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STF 191 in Cassiopeia

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#1 John Fitzgerald

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Posted 19 December 2019 - 09:44 PM

STF 191 mags 6.2, 9.1,  Sep 5.3",  PA=196.   This is an interesting, unequal pair.  Even fairly small scopes should show it.  WDS suggests it's a binary with a very long period.  It's a well separated gem in my 6" refractor at 173x.


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#2 rugby

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Posted 19 December 2019 - 10:45 PM

I have one observation of STF 191 from Oct 1990 probably using a C8 (my records are poor) Even more interesting to me were my hastily written notes about STF185 and STF 170 two nearby pairs to the North. Apparently I didnt resolve STF 185. With mags 6.7  and 8.5  at 1.1"  in PA 9  I can see why. Should be a good challenge in the 152 . I havent had a clear night in nearly two months.


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#3 John Fitzgerald

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Posted 19 December 2019 - 10:48 PM

Rugby,

I've had bad seeing for several sessions in a row, so I haven't been trying to go for pairs below about 2" separation.


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#4 fred1871

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Posted 19 December 2019 - 11:39 PM

I looked up my observing notes from California days, and found all three doubles mentioned above had been observed. Scope I had at the time was a C8. That was back in the period 1995-96.

 

STF 191  The companion was seen with 80x as a neat point nearly South of the much brighter primary. Not difficult. Showed well at 135x also.

 

The same night I observed the other two Struve pairs mentioned by rugby in #2 above. 

 

STF 170  At 80x "elegant moderately unequal close pair in a thin field" ... Also easy and nice at 135x.

WDS gives mags 7.5 and 8.2 (rounded), at 3.2"  (virtually unchanged 1830 to 2016).

 

STF 185   At 80x, a very wide pair, increasing power to 225x showed a less bright  companion close to star A, very tight separation. 335x showed it better.

WDS lists the ultra-wide pair, and gives the AB close pair as mags 6.8 and 8.6 (rounded). It is slowly closing, and Hipparcos measured 1.15" in 1991 with the Scardia group speckle at 1.09" in 2005 (4th interferometer catalog].


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#5 ssmith

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Posted 23 December 2019 - 02:52 PM

Here is a photo of STF 191.  STF184 (a wide optical pair) is in the same FOV.

 

STF191 Cass C9 12-21-19 3fr.jpg


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#6 John Fitzgerald

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Posted 23 December 2019 - 04:08 PM

Here is a photo of STF 191.  STF184 (a wide optical pair) is in the same FOV.

 

attachicon.gifSTF191 Cass C9 12-21-19 3fr.jpg

Wow, ssmith.  I view it, and then you image it.  Thanks.   Saves me a bundle on camera and imaging train.cool.gif lol.gif lol.gif



#7 John Fitzgerald

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Posted 23 December 2019 - 04:13 PM

Have you imaged STF 156 in Cas?  Mags 8.4, 11.1  Sep 5.9" PA 101 deg.  Really bad seeing last evening made this a difficult pair even at 173x, although the sky was quite clear.



#8 ssmith

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Posted 23 December 2019 - 05:42 PM

John -  I do not have a photo of STF156 - I have added it to my list !



#9 The Ardent

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Posted 23 December 2019 - 10:23 PM

That tiny triple below STF 191 is post #5 looks like an interesting challenge! Steve needs a WDS discoverer designation. 


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#10 fred1871

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Posted 24 December 2019 - 12:01 AM

That tiny triple below STF 191 is post #5 looks like an interesting challenge! Steve needs a WDS discoverer designation. 

Too dim, I'd think - and after using Simbad to find it and get a position, I didn't find it in WDS.

 

The position I measured off a DSS image via Simbad was 02 03 05 +73 44 28. I then looked at that position (radius 1') and found 3 stars of very similar position with Gmags of 14+ which makes them among the brighter ones in that small area. They had, incidentally, not shown up via Tycho/Hipparcos, which made me expect dim magnitudes.

 

Gaia DR2 lists the first of the three stars at J2000 position 02 03 05.076 +73 44 27.60 (rounded); so we have a position match.

 

Gmagnitudes of the three are 14.5059, 14.9143, and 14.9569.
The first two have very similar Proper Motion numbers, the 3rd does not; parallaxes for first two are compatibly close, 3rd is not.

 

So it's possible two of the stars are a physical pair, with the 3rd optical.

 

Anyone with a big scope wanting to try a visual observation? What it does show is the imaging advantage of smaller scopes, picking up objects that require a lot more aperture for visual observation.
 


Edited by fred1871, 24 December 2019 - 08:02 AM.

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#11 John Fitzgerald

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Posted 24 December 2019 - 09:08 AM

Update- seeing was better last evening and the companion to STF 156 was readily seen. 



#12 rugby

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Posted 25 December 2019 - 01:50 PM

My notes from Dec 24 2019:  Seeing much steadier than previous two evenings. Airy disc visible with small undulations. First ring prominent but not completely around the star. STF191 very easy in 120mm at 85x. To the N preceding about one third of a field a coarse faint pair found . Guessed 9.5-10  15-20"  at 360 degrees.

I think I stumbled upon STF184 (see prior posts for correct data)

 

Also, took time to re-observe STF185 a pair I had difficulty with some thirty years ago useing a C8. Once again I could not see a split. There was a thickening in the first ring but the PA was incorrect. STF 185 is 6.7-8.2. Current separation is close to one second. the  120 mm doesnt seem up to the task. I will tackle this problem pair with a bigger hammer.




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