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Double Stars ~ Why Observe Them?

To quote from the late Paul Couteau who observed from the Observatoire de NICE, " The contribution of amateur astronomers to the observing of double stars have been important. We can cite the example of S.W. Burnham (1838 - 1921) who used the largest instruments of his time, the Reverend T.H.E.C. Espin (1858 - 1934) in England, R. Jonckheere (1889 - 1974), Dr. P. Baize and M.V. Duruy (1894 - 1984) in France. The abundance and quality of these observers' measures are sufficient evidence of this.

Nowadays, astronomy has made fantastic progress with large ground-based telescopes so we may wonder if an amateur astronomer with his limited resources is still able to contribute efficiently to the observation of double stars. The answer is YES, for two reasons: To begin with, astronomical research does not belong exclusively to the professional astronomer because the amateur astronomer can gain access to large telescopes. In addition, amateurs can buy powerful instruments from firms specializing in telescope making and with a 50-cm aperture most of the binary stars can be observed."

I would go further. There are so many double stars within the range of even a 25-cm telescope that it would occupy the entire career of an amateur astronomer to measure even a modest proportion of them. Furthermore, whereas a decade or so ago access to the published measures and orbits was very difficult for the average amateur, the internet has changed all that.

Before you take the plunge and invest in a micrometer, which is admittedly an expensive piece of specialist kit, take time to familiarise yourself with some of the brighter pairs, especially those of contrasting spectral types. Sissy Haas has prepared a list of pairs that require a short description, which includes magnitude estimates, visual appearance, and difficulty: downloadlist.pdf [104Kb] (nb: unless you have either an ISDN or ADSL broad bandwidth internet connection please do not single click on the link _ instead click and hold and use the pop-up menu to select download link to disc).

For further information on double star measurement go to the United States Naval Observatory and the WDS catalogue.

For details of where to submit your measures and obtain assistance in getting started go to the Double Star Observer.

 

Micrometeric Measurement of

Visual Binaries

To make micrometric measures of double stars including gravitationally bound binaries all you need is either a bifilar micrometer or a double image micrometer and a heavy duty long focus equatorial telescope.

I own three micrometers:

Grubb Bifilar Micrometer

A Grubb bifilar micrometer that I have restored and retro-fitted with 10 micron diameter quartz filaments, illuminated with ultra-brite LEDs controlled by a rheostat. The bifilar micrometer has 50tpi screws with 80 revolutions travel. The position angle or PA circle is driven by a worm and wheel, and reads by verniers to ±30arcsecs. The micrometer has an eyepiece plate that is free to slide across the focal plane. It enables the measurement of very wide pairs, wider than 100 arcsecs. To learn how to set up and use a bifilar micrometer download this .pdf [624Kb] file to disc Bifilar Micrometer Calibration. (nb: unless you have either an ISDN or ADSL broad bandwidth internet connection please do not single click on the link _ instead click and hold and use the pop-up menu to select download link to disc).

Troughton & Simms

A Troughton & Simms divided lens micrometer c1858, restored by H.N. Irving & Sons 1994. The micrometer has five separate objectives for use in the microscope section. It can be used to accurately measure pairs between the Rayleigh Limit and approximately 80arcsecs. The PA circle reads to ±30arcsecs by means of verniers. A divided-lens micrometer is capable of delivering more consistent and accurate measures than a wire (filar) type micrometer. For more information on setting up and using this type of micrometer download this .pdf [2.2Mb] file to disc Double Image Micrometer. (nb: unless you have either an ISDN or ADSL broad bandwidth internet connection please do not single click on the link _ instead click and hold and use the pop-up menu to select download link to disc).

 

Lyot Micrometer

The third micrometer I own is a modern Lyot Spath Blade micrometer. It was purchased from Meca-Precis in France in 1994. The Lyot micrometer is an extremely accurate device capable of repeatabilties of ±0."10arcsecs or better. It has however a range restricted to approximately 10 arcsecs. For more information on setting up and using this type of micrometer download this .pdf [240Kb] file to disc Lyot Micrometer. (nb: unless you have either an ISDN or ADSL broad bandwidth internet connection please do not single click on the link _ instead click and hold and use the pop-up menu to select download link to disc).

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