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Delta Cygni with ED80


NGC 1502

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Last week my Skywatcher ED80 was returned to me after being on loan to a friend for 3 years.  I’ve had two sessions since its return, on one of those the seeing was intermittently steady for several seconds at a time.

To split Delta Cyg is described as difficult with a 3 or 4 inch scope in Burnham’s volume 2 page 758. Of course that does depend on the separation listed as 2.5 arc-sec in the Cambridge Double Star Atlas 2nd edition. The 2.5” separation was from 2013, and as the orbital period is estimated at 918 years that separation will have hardly changed by 2021.

During the previously mentioned session, with Delta Cyg overhead I was delighted with a clear split at 240x. Of course that’s very high power for an 80mm scope, achieved with my 2.5mm Vixen LV.  But I’ve found like many others that double stars can take very high power above theoretical limits.

I’d be pleased to hear of similar observations, especially if success was achieved with an aperture smaller than 80mm.

Ed.

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Ed - the separation is currently 2.8", so one might think it would be easily manageable with 80mm, but the problem is the large difference in magnitudes (2.9, 6.3) which requires more magnification.  I did it with my ED80 in moments of good seeing, and exceeding the theoretical max mag - but as you say, that is doable, as it is not a hard-and-fast rule.

Never tried it, but I reckon a smaller aperture would really struggle with it.

Doug.

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An excellent challenge Ed.

My smallest refractor is a Telementor at 63mm, f13.3 so I will give that a go at some point soon. I did some Googling and there is discussion about it being achievable in this scope so let’s see if my eyes are up to it! I have the TOE 4mm and HR 3.4mm which should give enough power!

https://www.google.co.uk/amp/s/bestdoubles.wordpress.com/2010/06/28/the-saga-of-delta-cygni/amp/

https://www.cloudynights.com/topic/708983-telementor-session-may-24th-2020/

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Last night I observed Delta Cygni with my ED120 refractor. A fairly straightforward split with the full aperture as you would expect. I then stopped the scope down to 52mm aperture using the opening in the stock objective end dust cap. The primary star was nice and clear at 225x with this limited aperture but the secondary star was rendered almost invisible. After careful study I concluded that I could just about see the secondary star but I do wonder if I would have managed to do that if I did not know, from the full aperture view, just where it was placed :icon_scratch:

So it's a "maybe" at 52mm aperture, at least where my observing eye is concerned.

Edited by John
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