Re: ATM Defining Super-Planetary

[Bratislav Curcic <epabcc@epa.ericsson.se>]

> figure my 10" f/7.3 newtonian as well as possible

Good choice.

> Where might I find his writings (in English)?

"High resolution astrophotography". I got mine from US, I think it
is available from Willmann Bell.

> Exactly what do you  mean by aesthetics--crisper? more contrast? Longer
> periods of good quality views? I do remember an old post where you
> described the the subtle advantages of refractor over high quality
> newtonian visual images(something like 'presented better' or a certain
> 'magic')

Well, all that really. The difference is subtle, but OBVIOUS. The lack
of scatter certainly plays role. Closed tube. High entrance pupil. Long
f/ratio. They all add to a great visual planetary performace. I
remember correspondence with a professional astronomer who uses
Catalina reflector and he said something like "although it was obvoius
that large scope showed FAR more detail on Mars, the image in 6" finder
scope (f/15 refractor) _looked_ better." Human eye/brain machinery is a
complicated thing. We often prefer something without really knowing why
(like valve audio gear, for example). Subjectiveness really works
against us in these situations, as we tend to exagerrate differences
once we become aware of them, almost subconsciously wanting to
find/see/hear them. With an objective device (like CCD or film), this
effect vanishes, and brute aperture easily wins.

> Thompson, Howard... suggest small newtonians in the
> f/10-f/13 class as superb visual planetary instuments.  I wonder if
> this is in part due to possibly less scattered light reaching the E.P.,
> aside from the smaller diagonal?

The amount of scatter will be the same, as all reflectors will have the
same surface roughness (if using same substrate) regardless of f/ratio
and will use same inferior/scatter prone coating techniques. The
advantage is that long f/ratio is far easier to make REALLY good, and
eyepieces like long f/ratios too. But have no doubt - well made 10"
will blow away ANY 6".

The "magic" of small long f/ratio reflector (and indeed a refractor, as
most of them will be in a 6" class) is that tunes so well to local
seeing conditions in an average amateur establishment. It is no
surprise to find that Pickering himself, when defining his famous
seeing scale said 'telescopes below 6" not recommended, above 6" not
allowed' or something to that effect. But patience, and especially CCDs
change that, and today practical "limit" is closer to 12" for most, and 
up to 16-20" for best amateur sites.

Bratislav