 @@
+import numpy as np
+def cone_search(ra_center,dec_center,ra_list,dec_list,angular_scale):
+    #--------------------------------------------------------
+    #  Function to do a cone search around any (ra,dec) pointing with respect
+    #  to a list of ra,dec entries.
+    #
+    #   Input:-   ra_center     = RA of center (Degrees)
+    #             dec_center    = DEC of center (Degrees) 
+    #             ra_list       = RA list of input catalogue (Degrees)
+    #             dec_list      = DEC list of input catalogue (Degrees) 
+    #             angular_scale = angular search radius in arcsec
+    #             
+    #
+    #   Output:-  out:- struture containing RA,DEC and logical operator
+    #               identifying the objects
+    #
+    #    Written by R.B.  Mar 11 2013
+    #---------------------------------------------------------
+
+    deg2rad=np.pi/180
+    rad2deg=180./np.pi
+
+    ra_center=deg2rad*np.array(ra_center)
+    dec_center=deg2rad*np.array(dec_center)
+    ra_list=deg2rad*np.array(ra_list)
+    dec_list=deg2rad*np.array(dec_list)
+
+    theta =np.arccos(np.sin(dec_center)*np.sin(dec_list) + np.cos(dec_center)*np.cos(dec_list)*np.cos(ra_center-ra_list))
+ 
+    sq= np.where(theta*rad2deg*3600<=angular_scale)
+    
+    if sq[0].size>0:
+        outstr={'ra':ra_list[sq],'dec':dec_list[sq],'index':sq,'angle':theta[sq]*rad2deg*3600}
+    else:
+        outstr={'ra':-99,'dec':-99,'index':sq,'angle':-99}
+    return outstr