Jump to content


Photo

Do you measure double stars??

  • Please log in to reply
51 replies to this topic

#1 nomosnow

nomosnow

    Ranger 4

  • -----
  • Posts: 371
  • Joined: 21 Mar 2011
  • Loc: Fort Saskatchewan,Ab ,Canada

Posted 04 April 2012 - 12:29 AM

Hi
I am having a lot of fun measuring double stars with my astrometric EP. And I am quite happy with my first time accuracy. I am using procedures that Bob Argyle suggests in his excellent book.
I am hoping that maybe I could "help out" in measuring some neglected doubles . Does anybody actually do this and if so where would you submit your results.
In anycase it is fun doing some "classic" astronomy. :grin:

#2 azure1961p

azure1961p

    Voyager 1

  • *****
  • Posts: 10474
  • Joined: 17 Jan 2009
  • Loc: USA

Posted 04 April 2012 - 07:05 PM

Yes there are people who do this - one individual comes to mind with a 90mm Questar. Heres an informative link to get you started;

http://www.skyandtel...rs/3304341.html

Pete

#3 buddyjesus

buddyjesus

    Vanguard

  • *****
  • Posts: 2236
  • Joined: 07 Jul 2010
  • Loc: Davison, Michigan

Posted 13 April 2012 - 04:52 PM

I am eager to get to measuring some of the doubles also. This journal has good articles that describe the methodology.

http://www.jdso.org/

#4 rookie

rookie

    Good Night Nurse

  • *****
  • Posts: 3070
  • Joined: 14 Jan 2006
  • Loc: St. Petersburg, FL

Posted 13 April 2012 - 06:51 PM

I have made a game of "Guestimate".
I make an observation, go check my results on Skytools, and then look again to see how I could have done better. I'm learning and improving but some nights are better than others. A reticle ep is a nice investment.

Hats off to those that take the time to make fine measurements. :bow:

#5 desertstars

desertstars

    ISS

  • *****
  • Posts: 42915
  • Joined: 05 Nov 2003
  • Loc: Tucson, AZ

Posted 13 April 2012 - 09:24 PM

I am eager to get to measuring some of the doubles also. This journal has good articles that describe the methodology.

http://www.jdso.org/


A good source of double star information all around. :waytogo:

#6 ken hubal

ken hubal

    Apollo

  • *****
  • Posts: 1079
  • Joined: 01 May 2007

Posted 14 April 2012 - 03:11 PM

I you can obtain a Filar Micrometer, do so. It is a good tool for making measurements. Otherwise, a good astrometric eyepiece will work.

#7 drollere

drollere

    Surveyor 1

  • *****
  • Posts: 1588
  • Joined: 02 Feb 2010
  • Loc: sebastopol, california

Posted 15 April 2012 - 12:54 PM

the u.s. naval observatory (USNO) curates the largest double star database (WDS). if you go to their home page you will find links to a list of "neglected doubles":

http://ad.usno.navy....text.html#files

perusing the list, you'll find many stars that haven't been measured since they were discovered, and many of those that haven't been measured in decades or even since the 19th century. most are brighter than v.mag 10. jump in.

you will need to document all your observations as well as your summary statistics for each pair. you'll need to make multiple measurements with the micrometer eyepiece on at least two different nights. it can get tedious if you're not motivated.

the JDSO ( http://www.jdso.org/ ) periodicals describe a variety of measurement methods and results. you should review those to get a sense of what's possible.

i believe the JDSO is the place to send your observations, so contact them for details. stuff they approve gets passed on to the guys at USNO for their review and eventual inclusion in the WDS.

i also have made a real effort to judge position angle and separation by eye. at present i can usually guesstimate values to around 20% of separation and plus/minus 20º PA. nothing formal; i do it so that i can recognize when the catalog source i'm using is probably incorrect, and can check the system in WDS. i've even found a few systems in obvious need of new measurement ... a project for later this year.

