For anyone interested, I joyfully received a Sky-Watcher Evostar 150 ED 4 days ago. The seeing conditions since then have not been kind (darn telescope gods) but last night, after the clouds cleared, the seeing unexpectedly settled down to about 7-8/10. Scope verdict: Absolutely stunning glass! As others have noted, once cooled, this lens is incredible. Who gives a flip what the glass elements are made of! With crisp images like this, I don’t care! DR. D, you were right!
After initial setup, and peering through the sucker holes in the clouds, the scope star tested out to about 1/5th wave @240X (according to Suiters book images, Ronchi, and Aberrator 3). Just an average scope. Testing again, after about an hour or so after the parting of the clouds (about 90min after sunset), revealed a smooth, highly corrected optic that almost knocked me off of my observing chair. WOW is truly the word for expressing this telescope's performance!
Using a 250lpi etched glass grating (@two bands on both sides of focus), and star tests (375X), revealed what appeared to me as a smooth 1/8th wave of total correction. It was actually better than this but most are not going to believe that conclusion without an interferometer image. They probably won’t agree my visual assessment either but I know what I have seen. No zones, astigmatism, edge defects, or roughness. This lens is so good that I was able to clearly test it at a mere two rings in the out of focus diffraction pattern (very critical). Just incredible! After all the scopes I have built or owned over the past 40 years, I can remember only a handful that could do this “cleanly.”
In focus stars (after cooling) revealed no false color to these 67 year old eyes, all the way up to 375X. Venus was surprisingly good. The very minor false color I did see came from seeing tremors. I had the same result with the moon. For the type of observing I do (moon, planets, multiple stars), this scope is “off-the-chain.” I’m looking forward, with great anticipation, to a night of good seeing and the coming evening planet parade.
I’ve been doing the "scope thing" for a long time (over 40 years). This has to be one of the best, if not the best, star test I have ever seen in a refractor of this size or greater. The star tests reminded me of a visual star test I performed on a ridiculously good 4” Alvan Clark up on Mt Pinos. The test image was very close to what you see when you reduce a scope’s aperture to about 1” to see a perfect out of focus diffraction pattern. The area of precise focus on this scope is so tight that using the 10 to 1 focus knob is a requirement, not an option. After some minor focuser rework (smooth as glass and now holds my 2" prism diagonal without slippage), this scope is about as close to optical perfection as this lowly scope user dares to get.
Never being able to lay down coin, or wait, for a high-end refractor in this size range doesn’t hurt so much now. Astro Psychic, Rock-a-hashi, TM Front, LZOOS, Penthouse? HA!
Don’t pinch me. I don’t want to wake up from this telescope dream…
Edited by ATM57, 05 May 2020 - 11:29 AM.