Re: [APML] New Images

["D. Kodama" <kodama@alumni.caltech.edu>]

Wei-Hao,

Thanks for the info.  I was thinking about the teleconverter primarily to
add focal length options for Pentax lenses and through the scope for
longer focal lengths on objects like the moon and sun, most likely with a
6" AP.  I've been hesitant about getting one because I haven't had much
luck in the past with teleconverters on 35mm systems.  With my Nikon 1.4x
and 2x teleconverters I get internal reflections at certain angles.

Dave


> Dave, the image quality of the 1.4x is OK, but not too excellent.  At the
> center of the field, the stars are as sharp as I hope.  At the corners,
> the
> image quality is good, too.  However, there is a ring-shape region between
> the corners and the center, where I can see significant aberration.  You
> can
> also see this on the larger image of M31.  I'm not sure if this will
> happen on
> your telescope.  My telescope is a flat-field refractor and its aberration
> is
> quite different from typical doublet APO.  Nevertheless, the field center
> is
> very sharp.  Are you going to use it on your Borgs?  Borg has its own
> rear-
> converters.  They are designed for doublets.
>
> Cheers,
>
> Wei-Hao
>
> --
> ________________________________________________________________
> Wei-Hao Wang  :)
>
> Institute for Astronomy at University of Hawaii
>
> Address:
> 2680 Woodlawn Drive         Personal Website:
> Honolulu, HI 96822             http://www.ifa.hawaii.edu/~wang
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