Expert: Tom Whiting - 11/7/2005

Question
Can you suggest a HS science project using a 5" Celestron telescope and/or a Nikon 35MM film camera?  Two years ago I demonstrated the relationship between declination and star trail length by photographing Orion (leaving the shutter open).  It was simple, but very enjoyable. I learned a little bit about photography and got to use some trigonometry.

Answer
Hi Michael,
Yes, just repeat the same experiment (assuming it's not
the same teacher) that you did two years ago!  (Just kidding
of course...)

Ok, you may not like this one...I don't do photography through a scope, but you seem to like to...so try this one on as purely my suggestion:

Dawe's limit states that the theoretical maximum resolution
of splitting a double star with a telescope is given by  R  =  4.56/diameter of mirror in inches.  (It was your 5 inch mirror that gave me this idea...very close to that 4.56 constant value in Dawe's equation above.)  For almost exactly 1.0
arc-second resolution - separation.

So with your 5 inch scope, your maximum theoretical
resolution with a 5 inch scope, would be splitting a close double star down to......4.56 divided by 5,  or 0.91 seconds of arc.
But let's not split hairs (no pun intended)....let's just
say your maximum resolution of excellent optics of a
5 inch telescope should be close to, or just under, one arc- second....
so go out and PROVE Dawe's Limit works for your scope!......
Go outside at night and photograph ever closer and closer double stars, down to one arc-second separation, with your camera attached to the scope.   Exposures should be very brief....several seconds at most, as there are a lot of double stars that are easy naked-eye stars, in fact,  over half the stars in the sky are doubles or multiples, so you'll have a very wide range of choices.  Naturally this will 'force' you to learn
your double stars in the night sky!

{Also as a side benefit, you'll learn a lot of double stars
this way, to observe in case a slight haze layer comes overhead, and you can't do deep sky objects, you can always
switch your observing schedule to the bright planets and
bright double stars...which I (we astronomers) often have
to do if sky conditions do not remain perfect clarity.}

I'd start with Polaris (it doesn't move), a double at 19 arc-seconds...then Mizar in the Big Dipper handle at
14 arc-seconds, then the famous double double Epsilon
Lyrae at 3 and 2 arc-seconds, and finally a double that
is only one arc second.....Lots of choices here......Omicron Persei,  Gamma Virginis,  Rho Capricorni, Mu Cygni....and there are many other close doubles down around one arc-second separation.  I leave it to you to research them
out, but I've given you a couple of very close doubles above.

For What it's Worth,
Hope this helps,
Clear Skies,
Tom Whiting
Erie, PA