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Old 29-09-2011, 06:11 PM
cmr (Chris)
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Join Date: Aug 2011
Location: Warragul Vic
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Parfocal? Do I need to do it at night with a star?

Hi,

I'm planning to make some of my eyepieces parfocal using some rings I have ordered. I mainly want to make two cheaper plossis that have parfocal with my Toucam , and my Canon DSLR - so I can use them to get a rough close focus then slip in the camera.

I may also make my Baader 17 and 21 parfocal.

It seems a relatively straightforward process, but is there any reason it can;t be done in daylight with some close objects (the car number plat 100 metres up the street) for example - or even books on a shelf 10 metres away. intuitiin tells me that if the eyepieces are made parfocal then, they should be parfcoal at infinity as well, but I am learning intuition doesn't always hold sway with telescopes!

Thanks Chris

Last edited by cmr; 30-09-2011 at 07:11 AM.
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Old 29-09-2011, 11:04 PM
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Merlin66 (Ken)
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No, you can do it any time with any object. The eyepiece doesn't know (or probably care) who or what provides the image to focus on.
If all eyepieces are brought to the same focus without re-adjusting the focuser, then they will be parfocal.
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