#8 Ed Wiley

Ed Wiley

    Apollo

  • -----
  • Posts: 1051
  • Joined: 18 May 2005
  • Loc: Texas, USA

Posted 19 April 2012 - 01:33 PM

As others have said, JDSO is the place to go. Look for articles by Russ Genet and his group, they make extensive use of astrometric EPs and there are articles you need to read about techniques that are scattered through several years. I use a webcam, which I find more efficient. But, use what you have. :)

Ed

#9 rookie

rookie

    Good Night Nurse

  • *****
  • Posts: 3070
  • Joined: 14 Jan 2006
  • Loc: St. Petersburg, FL

Posted 03 June 2012 - 06:13 PM

I've looked for 360 degree protractors in the past, couldn't find one and then forgot about buying one. Then today, spotted them on clearance at Staples for $.50. It's a nice sturdy 6" Staedtler. Apparently the rush from the double star measuring astronomers has passed and Staples has been caught with a plethora on their shelves. :imawake:

#10 WRAK

WRAK

    Apollo

  • -----
  • Posts: 1193
  • Joined: 18 Feb 2012
  • Loc: Vienna, Austria, Europe

Posted 04 June 2012 - 07:28 AM

I own a 12.5mm micrometer eyepiece but use it only if I have good reason for it - means clear differences between my guesses based on visual observation and catalogue entries (I usually avoid having all informations about the doubles in my sessions plans especially the position of the companion to be better able to counter check with catalogues if my observations are correct). The need to use different or several barlows and to have to do some calculations afterwards to translate eyepiece divisions into degrees and arcseconds takes somewhat the fun out of it. A Filar Micrometer would at least make the measurement of separations a bit more flexible but I found so far no source

#11 payner

payner

    Viking 1

  • *****
  • Posts: 909
  • Joined: 22 Mar 2007
  • Loc: Bluegrass Region, Kentucky

Posted 04 June 2012 - 04:02 PM

Check Van Slyke Instruments for a production bi-filar micrometer. Better be seriously into this endeavor because they are not cheap.

#12 WRAK

WRAK

    Apollo

  • -----
  • Posts: 1193
  • Joined: 18 Feb 2012
  • Loc: Vienna, Austria, Europe

Posted 05 June 2012 - 02:10 AM

Thanks payner, great tip with Van Slyke, will consider even if the price is somewhat stiff.
Only one drawback - my APO is for reasons of ease to use with 980mm rather short, so the included 25mm Plössl does not make much sense for me despite the included 2x barlow. But I think you should be able to use any 1.25" eyepiece with it, I will check this.
Wilfried

#13 Simoes Pedro

Simoes Pedro

    Messenger

  • *****
  • Posts: 457
  • Joined: 03 Feb 2009

Posted 07 June 2012 - 10:00 AM

If I purchased my own reticle from Edmund opticsto mate it to an eyepiece I already own, I has to be placed at eyepiece's field stop, right?

#14 David Knisely

David Knisely

    Hubble

  • *****
  • Posts: 15709
  • Joined: 19 Apr 2004
  • Loc: southeastern Nebraska

Posted 07 June 2012 - 12:55 PM

I am surprised no one has mentioned making a diffraction micrometer. They are very very cheap and give results equal to or better than some reticle eyepieces:

Observing and Measuring Visual Double Stars: the diffraction micrometer

It won't work for some fainter pairs, but for moderately bright ones, it is a simple and easy way to get into double star measurements. Clear skies to you.

#15 WRAK

WRAK

    Apollo

  • -----
  • Posts: 1193
  • Joined: 18 Feb 2012
  • Loc: Vienna, Austria, Europe

Posted 09 June 2012 - 01:01 PM

Quite interesting. There is another article on this topic "http://www.nyskies.org/articles/pazmino/diffmic.htm" - but the handling seems a bit time consuming, especially field rotation (I use an alt-az mount without tracking) is an obstacle.
I found an interesting article of Thomas G. Frey "Visual Double Star Measurements with an Alt-Azimuth Telescope" in JDSO Spring 2008 using an micrometer eyepiece and especially the measurement of the position angle does not seem so difficult to me anymore as after aligment of the double on the linear scale and positioning the primary on its central mark you have simply to wait until the primary reaches the angle scale giving you the value for the position.
Wilfried

#16 chascar

chascar

    Messenger

  • *****
  • Posts: 432
  • Joined: 14 Feb 2005
  • Loc: Franklin Massachusetts

Posted 13 June 2012 - 08:56 AM

There is a good article on Belt of Venus web site about putting together a protractor assembly for astrometric EP also second edition of Argyles book is due out Aug. 2012

#17 chascar

chascar

    Messenger

  • *****
  • Posts: 432
  • Joined: 14 Feb 2005
  • Loc: Franklin Massachusetts

Posted 13 June 2012 - 08:56 AM

There is a good article on Belt of Venus web site about putting together a protractor assembly for astrometric EP also second edition of Argyles book is due out Aug. 2012

