[Prev][Next][Index][Thread]
(IAAC) Two comets and thoughts on observing faint fuzzy objects
ear Lists
I have found a cure to my computer illiteracy through u-nets helpline so
have posted two drawings on their FTP uploads directory. The drawing of
Hartley2 was made Jan 22 1998 from 19.00-20.54 (north is down on this
picture), that of Temple-Tuttle on jan28 1998 19.30-21.30UT (west is about
20degrees left of upward vertical in this picture).
I have posted earlier the observation reports for these times but if anone
wants details please e mail me direct.
The address is FTP.u-net.com in directory /uploads
The files hart2.gif and ttut.jpg.
The files are quite large about 500K each as they are continuous tone
greyscale pictures on a white background. (Anyone know any downloadable,
useable by a moron, image compression programs.)
Harltey2 is a very different comet from Temple Tuttle. As the pictures show
it is a very structured comet with a well developed system of rays in the
coma including a fountain like ray emerging forwards from the coma and
turning backwards rapidly. The rays, like those in Hale Bopp are quite
persistent. My later observation of comet Hartley 2 on february 16, nearly
four weeks later showed that five rays were still present. Under the very
clear sky conditons then and with a greater elevation of the comet the
northern ray could be traced for nearly 60' and the southern ray for 18'
despite the fading of the comet. The fountain like ray was not observed but
cloud intervened before the X250 eyepiece could be used so it may have been
missed.
Temple Tuttle on the three occasions I observed it seemed much less
structured with mostly very diffuse features present.
Finally, after the comments from the gentleman last week about his problems
in perceiving glaxies, it is worth noting that the structures shown were
only observed after a long period of observation. The amount of detail
perceived increases with observation time up to about an hour. It takes
about half an hour before I can observe anything in the way of detail. I use
the standard tricks like averted vision and tube wobbling and rest my eyes
on the naked eye stars. I also try moving the object to slightly different
positions in the eyepiece field or even just out of the eyepiece field to
try to detect perception artefacts.
Drawing is made trickier, as even red light damages my night vision briefly
so it is difficult to switch attention quickly between paper and eyepiece.
So a cassette recorder is very valuable in recording my impressions.
The same factors apply to fainter deep sky objects with perceiving things
like the fainter parts of the irregular planetary Abell 21or the faint
galaxt IC10( see my Netastro postings). Doing rapid fire observing I would
miss so much.
It would be interesting to hear peoples views about ways to enhance
observations of faint fuzzies and in particular how to avoid perceptual
illusions like the tendency of the visual cortex to draw lines connecting stars.
Wishing everyone an end to moist air streams.
Nick
Nick Martin, Bonnyton House, By Ayr, Ayrshire, Scotland, U.K.
Latitude 55 24'55" Longitude 4 26'00".