Rick,

Usually I hear if you don't get the spacing ot the reducer right it
introduces all sorts of problems. How do you avoid this? Not using one
I'm pretty ignorant here. So it becomes a tele-extender if the spacing is
small enough? f/11 would be greater than native for the ACF series.

actually the Celestron/Meade f/6.3 reducers are quite tolerant when the
distance to the camera is concerned (at least if the camera has a small chip
like my SXV-H9).
I can use
"telescope--reducer--Baader focuser--filter wheel--camera"
for a distance of about 16 cm, which gives me a focal ratio of 1:5.6 or I
can use
"telescope--Baader focuser--reducer--filter wheel--camera"
for a distance of about 3.5 cm, yielding f/9 or
"telescope--Baader focuser--reducer--off-axis-guider--filter
wheel--camera"
for a distance of about 10.5 cm, resulting in an f-ratio of about 1:6.5

In all cases I get good starshapes over the whole field of my (smallish)
chip. With none of the above mentioned configurations I was able to get
decent starshapes over the whole field of my Canon EOS300D DSLR, neither
with my old ("made in Japan") Celestron reducer nor with my new Meade
reducer that was advertised to be suitable for the ACF scopes.
I'd like to buy a camera with a larger chip (Kodak KAF8300), but that
doesn't make sense as long as no suitable focal reducer exists (and the
current Meade Model is even slightly worse than my old Celestron). Otherwise
I'll have a larger chip but get the same FOV because I can't use a reducer
for the large chip...

My remark of the scope being at f/11 or f/12 meant that, with the Baader
Steeltrack focuser installed and without focal reducer, the focal point has
be be further away from the end of the scope, so it is no longer f/10 but
more like f/11 or f/12. The reducer than brings that down to f/9 when the
distance to the camera is short. Without the added distance of the Baader
Steeltrack I would probably end up at something like f/8 with the same
distance between reducer and camera.

Stefan







"Rick Johnson" schrieb im Newsbeitrag
ster.com...


Stefan Lilge wrote:
NGC 6675 is situated in Lyra. The object being quite small I used the
f/6.3 reducer with only a short distance to the camera, which gave a
focal ratio of f/9 (which also means that the "normal" focal lenght with
the Baader Steeltrack focuser installed is probably more like f/11 or
f/12).

Taken from the middle of Berlin with a 10" Meade ACF at f/9 on a G11
mount, SXV-H9 camera, 33x5 minutes.

The picture can also be found at
http://ccd-astronomy.de/temp2/6675-33x5gut.jpg

Stefan

I don't even have this one on the to-do list. So it must be small. In
any case it looks like one to pursue if I ever get 1x1 binning seeing.
Rare this time of year but not as much when Lyra is well placed in the
early fall.

Only small right now on my list are Arps. Most near the meridian right
now are too far south so in an Arp Gap from my declination. Still have a
dozen or so to process. Can't seem to get motivated. I like taking but
not processing so there's always a lag and a lot in the to process folder.

Usually I hear if you don't get the spacing ot the reducer right it
introduces all sorts of problems. How do you avoid this? Not using one
I'm pretty ignorant here. So it becomes a tele-extender if the spacing is
small enough? f/11 would be greater than native for the ACF series.

Rick

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Third character is a zero rather than a capital "Oh".