Here’s a Sky Safari screenshot of the region around the not-yet-visible-to-the-unaided-eye T CrB (aka The Blaze Star, bottom right):
at 10:34pm Adelaide (ACST) time on Sunday June 16. To disambiguate, Alphecca is the bright star (magnitude 2.2) to the lower left of that name, as is the case for Arcturus and Izar (which each appear in a less crowded part of the field).
Here’s a cropped iPhone picture of that region at the same time, above the roof of my house, showing Arcturus, Izar, Alphecca and the location where the Blaze Star (T CrB) will appear, as bright as Alphecca:
I showed an AAVSO finder chart in a previous post. This is the one I’m using for comparison stars down to magnitude 8, with T CrB in the cross-hairs at centre, and getting very familiar with through 7×50 binoculars from my backyard:
Here, Alphecca is the star marked “22” (magnitude 2.2) to the left of the cross-hairs, with Arcturus and Izar out of the field to the left. The 37 and 28 comparison stars are also visible in my iPhone image at right near the centre line.
I was having a conversation recently in which someone made the claim that “star hopping” (visually hopping between stars, with a star chart as your guide, to find a target object) is dead in the age of computerised telescopes. With visual variable star observing using binoculars, this is not the case. You have to get to know the field for every new variable star you want to estimate the brightness of. With DSLR photometry, before I added plate solving to my partially manual processing method, that remained true. Even now, especially when using a simple tripod, I still need to locate the right field.
In my suburban sky, at the low altitude of CrB, with 7×50 binoculars, I can see down to magnitude 7.1, so the reference (comparison) star just to the upper right of the cross-hairs.
In any case, if you want to be prepared for the T CrB eruption, get to know the field and the reference stars you can use to assist in an estimation.