#18 WRAK

WRAK

    Apollo

  • -----
  • Posts: 1193
  • Joined: 18 Feb 2012
  • Loc: Vienna, Austria, Europe

Posted 13 June 2012 - 12:21 PM

Charles, quite interesting article - but I find the method described by Thomas G. Frey in his article "Visual Double Star Measurements with an Alt-Azimuth Telescope" in JDSO Spring 2008 (Thomas G. Frey "Visual Double Star Measurements with an Alt-Azimuth Telescope" in JDSO Spring 2008) quite easier and more comfortable as you need not even make a protractor assembly but use instead only the angle scale already available on the micrometer eyepiece.
Wilfried

#19 Rutilus

Rutilus

    Surveyor 1

  • -----
  • Posts: 1889
  • Joined: 17 Dec 2010

Posted 29 July 2012 - 01:48 PM

With all the cloud here over the last couple, I've been spending more time making astro stuff. Yesterday I made
a protractor assembly, took about an hour. Amazingly the sky was clear last night, so could not resist trying it out.

Spent about an hour calibrating, using Beta Cygni as a calibration star. Moved onto Gamma Del, to try my first
measure of the P.A. with this instrument. Took 30 readings, then moved back to Cygni to observe various objects,
before going back to Gamma Del and finally making another 10 readings.

Ended up with a P.A. average of 266-267 degrees. Quite pleased with the result, and I built it to add more interest
and enjoyment to my double star observing.
I used the instrument on my 120mm f/8.3 Achromat, also used was a 2x Barlow giving a power of 166x.
Some pictures below showing it on the scope in the observatory.

Attached Files



#20 Rutilus

Rutilus

    Surveyor 1

  • -----
  • Posts: 1889
  • Joined: 17 Dec 2010

Posted 29 July 2012 - 01:50 PM

Another shot.

Attached Files



#21 Rutilus

Rutilus

    Surveyor 1

  • -----
  • Posts: 1889
  • Joined: 17 Dec 2010

Posted 29 July 2012 - 01:51 PM

Final one.

Attached Files



#22 rookie

rookie

    Good Night Nurse

  • *****
  • Posts: 3070
  • Joined: 14 Jan 2006
  • Loc: St. Petersburg, FL

Posted 29 July 2012 - 05:16 PM

Rutilus,
Very nicely done! It looks like fun too. Thanks for posting your pictures. :bow: :applause: :cool:

Fyi, I calibrated my ep with Psi Picium sep 30" for even numbers. If you ever decide to observe it you can double check your current reference measures to extrapolate your ep scale values.

#23 Rutilus

Rutilus

    Surveyor 1

  • -----
  • Posts: 1889
  • Joined: 17 Dec 2010

Posted 29 July 2012 - 06:34 PM

Many thanks Rookie, I will have to check out Psi Picium.
Just had a very short session this evening, thanks to the clouds that have rolled in again.

Only managed 5 readings for Alpha Her, got a P.A. of 107 degress, would have liked to obtain quite a few more
readings. Also think I need to increase the magnification,to help with making readings. Still this cheap to make
system appears to have potential.

#24 Rich (RLTYS)

Rich (RLTYS)

    Fly Me to the Moon

  • *****
  • Moderators
  • Posts: 5328
  • Joined: 18 Dec 2004
  • Loc: New York (Long Island)

Posted 30 July 2012 - 05:21 AM

Looks good. Have fun.

Rich (RLTYS)

#25 Ed Whitney

Ed Whitney

    Messenger

  • -----
  • Posts: 483
  • Joined: 08 Jul 2010
  • Loc: Palm Coast, Florida

Posted 13 August 2012 - 04:46 PM

Rutilus,

Any chance you could post info on how to make that neat device?

Does it measure PA and also separation? Or is sep measuring a separate operation?

Or, can you just post some info on its use?

I've been trying to get into DS observing and perhaps measuring but after reading some of the methodology have turned instead to simpler things.

Thing is, I would like to "just" be able to do this! :)

You're right about the clouds! Palm Coast has had rain and clouds now for weeks! When I get to see anything, it's usually thru a "mushy" sky. BUT! double stars are still doable! (sometimes)

Your pictures are great! Thanks!






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics