3
5. OPTICAL TRAIN
Telescope TAЛ-200K is developed on the basis of Klevzov’s original optical
train, which does not use any aspherical surfaces. Klevzov’s optical train
(fig. 7) consists of primary concave mirror and correcting unit consisting of
two single lenses 4,5. The lens 4 is made in form of negative meniscus directed
by concave side to the observed object. The lens 5 is negative one having a
reflecting surface.
Reflecting from the primary mirror a beam passes through correcting lenses
4,5, reflects from the reflecting surface of lens 5, passes through correcting lens
forming an image of observed object in the focal plane which is located behind
a primary mirror .
In the main the Klevzov’s optical train is an improved Kassegran optical train,
which has a spherical primary mirror and double lens corrector having a reflecting
surface that to allow reducing an aberration. A meniscus 5 corrects a spherical
aberration and coma and fully compensates a little longitudional chromatic
aberration with the help of negative lens 4. Because two lenses of corrector are
made of the same mark of glass a secondary color of system is extremely little
one, and correction of the residual aberration is perfect that to allow obtaining
an image of observed object which can be compared with the image of object
obtained with the help of mirror telescope. Besides, Klevzov’s optical train is not
subject to unadjastment.
Fig. 7.
Optical train of telescope:
- primary mirror; 2 - eyepiece; 3 - diagonal mirror- lens;
4 - secondary mirror; 5 -meniscus; 6 - viewfinder
6
1
2
3
4
5
