Double Stars

Hi all,
I have a question. I've been increasingly frustrated lately that I
can't find up-to-date separations and position angles on tight doubles with
fast orbits. Even information a year or two old is no good when you want to
know about Gamma Virginis or Xi Scorpii. I've tried my planetarium
programs. I've tried searching the web for the WDS catalog, but I'm either
reading it wrong or it too uses old information and we're supposed to know
how to extrapolate or something.
Is there a program or website where I can simply look up any given
double star and get exact info for now, tonight?
Thanks in advance.

Scott Ewart

Scott wrote:

Hi all,
I have a question. I've been increasingly frustrated lately that I
can't find up-to-date separations and position angles on tight doubles with
fast orbits. Even information a year or two old is no good when you want to
know about Gamma Virginis or Xi Scorpii. I've tried my planetarium
programs. I've tried searching the web for the WDS catalog, but I'm either
reading it wrong or it too uses old information and we're supposed to know
how to extrapolate or something.
Is there a program or website where I can simply look up any given
double star and get exact info for now, tonight?
Thanks in advance.

Scott Ewart

Try: http://www.obs-besancon.fr/www/sdg/etoiles_ang.html
http://www.edu-observatory.org/eo/double_stars.html

Hi Scott,

Scott wrote:
Hi all,
I have a question. I've been increasingly frustrated lately that I
can't find up-to-date separations and position angles on tight doubles with
fast orbits. Even information a year or two old is no good when you want to
know about Gamma Virginis or Xi Scorpii. I've tried my planetarium
programs. I've tried searching the web for the WDS catalog, but I'm either
reading it wrong or it too uses old information and we're supposed to know
how to extrapolate or something.

These systems require orbits to compute the accurate positions. The
only commercial "planetarium" software I am aware of that uses orbits to
compute the positions of multiple star components is my SkyTools.

It gives a separation of 0.71" and a PA of 222 for tonight (July 10,
2003). By the way, SkyTools also plots the relative positions of the
stars on the charts, can overlay the orbit, computes orbit ephemerides,
and will even give you a Dawes-limit based simulation of the pair in
your telescope...

http://www.skyhound.com/skytools.html

Clear skies,
Greg


--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools Software for the Observer:
http://www.skyhound.com/cs.html

Skyhound Observing Pages:
http://www.skyhound.com/sh/skyhound.html

Greg Crinklaw wrote:
It gives a separation of 0.71" and a PA of 222 for tonight (July 10,
2003).

That was for Gamma Vir by the way...

Greg


--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools Software for the Observer:
http://www.skyhound.com/cs.html

Skyhound Observing Pages:
http://www.skyhound.com/sh/skyhound.html

S
From: "Scott"
S
Subject: Double Stars
S
Date: Fri, 11 Jul 2003 00:29:55 -0400
S
Organization: OWDS Inc.

There is an Excel file of binary star orbits -- hipe some one here
gives the address! -- which caclks the aspect for a given epoch. Being
a clear file, you can update the elements or add other stars. It also
plots the orbit on a neat diagram.
By the sheerest of good luck, last week I acquired an iPaq
handheld computer which I then loaded with Taiyoukei. Uh, that's a
Japanese astronomy freeware, all in English except for the title,
which includes a selection of WDS binaties. When fou run the program
it calcks the aspect for the instant wpoch, altho you can shift to an
other date. In addition, the program plots the orbit and geneates a
tabular ephemris.
The downsides are that it's only for handhelds with WIndows CE and
that most of the stars are REAL close binaries, even, I susect,
spectroscopic ones.
Some planetarium programs, like Guide, include a binary star
calculator.
I would hpe you get the Excel file if any one here gts u the
address.



S Hi all,
S I have a question. I've been increasingly frustrated lately that I
S can't find up-to-date separations and position angles on tight doubles with
S fast orbits. Even information a year or two old is no good when you want to
S know about Gamma Virginis or Xi Scorpii. I've tried my planetarium
S programs. I've tried searching the web for the WDS catalog, but I'm either
S reading it wrong or it too uses old information and we're supposed to know
S how to extrapolate or something.
S Is there a program or website where I can simply look up any given
S double star and get exact info for now, tonight?
S Thanks in advance.

---
þ RoseReader 2.52á P005004

GC
From: Greg Crinklaw
GC
Subject: Double Stars
GC
Date: Fri, 11 Jul 2003 00:23:05 -0600
GC
Organization: CapellaSoft
GC
GC It gives a separation of 0.71" and a PA of 222 for tonight (July 10,
GC 2003).
GC
GC That was for Gamma Vir by the way...

The taiyoukei program, using WDS data, gives 0.75 arcsec and 227
degrees, rounded.
However!, gamma Virginis DOES have some orbit problems in that
there are several orbits in circulation for it. This topic came up a
couple years ago when we woke up to the coming periastron of this
star. See my article in Eyepiece for April 2000.
When you look at gaama Virginis, know that you're seeing just the
second periastron of this star ever observed. You may want to rad the
sccounts of the first one, in 1835 when vinary star astronomy was
still quite new, and hear the excitement.

---
þ RoseReader 2.52á P005004

In article , Scott wrote:
Hi all,
I have a question. I've been increasingly frustrated lately that I
can't find up-to-date separations and position angles on tight doubles with
fast orbits. Even information a year or two old is no good when you want to
know about Gamma Virginis or Xi Scorpii. I've tried my planetarium
programs. I've tried searching the web for the WDS catalog, but I'm either
reading it wrong or it too uses old information and we're supposed to know
how to extrapolate or something.
Is there a program or website where I can simply look up any given
double star and get exact info for now, tonight?

Though not quite that, these people seem to have computed annual
ephemerides of about 1300 visual binaries out through about 2007:

http://www.usc.es/astro/catalog.htm

Some stars have more than one prediction where there are
multiple sets of proposed orbital elements.

It's a big ASCII tabular list, arranged so that
you could write a program to read it.
They don't seem to have a star-lookup web service,
nor an interpolator to a specific date.

Stars are given by WDS number (based on J2000 coordinates,
e.g. 37 Pegasi is "22300+0426"), with ADS number and often one
other synonym, though not all possible cross-references.
E.g. the name "37 Peg" doesn't appear in 22300+0426's list of aliases.
Still it looks awfully useful.

A scan for short-period wide pairs turned up one amazing candidate
which seems to have a typo: 00184+4401 a.k.a. "GRB" (Groombridge)
34 AB, mags 8 and 11, period "2.600" years, semimajor axis 41.15".
Here's a snippet of its ephemeris (date, PA, sep) --
they've tabulated it at .25 year intervals since the period is so short:

2003.00 121.1 20.174
2003.25 182.9 25.883
2003.50 211.2 37.568
2003.75 228.6 40.919
2004.00 248.3 33.457
2004.25 288.1 21.512

You could probably see this one move from week to week!
.... but not really. Other references give Groombridge 34's period as
2600 years, not 2.6 years.

Stuart Levy