On Wed, 22 Jun 2005 02:09:27 -0500, Olga <hintauo@xxxxxxxxx> wrote:
>well....... its not just initial cool down, its adjustment time as the
>wears on in spring, summer, fall, but only you would be out there at -20
>looking for the great unknown.
All telescopes change focal length (due to their aluminum tubes)
but a gradual fall in tempertures does not produce the same effect
as taking an instrument from (say) a 20dec C car and exposing it
to a -20deg. C night. Yes, I observe when it's that cold, since
some of the best nights in terms of transparency happen then.
>> On 21 Jun 2005 00:45:12 -0700, "atasselli@xxxxxxxxxxx"
>> <atasselli@xxxxxxxxxxx> wrote:
>> >How can you possibly prove what you previously posted, eh? They do (or
>> >at least did) NOT use the same multicoatings (MK67DL's are f...ing
>> >better) and baffling is quite different. Optical quality in not even
>> >comparable. Plus, when something really never cools down what do you
>> >really expect?
>> >Andrea T.
>> "Never really cools down" is wrong. I've used the 7" in temps down to
>> -20 and though it does take time (2 hours) it does cool down.
>> Under more moderate observing conditions (summer) it's ready in
>> 30 minutes or less.
>> None of what you've said about multicoatings or baffling or optical
>> differences (which are minor) could possibly account for a major
>> difference in image contrast. Like most, you are over-emphasizing
>> the differences for whatever reason. I have't seen a graphic
>> difference in telescope performance since the bad SCTs of the 1980s.
>> Since then, "like" scopes have all been similar in performance.