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Orion’s Astroview 90mm f/10 Refractor

I have bought and tried many of Orion’s refractors (ShortTube 80, ShortTube 90, Astroview100, and Astroview 120ST) and found the 90mm f/10 the most useful. Its 910mm focal length provides very useful powers for most types of beginner to intermediate levels of observing. With a 10mm eyepiece, and Orion’s shorty barlow, I’ve been able to go to 182X on the moon, on some nights, and still clearly see the surface’s detail.

I’ve watched Io’s shadow cross the face of Jupiter for the first time in my life. On some nights I can detect details in the Northern and Southern belts of Jupiter. Cassini Division on Saturn is usually seen very clearly. I’ve been able to see Rhea, a moon of Saturn, as well as Titan. All this in my backyard with streetlights all around and my 51 year old eyes.
Unwanted colors, like a purplish hue, have not been a problem. Beyond the edges of the Moon a slight purple ring (at higher powers) can be noticed if looked for. None have been noticed in the area where viewing is concentrated (like around the Moon’s terminator). No purple-halo has been noticed around Jupiter like I’ve seen in the 120ST.

Orion sells this scope on a decent equatorial mount for $299. Vibration does become an issue at higher powers but things like using the scope on grass instead of cement will help. I owned a Skyview Deluxe (SVD) Mount that I bought from Orion to use with the above mentioned scopes and with the 90mm f/10 on it vibration is significantly reduced. I use it on this mount mostly but it performs well on the EQ3 mount that is supplied with it. Also, the EQ3 mount is lighter than the SVD mount. Normally, at worst, it takes about 3 seconds to settle down on the EQ3 after focusing on an object.

The focuser can be tricky to use at higher powers but this problem could possibly be fixed by taking the focuser apart and putting in a thinner grade of grease. With practice, I’ve been able to focus at higher powers very quickly without doing the mentioned modification to the focuser.

I’ve used a 32mm Sirius plossl, 25mm, 20mm, 17mm, 13mm, and 10mm Orion Explorer II (Kellner) eyepieces with this scope and have been pleased with their performance. Used with Orion’s 2X shorty barlow this gives me a good range of useful powers.

I did buy Stellarvue’s enhanced , 1.25”, 90 degree diagonal ($49) which states about a 98% reflectivity. A standard diagonal is usually around 89%. I realized about a 0.5 magnitude improvement for the magnitude of stars I could see through the scope. With higher powers (91X and above) I have seen down to 11.5 mag on average with this scope.

The computer program, The Sky (Student Edition) , Orion provides with their scopes is very handy but mainly for smaller scopes. Definitely 6” and larger scope owners will want to upgrade to a larger database version to have the program show the fainter objects and stars they can see.

I live in Greensboro, NC and humidity is usual fairly high so desert viewers should see even better performance out of this scope.

I also upgraded to Orion’s 8X50 right angle, correct view, viewfinder which fits easily in the dovetail mount on the scope. I went to this because I can detect many of the Messier objects in it where with the supplied 30mm finder this was not true. Also, the right angle allows for more comfortable viewing when trying to find objects.

One problem with this setup is that when you wish to look at objects at the apex of the sky. Even with the mount fully extended (which increases vibration) the eyepiece gets low to the ground. Chair viewing becomes difficult unless you own one like Orion’s Deluxe adjustable chair which allows you to raise or lower seat height as needed. A blanket on the ground will work as well.

If all the scopes perform like mine (I’ve read that these Chinese made scopes can vary in quality) then I highly recommend this scope. I feel this would be a much better beginner scope than anything smaller in aperture and a 6 inch or larger dobsonian. After the lure of the moon and planets wears off this scope will show more of the deeper sky objects than the smaller scopes and this scope is still light enough to move around and is easy to setup. It normally does not require to be collimated as long as it was done properly when made. The equatorial movement controls really help when tracking Jupiter at higher powers and there is a motor control option for the EQ3 mount from Orion.


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