Observations by Gary Frishkorn F3D
SL-9 Impact Sites on Jupiter
8/9/1994 8:15 - 9:45 P.M. EDT
8 Newtonian 200X
Transparency: Poor due to uniform haze - limiting magnitude = 3 overhead.
Seeing: fair.
The +K and +W sites were approaching the meridian at the start of
observing. They appear to have faded somewhat since last seen. Only a vague
hint of the two dark impact centers remain - apparently due to continued
dissipation as they are extended by shear in longitude. Contrast of the area
now appears to have weakened to a level like that of the North Equatorial
Belt, although poor seeing may have been partially responsible for this
perception. Toward the end of the observing period, the +L impact site
could be seen rotating into view. Currently, it looks like the +L and +G:
impact sites are holding up the best an appear to offer the best chance of
forming an easily visible belt.
8/8/1994 8:15 - 10:00 P.M. EDT
8 Newtonian 200X
Transparency is very good.
Seeing: Mostly poor with occasional brief intervals of improved seeing.
The +G, D, S, R group was on the western limb at the start of observing.
Two other impact sites, one near the meridian, the other halfway to the
western limb could be seen when the turbulence declined. These are the +H
and +Q1 , sites respectively. They have become less visible since last seen;
they now appear as tiny short dark streaks extended in longitude. After
around 9:00 P.M. the +E impact site was observed rotating in off of the
eastern limb. It s appearance was very similar to the +Q1 and +H sites.
The impacts on this face of Jupiter appear to be fading too rapidly to form a
complete belt that is easily visible. During periods of moderate turbulence
even the darker site centers appear to vanish.
8/7/1994 8:45 - 9:50 P.M. EDT
8 Newtonian 200X
Transparency good between passing high clouds.
Seeing: Very poor at first, then improves to good.
Three general impact regions were visible; a spot near the western limb at
the start of observing, and two elongated streaks stretching from the
meridian to the eastern limb. This region has changed significantly since
last seen over a week ago. The spot on the western limb was the +K and +W
pair. The two regions approaching the meridian are the +L and +G regions.
They have been dramatically extended in longitude. Counting the extreme ends
which fade somewhat from the center, they appear to cover nearly 90 degrees
of longitude with only a small gap of reduced density between them. This
face of Jupiter now appears more like it has a new belt that is interrupted
by gaps than a plain zone interrupted by impact sites. The +belt is not
uniform with the centers of the original sites still appearing slightly
darker - under good seeing these still showed hints of being quite dark and
point-like. Also, a fine dark line appeared along the northern edge of the
belt which appeared quite straight and uniform during average seeing but
showed hints knots or twisted irregularities during good seeing. Overall, as
the impact sites disperse, they are gradually losing their dark contrast and
are beginning to blend in better with other cloud belt features.
8/6/1994 8:20 - 10:00 P.M. EDT
8 Newtonian 200X
Excellent
Seeing: Very good - some low frequency distortion that leaves detail intact
Two impact sites were visible - both dark and point-like. The most visible
site was near the western limb at the start of observing, the other not quite
on the meridian. No gray halos were apparent surrounding these spots - they
were unresolved points like Europa s shadow but slightly less visible. The
spots are probably the +H and +E fragment impact sites - if so, then +A
and +C should also have been in view but were not seen. Since +A and +C
were the smallest of the impact sites previously visible, it now appears that
they have faded from view. A slight darkening at the impact site latitude
seemed to persist near the terminator on the eastern limb. This may be the
remains of +A and +C , now extended in longitude to form a very low contrast
belt. Since the feature persisted while Jupiter rotated, it could not have
been another impact site just rotating into view. The only question is, if
this is a belt forming, why is its contrast enhanced on the mourning
terminator? Sun angle effects? Jupiter s other belt features to not show
this kind of effect.
7/28/1994 9:00 - 10:30 P.M. EDT
8 Newtonian 200X
Transparency good between passing haze and clouds.
Seeing: generally poor
The +K and +W pair straddled the meridian at about 9:30 P.M. Their
separation seemed wider than before but no careful timings were attempted.
