Should the image stabilization be on or off when shooting astrophotography on a tracking mount?
On one hand i think that it might stabilize any vibration caused by the camera, shutter or whatsoever, on the other hand i am worried it might be compensating also for the tracking Mount movement.
I have experimented with this and found that I got blobs instead of sharp Stars with IS on.
I had a Canon 7D with an EF 35mm f/2 IS Lens, mounted on top of an Equatorial Mount on top of the actual Telescope. Both the “Right Ascension” and the “Declination” Axis’ were each driven with their own Motorised Clock drives in sync with the motion of the sky. The exposures ranged from 2 minutes to 1 hour.
The Images with the IS off, were sharper then they were with the IS on, which often resulted in blobs.
Therefore, I would suggest to keep all stabilisation off when on a tripod; Tracking or not. Your thought process may be the same as mine where you may be thinking that as the stars are moving very slowly, image stabilisation will help to keep them sharp for a longer period of time.
But that is not what happened with my experiment.
if you keep the IS on, you risk creating a "Feedback loop" or sometimes known as, “Shake Return", where the camera’s Gyros detect the continued IS Vibrations and starts to move around to correct this and as a result, you end up with a blurry image.
The best results I have found, have come from very Wide Angle lenses, such as the Canon 10-22mm Non IS EF-S Lens.
When to use and not use Image Stabilization/Vibration Compensation/Vibration Reduction/etc. is lens or camera specific, depending on whether the system ins lens based or camera body based. Not all implementations are the same, even within a single manufacturers ecosystem.
When shooting on a tracking mount Image Stabilization should probably be turned off, at least with every IS lens I have seen. This is because image stabilization is designed to counter movement of the camera/lens and in the case of a tracking mount the motion along the celestial equator is desired.
Some early implementations of Image Stabilization created "feedback loops" causes by the vibrations of the IS mechanism. Most newer lenses, though, can sense when a camera/lens is tripod mounted and adjust accordingly. So the oft circulated advice to always turn off IS when using a tripod is only partially correct.
There are some lenses that have panning modes that allow motion on one axis while attempting to counter it on the other axes. It might be theoretically possible to position the camera in such a way that the motion of the tracking mount is aligned with the horizontal axis of the camera and thus that desired motion would not be countered, but it is likely that in any mode that allows for panning there would also be the undesirable side effects associated with vibration created by the IS mechanism when panning as slowly as an equatorial mount moves.
There are a few very long telephoto lenses that have an IS mode designed specifically for tripod use, but those modes are limited to to eliminating vibrations created by mirror movement and would probably not allow for panning along one axis.
I would recommend turning off image stabilization. Recently I was shooting with a 70-200mm lens on a star tracker. Every image I took was plagued by tracking error in both the RA and DEC axes, and the brighter stars exhibited bizzare trails which could not be explained by a poor polar alignment or loose connections within the setup.
Turning off IS immediately resolved the issue.
I suspect that Abdul's explanation of a feedback loop causing severe image distortion may be accurate. Most lenses' stabilization mechanisms are designed to reduce large vibrations during handheld operation. At best, they will have no effect on image quality when shooting on a tripod. At worst, they may cause significant problems like in the photos attached.
Your camera manufacturer manual will tell you that using IS on a tri-pod will create image blur, you must switch IS off when using a tri-pod
