# Double Stars

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To give an idea of how difficult it is to split double stars what would be the minimumsize reflector and magnification size needed to split castor on an average seeing night.

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I can recall splitting Castor easily with a Tal 1 110mm reflector at 80x,

and my old Vixen 60mm refractor did the same, no problem.

I have the Cambridge Double Star Atlas. With that, I'm unlikely to run

out of new objects to find.

Best regards, Ed.

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At the moment the separation is around 4 arc seconds so a 60mm at around 80x should be enough I would have thought.

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A good challenge at the moment would be porrima next to saturn - a split of 1.7 arc seconds. I can get a clear split with my 102mm mak.

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I wish I could split these clouds!

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Hi,

Dawes Limit gives the following values for resolution:

Aperture (mm): 50, 60, 75, 100, 125, 150, 200, 250, 300

Closest stars (arsec) : 2.3, 1.9, 1.5, 1.2, 0.9, 0.8, 0.6, 0.5, 0.4

The formula is R = 11.6/D

D in centimetres, R in arcseconds

Obviously this is only theoretical and doesn’t take into consideration the viewing conditions.

Hope it goes some way to answering your question.

Paul

Edited by Paulb3098
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Castor is easy in my ED80

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tms48

under 'in space' conditions = 30mm apperture

average seeing = 60mm

remember that even with a massive apperture bad seeing conditions will stop you from seeing anything.

Edited by banner001
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tms48

under 'in space' conditions = 30cm apperture

average seeing = 60cm

remember that even with a massive apperture bad seeing conditions will stop you from seeing anything.

Should the aperture measurement be in mm here

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Thanks all that gives me a basis to work on

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Should the aperture measurement be in mm here

but it is in mm....

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