The prior post dealt with short period pairs. These additional notes are grouped by some things I noticed while reading the Catalog:
- Aperture, where aperture made the difference in discovery
- Pairs which Burnham himself described them as difficult
- Pairs which exhibit Burnham's "eagle eye" observing ability
- Some possible unverified discoveries
- Pairs with notable color
===========
Aperture: There are many cases where aperture made
the difference in discovery. These are
often discovered while making a measurement of a previously discovered pair:
BU 1143, 5.73/13.30 1.6”, of which Burnham writes:
"The close companion to the principal star of the wide triple STF 2816…was
discovered with the 36-inch. It is
probably too difficult for any of the instrument with which the other stars
have been observed."
BU 1024, components of STF 2476. "That instrument [the 36-inch] shows
four other stars [m 11.24, 13.90, 13.10, 13.10] nearer than the Struve
companion."
BU 1240, 6.29/6.21 0.15” at discovery with the
36-inch. "As the components are
nearly equal in magnitude, it is a comparatively easy object with that aperture.”
BU 131: "The close pair [AB, 7.54/9.30 2.0”
at discovery] was discovered with the 6-inch, and in measuring that, the third
star C was added with the 18.5-inch.” BC
= 9.30/11.75 4.6” at discovery.
BU 291:
9.80/9.80 0.4” at discovery with the 6-inch. "This star was suspected with the 6-inch
to be a close pair in 1872, and verified by me with the 26-inch at Washington
in August 1874. It is a difficult object
with a small aperture. It is clearly a
binary. Both angle and distance are
increasing, and it is much easier now than it was at the time of discovery....
This pair is within the triangle of 6m stars formed by 34, 35, and 37
Pegasi. The first of these bright stars
is BU 290, and the last STF 2912."
Obviously overlooked by STF. WDS
uncertain of binarity after 56 measures.
BU 663: The
C star was discovered with the 18.5-inch, and while measuring that "with
the 36-inch a still nearer companion [B] was detected. This is a difficult object with a large
aperture." AB: 6.6” 6.18/14.20.
BU 896 AB: 0.9” 7.17/10.31: "In looking over
my old observing books with the 6-inch recently I find that the close pair was
suspected with that instrument three years before its independent discovery
with the 18.5-inch."
BU 935 AB: 86 Vir.
AB, CD. "Both components of Struve's rejected pair [STF 1780] were
found to be double with the 18.5-inch.
With a large aperture it is one of the finest of the quadruple groups….
In making the measures of 1889.30 with the 36-inch, two new nebulae were discovered
in the field." WDS shows AB &CD
as uncertain, and incorrectly attributes CD to Struve. Steve Gottlieb helped me identify the two
nebulae discovered as IC 924 & IC 927.
BU 956: AB 0.6” 8.05/9.21: "This difficult
pair was suspected with the 6-inch in 1873 at the time of the discovery of BU
125, and referred to in the note to the latter pair. It proved to be a very difficult object to
verify, although it was examined many times with both the 6- and 18.5-inch
refractors. Finally in 1880 it was
fairly well seen and measured with the larger aperture [26-inch at USNO] ....
BU 125 is 20' s."
BU 106: Three different apertures used to discover
various pairs: AB with 6-inch (2.0” 5.61/6.62), AE with 18.5-inch (26.6”
5.61/12.6), and with the 36-inch AC (12.9” 5.61/14.70) & AD (25.7”
5.61/14.10).
============
“Difficult pair”: You know if Burnham calls a pair
“difficult,” it must be a challenge.
This would make a good observing list for fine nights. Discovery aperture shown. Includes a few short period. A number of these are neglected pairs and
really ought to have follow-up measures.
BU 89 AB 6-inch. "A difficult pair with that
aperture." 0.55" at discovery,
0.8” now so probably very doable with a 6-inch, 7.27/8.94
BU 135 AB, 6-inch. "Very difficult with this
aperture." 2” at discovery, 2” now, 6.58/10.6
BU 246 AB, 6-inch.
"This difficult pair…".
0.4” at discovery, 0.5” now, 8.4/8.27
BU 275 AB 9.4-inch. "A difficult pair with small
apertures. The measures do not show the
change which would be expected in a pair of this class." A very impressive 0.3” at discovery, 0.4”
now, 7.18/8.99.
BU 1009 AB, 12-inch. "This fine and difficult pair was
discovered at Mt. Hamilton with the 12-inch in 1881…. The measures are sufficient
to show from the common proper motion that this is a physical pair." WDS lists it as uncertain. 1.8” at discovery, 1.9” now, 4.41/11.00.
