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Coronado 90 III DS the sweet spotless scope!

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#1 dscarpa

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Posted 14 June 2019 - 02:20 PM

   The entire FOV is without sweet spot with any eyepiece used including 100*  ones and show no vignetting with the B15 or the Lunt BF1200 in single or DS mode! My single tilt etalon Lunt 60's sweet spot is about 80%. Also in DS  the proms show equal detail as single at 115X  which is the highest power usable today.  So far both etalons are best with no tilt which the manual says is optimal.  The Unistar-AP tripod the scopes on handles being used in DS or single without re-balancing though it's easy to do so. About the only negative so far is the UV hit I'm going to take using it. David


Edited by dscarpa, 14 June 2019 - 02:42 PM.


#2 rigel123

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Posted 14 June 2019 - 02:48 PM

Sounds like a winner!



#3 BYoesle

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Posted 15 June 2019 - 12:08 PM

 

So far both etalons are best with no tilt which the manual says is optimal.

Generally the secondary DS etalon would need some tilt and then be richview tuned to be exactly on-band.

 

It seems odd that you would not have to slightly tilt the DS etalon to remove retro reflections between the two etalons - unless they have added some pre-tilt to the secondary etalon... ?



#4 dscarpa

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Posted 15 June 2019 - 04:07 PM

 I doubt I've got it tuned optimally at this point. Not having any surface features and minimal proms to work with doesn't help.  David




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