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70mm Skies June 10/11 2018 - Two Doubles


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@John has sparked my interest in two double stars, Mu Librae and Delta Cygni; in particular whether they can be split with 70mm aperture. This session was under marginal conditions - according to Clear Outside, I should have been in bed - but I was at one of my better locations and Bjorn was along, so it was worth a shot.

Mu Librae

Currently above Jupiter, this one was located easily enough, but it wasn't going to come along quietly. That part of the sky was not the best quality just then, but we gave it all we had anyway. Still, all the way down to 200x, it wasn't apparent to me that this was indeed a double star. I took my time with it, and waited for any fleeting glimpse of a companion, but this time it was not to be. Aperture or conditions, I can't say, but I'll certainly be trying again in future.

Delta Cygni

Al Fawaris, as SkySafari alternatively names it, is the point from where the Swan's top wing sweeps back. It's in my observing list for Cygnus, but I haven't recorded a successful observation of it. Can't remember whether I've tried - perhaps I've reported to the contrary, but I'll leave it at that. If I have indeed tried in the past, I'm sure it must have been with a 6" newt, either a f/6 or an f/8. Not having seen a split would probably mean that on average, it's pretty challenging for me here.

It's in Cygnus that I find myself reminded of the value of a good finder scope. Bjorn is at his most humble little more than a very good finder scope, but when he's busy holding a shorter eyepiece, it's easy for me to get lost in the density of starry stuff up in the Swan. Mindful and swift eyepiece changes can alleviate this, but it wasn't quite working for me this night. Baader Zoom to the rescue; this helped me keep the target in view and got me down to 50x from where I could drop to 100x, 117x, 166x and finally 200x, where I ran out of Vixen HRs (had left the 1.6mm at home).

This also proved a tough little one - but my results were better. Not a clear split, but definitely an obvious brightening on one side of the diffraction ring, indicating that which I wanted to see, of course, but convincing enough. Again, the conditions were not great. This one also merits multiple future attempts.

Tonight isn't looking ideal either, but there may just be a gap within which to work. I'm at Starbase Newt tonight, so I do have the choice of aperture with which to have another go.

To be continued.

:happy11:

Edited by iPeace
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All,you can do is keep trying until the conditions allow.... there are some pretty tight and colourful doubles out there ? Good hunting.

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