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Main
Date: 01 Sep 2006 21:41:30
From: Terry A Haimann
Subject: Measuring Binary stars
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Is there any books or web pages that explains how to measure the
seperation and angle of binary stars with a goto (yes it is equatorially
mounted.) The problem as I see it is you need to know the angle of drift
through the e.p. and I don't think you can set your telescope to shut down
temporarily to check the drift.
Thx, Terry
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Date: 01 Sep 2006 22:08:57
From: MA-MA
Subject: Re: Measuring Binary stars
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"Terry A Haimann" <terry@Pegasus.oldboy > wrote in message
news:pan.2006.09.01.21.37.26.690028@Pegasus.oldboy...
> Is there any books or web pages that explains how to measure the
> seperation and angle of binary stars with a goto (yes it is equatorially
> mounted.) The problem as I see it is you need to know the angle of drift
> through the e.p. and I don't think you can set your telescope to shut down
> temporarily to check the drift.
>
> Thx, Terry
Why would you want to do that? Just look em up. They already have that
info.
You're just screwing around.
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Date: 02 Sep 2006 13:43:00
From: Paul Schlyter
Subject: Re: Measuring Binary stars
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In article <Zb2Kg.408$Hr1.255@clgrps12 >, MA-MA <am@telusplanet.net> wrote:
> "Terry A Haimann" <terry@Pegasus.oldboy> wrote in message
> news:pan.2006.09.01.21.37.26.690028@Pegasus.oldboy...
>> Is there any books or web pages that explains how to measure the
>> seperation and angle of binary stars with a goto (yes it is equatorially
>> mounted.) The problem as I see it is you need to know the angle of drift
>> through the e.p. and I don't think you can set your telescope to shut down
>> temporarily to check the drift.
>>
>> Thx, Terry
>
> Why would you want to do that? Just look em up. They already have that
> info. You're just screwing around.
Using your logic, it would be pointless to use your own telescope at all.
Why? Because there'll always be a Hubble picture which shows your object
in much greater detail than you can ever hope to see with your telescope.
So using your own telescope to look at stuff is just screwing around - right?
At least according to your logic....
And from where do you think that "They already have that info" came? Yep,
from people who measured it themselves.....
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
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Date: 01 Sep 2006 22:07:06
From: Chris L Peterson
Subject: Re: Measuring Binary stars
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On Fri, 01 Sep 2006 21:41:30 GMT, Terry A Haimann <terry@Pegasus.oldboy >
wrote:
>Is there any books or web pages that explains how to measure the
>seperation and angle of binary stars with a goto (yes it is equatorially
>mounted.) The problem as I see it is you need to know the angle of drift
>through the e.p. and I don't think you can set your telescope to shut down
>temporarily to check the drift.
The usual approach is to use a camera and compare with surrounding
stars. But if you want to do a visual approximation, it should be easy
enough to calibrate the angle of your reticle. Just use the handpaddle
to bop back and forth a little in RA, and rotate the reticle until stars
move parallel to it. There's no need to let things drift. To calibrate
distance, just use a pair of stars with a known separation.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 01 Sep 2006 14:52:48
From: Brian Tung
Subject: Re: Measuring Binary stars
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Terry A Haimann wrote:
> Is there any books or web pages that explains how to measure the
> seperation and angle of binary stars with a goto (yes it is equatorially
> mounted.) The problem as I see it is you need to know the angle of drift
> through the e.p. and I don't think you can set your telescope to shut down
> temporarily to check the drift.
If the telescope is accurately equatorially mounted, then you should be
able to calibrate the reticle eyepiece (assuming you're using one) at
the start, and then use that calibration for the rest of the session,
provided you don't switch eyepieces or move the diagonal. And the goto
telescopes I've used, you *can* shut down temporarily, once you've got a
star centered, in order to calibrate a reticle eyepiece. What about the
scope you're using prevents you from doing that?
--
Brian Tung <brian@isi.edu >
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html
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Date: 01 Sep 2006 23:57:23
From: Terry A Haimann
Subject: Re: Measuring Binary stars
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On Fri, 01 Sep 2006 14:52:48 -0700, Brian Tung wrote:
> Terry A Haimann wrote:
>> Is there any books or web pages that explains how to measure the
>> seperation and angle of binary stars with a goto (yes it is equatorially
>> mounted.) The problem as I see it is you need to know the angle of drift
>> through the e.p. and I don't think you can set your telescope to shut down
>> temporarily to check the drift.
