Quote:
Originally Posted by Satchmo
I couldn't help noticing the 7 zone foucault test claiming an 0.99 Strehl ratio. Such tests are useful for small slower mirrors but in larger fast mirrors are often idealized in relation to the reality as measuring the all important edge zones edge zones is much harder this way and of course complex figure distortions ( not just simple astigmatism ) more common with large fast and laminated mirrors are pretty much invisible to the maker using these methods. Do trust your eyes and star test diligently before making decisions on the optical quality.
I found the 16" F4 Fullham sandwich mirror I tested that was mentioned earlier in this thread , looked at with sensitive null interferometry to have results nothing like the documents presented here though I didn't see original foucault test results it was supplied with . I do wish you the best results with your new optics and as always trust your eyes.
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Yes nothing is caste in stone until I star and planet test it. I never take much notice of tests other than actual usage, fingers crossed it will be of a high standard we will see in the next month or two. It will be very close to a 14" Meade and Bird's 16" so a direct comparison should be easy enough. I did a comparison between Bird's 16" and my 14" Meade the other night on Jupiter which we were imaging at the same time and with the same cameras, the contrast was much better on the 16" as expected but I was impressed also with the finer detail apparent nr the GRS.
cheers, Phil.