Discovery of PLuto ...

wnowak writes:

Jonathan Silverlight writes:

Can you imagine the feelings of astronomers if Charon hadn't been
discovered until 1990, and they realised they had missed a series of
eclipses which won't recur for over a century? :-)

Yes I can, because when the satellite was discovered in 1978, the
orbit was known to be nearly edge on, but it was not known whether
it was opening or closing, thus there was a 50 percent chance that
the eclipses had been missed.

Hmm ... that is in contradiction with what Stern says in his book;

"... However, the fact that no observer had accidently stumbled onto one
in progress hinted it was more likely that the event were in future, than
in the recent past. " ( page #66 )

This suggests 50% ++, correct Mr. Tholen ?

I don't buy the argument. There wasn't a whole lot of accurate
photometry being done prior to the discovery of the satellite.
The events themselves lasted only about five hours, and that's
for a central event (less for the grazing events). With two
events per orbit and one orbit every 150 hours, you're talking
one part in 15. That is, if someone were making random observations,
there's a 94 percent chance that the observations would be at times
when no event was occurring. But as I said, there weren't a whole
lot of observations being made. I'd have to dig into the literature
to count the number of photometric points obtained in the 1970s,
but I'd guesstimate 30. If events were occurring, that's two
potential observations at the time of events. They could have been
easily dismissed as bad points. Furthermore, I don't know of
anybody who was taking high time resolution observations of Pluto
in the 1970s. You'd need several points during an event to see
the trend. A single low point could be easily dismissed as a
faulty observation.

Meanwhile, there is also a claim in the literature that events were
seen when we now know there could not have been events, which
demonstrates that faulty observations can be made.

To tell you the truth I do not quite understand what Stern is talking
about.
For sure you know, since your picture is in the same book a few pages down
the road. Please explain this to us.

I hope the above is sufficient.

Yes it is, and I agree 100% or to be more precise ( 50 + 50)% .

Talking about eclipses of PLuto and Charon, Stern says
"... Then exactly- half a Charon-orbit later - 3.194 days after Binzel's first
event, on February
20th, another young astronomer, the University of Hawaii's David Tholen, caught
Charon falling in PLuto's shadow, ...".
Binzel's and your discovery exactly 20 years ago. Happy anniversary

I understand that above you are referring also to observations made a month
earlier on 16th of January by Buratti and Tedesco, correct ?

Those observations are more controversial. Originally it was suggested
that an event had been seen, but it was later discovered that the CCD
dewar had run out of liquid nitrogen and had started warming up, after
which the data were considered suspect. After the time coincidence with
the Feb 17 and 20 events was noticed, the Jan 16 data were once again
put forward as representing an event. However, the data show an event
that is deeper than the Feb 17 event, despite the fact that we now know
from the orbit determination that less surface area was occulted on Jan
16 than on Feb 17 and therefore could be no deeper than the Feb 17 event.
Also, the event was not very symmetrical. In other words, the data were
once again considered suspect. What is certain is that observations
were being made at the time of an event on Jan 16.

So, we have a very precise date of the start, however the end is somehow not
clear. Some
sources say 1991, some other say 1990. Why is it like that ? The end was also
important since it would help us to calculate the precise date of the P+CH
equinox. Nobody rally cared to look for the end. People got tired ?

Not at all. I looked for the end as vigorously as I looked for the start.
They ended in 1990, twice. Prior to opposition, there were eclipse events,
but eventually Pluto's heliocentric motion caused the events to end as
seen from the perspective of the Sun. The Earth moved to the other side
of its orbit fast enough to move back into the region where occultations
could still be seen, thus events resumed after opposition, and then
ended again as the Earth started back over to the other side of its
orbit, moving out of the occultation region. There were no events in
1991. There were also no events near opposition in 1990. I have a
lightcurve taken in May that is flat to a couple thousandths of a
magnitude. They put a very tight constraint on the sizes of the two
bodies.

Mike Dworetsky writes:

Charon is more than two magnitudes fainter than Pluto.

