welcome.
picture looks noisy so I’d say it’s a subset of those:
- camera contains an UV-block filter (also commonly blocks IR)
- UV illumination is weak
- your UV-pass (everything-else-block) filter is passing hardly any UV
- camera aperture and exposure time are insufficient
remedies derive from the opposites of each.
- remove UV-block filter from camera assembly
- moar UV: wear goggles if you value your corneæ
- different filter? perhaps test this one using photo film and plain UV light, compare exposure times with vs without your UV-pass filter
- longer exposure time, perhaps “image stacking”/exposure stacking, i.e. sum exposures for an artificially longer one than the camera lets you do normally
the checkerboard should be the best choice here. a circles grid will become inaccurate when tilted out of plane (but it’s convenient sometimes), and more advanced patterns such as “charuco” require less noise/better resolution than you have there.