[Chaos-l] "Our Vanishing Night" at Morehead, Apr. 17 (questions!)

[Robert Nielsen]

Amy,

First, the limiting magnitude question ...

I specifically tried to figure this out, standing on the sundial the 
other night.   It's tough (given the moisture content of the air, all 
that) but I would say the sundial is about 2.5, based on what I could 
see and what TheSky6 shows me when I torque down the magnitude limit 
to 2.5.   On a good night, you might be able to get to 3.0 ...

At my house (east Chapel Hill near the Durham County line between 
15-501 and 54) it's probably around 4.5 ... maybe 4.0.   According to 
TheSky6, lots of the stars in the Little Dipper disappear at 4.0, and 
it really depends on the night whether I can see the Little Dipper or 
not.  I'm lucky, I live in a wooded neighborhood, and the trees keep 
the light pollution down from the surrounding houses.   Of course, I 
can't see most of the sky, either.   But I have a couple of good clear areas.

I've always thought Jordan Lake was roughly the same as my house ... 
perhaps a little better.   So I would say around 4.5 for Jordan 
Lake.   Again, it really depends on the relative humidity of the air ...

And I'm not sure about the dark sky site.  I think I remember Jon 
Stewart-Taylor saying it was about a 6.5 one time.  You can 
definitely see the Milky Way almost from horizon to horizon (not as 
good in the South).   I think we have an observing session this 
weekend ... you should come and see for yourself!  You can ride with 
me if you don't want to drive ...

Now what is there to show people ...

I will definitely show people Saturn and however many moons are 
visible that night.   M42 is pretty low on the horizon, but it may 
still be visible ... although not in all of its glory.   I could see 
some of the clusters in Auriga pretty well (again, you don't get the 
"falling into a mass of stars" effect ... but you can still see lots 
of stars in the eyepiece) and I will probably point out some double 
stars, like Castor and Mizar.   Most of the deep sky stuff is 
impossible or not worth it from the Sundial.   I could see M3 (one of 
my favorite globulars) but because it was so low it just looked like 
a smudge.   Perhaps I can bring my computer and show them pictures of 
what it SHOULD look like, and then show them the polluted version ...

So let's all hope for clear skies next Tuesday night.   If it is 
cloudy, is there a rain date?

Robert

At 10:45 PM 4/9/2007, you wrote:
>Hello CHAOS members,
>
>Mickey Jo recently emailed the list about a planetarium show light pollution
>that we're working on ("Our Vanishing Night").  It's happening Tuesday, April
>17 in the star theater at Morehead Planetarium and Science Center, as part of
>UNC's celebration of Earth Week.
>
>We'll begin the evening at 7:30 with the planetarium presentation and a couple
>of (brief) speeches, then a walking tour of the lighting in the surrounding
>area & observing at the Sundial in front of the building--many 
>thanks to Robert
>Nielsen, who I hear from Mickey did some scouting out of various possibilities
>for observing.
>
>We would love to see CHAOS members at this event!  It's free and open to the
>public, and we're hoping for a large crowd.  Note that we don't 
>control the pay
>lot in front of the building, but there is free parking at the 
>metered spaces on
>Franklin Street after 6 pm.
>
>Now a question for you:
>As part of the star theater show, I'll simulate varying levels of light
>pollution.  I'm wondering if anyone happens to have a sense of the limiting
>magnitude for any of the following places on a good night:
>  - downtown Chapel Hill? (especially the Sundial area in front of 
> MPSC--I feel
>like I ought to know this already, but I don't!)
>  - The "darker" parts of Chapel Hill, but still within city limits?
>  - Ebenezer Church Recreation Area at Jordan Lake?
>  - The CHAOS dark site? (I won't broadcast the address to the 
> general public.)
>The way things are set up, it's hard to "dial up" a specific 
>limiting magnitude
>for the star theater sky, but I think it'll be helpful if I have these figures
>in mind.
>
>And another question:
>If you're bringing a telescope to this event, what might you be 
>planning to look
>at?  I'd like to mention your telescope targets during the show 
>where possible,
>to encourage folks to come outside to look at the REAL sky with you.
>
>Thanks, and we hope to see many of you on April 17th!
>Amy
>
>--
>Amy Sayle
>Adult Programs Coordinator
>UNC Morehead Planetarium and Science Center
>
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