That depends on the wavelength. In visible light, Charon is 5.5 times
fainter than Pluto. That's less than two magnitudes.

wrote:

wnowak writes:

Jonathan Silverlight writes:

Can you imagine the feelings of astronomers if Charon hadn't been
discovered until 1990, and they realised they had missed a series of
eclipses which won't recur for over a century? :-)

Yes I can, because when the satellite was discovered in 1978, the
orbit was known to be nearly edge on, but it was not known whether
it was opening or closing, thus there was a 50 percent chance that
the eclipses had been missed.

Hmm ... that is in contradiction with what Stern says in his book;

"... However, the fact that no observer had accidently stumbled onto one
in progress hinted it was more likely that the event were in future, than
in the recent past. " ( page #66 )

This suggests 50% ++, correct Mr. Tholen ?

I don't buy the argument. There wasn't a whole lot of accurate
photometry being done prior to the discovery of the satellite.
The events themselves lasted only about five hours, and that's
for a central event (less for the grazing events). With two
events per orbit and one orbit every 150 hours, you're talking
one part in 15. That is, if someone were making random observations,
there's a 94 percent chance that the observations would be at times
when no event was occurring. But as I said, there weren't a whole
lot of observations being made. I'd have to dig into the literature
to count the number of photometric points obtained in the 1970s,
but I'd guesstimate 30. If events were occurring, that's two
potential observations at the time of events. They could have been
easily dismissed as bad points. Furthermore, I don't know of
anybody who was taking high time resolution observations of Pluto
in the 1970s. You'd need several points during an event to see
the trend. A single low point could be easily dismissed as a
faulty observation.

Meanwhile, there is also a claim in the literature that events were
seen when we now know there could not have been events, which
demonstrates that faulty observations can be made.

To tell you the truth I do not quite understand what Stern is talking
about.
For sure you know, since your picture is in the same book a few pages down
the road. Please explain this to us.

I hope the above is sufficient.

Yes it is, and I agree 100% or to be more precise ( 50 + 50)% .

Talking about eclipses of PLuto and Charon, Stern says
"... Then exactly- half a Charon-orbit later - 3.194 days after Binzel's first
event, on February
20th, another young astronomer, the University of Hawaii's David Tholen, caught
Charon falling in PLuto's shadow, ...".
Binzel's and your discovery exactly 20 years ago. Happy anniversary

I understand that above you are referring also to observations made a month
earlier on 16th of January by Buratti and Tedesco, correct ?

Those observations are more controversial. Originally it was suggested
that an event had been seen, but it was later discovered that the CCD
dewar had run out of liquid nitrogen and had started warming up, after
which the data were considered suspect. After the time coincidence with
the Feb 17 and 20 events was noticed, the Jan 16 data were once again
put forward as representing an event. However, the data show an event
that is deeper than the Feb 17 event, despite the fact that we now know
from the orbit determination that less surface area was occulted on Jan
16 than on Feb 17 and therefore could be no deeper than the Feb 17 event.
Also, the event was not very symmetrical. In other words, the data were
once again considered suspect. What is certain is that observations
were being made at the time of an event on Jan 16.

So, we have a very precise date of the start, however the end is somehow not
clear. Some
sources say 1991, some other say 1990. Why is it like that ? The end was also
important since it would help us to calculate the precise date of the P+CH
equinox. Nobody rally cared to look for the end. People got tired ?

Not at all. I looked for the end as vigorously as I looked for the start.
They ended in 1990, twice. Prior to opposition, there were eclipse events,
but eventually Pluto's heliocentric motion caused the events to end as
seen from the perspective of the Sun. The Earth moved to the other side
of its orbit fast enough to move back into the region where occultations
could still be seen, thus events resumed after opposition, and then
ended again as the Earth started back over to the other side of its
orbit, moving out of the occultation region. There were no events in
1991. There were also no events near opposition in 1990. I have a
lightcurve taken in May that is flat to a couple thousandths of a
magnitude. They put a very tight constraint on the sizes of the two
bodies.