BU 1219 AB 12-inch. "A difficult pair with that
aperture." 0.5” at discovery, 0.6”
now, 9.97/10.24.
BU 836 CD 15.5-inch. "The principal pair [AB] was discovered
with the 15.5-inch of the Washburn Observatory, and it was then stated that C
might also be double. This was verified
with the 36-inch in 1888, thus making a pretty but difficult quadruple
group." 1.2” at discovery, 1.4”
now, 11.28/12.30.
BU 524 AB 18.5-inch. "It is at all times a difficult pair,
and the motion is rapid. It is now known
to be one of the most interesting binaries in the heavens. The distance never much exceeds 0.2", so
that it is always a difficult pair, and beyond the reach of most
telescopes.". 0.3” (near apastron) at
discovery, 0.2” now, 5.79/6.8. Short
31.63-year period, coming off apastron and rapidly closing. I attempted in January 2019 with my 12.5-inch
and did not see any elongation.
BU 550 AB 18.5-inch. "It was a very difficult object to see
with the Chicago telescope, and might easily be overlooked even with the
36-inch refractor." Alpha Tauri. 30.5” at discovery, 31” now, 0.85/13.6
BU 552 AB 18.5-inch. "This pair was discovered with the
18.5-inch, but in looking over the old observing books used with the 6-inch, I
find that on December 14, 1874, this star was noted as 'possibly a close
pair'…There seems to be something singular about the appearance and difficulty
of this pair at times with larger apertures.
It was not noted as difficult at the time of the observation in
1877. In 1890 it was a hard star with
the 36-inch and on two nights in 1892, under favorable conditions, I failed to
see it double at all.". 0.8” at
discovery, 0.8” now, 6.41/8.89. Short
95.2-year period pair with a near edge on orbit (Stelle Doppie’s orbital
solutions appear incorrect). In 1890 the
star was near periastron, so certainly more difficult, but should have been observable
in the 36-inch.
Figure 1:
BU 552 in 1874 / in 1877
Figure 2:
BU 552 in 1891 / in 2020
BU 686 AB 18.5-inch. Component of STTA 220. "It is a difficult pair, and likely to
prove an interesting one. The estimated
magnitudes of B [by the five observers giving measures in the
Catalog]
are very discordant" – indeed they range from 8m to 13m. WDS confirms physical and sets B mag at 11.22. 0.4” at discovery, 1” now, 9.39/11.22.
BU 705 AB 18.5-inch. "A difficult object with that aperture
[18.5-inch]…. I could not see it on one
night in 1898 with the 40-inch. It
should be watched with large instruments."
There are only 2 observations in WDS!
1878 (Burnham) and 1905 (Aitken?).
Certainly a neglected pair, 1.5” at discovery, 1.8” now, 6.67/12.2 – likely
the large delta mag inhibits observation.
BU 733 AB 18.5-inch AB, 85 Peg. This is a rare case where Burnham writes
excitedly: “One of the most important
and most interesting of the known binary systems. The shortness of its period, the rapid movement
in space of both components, the relative nearness of this system to our own,
and the extreme inequality in magnitude and closeness of the stars, all combine
to give this a leading place among the binary stars. It is at all times an object of considerable
difficulty, and the reliable observations will necessarily be confined to the
larger refractors. It is an excellent
test for the definition of any object glass, however large, and no instrument,
whatever its aperture, can deal with a pair of this class unless the figure of
the objective will compare favorably with the Alvan Clark standard.” 0.7” (near apastron) at discovery, 0.4” now,
5.83/8.9. I attempted it in November
2020 with my 20-inch at 667x: “With apodising mask. Difficult, see a brightening with averted
vision and foveal coaxing, but does show as faint star briefly. My PA is ENE, which is slightly
incorrect. 26.28-year period, this one
is widening for apastron in 2035. I have
no doubt my 20-inch will get this one cleanly when it is wider! Interestingly, in 1899 when the book was written the right ascension put this pair at the end of the Catalog, but due to precession today it would be sorted to the front, having crossed the 0-hour line.
Figure 3:
BU 733 in 1877 / in 2020
BU 878 AB 18.5-inch. "A more difficult pair than the distance
and magnitude would indicate." 1.1”
at discovery, 0.7” now, 6.22/10.45.
BU 971 AB 18.5-inch "It is certainly a
binary, and in rapid motion. In 1891 it
has become a difficult pair with the 36-inch, and appeared to be rapidly
closing. Three years later Barnard found
it single with the same instrument.
