Sorry about the 'loose' term Doc! Of course I say upgrade as it will be
something new (and I hope improved!) for me. Does the 12" have the new Dec
bearings like the new 10"ers do now? The main goal was getting the
additional light gathering power compared to the 8" for CCD work. My FOV
will be decreasing quite a bit.

As you mentioned, the field of view will be changing dramatically for me as
I am going from 1280mm (8" f6.3) to 3050mm (12" f10). This will take some
getting used to. I believe it takes me from the 12' x 18' I get now down to
about 5' x 8' at f10. Bringing it to f5 would get me to 10' x 15', and f3.3
would be about 16' x 24'. The reason I was looking at increasing the FOV
was so that I can grab a bigger chunk of sky when I start some of the
experimenting I wish to do with asteroid astrometry and light curves. I
guess I have gotten spoiled at 1280mm!

I suppose there is the whole 'sampling' issue to deal with also, but that is
probably a whole other can of worms...As it stands, I would be at about .6
arcsec/pixel for f10, and 1.9 for f3.3 with my ST7E on the 12", with the
f6.3 and f5 in between there somewhere. The 8" used to give me 1.5 at f6.3.
Of course, double all those with the camera binned at 2x2 the way I used to
run it most of the time. Halve that with the barlow for planet work which I
think the longer focal length of the 12" will be much better for than my 8".

I do plan on keeping both scopes as it will give me some versatility. I can
use one visually while CCDing or doing video through the other, use them for
different targets when matching up the needed FOV as you suggested, and
maybe even use it as a source of emergency spare parts if the occasion
arises as it is wont to do from time to time.

Thanks for the notes Doc!

Anthony J. Kroes
Green Bay, WI


> -----Original Message-----
> R. A. Greiner
> Sent: Tuesday, August 28, 2001 1:00 PM
> Subject: Re: [M]: Focal reducer recommendation
>
>
> I would like to suggest that the term upgrade is not the correct term
> when you go from an 8" to a 12".
>
> If both are f10, you are simply changing the focal length of the lens
> from 2000 mm to 3000 mm. If you want a larger field of view, I would
> suggest you keep the 8" and not use a focal reducer at all. You will
> get a better quality image without a focal
> reducer.
>
> You will get the same exposure for extended objects with both scopes.
>
> I suggest using focal reducer only when absolutely necessary. But, I
> suggest picking the scope which has a focal length that is correct for
> you desired field of view.
>
> Keep and use both scopes. Then you have a camera with two nice
> telephoto lenses.
>
> Doc G
>
>
> "Anthony J. Kroes" wrote:
> >
> > I am upgrading my scope from 8" to 12"LX200 and was wondering what the
> > current opinion is for recommended focal reducers. I have the
> Meade .63,
> > but am looking at getting a bit wider field of view through the
> Meade 3.3 or
> > Optec 5.0 or 3.3 reducers via my ST7E.
> >
> > I have read the review/comparison by Chris V. in the archives, but was
> > wondering if there is a different current opinion, and whether
> anyone had
> > direct experience with the using either with the following
> optical train.
> >
> > 12" LX200 / NGF-S / (some brand of .33 FR) / CFW8 / ST7E
> >
> > I am used to working with an 8" LX200, f6.3 and my concerns are
> vignetting,
> > the 'yellow filter' problem with Optec FR's, sufficient
> backfocus with these
> > to still be able to use the CFW8, and if either will affect
> astrometry or
> > photometry - fields I wish to explore further with this setup.
> >
> > Any help or constructive opinion either way will be appreciated
> >
> > Anthony J. Kroes
> > Green Bay, WI
>

View index by [date] [author] [subject]
Previous message: Re: [M]: [M] Polar Alignment Questions -- long, Ted Van Sickle
Next message: Re: [M]: RE: green vs red lighting to preserve night vision, Daniel Kell
Next message in thread: Re: [M]: Focal reducer recommendation, R. A. Greiner
Previous message in thread: Re: [M]: Focal reducer recommendation, R. A. Greiner