NGC 7788, NGC 7790 & Berkeley 58 -- Open Clusters in Cassiopeia
Three Open Clusters in a Row
Yesterday evening the sky was crystal clear. The weather forecast indicated that clouds
would be moving overhead in 2 or 3 hours. For a couple of hours, after sunset, the sky was
as good as it gets over my house. When testing the 155mm refractor to see if it had
adjusted to the outside temperature, I pointed it to the Orion Nebula Trapezium. To my
surprise the 4+2 stars snapped into view with ease, indicating a fine sky for observing.
With limited time before the predicted clouds were to move in, I moved the telescope to
Cassiopeia to see if the tight Open Cluster threesome of NGC 7788, NGC 7790 and
Berkeley 58 were good enough to draw. These are small (4.0, 5.0 and 8.0 arcminutes
respectively) and reasonably dim (magnification 9.4, 8.5 and 9.7 respectively). Not easy
visual targets under suburban skies in a 6” telescope and objects that I had more than once
failed to get good views of from my backyard deck.
They did not disappoint. I used a low power eyepiece to place all three clusters in the
same eyepiece and a moderate-power eyepiece to tease out the dimmer stars in each of
the clusters (especially Berkeley 58).
The clouds were kind enough to stay a bay until I finished the drawing. Once done, I still had
time to observe for an extra hour before the sky became milky with high moving clouds
coming in from the west. Good skies are not common where I live. They may manifest
themselves for only short periods in-between long periods of clouds. One must always be
on the lookout.