This confirms what I have checked with HORIZONS online software.
This also contradicts Stern again. He says 1991. Where does he have the data from ?
The logical question here is; what was the date of equinox, and how precisely we know
that ?
The perihelion date is stated as 5th of September 1989. I did not find the date of
equinox
mentioned anywhere.

wrote:

Mike Dworetsky writes:

Charon is more than two magnitudes fainter than Pluto.

That depends on the wavelength. In visible light, Charon is 5.5 times
fainter than Pluto. That's less than two magnitudes.

For what value of PLuto's albedo ?

wnowak writes:

Jonathan Silverlight writes:

Can you imagine the feelings of astronomers if Charon hadn't been
discovered until 1990, and they realised they had missed a series of
eclipses which won't recur for over a century? :-)

Yes I can, because when the satellite was discovered in 1978, the
orbit was known to be nearly edge on, but it was not known whether
it was opening or closing, thus there was a 50 percent chance that
the eclipses had been missed.

Hmm ... that is in contradiction with what Stern says in his book;

"... However, the fact that no observer had accidently stumbled onto one
in progress hinted it was more likely that the event were in future, than
in the recent past. " ( page #66 )

This suggests 50% ++, correct Mr. Tholen ?

I don't buy the argument. There wasn't a whole lot of accurate
photometry being done prior to the discovery of the satellite.
The events themselves lasted only about five hours, and that's
for a central event (less for the grazing events). With two
events per orbit and one orbit every 150 hours, you're talking
one part in 15. That is, if someone were making random observations,
there's a 94 percent chance that the observations would be at times
when no event was occurring. But as I said, there weren't a whole
lot of observations being made. I'd have to dig into the literature
to count the number of photometric points obtained in the 1970s,
but I'd guesstimate 30. If events were occurring, that's two
potential observations at the time of events. They could have been
easily dismissed as bad points. Furthermore, I don't know of
anybody who was taking high time resolution observations of Pluto
in the 1970s. You'd need several points during an event to see
the trend. A single low point could be easily dismissed as a
faulty observation.

Meanwhile, there is also a claim in the literature that events were
seen when we now know there could not have been events, which
demonstrates that faulty observations can be made.

To tell you the truth I do not quite understand what Stern is talking
about.
For sure you know, since your picture is in the same book a few pages down
the road. Please explain this to us.

I hope the above is sufficient.

Yes it is, and I agree 100% or to be more precise ( 50 + 50)% .

Talking about eclipses of PLuto and Charon, Stern says
"... Then exactly- half a Charon-orbit later - 3.194 days after Binzel's first
event, on February
20th, another young astronomer, the University of Hawaii's David Tholen, caught
Charon falling in PLuto's shadow, ...".
Binzel's and your discovery exactly 20 years ago. Happy anniversary

I understand that above you are referring also to observations made a month
earlier on 16th of January by Buratti and Tedesco, correct ?

Those observations are more controversial. Originally it was suggested
that an event had been seen, but it was later discovered that the CCD
dewar had run out of liquid nitrogen and had started warming up, after
which the data were considered suspect. After the time coincidence with
the Feb 17 and 20 events was noticed, the Jan 16 data were once again
put forward as representing an event. However, the data show an event
that is deeper than the Feb 17 event, despite the fact that we now know
from the orbit determination that less surface area was occulted on Jan
16 than on Feb 17 and therefore could be no deeper than the Feb 17 event.
Also, the event was not very symmetrical. In other words, the data were
once again considered suspect. What is certain is that observations
were being made at the time of an event on Jan 16.

So, we have a very precise date of the start, however the end is somehow not
clear. Some
sources say 1991, some other say 1990. Why is it like that ? The end was also
important since it would help us to calculate the precise date of the P+CH
equinox. Nobody rally cared to look for the end. People got tired ?

