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My Lunar program for Windows computes separation angles between any two
bodies. It won't draw a helpful diagram or suggest suitable stars, but
if you know the designations of the stars, it computes the data.

The star catalog contains the names of all 57 navigational stars and all
names standardized by the IAU that are within the magnitude limit. It's
a subset of the Hipparcos catalog re-reduction (van Leeuwen, 2007)
complete to magnitude 3.0.

Star data may also be input manually. For example, you can enter data
from the Gaia catalog.

A useful output is the position angle from each body to the other. This
aids quick acquisition, especially if the separation is large. For
example, if the position angle is zero, hold the sextant vertically in
the usual orientation. If position angle is 45°, rotate the sextant 45°
counterclockwise from vertical. (This may seem backward, but if you
think in terms of the celestial sphere viewed from the outside, it's the
same sense as azimuth, but with the zenith as "north.")

The program is free on request. This page has a hint on how to contact
me privately.

http://fer3.com/arc/m2.aspx/SofaJpl-page-down-Hirose-apr-2019-g44768

Example: 2019 April 12 03:00 UT1, 40N 100W, 2000 feet, temperature 35 F,
altimeter setting 29.9 inches, humidity 50%.

16°47.44' Spica unrefracted altitude
00°03.03' refraction
16°50.48' refracted altitude
121°17.81' azimuth

61°08.33' Regulus unrefracted altitude
00°00.51' refraction
61°08.85' refracted altitude
165°02.02' azimuth

54°03.84' separation, unrefracted
00°02.47' refraction
54°01.38' separation, refracted

336° position angle, Spica to Regulus. This is a comfortable angle.
Position angles on the other side of zero are not so convenient since
the sextant frame must be rotated counterclockwise from vertical, i.e.
handle up instead of handle down.

   

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