Subject: Re: Telescopes slowly insinuating their way into mainstream photography
On Tuesday, October 24, 2017 at 2:59:09 AM UTC-4, android wrote:
> In article<firstname.lastname@example.org>,
> Rich A<email@example.com> wrote:
> > It's probably a side-effect of all the Milky Way photography people have been
> > doing. But it's interesting that people might try these devices as
> > extra-long telephotos. They'll never replace telephoto camera lenses, but if
> > people understand how to use them (there are rules) they can get some utility
> > out of them. A long time ago, a Japanese photog used a 3900mm telescope
> > (f/10) for doing photography, but it wasn't exactly mainstream.
> In the late seventies I carved a hole in a body cap from an OM-1 put the
> metallic tube form an ocular in it and then mounted that between said
> OM-1 and a 600mm amateur telescope. I was not exited by the results and
> went on with my life...
> teleportation kills
The two main problems with scopes are:
-Long focal lengths. (heat waves over long distances)
-Large apertures. (more susceptible to heat waves)
Both contribute to the degradation of images under certain circumstances. Heat waves can be so bad
they'll wipe out any kind of real detail.
The larger the aperture, the more susceptible to heat waves a lens or scope is. The best scope for
a beginner to use terrestrially is a small, fast apo with an aperture of 70-100mm. Focal ratios
beyond f/8 result in too much magnification. Large aperture scopes run into the problems mentioned.
Also, mirror-lens or mirror-based scopes are also impacted by temperature change. Going from a 70
deg. indoor temp to say a 50 degree outdoor temp, results in changes in the mirror's shape which
hurt images. The scope has to cool-down to outside temps. Lens-based scopes are impacted, but not
nearly as much.