Not at all. I looked for the end as vigorously as I looked for the start.
They ended in 1990, twice. Prior to opposition, there were eclipse events,
but eventually Pluto's heliocentric motion caused the events to end as
seen from the perspective of the Sun. The Earth moved to the other side
of its orbit fast enough to move back into the region where occultations
could still be seen, thus events resumed after opposition, and then
ended again as the Earth started back over to the other side of its
orbit, moving out of the occultation region. There were no events in
1991. There were also no events near opposition in 1990. I have a
lightcurve taken in May that is flat to a couple thousandths of a
magnitude. They put a very tight constraint on the sizes of the two
bodies.

This confirms what I have checked with HORIZONS online software.

How did HORIZONS confirm when events ended (twice) in 1990?

This also contradicts Stern again. He says 1991. Where does he have the data from ?

He doesn't.

The logical question here is; what was the date of equinox, and how precisely we know
that ?

1988. A more precise date is in one of my papers, which I do not have
at home.

The perihelion date is stated as 5th of September 1989. I did not find the date of
equinox mentioned anywhere.

I recall it being mentioned in one of my AJ papers that computed when
events would occur for that year.

wnowak writes:

Mike Dworetsky writes:

Charon is more than two magnitudes fainter than Pluto.

That depends on the wavelength. In visible light, Charon is 5.5 times
fainter than Pluto. That's less than two magnitudes.

For what value of PLuto's albedo ?

Pluto's albedo is a strong function of both rotational phase and
wavelength.

wrote:

wnowak writes:

Jonathan Silverlight writes:

Can you imagine the feelings of astronomers if Charon hadn't been
discovered until 1990, and they realised they had missed a series of
eclipses which won't recur for over a century? :-)

Yes I can, because when the satellite was discovered in 1978, the
orbit was known to be nearly edge on, but it was not known whether
it was opening or closing, thus there was a 50 percent chance that
the eclipses had been missed.

Hmm ... that is in contradiction with what Stern says in his book;

"... However, the fact that no observer had accidently stumbled onto one
in progress hinted it was more likely that the event were in future, than
in the recent past. " ( page #66 )

This suggests 50% ++, correct Mr. Tholen ?

I don't buy the argument. There wasn't a whole lot of accurate
photometry being done prior to the discovery of the satellite.
The events themselves lasted only about five hours, and that's
for a central event (less for the grazing events). With two
events per orbit and one orbit every 150 hours, you're talking
one part in 15. That is, if someone were making random observations,
there's a 94 percent chance that the observations would be at times
when no event was occurring. But as I said, there weren't a whole
lot of observations being made. I'd have to dig into the literature
to count the number of photometric points obtained in the 1970s,
but I'd guesstimate 30. If events were occurring, that's two
potential observations at the time of events. They could have been
easily dismissed as bad points. Furthermore, I don't know of
anybody who was taking high time resolution observations of Pluto
in the 1970s. You'd need several points during an event to see
the trend. A single low point could be easily dismissed as a
faulty observation.

Meanwhile, there is also a claim in the literature that events were
seen when we now know there could not have been events, which
demonstrates that faulty observations can be made.

To tell you the truth I do not quite understand what Stern is talking
about.
For sure you know, since your picture is in the same book a few pages down
the road. Please explain this to us.

I hope the above is sufficient.

Yes it is, and I agree 100% or to be more precise ( 50 + 50)% .

Talking about eclipses of PLuto and Charon, Stern says
"... Then exactly- half a Charon-orbit later - 3.194 days after Binzel's first
event, on February
20th, another young astronomer, the University of Hawaii's David Tholen, caught
Charon falling in PLuto's shadow, ...".
Binzel's and your discovery exactly 20 years ago. Happy anniversary

I understand that above you are referring also to observations made a month
earlier on 16th of January by Buratti and Tedesco, correct ?