The small +C impact site may have been glimpsed on the western limb - seeing
was too poor to be certain. Also, the +L site was easily visible rounding
the sunrise terminator on the eastern limb. The South Temperate Belt appears
to be darker along sections next to (North of) the impact sites; particularly
the +K and +W pair. Coincidence?
7/26/1994 9:45 - 10:05 P.M. EDT
8 Newtonian 200X
Transparency good between scattered clouds.
Seeing: fair at best, extreme fuzz ball turbulence at worst
The +L impact site was near the meridian with the +G complex right behind.
The +K and +W sites were nearly off of the western limb. Poor seeing
prevents detection of any changes to these sites which remain the largest and
most visible.
7/24/1994 8:45 - 10:45 P.M. EDT
8 Newtonian 200X
Moderate haze (limiting magnitude = 2 straight up) with scattered clouds.
Seeing: generally poor with a few moments that approach good.
At 8:45 P.M. the large +L and +G impact areas were visible equal distances
west and east of the meridian, respectively. Both appear significantly
elongated in longitude with +G appearing slightly longer and overall more
prominent. It is possible that the +G site has been enlarged by the +S and
+R fragments which were predicted to have impacted near +G since its last
favorable appearance on the meridian here on 7/19. During moments of
improved seeing it appeared that the center was on the verge of resolving
into separate dark cores. Between 9:45 and 10:00 four impact sites formed an
interesting series across Jupiter s disk. These were +L , now on the western
limb, +G just past the meridian, +Q not quite on the meridian, and +H just
off of the eastern limb. The +Q and +H sites are much less conspicuous
than +L and +G - mostly because of size. During moments of good seeing
however, the +Q and +H sites sharpen into compact, dark points which show
up quite well. If these impact sites have surrounding envelopes of lighter
gray like the larger sites appear to have, then they are apparently below the
threshold of visibility.
7/23/1994 10:00 - 10:40 P.M. EDT
8 Newtonian 200X
Some some clearing between scattered clouds.
Seeing ranges from very poor to good.
The very elongated impact site observed two nights ago was moving across the
meridian during observation. Somewhat more favorable viewing permits the
center to be cleanly resolved into two dark cores this time. Previously,
based on meridian crossing predictions it was assumed that the leading site
was +K and the trailing site was +U . More likely these are the +K and +W
sites which were both large fragments. The +U and +P sites should also be
near this area but both were probably too small to make visible impact sites
- especially near these very large sites. The presumed +K site crossed the
meridian at roughly 10:20 P.M. which is consistant with the original
predictions, while the presumed +W site crossed the meridian at roughly
10:35 P.M. which is 5 minutes later than original predictions. (Note: the
predications which were used have probably not been updated since the actual
impacts.) They form an interesting close pair. Also seen was a much paler
impact site near the western limb presumed to be the +C impact site. It
required good seeing and transparency to spot. The large +L impact site was
also visible rotating onto the eastern limb. No significant fading or
dispersion of the impact sites are apparent. The outer envelop of the +K and
+W sites possibly appeared a little fainter but this may have been an
illusion due to better sky transparency.
7/22/1994 9:30 - 10:00 P.M. EDT
8 Newtonian 200X
Some hazy gaps between a mostly cloudy sky.
Seeing was very poor.
Due to very poor sky conditions, only a few glimpses of the impact sites were
obtained. On the western limb the large +G impact site, now predicted to be
joined by +S and +R was visible. Another much fainter impact site,
halfway between the meridian and the western limb, may also have been
glimpsed momentarily. The +Q and +N impact sites were predicted to be
located near there. A more prominent site visible near the meridian was
probably the +H impact site. Finally, a very faint spot not far from the
eastern limb was apparent during a few rare moments of improved seeing. It
was assumed to be the combined +E and +F impact sites.
7/21/1994 9:15 - 10:30 P.M. EDT
8 Newtonian 200X
Mostly cloudy but with intermittent thin holes.
Seeing ranged from extreme turbulence to brief moments of average seeing.