Under fair conditions 1898.56 I could not see any certain elongation with
the 40-inch. The single observation of
Aitken [1n 1898.70] is noted as 'very difficult and uncertain.' The difference in magnitude of the components
makes it a much more difficult pair than it would at first seem to be. The measures indicate that the plane of the
orbit is nearly in the line of sight."
Appendix: "This will be an interesting system, but further measures
are necessary to show the apparent orbit."
0.5” at discovery, 0.5” now, 7.37/10.16.
WDS uncertain with 33 measures.
BU 1050 AB 36-inch. "A difficult pair of small stars in the
nebula of Orion". 0.7” at
discovery, 0.9” now, 11.3/12.5.
BU 1099 AB 36-inch. "close and difficult". 0.2” at discovery, 0.3” now, 6.11/6.53. Short period, 83.1-years.
Figure 4:
BU 1099 in 1889 / in 2020
BU 1105 AB 36-inch. In the Pleiades. 0.3” at discovery, 0.2” now, 9.3/10.4
BU 1106 AB 36-inch. "Another difficult pair in the
Pleiades." Aitken's measure in 1899
is "uncertain," "and the apparent change of more than 30-degrees
in the past ten years may not be real.
It is very difficult object with the largest aperture." WDS uncertain, only two measures, Burnham's
& Aitkens’! -- get this one
soon! 0.4” at discovery, 11.6/11.6.
BU 1131 AB 36-inch. "…a difficult object and beyond the reach
of all but large refractors…. It is evident from the measures that the faint
companion is moving with it, and we certainly have a most interesting physical
system." WDS uncertain after 9
measures only. 3.6” at discovery, 2.3” now,
4.5/12.9
BU 1151 CD 36-inch. "A difficult pair, and so far without
change. It is too faint to be included
in the Durchmusterung. In the
field with STF 3022.” WDS uncertain with
11 measures. 0.6” at discovery, 0.4” now,
9.3/9.3. Surprising that Struve or
others could have missed it previously.
BU 1153 AB 36-inch. "A very difficult pair of small stars…Too
faint to be given in the Durchmusterung. I have connected it with another pair in the
field, STT 511." WDS uncertain with
7 measures. 0.4” at discovery, 0.5” now,
9.7/9.9
BU 1159 AB 36-inch. "…very
minute and difficult pair."
Appendix: "Examined by Aitken (1899.89) and elongation suspected in
52-degrees +/-, with distance of 0.2" or less, but conditions not good
enough for accurate measurement."
WDS uncertain with 6 measures.
0.2” at discovery, 0.2” now, 9.9/10.1.
For Aitken to have only a suspected elongation, it may well be a rapid
motion pair.
BU 1162 AB 36-inch. "Difficult pair." 0.3” at discovery, 0.3” now, 10.1/10.3
BU 1170 BC 36-inch, component of X Persei. 0.3” at discovery, 0.3” now, 11.5/11.7. "It is a very difficult pair, and the
apparent change [from his measures to Aitken's of 1899] requires
confirming." WDS uncertain, only 4
measures.
BU 1179 AB 36-inch. "A difficult pair." 0.7” at discovery, 0.6” now, 4.72/7.34
BU 1217 AB 36-inch. "A difficult pair, and therefore the
change in angle requires verification."
WDS uncertain with 11 measures.
0.6” at discovery, 0.3” now, 7.91/9.48.
BU 1241 AB 36-inch. "It is a difficult pair of the 85 Pegasi
class." Appendix: "Change is
probable in the close pair." WDS
uncertain 15 observations. 0.5” at
discovery, 0.6” now, 5.9/8.48
BU 1260 AB 36-inch. Appendix: "A difficult object, but
without material change." 0.5” at
discovery, 0.3” now, 8.9/11.5.
BU 1280 BC 36-inch. "An examination of my observing book at
the Lick Observatory shows that the small star of this wide pair was noted as
double with the 36-inch on January 22, 1892, and estimated as given above. It was forgotten, and not subsequently
examined. I have looked at it several
times with the 40-inch, and on one occasion it had the appearance of being
double. It must be a difficult object,
and the distance is probably less than 1"." Aitken later measured it at 0.88". WDS lists it as uncertain.. 0.9” at discovery, 0.7” now, 9.43/11.32
BU 1283 AB 36-inch. "In my Lick Observatory observing book of
February 4, 1889, I find this star was under observation with the 36-inch and
it was noted: ‘The 9m star nf Theta Leonis is 0.5" double.' I have examined this several times with the
40-inch, and on one occasion it appeared elongated, but nothing further could
be done with it...I am certain this star will prove to be a close pair, and
therefore give it a place in this catalogue." WDS has 14 measures and lists it as
uncertain. 0.4” at discovery, 0.3” now,
9.8/10.4 – it may well be a short period pair and needs additional
observations.