Those observations are more controversial. Originally it was suggested
that an event had been seen, but it was later discovered that the CCD
dewar had run out of liquid nitrogen and had started warming up, after
which the data were considered suspect. After the time coincidence with
the Feb 17 and 20 events was noticed, the Jan 16 data were once again
put forward as representing an event. However, the data show an event
that is deeper than the Feb 17 event, despite the fact that we now know
from the orbit determination that less surface area was occulted on Jan
16 than on Feb 17 and therefore could be no deeper than the Feb 17 event.
Also, the event was not very symmetrical. In other words, the data were
once again considered suspect. What is certain is that observations
were being made at the time of an event on Jan 16.

So, we have a very precise date of the start, however the end is somehow not
clear. Some
sources say 1991, some other say 1990. Why is it like that ? The end was also
important since it would help us to calculate the precise date of the P+CH
equinox. Nobody rally cared to look for the end. People got tired ?

Not at all. I looked for the end as vigorously as I looked for the start.
They ended in 1990, twice. Prior to opposition, there were eclipse events,
but eventually Pluto's heliocentric motion caused the events to end as
seen from the perspective of the Sun. The Earth moved to the other side
of its orbit fast enough to move back into the region where occultations
could still be seen, thus events resumed after opposition, and then
ended again as the Earth started back over to the other side of its
orbit, moving out of the occultation region. There were no events in
1991. There were also no events near opposition in 1990. I have a
lightcurve taken in May that is flat to a couple thousandths of a
magnitude. They put a very tight constraint on the sizes of the two
bodies.

This confirms what I have checked with HORIZONS online software.

How did HORIZONS confirm when events ended (twice) in 1990?

This also contradicts Stern again. He says 1991. Where does he have the data from ?

He doesn't.

The logical question here is; what was the date of equinox, and how precisely we know
that ?

1988. A more precise date is in one of my papers, which I do not have
at home.

The perihelion date is stated as 5th of September 1989. I did not find the date of
equinox mentioned anywhere.

I recall it being mentioned in one of my AJ papers that computed when
events would occur for that year.

I did not say that I confirmed with HORIZONS "double ending". All I say is that I
confirmed
that it did not happen in 1991. If I am not mistaken it was 0.01 arcsec. short of contact
of discs
of two objects, again if I am not mistaken it was at the end of August 1991.
As for equinox 1988 is not a very precise date, isn't it ? Simple calculation from
1990-1985/2 + 1985 rather suggests 1987.5

One more question. In a long run the orbit of P. is chaotic, however in a short run it
librates.
In Stern's book he provided a diagram with librations of P. in relation to position of
Neptune.
He made a mistake there p.143 ( again ? ), since when you calculate the total number of
loops
( 60 ) it covers 15000 years, and not 40000 as he says.

The question is. What is the direction of librations ? Are the equinox and perihelion
points coming closer now, or they are going to be more separated with every next perihelion
?

wrote:

wnowak writes:

Mike Dworetsky writes:

Charon is more than two magnitudes fainter than Pluto.

That depends on the wavelength. In visible light, Charon is 5.5 times
fainter than Pluto. That's less than two magnitudes.

For what value of PLuto's albedo ?

Pluto's albedo is a strong function of both rotational phase and
wavelength.

My point is that in 1950 the polar regions of PLuto were visible from the
Earth, that are
more reflective as far as I know. So, in spite of the fact that PLuto was
fainter, the relative difference of brightness
between two objects could have been above 2 mag. making it a bit more
difficult to discover a moon.

Also, please remember that PLuto was farther so the max. angular distance was
.... let me calculate ... .
~ 0.74 arsec ? If these guys were not lucky, and observed at min. angular
distance then it takes us down to ...
~ 0.66 * 0.74 = 0.49 ! This is probably just a bit too little. Once I have
time, I will use HORIZONS again to verify
for the date of 21st of March 1950, or maybe somebody else is interested in
doing this.
Any volunteers ?

wnowak writes:

Mike Dworetsky writes:

Charon is more than two magnitudes fainter than Pluto.

That depends on the wavelength. In visible light, Charon is 5.5 times
fainter than Pluto. That's less than two magnitudes.

