I designed the RASA-8 for Celestron.
Why would you buy the RASA-8 rather than one of the alternatives mentioned above?
The RASA-8 is a dedicated instrument. It cannot be used at f/10 and is not as inexpensive
as an f/4 Newtonian or one of the other options one might consider.
The RASA-8 does one thing and does it extremely well. It has a 4-lens, 2-group corrector.
The use of two doublets helps to improve image contrast and reduce ghost images. The
corrector is designed to give exquisite image quality from 390nm to 800nm. While the
HyperStar is a fine addition to any Celestron SCT, it has a more narrow field of view, lower
image quality and is corrected for a much more narrow range of wavelengths. Simply put,
the RASA-8 really is a professional quality instrument available at prices that should be
attractive to most amateurs. With the Zero-Shift focusing mechanism, the RASA-8 will
be a pleasure to use.
While the RASA-8 does one thing, and does it very well, in the hands of the right
astronomer, that one thing can be used for many observing purposes. The RASA-8
could form the heart of an inexpensive tool for watching artificial earth satellites,
searching for comets and asteroids, searching for exoplanets, or just good old
wide-field imaging of the night sky.
The fully illuminated image field is 22mm in diameter, but the design of the
corrector lenses provide very high image quality out to at least 32mm diameter,
with only a little light loss (vignetting) past the 22mm inner region.
If you wanted a RASA-11 but it was a bit too expensive, the RASA-8 might be
for you. It will pull in many times more light that an APO refractor, and is
much more affordable. It has higher image quality than any Newtonian without
a coma corrector, and is much more compact, easy to use and really never
Maybe it's the right instrument for you. Maybe not. Any optical design is a
compromise, but Celestron has really pushed the envelope with the RASA
family. One really cannot come close to their performance for twice the
price with any alternative.
For those who would chose to pan me over this post, please note that
I have no financial interest in Celestron or in the success of the RASA family.
Celestron paid me to design various members of the RASA family and that
is the end of my financial contact with them. I continue designing for
Celestron as they have proven to be an absolutely first rate company with
an exceptional leadership team. They are dedicated to truly innovative,
high-quality instruments for the amateur and professional astronomical
community. For those who do not have insight into the professional
astronomical community, I can tell you that many RASA-11s and RASA-14s
are in use by professionals all over the world.