Halley's comet and HST

Halley's comet was picked up in 1982 with the 200" telescope at Mt. Palomar.
It was still beyond Saturn's orbit at the time. This was before the Hubble
Space Telescope was launched.

I'm not sure exactly how far away Halley is from us now, but I presume it's
well beyond Saturn's orbit again. Theoretically, could the HST pick up this
comet at its present position?

On Sun, 3 Jun 2007 22:36:46 -0500, "Matt J. McCullar"
wrote:

Halley's comet was picked up in 1982 with the 200" telescope at Mt. Palomar.
It was still beyond Saturn's orbit at the time. This was before the Hubble
Space Telescope was launched.

I'm not sure exactly how far away Halley is from us now, but I presume it's
well beyond Saturn's orbit again. Theoretically, could the HST pick up this
comet at its present position?

I don't see why not. However, it probably wouldn't do as well as many
larger ground-based instruments. A back of the envelope calculation
suggests that the Hale scope could still get it, with just a few minutes
of exposure time. It's probably even possible with some larger amateur
telescopes.

Detector technology has improved considerably since 1982.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peterson wrote:
On Sun, 3 Jun 2007 22:36:46 -0500, "Matt J. McCullar"
wrote:

Halley's comet was picked up in 1982 with the 200" telescope at Mt. Palomar.
It was still beyond Saturn's orbit at the time. This was before the Hubble
Space Telescope was launched.

I'm not sure exactly how far away Halley is from us now, but I presume it's
well beyond Saturn's orbit again. Theoretically, could the HST pick up this
comet at its present position?

I don't see why not. However, it probably wouldn't do as well as many
larger ground-based instruments. A back of the envelope calculation
suggests that the Hale scope could still get it, with just a few minutes
of exposure time. It's probably even possible with some larger amateur
telescopes.

Detector technology has improved considerably since 1982.

It's probably no longer outgassing at it's current distance, which would
certainly reduce it's albedo. Did you take that into account?

In article ,
lal_truckee wrote:

Chris L Peterson wrote:
On Sun, 3 Jun 2007 22:36:46 -0500, "Matt J. McCullar"
wrote:

Halley's comet was picked up in 1982 with the 200" telescope at Mt. Palomar.
It was still beyond Saturn's orbit at the time. This was before the Hubble
Space Telescope was launched.

I'm not sure exactly how far away Halley is from us now, but I presume it's
well beyond Saturn's orbit again. Theoretically, could the HST pick up this
comet at its present position?

I don't see why not. However, it probably wouldn't do as well as many
larger ground-based instruments. A back of the envelope calculation
suggests that the Hale scope could still get it, with just a few minutes
of exposure time. It's probably even possible with some larger amateur
telescopes.

Detector technology has improved considerably since 1982.

It's probably no longer outgassing at it's current distance, which would
certainly reduce it's albedo. Did you take that into account?

The lack of outgassing will certainly reduce the brightness of Halley,
but not necessarily its albedo. What the outgassing does is to
increase the diameter of the light reflecting region of the comet.
The overall albedo probably decreases when the comet is outgassing
(remember that the coma and the tail of a comet are almost completely
transparent), but since the coma is vastly bigger than the nucleus when
the comet is outgassing, the comets overall brightness will incerase a
lot even though its albedo decreases.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

Paul Schlyter wrote:
In article ,
lal_truckee wrote:


Chris L Peterson wrote:

On Sun, 3 Jun 2007 22:36:46 -0500, "Matt J. McCullar"
wrote:



snip


The lack of outgassing will certainly reduce the brightness of Halley,
but not necessarily its albedo. What the outgassing does is to
increase the diameter of the light reflecting region of the comet.
The overall albedo probably decreases when the comet is outgassing
(remember that the coma and the tail of a comet are almost completely
transparent), but since the coma is vastly bigger than the nucleus when
the comet is outgassing, the comets overall brightness will incerase a
lot even though its albedo decreases.


