Sitting near the top of Explore Scientific’s “ED” series of triplet refractors is the ED127, a 5” aperture f/7.5 apochromatic optical tube assembly. The telescope is available in a number of configurations, starting with the base model ($2,499), which includes a number of accessories to get you started. A carbon tube version is also available for $3799. The Essentials version ($1,999) comes without the finder or diagonal, and is the model reviewed here.
Although $2,000 may seem like a high price for a telescope to a beginner, this Chinese-sourced optical tube is a bargain compared to similar models from traditional cost-no-object brands like Takahashi and Astro-Physics. While the higher priced brands do offer better performance and build quality, the ED127 comes remarkably close at a fraction of the price.
Even in the Essentials configuration, the scope comes well-appointed with a large retractable dew shield, a push/pull collimation lens cell, and a 2” two-speed rotatable focuser. Weighing close to 21 pounds with the finder, diagonal, eyepiece, rings, and plate attached, the ED127 needs a suitably stable mount. While midsized mounts like the Meade LX85 and Celestron AVX are technically rated to handle this load, you are better off in the long term investing in a heavier duty mount in the class of the Orion Atlas, Celestron CGEM, or Sky-Watcher EQ6-R.
A 5” refractor is bordering on “Big Scope” territory, and you will feel it when you first use it, so don’t be in a huge hurry to move it around! While any good refractor will excel at the moon, planets, and double stars (and this one does), a 5” apo has enough aperture to start pulling in fainter deep sky objects. The outer members of globular cluster M13 in Hercules start to resolve into fine points, and the spiral arms of M31 (the Andromeda Galaxy) begin to take on definition.
While I’ll issue my usual warning not to jump into astrophotography too soon – it’s a pursuit that will keep a beginner busy for a long time before taking a single shot – I found distinct pleasure in taking images through the telescope. With each image, there was a palpable sense of “I wonder how that came out” whenever I took a photo.
Drawbacks? Not many. The major issue I found was that the quality of the focuser was not up to the level of the rest of the telescope. With heavier eyepieces or cameras attached, the focuser’s action was noticeably less smooth, and I found it had a tendency to “creep” outwards during long exposure photographs no matter how much I tightened down on the lock knobs. Explore Scientific sells a focuser upgrade for $179, which I highly recommend for owners of this scope. While $2000 is a bargain for an apochromatic refractor this large, the price will still be out of reach for many observers, and keep in mind a ~$2,000 mount is still required. Other than that, and provided the owner is willing to cope with the size and weight of the entire rig, the Explore Scientific makes a decent case for a “one and only” telescope in one’s collection.
For more on the Explore Scientific ED127, see Ed’s video at: https://youtu.be/6Jf3JMvlhQI