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STT 380 in Aquila

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#1 rugby

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Posted 16 July 2019 - 09:51 PM

Can anyone provide me with the most recent measures of STT 380 .  I can no longer access Stella Doppie



#2 fred1871

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Posted 17 July 2019 - 03:04 AM

Most recent measure I can easily find is from 2009, 0.394" at PA 76 degrees.  This is from Scardia's speckle group, who are reliable. The pair has been slowly closing, the early speckle measures from 1976 were around 0.46". That might suggest, with continued closing, that the current separation would be 0.37"/0.38". The PA has hardly changed over the 33 years of speckle measures; could be read as no change or maybe 1 degree decrease. My data is from the 4th Interferometric Measures Catalog, available online via the USNO/WDS web site.



#3 rugby

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Posted 23 July 2019 - 12:22 AM

I needed a good night: clear and moonless. I got that plus stable air last night  Setting up the Meade 8 sct I warmed up with two one arc second pairs in Lyra and then targeted STT 380 in Aquila. I am particularly fond of moderately bright very tight pairs with small magnitude differences. 

Using 333x and 675x I believe I could see an east west elongation but with no apparent mag difference. I am going to call my attempt negative on this one however.  I need a bigger and better glass. Anyone out there willing to tackle this pair?


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#4 fred1871

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Posted 23 July 2019 - 10:42 AM

The Tycho photometry gives a difference of 0.8 magnitudes; Hipparcos is similar, just under 0.9. So there should be a visible difference.

 

Given the separation, just under 0.4", I'd rather tackle this one with more than an 8-inch. At 333x I'd be surprised to detect elongation unless one had very good eyesight and very co-operative conditions. I've seen elongation on equal doubles at 0.35" with a Mewlon 210, but it will be the rare Meade or Celestron SCT that matches it (I've used plenty of both, and owned some).

 

675x would be more likely to show elongation at that close separation; it's what I used on the Mewlon with several doubles below 0.4", after getting some elongation suggested at 480x. My eyesight is above average but not remarkable. When the doubles get so close I start wishing for more aperture than 20cm or 21cm.



#5 rugby

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Posted 23 July 2019 - 02:47 PM

Thank you Fred 1871 for your input. I agree that my equipment is not up to the task for this double. Noticing a mag difference would be quite a feat so I expected only an irregular round  disc. I also do not observe  these pairs  mindful of the PA.

There is hope on the horizon. I have purchased a very fine 12.5 f6.5 dob. The primary and secondary are of known quality Also welcome is the tracking that comes with it.  First light comes this weekend



#6 mccarthymark

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Posted 23 July 2019 - 03:16 PM

I got an olive shape using 12.5" @ 553x with 6-7/10 seeing last year...




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