Re: Astro Imager's filter wheel question
- From: "canopus56" <canopus56@xxxxxxxxx>
- Date: 29 Jul 2005 17:00:23 -0700
Jon Hightower wrote:
> I just purchased one of these 5 position manual filter wheels. I'm
> wondering if there's any way to reduce the wheel tension so it turns easier.
> Anyone know?
I just purchased one myself and I can see what you say about the
tension. I don't know how to change the tension.
The positive lock and tension during turning appears to be an
astrophotography feature and not a bug.
Although the tension and positive lock may jar and offset the fine
tuning of your tracking, I believe it is intended to always register
the position of a filter with respect to a CCD chip in exactly the same
place and orientation. That way flat-fields made earlier in the
evening using more than one filter will always register the optical
defects in the filter at the same location. An error in the flat-field
registration of the filter cannot be corrected post-exposure.
Conversely, if tracking of the image is jarred slightly between
exposures as a consequence of rotating the filters in the filter wheel,
the digital images taken through each filter can be easily
re-registered post-exposure by using software.
- Canopus56
.
- References:
- Astro Imager's filter wheel question
- From: Jon Hightower
- Astro Imager's filter wheel question
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