Saturday, March 4, 2017

doubles in gemini

This week had three clear nights with above average seeing, so I tried to take advantage of it.  I haven't had the chance to write up about it until now.  I used the 12.5-inch at 553x the whole time.  The first two nights I was without the equatorial platform since I had broken its power cord.  The scope is very shaky so that was an annoyance.  I concentrated on challenging doubles from the Carro Catalog since the seeing was so good.  I had nice airy disks the whole time, Pickering 8-9.

Tuesday night I wanted to view the moon and Venus, but they were blocked by our yew trees.  I was able to see them Wednesday night, when both were a similarly thin crescent.  I viewed the moon without filter, since it was not yet bright enough to require one.  The surface was very pocked with small craterlets darkened with shadow -- giving the strong impression of a dry, battle scarred landscape.  Thursday night I didn't have time to view the moon before it set.

The first double Tuesday night was Sirius B.  I was using Sirius to align my 80mm finder (which I'm using at home now to better see hop stars through the light pollution).  I thought to try for the Pup and sure enough it was there, at first a condensation following the bright mess of Sirius's diffraction, flashing to a point when seeing stilled.  I think it has been two years since I saw the Pup last, and I had the impression it had moved slightly from following Sirius a little to the ESE to pretty might directly east.  I was surprised at the nonchalance with which I was able to observe what had been such a challenging object previously.

I was not prepared Tuesday night to view anything other than what was plotted in CDSA:

STT 145: Widely separated, N-S, 8-9th magnitude stars, 1 delta magnitude.  [7.43/9.93, 1.5", 338°. Seems this was a miss].

STT 143: Orange A, very faint B, ~3", PA due east.  3rd to the north?  [Correct!  AB 6.2/10.1, 7.6", 103°; AC = FOX 147, 6.2/11.41, 47.3" 346°].

STF 924: Near equal brightness yellowish stars, 0.5 delta mag, wide separation ~8", PA to the SW.  [AB 6.31/6.88, 19.9", 211°.  BC is 13th mag and 48.7".  A has a spectroscopic companion.  My separation estimates are way off.]

STTA 77 = Nu Geminorum: Not obvious what might be the pair.  Several possibilities among four stars, all widely separated.  [Seven visible stars in the system, with more not seen -- all the way to an AS pair!]

SHJ 70: Very pretty orange A, with a brown B; PA to the south, 1.5 delta mag.  [AB 6.65/8.18, 24.8" 202°.  There are four more pairings to AF, all 12-13th magnitude & fairly wide separations, not seen].

Anonymous to the east of Mu Geminorum: Orange, but don't see anything closeby--nice airy disk, and some faint stars about, wide separations if paired.

HV55 / 12 Geminorum: Very wide separation, ~3 delta mag, fairly faint.  [7.01/10.75, 62.2", 59°]

B1008 = Propus (means "forefoot") = Eta Geminorum: So cool!  Bright orange star with B very close, ~1.5", just preceding, ~3 delta mag. B is in diffraction but is well separated & has its own airy disk, bluish white.   [3.52, 6.15, 1.6" 252°].

S533 = Mebsuta: Bright orange star, B is in the diffraction as a small sharp point seen intermittently in the south rim of A's diffraction.  Some other widely separated stars about.  [What I saw in the diffraction must have been an interior reflection, as the pair is 110", 3.14/9.64, PA 94°]

STT 155: Pretty orange star with 2x fainter B, also orange, due west, ~6".  [7.14/10.93, 15.1", 261°]

Anonymous above STT 160: White star with 3x fainter B, PA to south, wide separation 6-7"

STT 160: Orange-yellow star, nothing close.  Very faint wide star to NNE.  [Missed; 6.66/9.92, 1.3", 188°]

Wasat = Delta Geminorum: Pretty white-yellow and red-orange pair, PA to west, ~4".  [3.55/8.18, 5.7", 228° -- Stelle Doppie's "now" sep is at 0" -- but the orbital elements graph matches my observation...?]

Anonymous east of Wasat: Small, faint, tight white pair, ~2", 0.5 delta mag

STF 1083: White, equal brightness, PA to NE.  [7.32/8.13, 6.8" 46°]

Eskimo Nebula, NGC 2392: Bright central star; bright, thick inner ring surrounded by a diffuse and round outer halo with ragged edges. Nice to see even with the light pollution (SQML 18.6).

Sh 368: 4x system? Bright star in center of a triangle of other stars.  [It is a four star system indeed, but I might doubt I saw exactly the system -- some are 10th magnitude and my sketch is of brighter stars]

S 548: Orange with a 2x fainter white star, PA slightly SW.  [AC of the system seen, 6.98/8.89, 35", 277°.  AB is 12th mag and not seen]

STF 1108: Orange stars, 2 delta mag, PA to south, ~8" [6.62/8.21; 11.6", 179°]

NGC 2420: open cluster.  10 stars in smooshed Capricorn shape, with fine mists of stars behind.  Must be a pretty cluster in a dark sky.  Neighbor's porch light is on, spoiling the view.  

