[APML]: Teleconverter or Barlow?

[Jim Fakatselis <jimfak@netusa.net>]

I will be leaving shortly for Aruba to photograph the solar eclipse this
Thursday and had a question. I am using my Genesis SDF scope and Olympus OM-1
with Elite II Ektachrome film. I think that the prime focus solar image at
550mm is too small on film. If I try to record outer corona beyond a few solar
radii I'm afraid the central dark disk of the moon will start getting
overexposed. I don't know if I should try a TeleVue 2X Big Barlow, or my
Olympus 2X-A teleconverter. Any ideas concerning which would give sharpest
images at around 1100mm with the Genesis?
Jim Fakatselis

Martin C Germano wrote:

>
> Wil,
>
> >> Bob Fera wrote:
> >>
> > > I, like many other astrophotographers, am of the opinion that you can't
> >>have too much mount -- my C-11 sits on a AP 1200. Given that, I'd
> >>definitely recommend the 900 over the 600. I previously owned a G-11 and
> >>felt that it was inadequate for shooting with a C-11 (fine for visual,
> >>though). The slightest amount of wind was enough to give it  and the
> >>autoguider fits.
> >
> > I don't shoot when gale-force winds are blowing :-), but under more
> normal conditions I've experienced no such problems with a C11 on a G-11
> mount.
> >
> > I *have* had the experience of high winds playing havoc with guiding even
> though the winds were *not* blowing on the mount. In that case the
> guide-star jitters were due to the wind howling over the hill behind me
> (the "hill" was actually the top of a mountain ridge; I was located just
> below the top). The extreme turbulence caused by the wind cresting over the
> peak
> > above caused jittery guide stars and erratic guiding, looking very much
> like mount vibration, but in fact the mount was in still air. (That was an
> AP mount with an smaller scope, but it wouldn't have mattered if it was
> Palomar 200" mount; the motion was due to the air moving, not the mount.)
> >
> > As a practical matter I've found that when strong winds are blowing the
> seeing will be so poor that it's not worth bothering with narrow-angle
> photography. Even when wind on the mount is not a factor (as above), the
> star images will balloon to the point that the photo will never be
> outstanding.
> >
> > Wil M.
>
> Bob Fera was just voicing a fact of life for Mt Pinos, where it can be
> windy AND have *good* seeing. As a long time (1976) photographer from the
> Mt Pinos (California) parking lot, I have quite often experienced good
> seeing and high (est 15-30mph) winds. At nearby Pine Mt (due south across
> the Lockwood Valley, known for its terrible seeing) some of the best seeing
> I have ever experienced occurred with the wind howling 50 feet over my back
> at the ridgetop.
>
> Conversely, at another mountaintop ridge I frequent (Figueroa Mt), the
> seeing is most often fair to poor when the wind blows. I guess the real
> reason we like to "over-mount" our tube assemblies is for stability when
> the wind strikes our unshielded telescopes, as is unfortunately a way of
> life in our Southern California mountains. *Bad* seeing will cause problems
> whether the wind is blowing or not. I guess we just have to take what we
> get out in the field, as my experience with wind verses seeing is a mixed
> bag in the Southern California area.
>
> Martin C Germano
> Thousand Oaks, Calif
> mgermano@gte.net