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Old 16-10-2019, 08:16 PM
Wavytone
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Wavytone is offline
 
Join Date: Jul 2008
Location: Killara, Sydney
Posts: 4,050
Daniel the same focal ratio, and a difference between the two of a mere 15% in aperture/focal ratio and 33% in light-grasp. Not a significant difference.

Changing the parameters by a factor of 2 is where it gets interesting - focal ratio, aperture or focal length.

Hence I’d say look for an 8” f4 or 5 Newtonian, or a 190 mm Maksutov Newtonian (Skywatcher and Orion made some suitable for imaging). The latter are rare but do work well, occasionally one appears secondhand.
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