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Home > Reviews > Telescopes > Refractors > Orion’s Explorer 90mm Altazimuth Refractor

Orion’s Explorer 90mm Altazimuth Refractor
By Blair Slayton - 10/23/2004

The Orion 90mm Alt Az
This is a very good first telescope or a very good quick look scope for those that have larger telescopes.

It does show some chromatic aberration on the Moon’s outer edge but not enough to bother me nor is it noticeable on the terminator at powers up to 180X.

On Jupiter I’ve seen the shadow transits of its moons across its surface. I’ve not been able to see the Great Red Spot (GRS) with it but this is more because of my poor seeing conditions (Greensboro, NC typically has high humidity at night) and my 53 year old eyes. Others that I have talked to that live out West have seen it with this scope.

On Saturn it shows the rings and some surface detail. Double stars are nice in this scope. At 150X to 180X I have received nice views of the Double Double in Lyra, Izar in Bootes, Rasalgethi in Hercules and at about 100X, Almach in Andromeda.

On an average seeing night for me (which is about 4 mag skies as judged by stars seen in Ursa Minor) this scope shows a nice view of the Open Clusters M36, M37, M38 in Auriga, M11 in Scutum, M35 in Gemini, The Pleiades, and the Beehive Cluster as well as a number of others especially when they are near the apex of the sky.

It also gives nice views of the Orion Nebula, the Ring Nebula, and the Dumbbell Nebula. It doesn’t show the colors as shown in photographs but typically just shades of gray though I have seen a slight hint of green in the Dumbbell Nebula when it was high in the sky and seeing was above average.

The AZ-3 mount takes some patience and some trial and error to get it to work for astronomy but it can be used effectively up to 180X. The slow-motion controls work well as the mount is stable enough to settle down quickly after each adjustment. The key thing to do is to balance the scope and keep a wrench handy to tighten the Altitude nut from time to time.

The scope comes with very good 25mm and 10mm eyepieces. I suggest buying a 32mm Plossl eyepiece as this will give a large enough field of view to see all the sisters in the Pleiades. I also have used Orion’s Explorer II 6mm Kellner on double stars and the Moon with nice results. I have also used Orion’s Shorty-Plus 2X barlow with the 25mm and 10mm eyepieces with good results. Other eyepieces I have used with this scope is University Optics Orthoscopics and Televue’s Plossls but they are significantly more costly than the previous mentioned eyepieces but can be reasonable if bought used on Astromart.

I did upgrade the viewfinder to a 6X30mm right angle, correct view viewfinder as this makes it easier to star hop and bought a 90 degree diagonal as the 45 degree diagonal that comes with the scope is good for terrestrial use but not for Astronomy.

Basically, this is an inexpensive way to enter the world of visual astronomy.

Blair Slayton
October 2004

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