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Observing >> Double Star Observing

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Post Laureate

Reged: 04/17/06

Loc: Florida
Propus new
      #5788586 - 04/09/13 04:10 PM

Propus B has disappeared! least for me. Propus, eta Gem, has been one of my favorites with a 4 inch scope. However, for the last few years, I just cannot see it even in my f/15 4 inch. Would like to hear other observer results. Maybe I need to see an eye doctor.

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scholastic sledgehammer

Reged: 03/22/09

Loc: Australia
Re: Propus new [Re: Bonco]
      #5789128 - 04/09/13 08:55 PM

Eta Gem (Propus) is listed as a long period binary. Separation has been slowly increasing over time. The most recent measures of 2004 and 2008 are 1.8" separation. The orbit - a grade 5, therefore preliminary - suggests 1.6" (and widening) but in the 6th orbit catalog, the diagram of measures plotted against the orbit, suggests the orbital parameters need revision - recent measures are wider than the calculated orbit would suggest.

So, the likely explanation for your difficulty is "seeing" in the sense of atmosphere wobbles. The brightness difference of the stars (~2.7 mags) makes it harder, and more subject to atmosphere not co-operating, despite the separation being wider than Dawes for a 3-inch scope.

Last time I looked at it (5.5-inch refractor) I needed 160x-200x in 7/10 seeing to show the pair. I'd expect a 4-inch would depend more on steady seeing, being only a little less sensitive to atmosphere.

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Reged: 01/17/09

Loc: USA
Re: Propus new [Re: fred1871]
      #5789172 - 04/09/13 09:24 PM

Sounds like a seeing issue.

Sometimes revisiting close pairs like that can be a reminder of just how good the seeing needed to be to really show it off. I've often been so taken with the great view that can be so vivid I want yo believe its easier to see than it was. Then a night comes doing, the seeing smears the companion into oblivion and I realize how exclusive those conditions really were,

I'm sure your eyes are fine.


Edited by azure1961p (04/09/13 09:26 PM)

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Reged: 11/23/07

Loc: Bergen county, New Jersey
Re: Propus [Re: Bonco]
      #5795521 - 04/12/13 10:32 PM

I've been able to split it several times this year with my excellent quality C8 but the seeing has to be very good. Gerry

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