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91
TAC Visual / Re: Moon and Aldebaran
« Last post by smigol on March 14, 2017, 09:28:39 AM »
Nice report.  Reminded me of the time I saw the moon occult the Pleiades back in 1992.
92
Observing Reports / Re: Some doubles around Gemini
« Last post by sgottlieb on March 05, 2017, 06:38:15 PM »
Well done, Mark!  I'm guessing you were just running up against the mag limit of your scope/sky.  Also for some reason I often find the fainter companion of a close unequal, double appears dimmer than its magnitude suggests.

My notes on a several of these pairs are appended at the end, but here are a few more 2" or closer pairs in Gemini you might want to look at another time --

∑899 = ADS 4991
06 22 49.6 +17 34 27
V = 7.4/8.0;  Size 2.2"
18" (1/28/12): tight 2" white pair just cleanly split at 175x in fair seeing.  Crisper view using the 6" mask.

∑932 = ADS 5197
06 34 21.6 +14 45 08
V = 8.1/8.2;  Size 1.7"
18" (1/19/08): well-matched tight pair that at 1.65" that is just resolved at 175x.  Easy at 225x in good seeing.
18" (1/3/04): excellent evenly matched pair of mag 8 stars at 1.7" separation.  Splits at 160x and cleanly resolved at 215x.  Tangent airy discs with 6" mask at this power but easily resolved.

∑1037 = O∑166? = ADS 5871
07 12 49.1 +27 13 30
V = 7.2/7.2;  Size 1.1"

18" (3/10/04): clean split with 6" mask even at 220x!  This is a perfectly matched white pair.  This binary has a period of 119 years and is just past maximum separation (1.1").
18" (1/3/04): very close 1.1" pair of equal mag 7 stars.  Clearly double at 160x but not cleanly split.  Nicely resolved at 300x and with a 6" mask two nearly tangent airy discs are just cleanly resolved at 300x!
18" (3/24/03): very close, evenly matched pair (white/white) at 1.1".  Clean split in good moments at 300x.

∑1070 = ADS 5999
07 21 21.9 +34 01 36
V = 8.6/9.3;  Size 1.7"
18" (1/19/08): tight 1.7" pair but just cleanly resolved using 175x.  At 450x, tiny airy discs were resolved when the seeing was steady.

∑1081 = ADS 6038
07 24 08.9 +21 27 28
V = 7.7/8.5;  Size 1.8"
18" (1/19/08): fairly close 1.8" white pair is resolved at 175x.  Upping the power to 450x gave a wide split with clean star images.
---------------------------------------

Eta Gem = Bu 1008 = ADS 4841
06 14 52.7 +22 30 24
V = 3.3-3.9/6.5;  Size 1.6"
18" (4/10/03): Eta Gem is a challenging mag 3.3-3.9 (variable)/6.5 pair at 1.6" (slowly increasing).  Very large mag contrast with a yellow/orange primary.  Excellent at 300x and easy at 435x in good moments.  Supernova remnant IC 443 is close following.

∑942 = ADS 5258
06 37 40.6 +23 38 53
V = 10.1/10.1;  Size 3.5"
18" (1/28/12): perfectly matched 10th magnitude pair at 175x.  Fairly close (3.5") and nicely split at 175x.  Located 4' NW of mag 6.7 HD 47086.

∑981 = ADS 5570
06 55 28.4 +30 09 45
V = 8.8/9.0;  Size 1.1"
18" (1/19/08): this 1.1" pair was barely resolved at 175x and cleanly split at 225x.  At 450x, tiny airy discs were resolved and well separated.  This binary has a period of 5343 years and is still closing.

18" (3/7/04): very close 1.2" pair but cleanly resolved evenly matched duo.  Used both the 6" mask and at full aperture with a 9mm Ortho (250x).  Current separation at 1.2" is close to minimum.  Closing since discovery in 1831 (3.7").

Ho 342 = ADS 5725
07 02 50.5 +13 05 22
V = 8.0/8.7;  Size 1.2"
18" (1/19/08): very close 1.2" pair cleanly resolved at 300x.  Superb in good seeing at 750x with small airy discs.

∑1014 = ADS 5770
07 05 44.9 +26 08 25
V = 9.9/9.9;  Size 2.0"
18" (1/28/12): excellent perfectly matched 2" pair at 175x.  Cleanly split at this power but very close.