The impact sites of the largest fragments were on the face of Jupiter during
observations and were visible in spite of very poor observing conditions.
The +K impact site had already past Jupiter s meridian at the start of
observing. It appeared rather elongated compared with other spots previously
observed; roughly twice as long as its width in the direction of the cloud
belts. The elongation may have been caused by the recent (~3 hours earlier)
+U fragment impact which was predicted to impact just 2.5 degrees in
longitude behind the +K impact site. During one or two brief moments of
reasonable seeing, the center of the spot even appeared to resolve into two
dark cores, one ahead of the other. Poor conditions make the observation
somewhat suspect however, especially because the +U fragment appeared to be
extremely tiny in the HST images - it seems unlikely is could have left such
a prominent impact site. (update: based on 7/23 observations the new impact
site next to +K was probably produced by the large +P fragment some 34
hours earlier, rather than the +U fragment.) The large +L impact site was
also observed between the eastern limb and the meridian. As far as
conditions permitted, it did not appear that this impact site had changed in
any way since last observed two days ago. By ~10:00 P.M. the +G impact site
had become very noticeable rotating onto Jupiter s terminator and looking
like a big dent in the limb. Solid cloudiness prevented further observations.
7/20/1994 9:15 - 10:00 P.M. EDT
5 Refractor & 11 SCT ~100X
Clear
Seeing is variable from fair to good.
Better sky conditions tonight. The impact sites that are visible are older
and apparently produced by smaller fragments. Three impact sites were
visible at ~9:15 P.M. The most prominent spot was about to cross the
meridian. It was smaller than the +L and +G fragment sites observed
yesterday and its outer envelope appeared round rather than oval. It still
had a very dark center which was unsurpassed by any other feature on
Jupiter. Based on predictions it was probably the +E impact but this is not
certain. The +F impact was predicted to be just ahead of +E but nothing
was visible in that location. The other two impact sites were much less
visible, partially due to smaller size, but mostly because of lighter
shading. Since they appeared similar in brightness and color to the
surrounding cloud features they required a careful look and good seeing to
spot. One of these was near the western limb and though to be the +H impact
site. The other was following the most prominent impact site and assumed to
be the +A impact site, but again this was not certain because the
predictions did not seem to match observations particularly well. The impact
sites for +C and +P for example, were also predicted to be rotating into
view but were not visible in the expect locations. Toward the end of the
observing session ( ~10:00) another impact site was rotating onto the eastern
limb; the best guess is that this was the +K impact site. It had an
elongated appearance, which being near the limb may suggest two nearby sites
which were not resolved. As the number of impact sites increases, the job of
keeping track of which spots are due to which fragments may become
increasingly difficult, particularly as they fade or merge together.
7/19/1994 8:45 - 10:45 P.M. EDT
8 Newtonian 200X
Hazy skies with scattered thin clouds.
Seeing is variable ranging from poor to good.
Despite less than ideal conditions, three large impact sites were visible
~8:45 PM. Based on predictions these were produced by the +K fragment,
visible right on the western limb and looking like a notch cut out of
Jupiter, the +L fragment site, visible near the meridian which had impacted
less than 3 hours earlier, and the +G fragment site located halfway from the
meridian to the eastern limb and making its fourth trip around Jupiter.
These were among the largest fragments to hit Jupiter and their effect
appears quite dramatic. The +K fragment impact site rotated out of view in
about 15 minutes leaving only the +L and +G sites. Both appeared similarly
large and dark. Their centers seemed like a very dark eclipse shadow of one
of the Galilean moons and was surrounded by a lighter gray region which fades
toward the edges. The outer region was slightly oval in the direction of the
belts and similar in size to the Great Red Spot. The dark central spots
appeared slightly off-center in the ovals, both shifted to the eastern
side. Unlike the usual tans and browns of Jupiter s clouds, the spots
appeared colorless, showing only neutral grays or black. They appeared
significantly darker than any other cloud features on Jupiter. One can t
help but come away from the eyepiece with the feeling that Jupiter has taken
a tremendous pounding.