For what value of PLuto's albedo ?

Pluto's albedo is a strong function of both rotational phase and
wavelength.

My point is that in 1950 the polar regions of PLuto were visible from the
Earth, that are more reflective as far as I know. So, in spite of the fact
that PLuto was fainter, the relative difference of brightness between two
objects could have been above 2 mag. making it a bit more difficult to
discover a moon.

Suppose the pole of Charon is also brighter? All we know is that there
isn't much variation in brightness of Charon as a function of longitude.
We have practically no information on the variation in brightness as a
function of latitude.

Also, please remember that PLuto was farther so the max. angular distance
was .... let me calculate .... ~ 0.74 arsec ?

On the other hand, the minor axis of the projected orbit was larger,
so Charon didn't get as close to Pluto.

If these guys were not lucky, and observed at min. angular distance
then it takes us down to ... ~ 0.66 * 0.74 = 0.49 ! This is probably
just a bit too little. Once I have time, I will use HORIZONS again
to verify for the date of 21st of March 1950, or maybe somebody else
is interested in doing this. Any volunteers ?

wrote:

wnowak writes:

Jonathan Silverlight writes:

Can you imagine the feelings of astronomers if Charon hadn't been
discovered until 1990, and they realised they had missed a series of
eclipses which won't recur for over a century? :-)

Yes I can, because when the satellite was discovered in 1978, the
orbit was known to be nearly edge on, but it was not known whether
it was opening or closing, thus there was a 50 percent chance that
the eclipses had been missed.

Hmm ... that is in contradiction with what Stern says in his book;

"... However, the fact that no observer had accidently stumbled onto one
in progress hinted it was more likely that the event were in future, than
in the recent past. " ( page #66 )

This suggests 50% ++, correct Mr. Tholen ?

I don't buy the argument. There wasn't a whole lot of accurate
photometry being done prior to the discovery of the satellite.
The events themselves lasted only about five hours, and that's
for a central event (less for the grazing events). With two
events per orbit and one orbit every 150 hours, you're talking
one part in 15. That is, if someone were making random observations,
there's a 94 percent chance that the observations would be at times
when no event was occurring. But as I said, there weren't a whole
lot of observations being made. I'd have to dig into the literature
to count the number of photometric points obtained in the 1970s,
but I'd guesstimate 30. If events were occurring, that's two
potential observations at the time of events. They could have been
easily dismissed as bad points. Furthermore, I don't know of
anybody who was taking high time resolution observations of Pluto
in the 1970s. You'd need several points during an event to see
the trend. A single low point could be easily dismissed as a
faulty observation.

Meanwhile, there is also a claim in the literature that events were
seen when we now know there could not have been events, which
demonstrates that faulty observations can be made.

To tell you the truth I do not quite understand what Stern is talking
about.
For sure you know, since your picture is in the same book a few pages down
the road. Please explain this to us.

I hope the above is sufficient.

Yes it is, and I agree 100% or to be more precise ( 50 + 50)% .

Talking about eclipses of PLuto and Charon, Stern says
"... Then exactly- half a Charon-orbit later - 3.194 days after Binzel's first
event, on February
20th, another young astronomer, the University of Hawaii's David Tholen, caught
Charon falling in PLuto's shadow, ...".
Binzel's and your discovery exactly 20 years ago. Happy anniversary

I understand that above you are referring also to observations made a month
earlier on 16th of January by Buratti and Tedesco, correct ?

Those observations are more controversial. Originally it was suggested
that an event had been seen, but it was later discovered that the CCD
dewar had run out of liquid nitrogen and had started warming up, after
which the data were considered suspect. After the time coincidence with
the Feb 17 and 20 events was noticed, the Jan 16 data were once again
put forward as representing an event. However, the data show an event
that is deeper than the Feb 17 event, despite the fact that we now know
from the orbit determination that less surface area was occulted on Jan
16 than on Feb 17 and therefore could be no deeper than the Feb 17 event.
Also, the event was not very symmetrical. In other words, the data were
once again considered suspect. What is certain is that observations
were being made at the time of an event on Jan 16.

