If I am using DSLR lenses like Canon / Zeiss / Samyang 85mm to 135mm I have not bothered to brace them.
When using larger DSLR telephoto lenses, particularly those that have a lens foot (Canon 200mm f/2, 300mm f/2.8 ... up to 600mm f/4) I have not braced them either.
Do these lenses need bracing when used for astrophotography with an equatorial mount? I am worried about flexure as are pointed at various angles in the sky.
But maybe I worry too much?
There are some bracing systems available, but all for terrestrial photography. One set of them are only for larger lenses - the brace extends back from the lens foot, and has a vertical section that engages the camera. This prevents looseness at the camera / lens intersection, but does nothing for the lens itself.https://www.bhphotov...ease_plate.html .
Another kind of brace is intended for a lens that does not have a lens foot. https://www.manfrott...ns-support-293/ That has a strap that goes over the lens. But its only for fairly small lenses that don't have a foot.
The Really Right Stuff lens support, https://www.bhphotov...ml?sts=pi&pim=Yand several others similar to it has a "Y" shaped support for the lens, but that only works when upright, not on an equatorial mount. Presumably a strap could be arranged.
Similar yoke shaped supports are meant to be used with carbon fiber support rods https://www.bhphotov...ml?sts=pi&pim=Y
All of these braces or supports seem assume that the lens is pointed parallel to the ground so not really useful for astro.