Svbony Filter Drawer
Holds a 2 inch filter in a slide-out drawer so filters can be changed without taking the imaging train apart. Focus and backfocus spacing stay untouched, which removes the main reason to avoid swapping filters part-way through a session.
A small part that removes a real obstacle
Changing a filter in a threaded imaging train means unscrewing the camera, swapping the filter and screwing everything back together. In the dark, on a mounted telescope, that risks disturbing focus, rotating the framing, and dropping something. The usual consequence is that people simply do not change filters mid-session.
A filter drawer holds the filter in a sliding tray that pulls out sideways. The imaging train stays assembled, focus is undisturbed, and the camera never rotates. What was a five-minute operation with real risk becomes a few seconds.
The backfocus point, which matters
The drawer occupies space in the optical train, and that space has to be accounted for. Every imaging train has a required distance between the flattener or reducer and the sensor, and getting it wrong produces elongated stars towards the edges of the frame that no amount of processing will fix.
In practice this means the drawer needs to be installed once, deliberately, with the spacing worked out and the other spacers adjusted to compensate. It is not a component to add casually the night before a session.
Worth knowing
Check that the drawer is properly light-tight when closed, and that the tray seats consistently. A drawer that allows the filter to sit at a slightly different position each time defeats the purpose.
Filters need to be mounted in the correct carrier for the drawer. Unmounted filters and cells of the wrong depth will not seat reliably.
Who it suits
Anyone who owns more than one filter. If you own exactly one and never change it, this solves a problem you do not have. If you own a narrowband filter for nebulae and a broadband filter for galaxies, it is the part that makes owning both practical.