>
> If the telescope is accurately equatorially mounted, then you should be
> able to calibrate the reticle eyepiece (assuming you're using one) at
> the start, and then use that calibration for the rest of the session,
> provided you don't switch eyepieces or move the diagonal. And the goto
> telescopes I've used, you *can* shut down temporarily, once you've got a
> star centered, in order to calibrate a reticle eyepiece. What about the
> scope you're using prevents you from doing that?
Its a lx-90, I don't remember reading of the capability, but I'll look
into it.
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Date: 01 Sep 2006 22:54:45
From: canopus56
Subject: Re: Measuring Binary stars
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Terry A Haimann wrote:
> Is there any books or web pages that explains how to measure the
> seperation and angle of binary stars with a goto (yes it is equatorially
> mounted.) The problem as I see it is you need to know the angle of drift
> through the e.p. and I don't think you can set your telescope to shut down
> temporarily to check the drift.
Visual technique:
1) Point your scope at the zenith.
2) Insert the illuminated reticule.
3) Turn off the drive.
4) Align the 90 deg and 270 deg line to the stars drifting east-west
through the AFOV.
5) Lock the reticule in place and do not move it for the rest of the
session. It now marks celestial north.
6) Turn drive back on and realign to your nearest alignment stars.
7) Put the target primary in the center of the main reticule or if
there is a smaller hemispherical target (as in the Meade illuminated
reticule) use that.
8) Read off the P.A. of the secondary.
Argyle, R. (ed). 2004. Observing and Measuring Visual Double Stars.
Springer. ISBN 1-85233-558-0 http://www.springer.com/
Chris mentioned photographic techniques. Relatively inexpensive
software like AIP4WIN ( www.willbell.com ) contain astrometry tools to
make the measurement off an image.
- Canopus56
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Date: 02 Sep 2006 18:41:28
From: canopus56
Subject: Re: Measuring Binary stars
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Terry A Haimann wrote:
> Is there any books or web pages that explains how to measure the
> seperation and angle of binary stars with a goto (yes it is equatorially
> mounted.)
Terry,
Two other techniques are described in Argyle's book, in addition to the
one I described based on the Meade illuminated reticule instructions.
Argyle draws them from two S&T articles that may be obtained from your
local library.
Tanguay, R.C. Feb. 1999. Observing Doubles Stars for Fun and Science.
S&T __:116
Teague, T. July 2000. Double-Star Measurements Made Easy. S&T
100(1):112
Argyle reviews both Tanguay's and Teague's methods but expands on them
with alot of extra reduction math in order to increase accuracy.
Tanguay, may be of particular interest to you since it does not involve
turning the drive off in order to measure position angle. He puts a
piece of foam board with a protractor glued to it around the focuser
tube and adds a pointer to a basic Celestron (or Meade) illuminated
reticule. See his S&T article for pictures of these kludge gizmos. (His
demonstration scope is a 90mm Questar - similar in size to your scope.)
Using the reticule, he aligns this foam mounted protractor to
celestial north. The foam mounted protractor is then fixed for the
rest of the evening and you can move (or remove) the reticule eyepiece
as needed throughout the night.
Teague notes that his method is simplier, since you do not have to use
any foam mounted gizmos or align the reticule to celestial north.
Simply put the linear scale through the primary and secondary stars
with primary at the center of the linear scale. Pause the tracking
motor. On my mount, the hand-controller contains an option to turn
tracking on and off momentarily. When primary drifts to the outer 360
deg scale, turn tracking back on, so the primary rests on the outer
scale.
The star has drifted along the east-west celestial line by definition.
The angle between the linear scale and where the primary drifted onto
the 360 deg scale gives you the angle defined by the east-west drift
line and the line between the primary and the secondary.
You'll also need to figure out where the north celesital pole is in
which eyepiece hemisphere - perpendicular to the east-west drift line.
A good trick to do this is to simply roughly align your red flashlight
to Polaris at the end of the telescope tube and then move it in front
of the telescope tube while looking in the eyepiece. The red light
will move in to your e.p.'s AFOV from the North.
Rather than go into a lengthy explanation of how to compute the
position angle of the star with this information from the illuminated
reticule and Teaque's method, the easiest way to find the p.a. is to
sketch what you see in the eyepiece onto an observing form, using a
compass and protractor. From your sketch, you can work out how what
the position angle relative to the north celestial pole. Remember to
label West and East on the form.
Hope that info helps.
- Canopus56
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