In this 2010 AAVSO article about alf Ori we have:
When observing for the AAVSO, please use magnitude 0.5 for Procyon (alpha CMi) and a magnitude of 1.1 for Aldebaran (alpha Tauri). An AAVSO a-scale chart is also available.
Is this still a valid statement?
For example, the magnitude value for Aldebaran in the Southern Gems alf Ori chart is shown as 0.9.
mV 0.5 for Procyon and 1.1 for Aldebaran are consistent with 054907 (a) chart I still use for Alp Ori but Mu Gem, Eta Gem and Zeta Gem too running naked eye estimations. It dates back to June 9, 1953, but it works. Aldebaran is a slight variable star too, then a suitable alternate is Pollux at 1.2 , especially when Orion is rising and Betelgeuse, Alhena and Pollux share roughly the same elevation. Next one comparisons are Castor at 1.6 and Gam Ori - Bellatrix at 1.7. Unfortunately they're white and light, light blue, but they're bright enough to compensate color difference.
If you want go deeper, for example working with a 18 mm wide field lens and a DSLR, here you can find two decimal digit for Betelgeuse comparisons. They're from SIMBAD database, Visual V band. But of course, AAVSO can support you better than me about selecting DSLR sequences.
Rigel 0.17 - 0.22 (0.18) ; Procyon 0.37; Aldebaran 0.75 - 0.95 (0.86); Pollux 1.14; Castor 1.58; Bellatrix 1.64; Alnitak 1.79; Alhena 1.92
The mean V mag. of Rigel is 0.12.
Procyon 0.36, Aldebaran is almost constant at 0.87. Pollux has V= 1.14, Castor 1.58 and Bellatrix 1.64, but beware of the colour differences. The last two are white and blue respectively.
The best source of magnitudes for bright stars is the GCPD.
Happy New Year everyone!
I revisited the 2010 VSOTS article and updated the magnitudes of Procyon and Aldebaran to 0.4 V and 0.9 V, respectively. I also added the link to the chart provided in the AAVSO's 10-Star Tutorial, which I think is the most practical chart for observing Betelgeuse, as it shows Orion, comp stars, and nearby constellations.
What about PEP comparison charts? I tried to create one using VSP but failed? Could you please point me to a good one?
Wishing clear skies for 2020,
AAVSO Alert Notice 690 requests photometry and spectroscopy of alpha Ori (alf Ori, Betelgeuse) during and beyond its current minimum. Please see the notice for details and observing instructions.
Many thanks, and Good observing,
Elizabeth O. Waagen, AAVSO HQ
I would perhaps belatedly point out to my fellow observers that, following a lifetime of coupious variable star observing by eye, I've found that CCD V is by no means truly equal to Visual v ; that with only the exception of Aldebaran none of our comp stars for Betelgeuse are even remotely of a similar color to it and thus not truly comparable to it; that differential extinction can play a significant roll in any determinations, as well as the orientation of the comp. stars relative to Betelgeuse. Also, with many of us observing from urban areas these days I would add that with the potential of the comp. stars being situated quite remotely from Betelgeuse, the brightness of the background sky at different points on the compass could likewise play into the accuracy of our estimates if the background of Betelgeuse and the comp star(s) differ. Thus, considerable care is going to be needed for a good visual determination of Betelgeuse's brightness, not just a quick upward glance at the star and its comps.