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Old 12-05-2019, 01:10 AM
Mokusatsu (Australia)
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Focal length of guidescope

Often short focal length guidescopes come with a warning that they're only suitable to guide main scopes up to certain focal lengths, because longer FL scopes require more precision in their guiding.

Is this something one could rectify by chucking a barlow into the guidescope if you needed a higher precision guide?
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Old 12-05-2019, 09:45 AM
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Merlin66 (Ken)
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In theory , yes.
But not all "finder guiders" are capable of taking a barlow....
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Old 15-05-2019, 10:50 PM
RyanJones
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Quote:
Originally Posted by Mokusatsu View Post
Often short focal length guidescopes come with a warning that they're only suitable to guide main scopes up to certain focal lengths, because longer FL scopes require more precision in their guiding.

Is this something one could rectify by chucking a barlow into the guidescope if you needed a higher precision guide?
Im glad you asked because Id recently wondered the same thing
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Old 16-05-2019, 02:22 AM
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billdan (Bill)
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By doubling the focal length it's a double edged sword, in that you Field of View of the width and height of your sensor is halved.

Also each pixel will only see one quarter of the light than before.
Lets say a stars photons covers 2 pixels x 2 pixels without the Barlow, with the Barlow installed the star now spreads out to 4 pixels x 4 pixels. Or in area, 4 square pixels vs 16 square pixels.
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