A well designed, compact 5″ telescope and mount for $200? It may sound too good to be true but despite a few caveats this 130mm f/5 reflector is a capable telescope at an outstanding price.
Astronomers Without Borders (AWB) is an organization that offers astronomy outreach programs all over the world. The OneSky telescope is made for Celestron in China and sold in the US by AWB to help fund these programs. My intent in purchasing the OneSky was for use as a travelscope but for now I want to focus on its suitability as a general use telescope.
[Update Read more about using the OneSky as a travelscope.]
What’s in the Box
The OneSky comes with a wooden (particle board and laminate, to be specific) table-top mount, red dot finder, 25mm and 10mm eyepieces yielding 26x and 65x respectively, and a cheshire collimation tool. The included eyepieces are of decent quality though the scope is good enough that investing in an extra eyepiece or two is worthwhile.
Setting up the Scope
The telescope is shipped assembled in a fairly large box. My telescope arrived undamaged and setup required only mounting the included red dot finder to the upper end of the tube assembly. The scope has a long Vixen-style dovetail rail attached, which allows the scope to be balanced easily balanced fore and aft while in use.
After setting up the scope I noticed a separately bagged screw whose purpose I wasn’t sure about until I saw that it fit in the threaded hole at the top end of the dovetail. Here it works as a stop to prevent the scope from sliding out of a loose dovetail mount. I haven’t had the scope slip on me in any of my mounts but the stop screw does provide peace of mind.
Design and Mechanics
The telescope is a 130mm f/5 Netwonian reflector of similar optical design to other scopes made by Synta but with a few tweaks to the tube assembly for this scope’s intended application. The biggest difference is that upper half of the OTA collapses down, making the tube only about 16″ long when not in use. When extending the OTA the trusses seem to click into place and two large thumbscrews allow the position to be locked.
The 1.25″ plastic rack and pinion focuser used on similar telescopes has been replaced by a plastic helical focuser with a much lower profile. The design choice makes sense but the quality of the focuser assembly reflects the price and there is some play in the mechanism when focusing. Adding some teflon plumbing tape to the threads on the focuser can help tighten up the action.
The wooden table top altitude-azimuth mount is sturdy and the motions were fairly smooth out of the box. Tension is adjustable on both altitude and azimuth bearings and the integrated carry handle makes it easy to get outside and start observing.
Observing with the OneSky
The 130mm f/5 reflector is a versatile design capable of fairly wide fields at low power and crisp views at high powers. The provided 25mm eyepiece gives a true field of view of nearly 2º at 26x, which is very good for viewing many open clusters. While the Pleiades won’t quite fit in this field, adding a 32mm Plossl will get you to 2.5º at 20x and give a fantastic view of this showpiece cluster.
The included 10mm eyepiece gives 65x and will give a taste of what the scope is capable of at higher powers. Jupiter’s two main bands will be seen and many features on the Moon will be visible. Adding a good quality Barlow or investing in a higher power eyepiece is recommended. The OneSky has impressed me with its views of Saturn at 180x using a 8mm eyepiece and 2.25x Barlow, with the Cassini Division easily visible and the planet showing some nice color and subtle banding.
I’ve found the scope’s red dot finder to be accurate once aligned, making it easy to get the scope pointed at objects I can either see or know where to find. When finding new objects that are too faint to see the OneSky’s 2.5º max field of view is workable for star hopping but the addition of a supplemental finder goes a long way in improving the ease of finding faint subjects.
Unless you want to sit on the ground (in good weather laying out a blanket and using the scope this way works well) the table-top mount requires a sturdy surface. A milk crate can be used in a pinch but if you have some basic tools you can follow David Fuller’s instructions for an inexpensive custom support.
The collapsible design is one of the OneSky’s strengths but it does leave the secondary mirror exposed making it quite susceptible to dew and, if used in an area with lights nearby, loss of contrast. Adding a shroud made of Kydex plastic or craft foam is simple and virtually eliminates these issues.
Enhancements and Potential
As a general use scope the OneSky brings a lot to the table right out of the box but one of the best aspects of the scope is in its potential to adapt to your changing needs. The optics and design of the telescope are of high enough quality that it makes a nice platform for enhancements and customization. The fact that the telescope uses a standard Vixen-style dovetail allows the OTA to be used with many other astronomical mounts and makes the scope even more versatile.
Stay tuned for more on this impressive little scope.
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