Wednesday I prepared AAVSO finder charts for some challenging doubles from the Carro Catalog and was able to spend the whole session chasing them down.  My equatorial platform was still without power, but I still had a fine session:

STF 942: Faint near equal brightness, well split, PA W-E.  [10.07/10.1, 3.4", 246°]

BU 571: not seen [AB 6.0/11.9, 2.9", 342°]

BU 1191: Not seen pair.  I see a glint to the NE but it's the wrong PA and it did not stay in view.  [6.7/11.5, 2.4", 313°].  

STF 982: Pretty yellow and orange, 2 delta mag, wide separation, PA to SW.  [I believe I saw the AB pair, 4.75/7.8, 7.3", 143°.  There are AC and AD pairs, the C being 11th mag and very wide, the D 15.5 mag and even wider...]

BU 100: !! Pretty orange and blue.  4 delta mag, PA to west.  Wide separation ~3"  B is just seen, a very fine point. [7.34/11.1, 3.2, 143°.  Burnham's discovery in 1873 was at 2.5" separation.  Last WDS observation in 1978 -- deserves one now]

STT 163: Not perfectly round AB; a faint bluish haze in the diffraction to the south.  Not a reliable observation.  [AB 7.18/8.18 0.2" 117°.  AB,C 6.41/12.0, 14.1" 166°].

STF 1107: Wide separation, 1 delta mag, PA to NW.  [AB 7.43/11.4, 14.9", 300°.  AC and AD components, 10.00 & 7.4, wider separations, not recorded.]

HO 342: ! Yellow-orange and blue stars, PA to the east, 1 delta mag, tight but well split ~1".  [7.99/8.71, 1.1", 87°]

WEI 14: A yellow-orange, blue B, 1 delta mag, PA to south.  Nice!  [7.77/8.91, 2.1", 160°].

A 2527: Not seen as a pair.  8.58/11.85, 2.2.  I seem to have a visibility limit of 10th magnitude for very close pairs -- due to light pollution?

STF 1068: Pumpkin orange pair, near equal magnitude, PA to north.  Well separated ~4".  Nice.  [AB 9.29/.8, 4", 349°]

STF 1116: Pretty tight white, near equal magnitude, 2-3", PA to east.  Nice pair.  [7.81/8.5, 1.8" 96°]

STF 981: Very close orange pair, equal magnitude.  Clean split, ~1".  Worth the hop from Tau Geminorum.  [8.72/8.97, 0.95", 292.3°]

STF 991: White and orange, 2 delta mag, ~5", PA to S. [3.47/7.95, 3.7", 164°.  Also AC and CD pairs, 10th & 11th, wide from the main pair].

STF 1014: !! Tough find, faint field.  Very faint near equal brightness pair, ~3", PS to the SW.  [9.91/9.93, 2", 219°]

STF 1070: Pretty close, 1.5", white, 1 delta mag, PA to NW.  [AB seen, 8.65/9.3, 1.8", 324°.  AC is 11th mag and 88", not seen]

BU 579: Too faint, too close, not seen.  [7.95/12.3, 1.1"]

A 674: B more a blue haze than a point off the yellow A.  I believe I have it, very close and faint.  PA to SE.  [8.21/9.77, 1.1", 125°]

AGC 2: No.  [7.76/9.73, 1"]

STF 1147: Very fine 2", equal magnitude blue - white pair, PA to south, ~2".  [9.66/9.68, 2.2", 174°].

Finally Thursday night's observing.  I had a late start, and transparency was a little off as a front was to come through the next day.  And my heart wasn't quite in it, and I was tired, so I observed for about an hour.  But, it was rewarding.  It was good to have the platform working for this session:

STF 1126: !! Wow, very close <1" hair-split, near equal brightness; almost overlapping disks.  [6.55/6.96, 0.8",  175°]

STT 182: Very close, ~1", near equal brightness white.  [7.82/7.93, 0.8", 11°]

Sh 87: Not seen, suspect very wide separation.  [Four stars visible, all of them >100" -- seems to be a chance alignment]

STF 1210: Pretty wide greenish yellow pair, wide separation, 2 delta mag.  [AB 7.25/9.45, 15.5", 113°.  AC is 13.5 mag and 68", not seen]

Anonymous east of STF 1182: Faint field, tough hop; must be a 4x multiple, wide separations

STF 1182: White and reddish, 1 delta mag, PA due east.  [7.48/8.76, 4.7", 74°]

Anonymous east of Epsilon CMi: Wide separation; could be any of a number of stars