JSP EasyTester 133 LPI Ronchi Grating Tester

The EASYTESTER (by Jack Schmidling Productions) is an eyepiece-like device that allows the owner or user of any type of telescope to quickly determine the quality of the optical train with no previous experience or skills.

Anyone who has ever purchased or built a telescope has experienced that uncertain feeling of not knowing whether those un-textbook-like images are the fault of the optics, faulty adjustments or just seeing conditions.

The EASYTESTER consists of a classical Ronchi grating mounted in a standard 1-1/4" eyepiece tube. When the device is focused on a bright star, a pattern of parallel lines appears that can be used to determine the optical quality of the system and identify many of the common faults that plague commercial telescopes these days. If the lines are straight and parallel to the edge, one can conclude that the mirror or objective lens is well figured and that the secondary (and) corrector plate are properly figured. If the lines appear to be anything other than straight and parallel, a quick comparison to the included defect chart will identify the type of error involved.

The EASYTESTER has many uses in addition to verifying the quality of purchased telescopes. Many folks bring their newly made scopes to star parties to get expert opinions on their labor of love and welcome inputs. Some don't welcome such inputs so you need to be a little diplomatic here because the EASYTESTER makes an "expert" out of anyone who has one.

Although the standard "star test" is probably still the most precise test, it is very difficult for the inexperienced observer to comprehend and very subject to mis-interpretation. Furthermore, unless seeing conditions are excellent, even experienced "star testers" can learn little from the dancing images. The EASYTESTER, on the other hand, will tell its story under the most dismal of conditions, including fog, haze, turbulence, bright lights and full moon.

The EASYTESTER consists of a 133 line grating mounted in a 1 1/4" diameter tube made of instrument quality brass and a plastic eye cap. The grating can be moved up or down and locked into position with a setscrew to accommodate various backfocal distances.

Comes with a plastic bolt case. Lifetime manufacturer's warranty.