Quote:
Originally Posted by sil
I was wondering about making a small extension tube/column/pier to attach to the turning part of the vixen polarie and have my ball head and camera on top of that. Mainly to get the camera away from the polarie body, as it can sometimes be impossible for me to angle the camera enough for the direction I want without the camera body or ball head adjusters touching the body of the polarie. I figured if I add an extension layer to get it up away from the polarie body it should give me a little more angle freedom, but the I was wondering if it would make any difference to the function of the polarie (ignore flex and weight). The Polarie and similar have no mention of height of the focal plane above the turning mountand they are fine with dslr and compact cameras so it cant be critical.
So it got me wondering if it has any difference at all, or if there is a critical height where tracking is badly effected by the offset? I'd guess a 6in extension wouldnt matter but a 6ft one would. Conic sections are coming to mind here.
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Hello Sil,
It would help to get an idea of the load, i.e: compact cam, DSLR, DSLR with large lens etc..., but leaving that aside for the moment, some considerations would be:
1. your existing ball head mount is probably some 50-70mm from the mount to pivot ball centre, are you wanting to add 150mm to that distance, i.e >200+ mm ? If so that quadruples the load (moment).
2. you could potentially avoid the work /fabrication of any such extension by finding a ball head with longer base to ball distance.
3. Minimise the extension length to the minimum possible/practical for your goal, due to increased loading (as per 1 above) and the resultant amplification of any small difference in the position of the South Celestial Pole, due to differences in the loading states on Polaire's bearing/s and base/tripod interface: one DURING POLAR ALIGNMENT where the mount is essentially unloaded (alignment scope only) and the other DURING IMAGING where the mount is fully loaded (DSLR, lens, brackets etc..). This may make any perfectly acquired polar alignment (polar scope only), I won't say meaningless, but possibly somewhat in error, compared with the fully loaded state, where the South Celestial Pole would then tend to inscribe a circle rather than simply appear as a stationary point. The only way to counter any such differences would be with an extension arm that enabled the polar scope to remain in place with the mount fully loaded- Maybe that could be fabricated.
Here is a pic of another application with an extension arm. Not sure that such loading is a good idea on a small probably 5mm engagement (1/4-20) tripod screw. Long term I would seek a more rigid way to hold the Polaire
Best
JA
