Sky-Watcher’s Evoguide 50 looks like a conventional telescope finder, but it’s much more. The name “Evoguide” suggests it can be used as a guide scope for astrophotography. Since the Evoguide’s visual back terminates in a telescope-standard 1.25-inch format, you can put eyepieces in it and use it as a telescope. Put a T-ring on your DSLR or mirrorless camera with a 1.25-inch nosepiece, and it becomes a telephoto lens. Perhaps most intriguing of all, Sky-Watcher sells a dedicated field flattener (about $110) for the Evoguide, turning it into an astrophotography-specific imaging rig.
As a finder, the Evoguide is better than most conventional units. It weighs a hefty 1.6 lbs (0.73 kg). Its construction is solid, it has an ED glass element that keeps false color at bay, and it has a helical focuser with fine threads so you can draw fine focus with little effort. As a nice bonus, the helical focuser, unlike many others, does not rotate whatever you place behind it. Some might find the Evoguide overkill as a finder, but if overkill is your thing, go for it.
I used the Evoguide briefly as a telescope. It was interesting, to a point. While the optics are of good quality, the device only gathers 50 mm of light, limiting what you can see. I managed to find the Orion Nebula, the Pleiades, and open clusters M37, M36, and M38 in Auriga.
The Evostar’s use as an astrophotography camera is what most people will find most intriguing. With the dedicated field flattener in place, Sky-Watcher claims full illumination up to a 28-mm sensor, an impressive achievement for such a small device. Experienced imagers know one main challenge of astrophotography is focus. Will my camera be able to find focus, both with and without the field flattener? Sky-Watcher supplies an extension tube so that the user can accommodate the maximum variety of cameras. I ran several experiments and came up with this table.
Notice that I was not able to find focus with any of my Canon DSLRs with the field flatteners in place. DSLRs have a large amount of back focus distance, beyond what the flattener can accommodate. Sky-Watcher specifies a maximum back focus distance of about 17.5 mm, and most DLSRs are way beyond that point, at near 40 mm. It may be possible that some of the new mirrorless cameras, with their decreased back focus distances nearer to 20 mm, may be able to find focus, but I did not have any on hand.
I ran some brief tests on the unit as an astrophotography telescope:
In conclusion, is the Evoguide 50 a finder, a telephoto lens, an autoguider, a telescope, or an astrophotography rig? It could be one, or all of these! The decision is up to you.
For more on the Evoguide, including a demonstration of how the parts fit together, watch Ed’s YouTube video: