Haversine Calculator: Angular Separation Between 2 Stars
RA1:   h   m   s		RA2:   h   m   s		RAd1: 00.000   RAd2: 00.000
DE1: °   '   "		DE2: °   '   "		DEd1: 00.000   DEd2: 00.000
∠ Separation (dd):		∠ Separation (° ' "):
Sirius Canopus Rigel Kent Arcturus Vega Capella Rigel Procyon Betelgeuse Achernar Hadar Altair Acrux Aldebaran Spica Antares Pollux Formalhaut Deneb Mimosa Regulus Adhara Castor Gacrux Shaula Bellatrix Alnath Miaplacides Alnilam Alnair	Alnitak γ Vel Alioth Mirphak Kaus Australis Dubhe Wezen Alkaid Avior θ Sco Menkalinan Atria δ Vel Alhena Peacock Polaris Mirzam Alphard Algieba Hamal Deneb Kaitos Nunki β Gru Menkent Kochab Alpheratz Mirach Saiph Rasalhague Algol	Almaak Denebola γ Cas γ Cen ζ Pup Aspidiske Alphekka λ Vel Sadr Mizar Etamin Schedir Mintaka Caph ε Sco α Lup; ε Cen δ Sco η Cen Merak Izar Enif κ Sco Ankaa Phad Sabik Scheat Alderamin Aludra κ Vel	ε Cyg Merkab Menkar ζ Cen ζ Oph Graffias Zosma Arneb Gienah Ascella Zuben Elschemali θ Aur Phaet Sharatan Unukalhai β Lup η Boo μ Vel ν Sco π Pup Kaus Meridionalis Ruchbah Tarazed Zuben Elgenubi β Her Kaus Borealis β Ara τ Pup	Star1: Betelgeuse   Star2: Sirius

Above is a list of the 118 visually brightest stars down to mag ~ 2.9 with the brightest at top left to faintest at lower right. This range of stars covers a visual span of 4.4 magnitudes (or equivalently a brightness difference of approximately 55x). The clickable images at right display plots of the distances for the first 96 of these brightest stars. (There are of course many stars within the vertical distance range of 3300 l.y. but these are fainter than the 2.9 magnitude faintest star on this short list of 118. On a given clear night, ~ 3000 stars are visible to the naked eye at any given time which are magnitude 6 or brighter. The list of 118 stars here is only 4% of the visible stars.).

Select a star from the list (click any radio button) and click Load St1.
Select a 2nd star from the list and click Load St2.
The RA and DEC fields at top should show the loaded values for the 2 stars.
Finally, click the red Sep ∠ button. This calculates the decimal degrees values for both stars (shown at upper right) and then calculates the angular separation using the Haversine expression which is displayed in the 3rd row.
Alternatively, enter the RA and DEC values manually in the top 2 rows in which case the star names indicated are irrelevant. Manually entered RA and DEC data supports full resolution: hr  mins  sec  for RA and °   '  ''  for DEC.
The check box at left of data entry for DEC is to indicate south (-) declination.
Defaults button loads the default values: St1 Betelgeuse and St2 Sirius.
After an angular separation result is calculated, it can be added to the History list at right.
Clear button at top clears all fields and values.
2 Star Info displays info for the 2 stars after the angle separation is calculated.
1 Star Info displays info for any currently selected star in the 118 star list.
The Clear button at bottom of History window clears both the cumulative displayed history and any star info displayed at the bottom. It does not clear the 2 selected stars nor the calculated angle separation.

Stars by Magnitude
Stars by Common Name
Stars by Bayer Name
Stars by Distance

The list of stars here is essentially the list of brightest stars down to mag ~ 2.9 as shown in The Edmund Mag 5 Star Atlas (4th printing 1977) with star positions for 1970.
The positions are updated to 2000 positions following the data from these sources:
The Cambridge Star Atlas, Wil Tirion, 4th Edn 2011 12th printing 2022, Cambridge University Press.
A Field Guide to the Stars and Planets, Jay M. Pasachoff, Peterson Field Guide, 45th Edn 2012