Guide to R Scuti

R Scuti, located a degree north west of the Wild Duck cluster (Messier 11), is a variable star that can be relied on to produce a good amount of brightness changes, although attempts to predict the timing and depth of the next minimum often fail!

r sct

As can be seen from the above light curve, the amplitude observed changes from year to year.

It is usually described as showing alternate deep and shallow minima, but sometimes decides to do something different!  In 2014, for example, it produced consecutive deep minima.

R Scuti is a yellow-orange supergiant star. The brightness changes are due to pulsations in the star’s outer layers. The depth of the deep minima seems to vary from year to year – in some years they drop below mag 8.0 ; in others they don’t even reach mag 7.0. There may even by a long term periodicity (about 30 years?) regarding this.

Extreme brightness range 4.5- 8.6
More typical range 5.0 – 7.5
Period of variation 142 days (often including one deep and one shallow minimum)
Frequency of observation Worth checking a couple of times per week – possibly every other day during deep minima
Observe using 40mm or 50mm binoculars will suffice for most of the time, but 50-80mm binoculars may be required during the deeper minima
Visibility Can be observed from mid January to mid December, but is rather low in the morning sky until April

Here are two finder chart that show the location of R Scuti. Both have north at the top.

The first shows its general location (Altair is a good starting point when using binoculars to locate R Scuti).

Wide field finder chart for R Scuti

You can follow the brightness changes of R Scuti by comparing it with the lettered comparison stars on this second chart (which is approx 7 degrees by 4 degrees). At maximum, R Scuti will be easily the brightest of the stars in the small trapezium that also contains stars F, G and H. In deeper minima it can become fainter than comparison K.

Binocular chart for R Scuti