On Thu, 26 Aug 2004 19:57:49 -0400, "Paul Hyndman" nospamma-mia
wrote:

The etalon is an important part of the system, working in concert with a
blocking filter to restrict the frequency to sub-angstrom levels. To put the
level of precision in perpsective, consider this: an angstrom is one
hundred-millionth of a centimeter, and this filter's passband is "tighter"
than that!

Even small changes in ambient temperature could be fatal to solar H-a image
quality, if proper engineering provisions have not been implemented. Some
solar H-a designs require heaters to maintain "on-band" performance while
others use tunable stages that are adjusted throughtout the session, but the
etalon design as employed here requires no heaters or continued fidgeting.


Yes, I remember using one with a little "tilter" knob on it. Don't
remember the brand.

Non-etalon, rear-mount filter configurations usually require long f/ratios
(f/30-f/32 is not uncommon), making full-disk views less accessible. I
believe the PST works at f/10.. another benefit of an etalon design (the
filter can be mounted in front of or behind the objective).

Increased aperture can impart greater resolution (no secret there) and a
decrease bandpass can enhance contrast. For either though, the cost climbs
logarithmically! Given the price-point of the PST, there is currently
nothiing on the horizon that even comes close to the amount of
bang-for-the-buck it delivers.

One last thought... you can easily spend far more than $499 for an eyepiece
(been there many times over!)... but this little puppy even includes that in
the package price!

Paul


Yes, it is amazing. I can see greater interest in solar observing now
these have hit the market. It's nice to see things have come this way
for Coronado, remembering the beginnings of the company.
-Rich