So, we have a very precise date of the start, however the end is somehow not
clear. Some
sources say 1991, some other say 1990. Why is it like that ? The end was also
important since it would help us to calculate the precise date of the P+CH
equinox. Nobody rally cared to look for the end. People got tired ?

Not at all. I looked for the end as vigorously as I looked for the start.
They ended in 1990, twice. Prior to opposition, there were eclipse events,
but eventually Pluto's heliocentric motion caused the events to end as
seen from the perspective of the Sun. The Earth moved to the other side
of its orbit fast enough to move back into the region where occultations
could still be seen, thus events resumed after opposition, and then
ended again as the Earth started back over to the other side of its
orbit, moving out of the occultation region. There were no events in
1991. There were also no events near opposition in 1990. I have a
lightcurve taken in May that is flat to a couple thousandths of a
magnitude. They put a very tight constraint on the sizes of the two
bodies.

This confirms what I have checked with HORIZONS online software.

How did HORIZONS confirm when events ended (twice) in 1990?

This also contradicts Stern again. He says 1991. Where does he have the data from ?

He doesn't.

The logical question here is; what was the date of equinox, and how precisely we know
that ?

1988. A more precise date is in one of my papers, which I do not have
at home.

The perihelion date is stated as 5th of September 1989. I did not find the date of
equinox mentioned anywhere.

I recall it being mentioned in one of my AJ papers that computed when
events would occur for that year.

I did not say that I confirmed with HORIZONS "double ending". All I say
is that I confirmed that it did not happen in 1991. If I am not mistaken
it was 0.01 arcsec. short of contact of discs of two objects, again if I
am not mistaken it was at the end of August 1991.

I'm not following you. It was 0.01 arcsec for what?

As for equinox 1988 is not a very precise date, isn't it ?

Best I can do with limited time and what I have at home.

Simple calculation from 1990-1985/2 + 1985 rather suggests 1987.5

A bit too simple.

One more question. In a long run the orbit of P. is chaotic, however in a
short run it librates.

Why do you say it's chaotic? Long integrations of Pluto's orbit show it
to be fairly stable.

In Stern's book he provided a diagram with librations of P. in relation
to position of Neptune. He made a mistake there p.143 ( again ? ), since
when you calculate the total number of loops ( 60 ) it covers 15000 years,
and not 40000 as he says.

I'd have to look at it.

The question is. What is the direction of librations ? Are the equinox and
perihelion points coming closer now, or they are going to be more separated
with every next perihelion?

Again, I'd have to look at it. Not a high priority for me right now.

The angular distance that I am talking about is a minimum distance between the edges of
two discs in 1991. Since at that time the orbit was visible as a very narrow ellipse, two
objects were passing by each other every half period, coming very close to each other. Since
the Earth
also moves on its own orbit, it also has an impact on the size of the visible ellipse. So,
what I
discovered is that the best chance for eclipse was in August or early September ( if I
remember correctly ), but
still it was not enough for two discs to "touch each other". At least based on HORIZONS

The orbit of PLuto is chaotic; it was confirmed with the simulation of the Solar System
software
in 1985 ?, 1990 ? In this case PLuto could have been a satellite of Neptune, what
astronomical
community rejected based on the argument that two objects are too far from each other.
Random walk could have placed PLuto where it is now.
High density of PLuto is one of factors, plus the fact that it seems to be too big as a TNO,
what astronomical community tried to "deny" for the last 13 years, assuming very low
albedoes ( 4% ) for newly discovered TNOs. What turns out to be wrong after all.

I am afraid that we cannot say if perihelion and equinox points are coming closer, or there
are going to be more separated with
every next perihelion/aphelion. I am afraid that current astrometry is not precise enough to
answer this question. Although I am not sure, so I asked the question.

Stern made a mistake on the diagram; no need to check this. He confirmed that.