Weisse 14 = ADS 5875
07 12 48.2 +15 10 42
V = 7.8/8.9;  Size 2.1"
18" (1/19/08): this excellent 2" pair was just resolved at 175x and was beautiful at 300x.  Subtle colors.

∑1116 = ADS 6180
07 34 32.0 +12 18 17
V = 7.8/8.6;  Size 1.7"
18" (3/10/04): striking pair at 220x with the 6" mask.  Easily resolved at full aperture at 1.7".

∑1147 = ADS 6394
07 50 19.7 +24 31 56
V = 9.7/9.7;  Size 2.2"
18" (1/28/12): perfectly matched 2" pair just cleanly split at 175x.  Very similar appearance to ∑1014 = 9.9/9.9 at 2.0" observed a little earlier in the evening.
93
Observing Reports / Some doubles around Gemini
« Last post by mccarthymark on March 05, 2017, 10:08:31 AM »
Last week we had three nights of better than average seeing, so I spent the time splitting doubles with my 12.5-inch f/7.  The perimeter of the mirror is masked down to 11.5-inch to deal with a turned edge, so I suppose it is correctly stated as an 11.5-inch f/7.6.  On such nights I focus primarily on very close and fainter doubles, for which I print out AAVSO finder charts since most of them are not plotted in my Cambridge Double Star Atlas.  I stayed at 553x the whole time; here are some of the highlights, which are my observation followed by the confirming data in brackets (A/B magnitudes, separation, position angle) I retrieved from Stelle Doppie afterward:

Propus (means "forefoot") = Eta Geminorum = B 1008: So cool!  Bright orange star with a very close B, ~1.5", just preceding, ~3 delta mag. B is in diffraction but is well separated & has its own bluish white airy disk.   [3.52, 6.15, 1.6" 252°].  06H 14M 52.69S +22° 30' 24.6"

STF 942: Faint near equal brightness stars, well split, PA W-E.  [10.07/10.1, 3.4", 246°] 06H 37M 40.87S +23° 38' 54.2"

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 another measure now] 07H 00M 56.55S +12° 24' 00.4"

HO 342: ! Yellow-orange and blue stars, PA to the east, 1 delta magnitude; tight but well split ~1".  [7.99/8.71, 1.1", 87°] 07H 02M 50.54S +13° 05' 21.7"

WEI 14: A yellow-orange, B blue, 1 delta mag, PA to south.  Nice!  [7.77/8.91, 2.1", 160°]. 07H 12M 48.16S +15° 10' 41.9"

STF 1068: Pumpkin orange pair, near equal magnitude, PA to north.  Well separated ~4".  Nice.  [AB 9.29/.8, 4", 349°] 07H 19M 49.31S +13° 22' 22.4"

STF 1116: Pretty tight white, near equal magnitude, 2-3", PA to east.  Nice pair.  [7.81/8.5, 1.8" 96°] 07H 34M 32.02S +12° 18' 16.9"

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°] 06H 55M 28.54S +30° 09' 42.3"

STF 1014: !! Tough find, faint field.  Very faint near equal brightness pair, ~3", PA to the SW.  [9.91/9.93, 2", 219°] 07H 05M 44.95S +26° 08' 25.3"

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°] 07H 44M 38.11S +31° 06' 50.1"

STF 1147: Very fine 2", equal magnitude blue - white pair, PA to south, ~2".  [9.66/9.68, 2.2", 174°]. 07H 50M 19.69S +24° 31' 55.8"

STF 1126: !! Wow, very close <1" hair-split, near equal brightness; almost overlapping disks.  [6.55/6.96, 0.8", 175°]  07H 40M 06.99S +05° 13' 51.9"

STT 182: Very close, ~1", near equal brightness white.  [7.82/7.93, 0.8", 11°] 07H 52M 42.12S +03° 23' 02.2"

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] 08H 15M 48.54S +02° 48' 05.0"

STF 1182: White and reddish, 1 delta mag, PA due east.  [7.48/8.76, 4.7", 74°] 08H 05M 24.43S +05° 49' 38.9"

