diff --git a/sql/s15/q13.sql b/sql/s15/q13.sql
new file mode 100644
index 0000000000000000000000000000000000000000..90ad0cbfd66ca2e2ffbd167ec37ea84946a8b68d
--- /dev/null
+++ b/sql/s15/q13.sql
@@ -0,0 +1,37 @@
+/*select count(*) from Object o1, Object o2 
+ where qserv_areaspec_box(90.299197, -66.468216, 98.762526, -56.412851) 
+   and scisql_angSep(o1.ra, o1.decl, o2.ra, o2.decl) < 0.015;
+
+From the black-box UDFs we cannot tell exactly how this traslates
+to plain SQL
+
+Is it this:
+select count(*) 
+  from Object o1
+      ,Object o2 
+ WHERE o1.ra BETWEEN 90.299197 AND 98.762526
+   AND o1.decl BETWEEN -66.468216 AND -56.412851
+   AND o1.decl BETWEEN o2.decl - 0.015 and o2.decl + 0.015
+   AND o1.ra BETWEEN o2.ra - alpha(o2.decl, 0.015) AND o2.ra + alpha(o2.decl, 0.015)
+;
+or the one below?
+*/
+
+select count(*) 
+  from Object o1
+      ,(select decl - 0.015 as decl_min
+              ,decl + 0.015 as decl_max
+              ,ra - alpha(decl, 0.015) as ra_min
+              ,ra + alpha(decl, 0.015) as ra_max
+         from Object
+        where ra BETWEEN 90.299197 AND 98.762526
+          and decl BETWEEN -66.468216 AND -56.412851
+       ) o2
+ WHERE o1.ra BETWEEN 90.299197 AND 98.762526
+   AND o1.decl BETWEEN -66.468216 AND -56.412851
+   AND o1.decl BETWEEN decl_min and decl_max
+   AND o1.ra BETWEEN ra_min AND ra_max
+;
+
+
+