BU 604 AB 36-inch AC. "The fainter attendant, AB, was added by
Aitken with the 36-inch. He calls it
exceedingly faint and difficult with that instrument.". 39.7” at discovery, 39.7” now, 2.14/15.7.
BU 1296 AB 40-inch. "A close and difficult pair found in
measuring H 2315." WDS uncertain
with 10 measures. 0.2” at discovery, 0.3”
now, 7.94/9.03
BU 1298 AB 40-inch. Component of STTA 150. "A close and difficult double." WDS uncertain with 39 observations. 0.3” at discovery, 0.4” now, 8.25/9.56
BU 1308 BC 40-inch. "A difficult object." 1.1” at discovery, 1.1” now, 13.0/14.7
===========
“Eagle eye” Burnham: These pairs impressed me by
the difficulty of the observation at the time of discovery. Burnham did not make any special descriptive
comment about them, but the characteristics of the pair against the aperture
used is impressive.
BU 328 AB 6-inch, component of STF 1026, 0.7” at
discovery, 0.6” now, 5.7/6.91 more than one delta magnitude.
BU 332 AB 6-inch, component of STF 1097. 0.8” at discovery, 0.7” now, 6.22/7.35, more
than one delta mag.
BU 355 AB 6-inch AB, 0.34" at discovery in
1876, 0.2" now, 7.45/8.82. AB-C
(13.29m) added with the 36-inch in 1892.
BU 579 AB 6-inch, component of STT 173 (rej.). 0.8” at discovery, 1.1” now, 7.95/12.3". “…suspected with the 6-inch in 1875, and
verified subsequently with the 18.5-inch
BU 773 AB 6-inch, 1.2” at discovery, 0.9” now,
5.7/8.24. "This star was suspected
to be a close pair with the 6-inch at Mt. Hamilton in 1879. With the 12-inch in 1891 I could not be
certain of any real elongation. It
should receive further attention in southern latitudes." WDS uncertain after 18 measures.
BU 774 AB 6-inch, while doing the seeing survey on
Mt. Hamilton. 0.5” at discovery, 0.6” now, 8.68/9.65. “It is a difficult pair with a much larger
aperture. Retrograde motion?" WDS uncertain with 28 measures.
BU 1032 AB 12-inch. 0.26" at discovery, 0.3” now, 4.07/5.27. Component of STF 762. "It is certain to be a binary, and the
measures already made indicate retrograde motion. The maximum distance probably does not exceed
0.25"; otherwise I would have found it before.” Short 159.9-year period, and indeed the orbit
is nearly circular from our vantage point, just barely exceeding 0.25”
==========
Unverified Discoveries: of Burnham and others:
BU 1288 AB 12-inch. 0.2” at discovery, 0.2” now, 5.5/5.5. "In looking over my Mt. Hamilton
observing books I find that on June 7, 1889, I examined this star with the 12-inch,
and recorded it as a close equal pair, with magnitudes 5.5 and 5.5, and
'distance less than 0.2".' The
angle was measured with the highest power of that instrument, giving
340.7-degrees. This observation was
overlooked by me, and the star not subsequently examined either with the 12- or
36-inch. As I have no reason to doubt
the substantial correctness of the original observation, I give this star a
place here, with the confident expectation that it will be hereafter verified. Professor Aitken has examined it with the
36-inch several times this year (1899) at my request. At one time there was a slight suspicion of
possible elongation, but if double it was too close for even that
instrument." WDS only has one
measure, Burnham's! It really requires
re-observation.
BU 555 BC 6-inch.
Component of Rigel. “In 1871,
while examining Rigel with the 6-inch, I suspected an elongation of the
companion, and called attention of observers with larger instruments to this
star. In 1878 I examined it very carefully
with the 18.5-inch, and saw and measured what I felt certain was a real and
measurable elongation of the small star.
