Focal Length: 400mm
Eyepieces: 25mm Coronado Cemax, 1.25-inch fit
Finderscope: Sol Ranger
Supplier: Telescope House
Telephone: 01342 837098
The Coronado SolarMax 40 is a solar telescope with a focal length of 400mm and a 40mm aperture.
It’s etalon – the precision filter that blocks out all but H-alpha light, and so allows you to look at the sun – is front-mounted, full aperture and obstructed with an internal spacer.
We would have preferred nylon-tipped metal eyepiece locking screws rather than the plastic ones supplied.
A 10mm blocking filter/eyepiece holder screws into the top of a 90° diagonal at the rear of the scope.
Being so large, the blocking filter provides a lot of extra space around the Sun and removed a feeling of tunnel vision from the view.
The SolarMax 40’s bandpass is quoted at 0.7Å and indeed the view was significantly better defined than cheaper models we’ve used. Tuning is via a T-Max tuner, which sits between the etalon and tube.
This allows you to obtain a well-defined view and alter the scope to follow material speeding away from the Sun.
This is the same type of mechanism found on other Cornado solar scopes, and in use we found it to be extremely responsive.
The focuser on the SolarMax 40 is excellent.
A drawtube allows you to slide the eyepiece or diagonal assembly into the rough focus position, where it can be locked in place.
A twist-ring focuser is then used for fine focusing.
This works much better for imaging than the drawtube and helical focuser found on some other models because the twist ring doesn’t rotate the camera.
The drawtube was also fitted with a stop to prevent it from completely falling out of the scope when unlocked.
The view through the eyepiece showed excellent detail on the Sun’s disc and contrast within prominences.
The chromosphere was especially well defined.
The extra field of view space provided by the large 10mm blocking filter really came into its own when using the scope’s own 25mm Cemax eyepiece.
This scope delivered a great overall low-power view of the Sun.
It really looked like a 3D ball of turbulent plasma hanging in space, and the limb of the Sun was full of contrast and detail.
During our imaging tests, the SolarMax 40 performed very well indeed.
It wasn’t in the slightest bit fazed by having our high frame-rate camera inserted at prime focus.
The SolarMax 40 is an excellent all-round solar telescope, but it comes at a price.
This review appeared in the August 2010 issue of Sky at Night Magazine