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Separation Alpha Her

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#1 WRAK

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Posted 21 July 2014 - 07:13 AM

After an interesting but rather difficult session in Aql (several very faint doubles were simply too faint for my setup to be resolved) I took as comfort a look at Alpha Her and it was due to low transparency and bad seeing not as easy as I expected. Two nice yellow golden suns (had a note to expect a blue-green companion but this was not the case) appeared with a magnification of x180 in my 120mm refractor not as crisp disks but rather cottonwool balls and I could then with some difficulties reduce the aperture to 60mm and call it still resolved.
As far as I remembered the parameters for Alpha Her I would have expected rather ~40mm. So I checked then WDS and found the latest measurement as 5". Checked then earlier WDS values for Alpha Her and got 4.5" for 2013.8 and 4.7" in 2012.5. Checked then the 6th orbit catalog and got a value of 4.64". This did not help much to make my result seem more plausible but reminded me instantly on the recent discussion about separation of Izar and the obviously wrong last measurement. May be it's the same here too.
Wilfried

#2 fred1871

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Posted 21 July 2014 - 08:06 AM

One of the problems for the WDS is that they collect new measures as these are published but don't always check on the quality, so long as they're not a radical change - there are alarmbells for big changes. But Alpha Her was listed at 4.8" in 2003 (as per the Haas book),and likewise 4.8" in 1993 (WDS 1996 edition). The 2009 measure is also 4.8" (WDS Sept 2010).

The VERY preliminary orbit, suggesting a period of thousands of years, does not tell us much because so little of the orbit has been traversed in all likelihood, since Struve. (Alpha Her is STF 2140).

I'd be inclined to think the most recent measure slightly anomalous; and treat the likely separation as still being 4.8". The main change from Struve until now is a slow decrease in angle. The 1777 measure (pre-Struve) that's now listed is most likely an estimate; I think FGW Struve's measure in 1822 is the first one likely to be accurate, almost the same as recent measures - 4.7" is given in the 1996 WDS for 1822.

#3 jimbo728

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Posted 21 July 2014 - 04:02 PM

My data for Alpha Her shows a separation of 4.7" . It seemed to be correct for Epsilon Bootes,2.8", but my data sheet was generated in 2001.
Clear Skies,
Jim

#4 azure1961p

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Posted 06 August 2014 - 11:57 AM

I too have read of some seeing a blue or green companion here but my distinct impression was a coppery primary and cream colored secondary (8"). It truly is a striking pair. Nice report.

 

 

Pete



#5 jrbarnett

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Posted 06 August 2014 - 06:23 PM

Two nice yellow golden suns (had a note to expect a blue-green companion but this was not the case) appeared with a magnification of x180 in my 120mm refractor not as crisp disks but rather cottonwool balls and I could then with some difficulties reduce the aperture to 60mm and call it still resolved.

 

That's rather odd.  Rasalgethi A has always looked decided red-orange to me, and the companion white to greenish even.  The primary is class M so should definitely have some red in its yellow, if you know what I mean.  The secondary is actual a spectroscopic binary with the larger sun class G and the smaller class F, so  the ruddiness of the primary makes the twin-secondary look straw whitish or even bluish by comparison.  I've never not found the color contrast obvious and pronounced.  I wonder if it has something to do with extinction.  I am at 38N.

 

- Jim 


Edited by jrbarnett, 06 August 2014 - 06:24 PM.


#6 ssmith

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Posted 06 August 2014 - 08:00 PM

Here is a recent photo I took of Alpha Herc.  FWIW I measured the separation at 4.7 arc-sec.

 

Attached File  Alpha Herculis 7-17-14.jpg   49.16KB   2 downloads


Edited by ssmith, 06 August 2014 - 08:01 PM.


#7 azure1961p

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Posted 06 August 2014 - 08:07 PM

Nice work and presentation. 

 

Pete



#8 Rich (RLTYS)

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Posted 07 August 2014 - 05:45 AM

Here is a recent photo I took of Alpha Herc.  FWIW I measured the separation at 4.7 arc-sec.

 

attachicon.gifAlpha Herculis 7-17-14.jpg

Nice image.

