[extropy-chat] Watching the comets, Part II

Amara Graps amara at amara.com
Fri Apr 16 17:02:08 UTC 2004


I should have said more in that last messages regarding these comets.
Visual magnitude equals 5 or 6 (depending on sky conditions) is the
cut-off between a naked eye object and an object only visible with
binoculars (or a telescope). A visual magnitude of 4 is already naked
eye. The lower (and more negative) the value, the brighter is the

I didn't realize that the newly-discovered comet Bradfield is *also* a
naked eye object.

So then THREE naked eye comets visible during the next week(s) (??!)

http://www.skyhound.com/sh/comets.html  (Nice overview page)


C/2004 F4 (Bradfield)

from the above page:

"A twilight comet visible to the naked eye As of April 12 this comet
was 3rd magnitude with a 30" coma and a 30' (*) tail, visible from the
southern hemisphere in evening twilight. It will brighten as it
approaches the sun but will soon be lost in it's glare.  Later in the
month it will reappear in the morning sky.  The comet will move away
from the sun, becoming higher in the morning sky each day, fading
rapidly as it does.  By May 1 it may be as faint as 6th magnitude.  As
the comet moves north it will be best viewed from mid-northern
latitudes.  Caveats: the orbit for this comet is approximate at this
time as are the predicted magnitudes.  Based on this early data John
Bortle suggests that this comet is unlikely to survive perihelion.  In
other words, it may not still be around after the third week in

(*) Note: 30' (arc minutes) = 1 Moon diameter


Comet C/2002 T7 (LINEAR):

A recent photo of C/2002 T7 (LINEAR) is here, from February 2004.


According to the text at Gary Kronick's page (above):

"The first observation following conjunction with the sun appears
to have been made on April 9, when Alexandre Amorim (Florianopolis, Brazil)
saw it in bright twilight using 20x80 binoculars. He gave the magnitude as
4.6 and said the coma was 6 arc minutes across (*). Such a brightness would
indicate the comet will not exceed magnitude 2 when at its brightest in
mid-May, but time will tell."

(*) Note: 6' (arc minutes) = 1/5 Moon diameter

1 degree = 60' (arc minutes) = 2 Moon diameters
1' (arc minute) = 60" (arc seconds)

Also a chart and some description from New Zealand


Comet C/2001 Q4 (NEAT)

Mostly a Southern Hemisphere object, but if one is near the equator...

The coma brightening appears to be following predictions, and I guess
it is a naked eye object now.

http://members.ozemail.com.au/~lovejoyt/2001q4.htm  from Australia
http://www.rasnz.org.nz/comets/C2001Q4.htm   from New Zealand



Amara Graps, PhD          email: amara at amara.com
Computational Physics     vita:  ftp://ftp.amara.com/pub/resume.txt
Multiplex Answers         URL:   http://www.amara.com/
"Oh you damned observers, you always find extra things."
    -- Fred Hoyle [quoted by Richard Ellis at IAU Symposium 183]

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