I finally managed to drag myself out to Mickie Gordon Regional Park a few weeks back to snag a few hours of observing under skies somewhat darker than those under the street light in front of my house. I was wandering around some star fields in Aquila hunting down obscure NGC open clusters when I was struck by the number of faint double stars I was encountering, some in the clusters and many more in adjacent fields. Many of these are bright enough to be seen from suburban skies with modest- to large-aperture 'scopes.
I had started the AL double-star list last fall as a project for the front yard, but often I'd whiz through the list of those stars available on a particular night quickly, leaving me looking for something else. Well, I think I've found it...
As you probably know, we here at USNO are the keepers of the Washington Double Star Catalog (WDS), the most extensive such catalog currently available. It is now closing in on 100,000 stars. Out of all of these systems, there are a huge number that are "neglected", i.e. nobody's looked at them in at least 20 or more years. In fact, there are quite a few that haven't been recorded since their discoveries by the likes of William and John Herschel! We'd like to confirm as many of these systems as possible. You don't even have to make precise measurements...all we need to know is "Yup, it looks like a double to me, the bright one's thisaway and the faint one's thataway, and they're about this far apart". We've even done the dirty work for you, parsing out the "easy" ones and making finder charts for them. You can see these at http://ad.usno.navy.mil/wds/wdstext.html#neglected.
You never know what you may find. Just this past September one of our
observers was looking at a star last observed by John Herschel in 1830.
It proved to be a genuine double and then some...one of the components
may itself be double! So, if you're looking for a back yard program, here's
a chance to follow in the footsteps of some of the legendary observers
of yesteryear and help us track down some "lost" stars.
Here's a brief description of one class of these doubles from the WDS Home Page:
Here's a sample of the first 12 stars in the northern list; these are currently visible in the evening sky:A large number of systems in the WDS may be characterized as "neglected.'' These include unconfirmed binaries as well as systems which have not been resolved for many years. The reasons for this neglect are varied: poor coordinates or large proper motion (so the systems are "lost''), erroneous magnitude or delta-m estimates (so the systems are skipped over or misidentified), or true neglect (too many binaries and too few observers). While the veracity of some of these systems is certainly suspect, many (if not most) of these are bona fide double stars. Three sets of lists are provided in observing list format.
The first set was compiled using the following selection parameters:
A total of 6442 objects meet these criteria. 3072 of them lie north of +20 degrees declination.
Separation greater than three arcseconds Delta-m (V band) of less than three magnitudes Both components brighter than 11th magnitude and one of three possible parameters meriting inclusion Not observed in twenty years (an N code) Unconfirmed (a C code) Orbit system in the above parameter space, possibly useful for calibration (a * code)
|STI1248||10.9||10.9||1961||12.3||42||00 00 24||+60 26||N|
|ES 1292||9.7||9.8||1980||3.3||92||00 01 30||+46 17||N|
|BU 482 AB||9.4||10.4||1955||4.3||342||00 01 54||+63 19||N|
|BU 482 AC||9.4||11.0||1955||10.1||125||00 01 54||+63 19||N|
|MLB 591||9.8||10.2||1928||4.1||345||00 03 06||+30 33||C|
|ES 2400||10.5||10.5||1929||6.1||105||00 03 12||+33 15||C|
|ES 2444||10.0||10.3||1930||6.8||256||00 03 12||+37 14||C|
|HJ1931||8.0||10.7||1908||22.5||115||00 04 12||+49 59||N|
|STF3056CD||9.1||9.7||1981||111.8||227||00 04 42||+34 16||N|
|ES 864||9.4||10.9||1909||9.0||174||00 04 54||+49 39||C|
|HJ 1933||10.9||11.0||1913||14.8||98||00 05 06||+63 23||N|
|STT 547 AB||8.2||8.3||1998||6.1||182||00 25 42||+45 49||*|
Let's look at HJ 1931: It was discovered by Sir John Herschel
in the 1830's and last observed in 1908 to have components of magnitude
8.0 and 10.7, separated by 22.5 arcseconds in Position Angle (PA) 115 degrees.
It is located in Cassiopeia, about 6 degrees southwest of Zeta Cass.
Below is a sample of the finder charts associated with these doubles. HJ 1931 is frame number 0008. The charts are digitized renderings from the Palomar Observatory Sky Survey (POSS). The cross-hairs mark the location of the double in question. In some cases there's a bit of an offset due to the proper motion of the stars since the initial images were made. The chart is there to help you locate the field. It's fairly straightforward to go from there to the eyepiece and look for a double that closely matches the parameters in the catalog. The charts may be found on the WDS web page in PostScript, Acrobat (PDF), or GIF formats.
Most of these stars are fairly faint, but they should all be within the grasp of a good 8-inch telescope at a typical suburban location. Observation is pretty straightforward. Choose a moderately high power of about 20x - 25x per inch of aperture. Observe a few of the well-known doubles on the AL list to get a "feel" for estimating the component separations and position angles of the secondary with respect to the primary. The latter are measured from north (0 degrees) through east (90 degrees), south (180 degrees), and west (270 degrees). One easy way to figure the orientation of the field is to turn off your telescope's drive (if any) and watch which way the stars drift. They will always drift toward the west, so a star whose secondary "precedes" the primary will be at a PA of somewhere around 270 degrees. If you're observing without a star diagonal, north will be 90 degrees "clockwise" from west; with a diagonal it will be 90 degrees "counterclockwise".
Your observations do not need to be precise, but you should note a few things in your logbook, such as UT date and time, observing site, the target star, instrument aperture and magnification, "seeing" conditions (steadiness or turbulence of the atmosphere), and the estimated separation and PA. Who knows...you may be the first person to observe one of these systems in over a century! You may feel free to submit your observations to me at firstname.lastname@example.org, or directly through the "comments" form on the WDS web page.
Good luck and good hunting!