 

Rich (RLTYS)



#9 ssmith

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Posted 07 August 2014 - 01:03 PM

Pete, Rich -  Thanks!



#10 drollere

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Posted 07 August 2014 - 01:31 PM

my recollection of alp HER is, like william herschel's report, of an orange red primary and a distinctly tinted blue or blue green secondary. as jim points out, complementary contrast will have an effect on the color perception.

 

as i documented in my "color" post, a G spectral type can have almost any color index short of carbon star red orange. it's perhaps the single most erratic spectral type in terms of the photometric or visual color it can present.

 

this thread demonstrates, once again, the unreliability of visual color reports, a fact first called out by william herschel. star colors are esthetic, rather than substantive; amusing rather than informative. this is perhaps what guided herschel to use an extremely limited set of terms for reporting star colors.



#11 jrbarnett

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Posted 07 August 2014 - 11:31 PM

Herschel's problem was that he was a German writing in English.  There is no English equivalent for blaudonaudampfschiffahrtsgesellschaftskapitän, so he reported it as "blue".

 

:grin:

 

- Jim



#12 Rich (RLTYS)

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Posted 08 August 2014 - 05:55 AM

my recollection of alp HER is, like william herschel's report, of an orange red primary and a distinctly tinted blue or blue green secondary. as jim points out, complementary contrast will have an effect on the color perception.

 

as i documented in my "color" post, a G spectral type can have almost any color index short of carbon star red orange. it's perhaps the single most erratic spectral type in terms of the photometric or visual color it can present.

 

this thread demonstrates, once again, the unreliability of visual color reports, a fact first called out by william herschel. star colors are esthetic, rather than substantive; amusing rather than informative. this is perhaps what guided herschel to use an extremely limited set of terms for reporting star colors.

You can ask 10 different people to describe the colors of a double and you'll get 10 different answers.

 

Rich (RLTYS)



#13 Love Cowboy

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Posted 09 August 2014 - 12:45 PM

For what it's worth, I viewed alpha Her last night and did find the companion blue as Herschel reported.  However, I was using a C-14 at 488x.  If contrast skews color perception as some have noted above, perhaps contrast is in turn affected by how close the stars appear?  Just a thought.  There was another star I viewed last night, Delta Serpentis, where I literally could not figure out what the heck the color of the B star was... at different times it looked blue, orange, even brown or purple.  I looked it up today and apparently for Delta Ser both stars are F spectral type but historical visual observations from Smyth, Webb, etc. list all sorts of varied colors like yellow, blue, and even "olive." 

 

So yeah, double star colors are wacky



#14 Fireball

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Posted 11 August 2014 - 07:50 AM

For me, they look golden and white  :cool:



#15 drollere

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Posted 11 August 2014 - 11:15 AM

in defense of WRAKs observation, i was using alp HER as a target to evaluate my surplus of ortho/RKE/plossl eyepieces, and indeed i found the pair did appear to be the same yellow or orange yellow color when observed at around a 1.5mm exit pupil or 80x in my ƒ/7 140mm refractor. the airy disks were barely discernable.

 

the yellow orange/pale blue contrast was most apparent at an EP around 0.7 or 200x, with two fine and unequally sized airy disks. the colors seemed weaker at an EP of 0.5 or 280x. wilfried seems to have had poor seeing ("cottonwool balls") and this may have degraded the color.

 

herschel's precision in color terminology is remarkable: he seems to have been aware of many of the visual issues. "gelb" for example is a perfectly good german word and easily translated into english, but he never used the term "yellow" to describe a star color. either he was colorblind and had learned that his use of the term was erratic, or he recognized the basic star color contrast is red vs. white vs. blue, and found "yellow" superfluous.



#16 Rich (RLTYS)

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Posted 29 August 2014 - 06:43 AM

Took a look at Alpha Her last evening (I was working on the AL Stellar Evolution Program) with my 10" refl, at 174x, under partly cloudy skies and seeing 5-6/10. Primary appeared a straw yellow color while the secondary appeared a pale bluish green color.

 

Rich (RLTYS)



#17 GlennLeDrew

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Posted 29 August 2014 - 01:34 PM

Anyone tried an occulting bar to mask the primary when assessing the color of a dimmer companion?








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