Visible/Invisible planets

Hi everyone,

Does anyone know where I can get a list of the dates at which the visible
planets are invisible (because of their proximity to the sun from a
geocentric perspective)? Is this info available in an almanac, or does some
website have such lists? I would also like to have this information as it
pertains to epochal dates so that I could add the information into a
program, unless someone knows of a program that provides such an ephemeris.
Thanks.

Roy

"Roy Kirkland" wrote in message
...
Hi everyone,

Does anyone know where I can get a list of the dates at which the visible
planets are invisible (because of their proximity to the sun from a
geocentric perspective)? Is this info available in an almanac, or does
some
website have such lists? I would also like to have this information as it
pertains to epochal dates so that I could add the information into a
program, unless someone knows of a program that provides such an
ephemeris.
Thanks.

Roy



As planets get closer to the Sun they get harder to see clearly. The only
time they would be "invisible" (impossible to see) is when they are directly
behind the Sun. This would happen only extremely infrequently (perhaps once
every few hundred years) to never, depending upon the planet in question.

I don't think you would be able to find this information from a table, as an
eclipse of a outer planet by the Sun would be almost impossible to observe
and I cannot see any astronomical interest in such an event (of course, this
may just be a failure of my imagination).

"Roy Kirkland" wrote in message
...
Hi everyone,

Does anyone know where I can get a list of the dates at which the visible
planets are invisible (because of their proximity to the sun from a
geocentric perspective)? Is this info available in an almanac, or does
some
website have such lists? I would also like to have this information as it
pertains to epochal dates so that I could add the information into a
program, unless someone knows of a program that provides such an
ephemeris.
Thanks.

Roy



As planets get closer to the Sun they get harder to see clearly. The only
time they would be "invisible" (impossible to see) is when they are directly
behind the Sun. This would happen only extremely infrequently (perhaps once
every few hundred years) to never, depending upon the planet in question.

I don't think you would be able to find this information from a table, as an
eclipse of a outer planet by the Sun would be almost impossible to observe
and I cannot see any astronomical interest in such an event (of course, this
may just be a failure of my imagination).

"Roy Kirkland" wrote in
:

Hi everyone,

Does anyone know where I can get a list of the dates at which the
visible planets are invisible (because of their proximity to the sun
from a geocentric perspective)? Is this info available in an almanac,
or does some website have such lists? I would also like to have this
information as it pertains to epochal dates so that I could add the
information into a program, unless someone knows of a program that
provides such an ephemeris. Thanks.

Roy



You may be thinking of heliacal risings and settings. This is the date when
a planet (or star) is deemed to become visible (or invisible) in twilight
due to its proximity to the Sun. By determining the date of disappearance"
and "reappearance" you will have the period the planet is "invisible".

The date of heliacal risings and settings depend on the brightness of the
planet (predictable) and the transparency of the atmosphere (unpredictable)
that varies for different dates and places, subject to the vagaries of
weather and seasons. So the answer is not simple.

There is however basic code available that will do a calculation for you.
http://skyandtelescope.com/resources...icle_326_4.asp
(Go down the list until you find HELIAC.BAS)

Note: You need to run the code in QBasic, PowerBasic, GWBasic or any other
basic interpreter (many are free on the web).

You must enter the brightness of the object, its RA and Dec, your latitude
and limiting magnitude. It calculates for a standard atmosphere and
presumably a "standard twilight".

For stars the answer is straightforward but planets move every day and this
means you have to trial several days around the heliacal event to get the
answer.

Martin Lewicki
--
Replace username: mlewicki
Relpace dot delimited numbers with ozemail com au

"Roy Kirkland" wrote in
:

Hi everyone,

Does anyone know where I can get a list of the dates at which the
visible planets are invisible (because of their proximity to the sun
from a geocentric perspective)? Is this info available in an almanac,
or does some website have such lists? I would also like to have this
information as it pertains to epochal dates so that I could add the
information into a program, unless someone knows of a program that
provides such an ephemeris. Thanks.

Roy



You may be thinking of heliacal risings and settings. This is the date when
a planet (or star) is deemed to become visible (or invisible) in twilight
due to its proximity to the Sun. By determining the date of disappearance"
and "reappearance" you will have the period the planet is "invisible".

The date of heliacal risings and settings depend on the brightness of the
planet (predictable) and the transparency of the atmosphere (unpredictable)
that varies for different dates and places, subject to the vagaries of
weather and seasons. So the answer is not simple.

There is however basic code available that will do a calculation for you.
http://skyandtelescope.com/resources...icle_326_4.asp
(Go down the list until you find HELIAC.BAS)

Note: You need to run the code in QBasic, PowerBasic, GWBasic or any other
basic interpreter (many are free on the web).

You must enter the brightness of the object, its RA and Dec, your latitude
and limiting magnitude. It calculates for a standard atmosphere and
presumably a "standard twilight".

For stars the answer is straightforward but planets move every day and this
means you have to trial several days around the heliacal event to get the
answer.

Martin Lewicki
--
Replace username: mlewicki
Relpace dot delimited numbers with ozemail com au