salutations celestial sight seers i'm david fuller from eyes on the sky. ngc 869 and 884 are more
commonly known as simply the double cluster. so well known as this object in the northern
hemisphere that if one mentions the ngc numbers most amateur astronomers will ask which ones are
those? and what a double cluster it is! while between the two there are some 700 to 800 stars
these collections of suns contain some 6,500 solar masses meaning most stars here are a
lot more massive and hotter than our sun. and yet they are babies! just 12.8 million years old each
which is less than one percent the age of our Sun. and that's both too! so yes
they're twins! okay maybe fraternal twins, but twins nonetheless. let's learn how to find them.
to find the double cluster in the constellation of perseus first look for cassiopeia in the northern
sky. if you're not sure where to look for it check out my shapes in the sky cassiopeia video for how
to find it. a link to that is in the description of this video. start at the center of the W or M
at navi and then move to the dimmer point star here delta cassiopeiae. as you can see the double
cluster is on a perfectly straight line here but it is just beyond seven degrees. so we'll
discuss how to get there in a magnified finder scope and red dot finder next.
now no matter what kind of finder you're using this method works for both the
magnified and non-magnified finder types. following the navi to delta line of stars
from cassiopeia look 15 degrees beyond delta. that gets you to third magnitude gamma persei.
now don't mistake it for the second magnitude mirfak which is brighter.
that's a bit further out. now the problem with the double cluster is that it is just outside
of the magnified field of view from delta in one direction and gamma persei in the other direction
because that total distance between them is 15 degrees and half of that is 7.5 degrees
which is a little more than most finderscopes that are at only 7. so do this instead: aim your
finderscope exactly halfway between gamma persei and delta cassiopeiae and that halfway point
is where the double cluster is located! red dot finder observers can do that too. plus it's
large and fairly bright so it may even be visible in most finder scopes. visually sometimes i start
from cassiopeia using the navi to delta line placing delta just at the edge of my finder scope
and then trusting that a small movement along that line will put the double cluster into my
view. it might take you a few tries but you will know when you found it!
the double cluster is quite large visually. for short focal ratio telescopes of f4 or f5
it may be possible to place both clusters in the same field with many of the less expensive
low magnification eyepiece options. but often both clusters completely fill the field of view.
while certainly okay to look at them this way try centering one cluster and observing it first
then re-aim the telescope at the other cluster and observe it next. this is one of the finest
objects in the entire night sky so be sure to share this one with family and friends if you
get the opportunity. and if you like this video and it helped you find this object successfully
check out the other 39 telescopes on the sky objects. i'll lead you step by step to the best
and easiest objects to find from the northern hemisphere. and don't forget to subscribe to
this channel by clicking on the subscribe button just below this video to the right on youtube.
i make regular updates on how to find all kinds of interesting objects in the sky
naked eye with binoculars telescopes and occasional reviews too and have
since 2010. thanks for watching i'm david fuller wishing you clear and dark skies.