Folks,

I tried getting the ephemerides for the comet using MPC and it seems to
insist on some asteroid named Halley. I tried "1/P Halley" but that failed.

Any ephemerides (or a source to them) would be appreciated. ;-)

Anthony.

Anthony Ayiomamitis wrote:

Paul Schlyter wrote:

In article ,
lal_truckee wrote:


Chris L Peterson wrote:

On Sun, 3 Jun 2007 22:36:46 -0500, "Matt J. McCullar"
wrote:



snip


The lack of outgassing will certainly reduce the brightness of Halley,
but not necessarily its albedo. What the outgassing does is to
increase the diameter of the light reflecting region of the comet.
The overall albedo probably decreases when the comet is outgassing
(remember that the coma and the tail of a comet are almost completely
transparent), but since the coma is vastly bigger than the nucleus when
the comet is outgassing, the comets overall brightness will incerase a
lot even though its albedo decreases.


Folks,

I tried getting the ephemerides for the comet using MPC and it seems to
insist on some asteroid named Halley. I tried "1/P Halley" but that failed.

Any ephemerides (or a source to them) would be appreciated. ;-)

Anthony.

PS. I think I can scratch this potential project. See the text at
http://antwrp.gsfc.nasa.gov/apod/ap031003.html ... too bad!

On Mon, 04 Jun 2007 14:52:11 +0300, Anthony Ayiomamitis
wrote:

I tried getting the ephemerides for the comet using MPC and it seems to
insist on some asteroid named Halley. I tried "1/P Halley" but that failed.

Any ephemerides (or a source to them) would be appreciated. ;-)

For my estimate, I used the data from
http://ssd.jpl.nasa.gov/horizons.cgi , with "1P/Halley" as the target
body. This gives an "apparent visual magnitude" of 24.9, and a "nuclear
magnitude" of 28.6. This suggests to me that there's still a little
outgassing occurring. In the case of Halley, even a little outgassing
should substantially increase its albedo, since the nucleus is coal
black.

Anyway, at m=25 you are looking at several minutes of exposure time with
a multimeter telescope, and 10s of hours with a ~0.5 meter scope (one
with programmed tracking). If the m=28.6 value is more accurate, then
I'd say it's probably out of range of ground based scopes because of
skyglow impact on S/N. HST shouldn't have a problem, though.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

"Matt J. McCullar" writes:

I'm not sure exactly how far away Halley is from us now, but I presume it's
well beyond Saturn's orbit again. Theoretically, could the HST pick up this
comet at its present position?

Halley's comet was succesfullt imaged a few years back by ESO, at a distance
of 4.2 billion km. The details are he
http://www.eso.org/public/outreach/p...hot-27-03.html

pej
--
Per Erik Jorde

Chris L Peterson writes:

If the m=28.6 value is more accurate, then
I'd say it's probably out of range of ground based scopes because of
skyglow impact on S/N. HST shouldn't have a problem, though.

The magnituda was V = 28.2 on Sept. 1. 2003 according to ESA, who
used a total of 9 hour exposure with the VLT to image it.

I think I'll save this one for it's next return, while preparing for
my 99th birthday party ;-)

pej
--
Per Erik Jorde

First it was 1982i then 1986III which I believe is still its designation.

I dug these up from Dance Of The Planets software.

This is still the only program I know of that actually uses the gravity of
the planets as well as the Sun and creates osculating elements sets on the
fly. I would like to know if there is any orbit simulator like it out there
now. You can simulate earth-moon flybys of spacecraft and asteroids and
model gravity assist trajectories etc etc.



Comet peri(au) e i êø
wø peridate name

1986III 0.587104 0.967277 162.2422 58.8601 111.8657
1986.02095 P/Halley



Dale Ireland




Folks,

I tried getting the ephemerides for the comet using MPC and it seems to
insist on some asteroid named Halley. I tried "1/P Halley" but that
failed.

Any ephemerides (or a source to them) would be appreciated. ;-)

Anthony.