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Celestron C8

The Celestron C8 is one of the most famous optical tubes in the commercial landscape, known by virtually all astronomers. Its optical design is the famous Schmidt-Cassegrain (SC), consisting of a primary mirror for moving the focus to open ball f2 and a spherical secondary that always multiplies to 5x, so the classic f10. The secondary mirror is held in place by a sheet correttrice.La plate has the task to diverge and converge towards the borides the center, that serves to correct residual optical aberration.

The C8 is a tool designed for people who must move in search of dark skies because of its size and light weight considering its 8-inch (203 mm).
Like all catadioptric you must deal with the obstruction of the secondary mirror that for the C8 is 34%.
Celestron, like other manufacturers, has over the years improved its optical introducing different treatments of the optical surfaces, the first treatment was the Starbright to increase the brightness of the instrument, in recent years has introduced the treatment to further improve the brightness of the XTL slab.
The C8
lends itself well to be a tool to do everything, having a good opening allows him to collect enough light to bring out deep-sky objects and also thanks to the focal length is also suitable for planets and moon. Unfortunately, being an instrument is also a limit to everything, being good for all not excel in anything. The C8
then holds collimation very well, in fact, even after several nights, and travel miles I never had to diverge.
One of the major flaws that I noticed on the C8 is the system of focus, because in addition to the sensitivity of the knob, certainly much improved, there is the so-called image shift, ie the shift of the primary. I solved the first problem and partially the second dotandomi in an external focuser.
Another flaw of the C8, but in general for all SC, is the ease of Appanoose the corrector plate in the humid nights as well as the time to acclimatise optics abbastenza long. Last note about the rather long focal length makes it a little difficult viewing deep-sky objects, a problem solved in astrophotography with focal reducers.
Last note is the sensitivity to poor seeing, but this is definitely a problem of Mak or Newton.

Focuser Series C8

corrector plate and secondary

Celestron C8 on Orion Atlas EQ-G Goto

From personal experience I can say that my C8 is optically very good in seeing decent evenings, from 5 / 10 up Saturn will begin to see details of the atmosphere of the planet and we can see the Cassini Division rings; on Mars but you can see various details like the polar caps and the diversity of the area.
In a particularly good night with seeing that I could reach to 400x without losing sharpness.
The moon however is always spectacular, with the possibility to observe very small craters with a good contrast.
Unfortunately, to date, I have not been able to observe Jupiter, but certainly will give me a good seeing a lot of emotions ... In the deep sky
I had few opportunities to test my C8, except for brief and fleeting tests on M42, M44, M45 and M57 with more transparency and seeing little or M42 mediocri.In the most I could see quite easily the nebulosity around the nucleus of some stars, while open clusters M44 and M45 of the long focal length did not allow me to frame if all the clutter (when I was still not observed have a wide field eyepiece and I refer to a review soon), and M57 are able to discern its shape wad but could see many details.

In short, the C8 is a great tool for anyone who wants a good opening for an affordable, easily transportable and usable in any field always Taking into account of its shortcomings, ultimately due to the optical compromises ..