The measured distances were noted at the time as being too large. When on Mt. Hamilton with the 6-inch, in
1879, I again measured the position angle, and regarded the elongation as not
due to atmospheric causes. This star was
scrutinized with the 18.5-inch at Chicago a number of times from 1880 to 1882,
but at all times it appeared either round or very doubtful, in 1880 and 1890 it was certainly single with
the 36-inch with the highest powers under the very best conditions. If the distance had been as much as
0.05", it would have been noticed on some of these occasions with the
large refractor." Appendix:
"This pair may have a period less than that of any known binary....The
measures can be represented by a period of about five years, but upon any
assumption the elongation should have been seen at some of the times when it
was noted as single by apertures large enough to show it. If it is carefully watched with the largest
telescopes, as it doubtless will be, the approximate period will be determined
with a few years." WDS uncertain
with 25 observations. In An Anthology
of Visual Double Stars” Bob Argyle notes there have been positive
measurements of the pair as recently as 1973 Frank Holden with the Lick
36-inch, 1971 by van Biesbroeck with the 2.1-metre at Kitt Peak, and an
uncertain one in 2005 by Mason with the 26-inch at USNO. But because “several attempts” with 4-meter
telescopes failed to resolve the pair, Argyle (I think unfairly) consigns this
to his chapter “Myths, Mysteries, and One-Offs.”
BU 1008: Speaking of the main component of BU
1008: "In 1852 Gilliss observed a double or peculiar occultation of this
star (A.N. 813), which he explains as the temporary eclipse of the star by a
projecting lunar mountain. Tatlock has
shown that on another occasion the same observer saw this star occulted." I don’t find any close-in companion on
Aladin.
BU 282: Writing of the primary star: “The
Cincinnati observers thought the principal star was a close pair. I have examined it many times under favorable
conditions with apertures of 15.5-, 18.5-, and 36- inches, and am satisfied
that it is not double." SIMBAD says
the primary star, SAO 160402, is a spectroscopic binary, perhaps discovered (or
published) in 1986 by the E.W. Fick Observatory, but I can't yet sort out what
possible magnitude or separation they estimate for the secondary, or whether it
would be detectable by the 11-inch Merz refractor in use in Cincinnati in the
late 1800s.
BU 1083: Component of HJ 2638. "There is a faint nebula in the field
(Dreyer 4966)….On the occasion of my second measure of these stars with the
40-inch in 1898, I saw as I supposed a very minute star near A, at a distance of perhaps 2" in the second
quadrant. When the measure then being
made was finished, the conditions had changed, and the new star could not be
seen. It was looked for several times
subsequently with the 40-inch without success.
I think it is a real star."
There is a LYS 10 but it is 139.3" from A too far separated. Aladin does not show any star within 5"
of A.
BU 1125: 68 Oph.
"The relative change [of proper motion] is slow, but there is not
much doubt of these stars forming a physical system….Schiaparelli finds the
principal star a close pair, and from a single measure gives 320.0 degrees
0.3". There are no other observations
of this, and I have had no opportunity to examine it under sufficiently
favorable conditions since receiving recently the measures of Schiaparelli. It would seem to be a triple of extraordinary
interest." Burnham's AB is physical
with a 213.97-year period. SP 3 AB-C
still has only the one observation, that of Schiaparelli’s discovery. FWIW, Aladin does not plot any star within
0.5”.
BU 1285: "In my Mt. Hamilton observing book
of May 27, 1892, I find this star noted with the 36-inch, 'possibly a close
pair….' I have looked at this a number
of times with the 40-inch, and measured the distant companions as given above,
but cannot say whether or not the large star is a close pair. Further observations with a large aperture
are necessary to settle this point.
Aitken found the principal star single 1899.44 with the 36-inch on a
good night with power of 1000." No
close companion noted in WDS, Aladin does not plot any additional close
companion star.
===========
Color: Burnham
very rarely comments on the color of stars, so when he does it is notable.
BU 1294: "The components are red and
green."
BU 130: 90 Her.
"…a beautiful pair, even with small aperture. The components have a striking difference in
color -- golden and blue…. [Due to common proper motion] there is little doubt
of its being a physical system."
WDS uncertain after 49 measures.
BU 198: "The larger star is red"
BU 87: "A fine colored pair, golden:blue"
HJ 2852 AB: 22” 10.34/11.10. “H called the components red:blue green.”
HJ 350 AB: 5.4” 10.9/11.5 "Herschel describes it as 'extremely
delicate and beautiful'."
HJ 1364 AB: 2.9” 10.71/10.88 Described by Herschel,
"a most elegant double star; chief of a small cluster.” It was 1.0” at discovery, and the additional
1.9” separation since might have ruined the appearance!