It struck me that I was having trouble detecting any close pair of more than 10th magnitude when it was close to a brighter star.  Examples of my negative sightings are A 2527: 8.58/11.85, 2.2”; BU 579: 7.95/12.3, 1.1"; and AGC 2: 7.76/9.73, 1".  I wonder if it was due to light pollution?  The SQML from my back yard is 18.60.  Maybe it's just bad timing with the seeing?  I used my full aperture through the session, so perhaps a mask would have helped?  I have a 5-inch off-axis mask but I rarely use it since my impression is it dims the stars too much and I lose resolution.  I’m interested to know what others think.
94
TAC Visual / Re: Moon and Aldebaran
« Last post by DDK on March 04, 2017, 08:41:42 PM »
So there I was trustingly staring at the first quarter Moon in crappy seeing. Sure enough, this gem-like gleam shows along the edge of the Moon, a second later it had separation, with black in between. Showed right away in the 9x50 finder. Aldebaran is a very bright star.
That was fun.
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TAC Visual / Re: Moon and Aldebaran
« Last post by DDK on March 04, 2017, 07:29:01 PM »
Man, that was cool. Do hope some of the good little TACos and TAQueritas caught that. You really get the idea that the Moon has no atmosphere. The very bright star goes from hanging right on the dark edge of the Moon, to poof it's gone.

Plus here there were clouds going right overhead, so thru the eyepiece, tendrils of cloud were flowing thru the view, while the Moon's edge was closing in on Aldebaran. It was like Buffy doing patrol in the cemetery.

Emergence will be soon after 8:20, I'm gonna be glued to the eyepiece.
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TAC Visual / Moon and Aldebaran
« Last post by DDK on March 04, 2017, 06:30:03 PM »
Right now the Moon is in the clear overhead. That occultation is due not long after 7, far as I can discern. I do remember how very cool this looked last time we saw the Moon occult a bright star, both on disappearance and on coming back out.
97
Registration is open for the 2017 OzSky "Southern Spring" star party in Coonabarabran ("astronomy capital" of Australia), which runs from October 15-22 (7 nights).  If you have any interest in observing in the southern hemisphere check out http://www.ozsky.org/spring.asp.  That's me on the ladder of a 30" in SQM 21.8-21.9 skies.

I'm planning to attend again (this is my 8th trip to Australia!), as this is a remarkable opportunity to see the Magellanic Clouds and more.  All equipment is provided (mostly 18" to 30" scopes) -- you basically just have to show up and enjoy the dark skies.  A number of bay area amateurs have participating in OzSky star parties including Bob Douglas, Peter Natscher, David Cooper, Dennis Beckley, James Webster.  If anyone has any questions or possible interest, let me know.
98
TAC Visual / Re: Double Star Epsilon Canis Majoris
« Last post by sgottlieb on March 03, 2017, 09:18:07 PM »
Mark, here are two observations I've made.  I've split it in both 6" and 8" apertures -- even at a low elevation if the seeing was good.  I don't have a good quality small refractor, but I'm sure it can be resolved.  So, Wikipedia is certainly wrong.

6" (2/19/07): mag 1.5 Adhara is a challenging double with a 7.5-mag companion at 7.5" separation.  It was cleanly resolved in moments of steadier seeing (viewed at 15° elevation) at 175x using a 6" mask.

C8 (seen several times in the early 1980's) : difficult pair due to very large mag difference.  Visible with at least 100x and fairly easy at 165x in excellent seeing.
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TAC Visual / Re: Double Star Epsilon Canis Majoris
« Last post by Mark on March 03, 2017, 02:18:49 PM »
Thanks.... looks like a tough one.  I didn't google the common name - I almost always use the Greek.

Joe Bergeron, who used to be in the Santa Barbara club and would come to CalStar, wrote this:

"In my 92mm refractor it resolves neatly at 120X with good seeing from Florida, but is rarely resolvable from my New York site, which is eighteen degrees farther north."
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TAC Visual / Re: Double Star Epsilon Canis Majoris
« Last post by mccarthymark on March 03, 2017, 12:21:39 PM »
I've not split it myself (though I will try--wish you posted this earlier! I was out the last three nights splitting challenging doubles from my backyard, with the good seeing we've had).  Searching under the common name Adhara turned up plenty of reports of splits, down to 5-6" scopes
 http://www.cloudynights.com/topic/98926-epsilon-canis-major/
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