[BAA Comets] NEW - Interactive comet finder charts

[David Storey]

Hi Graham,
          Just for everyone's info, I downloaded the test chart on my XP
machine. The page loaded but with error on page. The mouse over star data
would not display. I tried the same on a Vista laptop with the same error
and no star data. I am using Internet Explorer 8 on both computers. So, I
attempted to upgrade to IE 10 on the Vista laptop, but IE 10 is not
compatible to IE 10. So, I then installed IE 9 and the chart downloaded fine
and now I see the star data. I didn't even try upgrading the XP machine as
this is not compatible with IE 9. (Well, it doesn't work on my computer!)
Great work on producing a useful tool.

Regards

Dave Storey

-----Original Message-----
From: comets-disc-bounces at britastro.org
[mailto:comets-disc-bounces at britastro.org] On Behalf Of Graham Relf
Sent: 24 May 2013 19:13
To: BAA Comets discussion list
Cc: Sheridan Williams
Subject: [BAA Comets] NEW - Interactive comet finder charts

In response to requirements elucidated at the Comet Section meeting on 18th
May, the comet ( http://britastro.org/computing/charts_comet.html ) and
asteroid ( http://britastro.org/computing/charts_asteroid.html ) finder
charts on britastro.org/computing will have a new feature from now on. A
preliminary sample can be seen at
http://britastro.org/computing/ch/_63PTest.html (63P/Wild).

As you move the mouse over the chart certain data for the nearest star are
displayed below it:

Star id (Flamsteed/Bayer or H... Hipparcos or T... Tycho) V magnitude (+
"variable" if the star is variable in the Hipparcos/Tycho
data)
B - V (colour index; just a few stars do not have the data for this)

The id is given so that further information can be found elsewhere if
desired.
V magnitude is given to enable visual comet magnitude estimation using the
defocussing technique (see J.Shanklin, BAA Observing Guide to Comets, 2002).
B - V is given so that stars with a similar colour index to the Sun can be
used. Dust comets are reflecting sunlight so comparison magnitudes need to
be for similar stars. The Sun's B - V value is reckoned to be
0.66 (see
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1992PASP..104.1035G&
db_key=AST&data_type=HTML&format=&high=44b52c369023103
David F. Gray, The inferred colour index of the Sun, 1992).

The chart also displays green boxes around the most Sun-like stars: 
those in the range 0.60 < B - V < 0.72.

The interaction is done using standard HTML/JavaScript techniques that have
been around for many years and so should work in all browsers. It has been
tested in FireFox 20 and Internet Explorer 10. The code is generated
automatically by our own chart generator using Hipparcos/Tycho data. Once
you have the chart in your browser no further internet connection is need
for the interaction.

If you print the chart you will not get the star data. The idea is that you
select the stars you want and make a separate note of their characteristics,
perhaps written on the print. However, if you save the whole page from your
browser you should be able to view it from disc with the full interaction.

The interactivity is not yet in the red-on-black versions of the charts but
that will come soon.

Please tell us about any problems or modifications you think would be
useful. I have already had feedback that the star data do not follow the
mouse in early versions of FireFox. It would be useful to know about other
exceptions, though I am not sure at this stage what could be done.

I hope I have demonstrated with this that having our own chart generator is
an advantage because we can make it do what we really need. (And I enjoy the
challenges involved.)

Graham
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