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Secondary mirror comparsions?

Started by dj123, 09/18/2005 07:41PM
Posted 09/18/2005 07:41PM | Edited 09/18/2005 10:54PM Opening Post
I'm looking at recoating my 3.1" secodary mirror or possibly upgrading to an Antares or Protostar and I'm confused as to how to compare these 3 mirrors,

Discovery $175.00 "EVERY diagonal mirror is tested in our own Fizuea interferometer...We guarantee 1/8 wave or better" About $60.00 to recoat.

Antares $175.00 "Each piece is tested before and after the coating process" 1/14 wave PV

Protostar $175.00 "Each new batch is randomly sampled with a Zygo interferometer" 0.080 typ 0.110min FLATNESS,
(fraction of wavelength).

Discovery 1/8 wave, PV?,RMS?,Surface?

Protostar .080 typ, .110 min? How does this compare to wave PV?

Antares 1/14 wave PV, now I think I understand this and I like that they test each mirror.
Would the Antares or Protostar be much of an upgrade to a Discovery 1/8 wave? Should I see a difference if I upgrade?
Thanks
Dave
Posted 09/18/2005 11:15PM #1
You will only see a difference if the original secondary was not very good. If it was good, then the improvement would be marginal. Also, the quality of the secondary is only one factor in the optical performance, the primary will have much to do with this.
If you put on a 1/30 to a 1/50 wave secondary, it might show a better resolution at high powers, but not at low wide field powers. Again, more visual gains would be noticed if the original secondary was not performing well.
I replaced an unknown secondary on my last 15" that was a 1/30 wave Antares Quartz model and it made a big difference that you could see. I feel that was because the old secondary was not that good.
My newest scope I used a 1/50 wave Antares and it works splendidly, but the primary is a Zambuto with high marks too. You would have to put a 1/8 wave secondary in the scope and test it again to see if there was any difference I would say. smile

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