First impressions of the Orion 90mm f/10 Explorer with the altazimuth mount. This scope is the replacement for the Celestron 90mm f/11 FirstScope with the altazimuth mount, that had a bad objective lens among other problems. Along with my impressions of the Orion scope, I will attempt to describe the differences between the Orion and Celestron as they are very similar models. I should also add that I have no affiliation with Celestron or Orion. The Celestron was purchased from an online vender, and the Orion scope was purchased from Orion directly, I don’t know if this makes any difference, but I figured I would mention it. The reason for purchasing this scope was to have a good grab-n-go scope; as well as a scope the kids could use. I went with an achromat, because I am not rich. I chose the 90mm as it can see the brighter DSOs, and the planets, but is still portable; and I wanted a long focal length to control CA.
The Orion is a 90mm f/10 achromatic refractor mounted on an altazimuth mount, and the Celestron is a 90mm f/11 achromatic refractor mounted on an altazimuth mount. There were some interesting differences between the Celestron and the Orion. The Celestron comes with a zero power red dot finder; the Orion has a 6 x 26 erect image finder. I tried the red dot finder and found I didn’t like it much. This may have been due to the fact that the red dot finder requires you to use both eyes; which for me means using my glasses. The mounts were similar except for the accessory tray. The Celestron has a circular tray with eyepiece holes, and the Orion has a large triangular tray no holes. I like the Orion tray better, because it is larger and I can never hit those eyepiece holes in the dark. Though the mounts were similar, the Orion seemed to have smoother motions and a little better build quality. The eyepieces were quite different; the Celestron comes with 20mm and 10mm Kelners, and the Orion comes with their 25mm and 10mm Sirius Plossls. I think the Orion eyepieces are the better match for a scope of this type. The OTAs are metal, and the lens cells are plastic on both the Celestron and the Orion; however the Orion dew shield is metal while the Celestron dew shield is plastic. I am unsure if this difference would effect how long the scope stays dew free. Both scopes come with a 45 degree erecting prism diagonal. The prism in the Celestron diagonal was loose and could be heard moving inside. The Orion diagonal was heavier, and had no loose parts. I didn’t check the collimation of the Celestron; with all the rattling around I didn’t see the point. The Orion diagonal was in collimation. Both scopes come with the standard Synta rack and pinion focuser. Lastly, the Celestron comes with the standard black paint with orange logo. The Orion is White with black logo; makes me feel like I am looking at a Meade. This is where the comparison ends; as the Celestron had a bad objective, and was sent back.
Setup of the Orion and first light. The scope arrived in one piece; thanks to it being well packed, and double boxed. Putting things together was very straight forward. I put in my Cheshire eyepiece, and found the collimation to be fair. I haven’t had much time with it outside, as the new scope curse is in full swing. I did get a chance to look at Luna. I used my Orion dielectric diagonal and UO Orthos for astronomical viewing. The image was sharp and clear, CA only showed up at higher powers and only on the lunar limb. Stars focused down to fairly sharp points, but this is where the only fair collimation reared its ugly head. The star was offset into the first diffraction ring, not a problem at low power, but when splitting double stars this would be a real pain. I found after some testing with an artificial star, that the errors were on both ends of the OTA. While there are no collimation adjustment screws, I found that some thin shims on the focuser and objective cell seemed to correct the problem. The only thing I have been able to do since the last adjustments is to use my solar filter and view the sun. The view was sharp and some sunspots were visible; now all I can do is wait for the clouds to part and test it again under some real stars. I should mention that I did try the 25mm plossl, and found it to be sharp, but not as contrasty as the Orthos.
The best part though was looking at the sunspots with my kids. They had a great time and are excited about using the new scope. I think this easy to use scope will really cultivate their interest in astronomy, as well as being a great grab-n-go scope.
Let me know what you think of this review. Should I submit it to the CN reviews?
Thanks and Clear Skies
