I just got a new Orion Astroview 90 (f/10.1) and I am real pleased with the images. After reading reviews I wasn't expecting as much image quality as I got. I can see belt detail on Jupiter (NEB split into two components, showed irregularities, and GRS was in my face) and even at a measly 7.6" I can still see detail on Mars. Polar cap, surface detail (although small), etc. A nice view with nice shading on the planet. Saturn showed Cassini all the way around and up to 160X was razor sharp. I haven't pushed past 160X yet. I could also see (crisply) the shadow of the planet against the back of the rings, even this close to opposition when the shadow is smallest. The southern limb contrasted nicely against the rings and darkened toward the top. I looked again to make sure this was only a 90mm. Color error was not at all bad (had to look hard at 130X to see it around Saturn). The violet was more pronounced with Jupiter but I was so absorbed in checking for detail I forgot all about it until now. So it wasn't too obvious.
However, the star test showed spherical abberation. Out-of-focus patterns showed the outermost ring quite bright on one side of focus and quite dark on the other. I'm not that star-test literate so maybe I can get some help here.
Is this normal or could another Astroview 90 do better? I find that hard to believe based on planetary views.
I've had a Skyview 120 (sold), ETX-90 RA (sold), Celestron 8 inch SCT, homebuilt 6 inch Newtonian with Parks optics (whick kicks butt), and a 10-inch Dob (sold), also with Parks optics. I got the 90mm for quick outings with my daughter. She's used to a 60mm f/15 Monolux from the 60's, which is great for its size, not at all like the junk they make these days. I also tried a TAL OTA-100RS and was dissapointed. The 90 does better than the Tal especially on color. (The Tal unit I tried had some other problems as well.) It also outdoes the ETX-90 for detail.
This scope should get a lot of use considering what it's delivering. Views in the 6 and 8 are of course bigger and brighter and make detail easier to see, but not by as much as I thought. If I went broke and had to sell all else, this scope would keep me happy. 90mm? I shake my head.
The star test difference inside/outside of focus looks pretty pronounced. That bothers me. Any thoughts?
Thanks,
Bob
However, the star test showed spherical abberation. Out-of-focus patterns showed the outermost ring quite bright on one side of focus and quite dark on the other. I'm not that star-test literate so maybe I can get some help here.
Is this normal or could another Astroview 90 do better? I find that hard to believe based on planetary views.
I've had a Skyview 120 (sold), ETX-90 RA (sold), Celestron 8 inch SCT, homebuilt 6 inch Newtonian with Parks optics (whick kicks butt), and a 10-inch Dob (sold), also with Parks optics. I got the 90mm for quick outings with my daughter. She's used to a 60mm f/15 Monolux from the 60's, which is great for its size, not at all like the junk they make these days. I also tried a TAL OTA-100RS and was dissapointed. The 90 does better than the Tal especially on color. (The Tal unit I tried had some other problems as well.) It also outdoes the ETX-90 for detail.
This scope should get a lot of use considering what it's delivering. Views in the 6 and 8 are of course bigger and brighter and make detail easier to see, but not by as much as I thought. If I went broke and had to sell all else, this scope would keep me happy. 90mm? I shake my head.
The star test difference inside/outside of focus looks pretty pronounced. That bothers me. Any thoughts?
Thanks,
Bob
