Filter Drawers

Filter Drawers Versus Wheels

Both hold filters in the light path. The difference is whether a computer changes them or you do, and how much back-focus each consumes.

• Fixed optical thickness: The drawer body stays in the train, so once your spacing is set it never changes regardless of which filter is loaded.
• No rotation or spacing disturbance: Swapping filters does not require unthreading anything, so camera angle and back-focus are preserved exactly.
• Slimmer than a wheel: Typically consumes considerably less back-focus than a motorized wheel, which matters in tight imaging trains.
• Manual operation: You must be present to change filters, which rules out unattended multi-channel sequences.
• Ideal for one-shot colour: A colour camera user typically alternates between a dual-band and a UV/IR cut filter, which is exactly two changes a drawer handles perfectly.
• Filter sizes: Available for common mounted sizes and unmounted formats, with the same sensor-diagonal sizing rules as a wheel.

Why Choose David Astro for Filter Drawers

A drawer is the right answer for a specific kind of imager, and the wrong one for another. We will tell you which you are.

• Honest wheel-versus-drawer advice: If you intend narrowband monochrome sequences that run all night, we will say a wheel is the correct purchase rather than sell you the cheaper option.
• Back-focus calculated with the drawer in place: We supply the full spacing list treating the drawer as a permanent element.
• Filter size checked: We size against sensor diagonal and filter-to-sensor distance so corners are not clipped.
• Authorized dealer: Genuine products with manufacturer warranty, in Canadian stock.
• Ships from Canada: No duties or brokerage fees for Canadian buyers.

Filter Drawers in Canada — Frequently Asked Questions

Drawer or filter wheel?

A drawer if you use one or two filters and are present at the telescope, which describes most one-shot colour imagers. A wheel if you run monochrome LRGB or narrowband sequences unattended.

Does changing a filter shift focus?

Slightly, if the filters differ in thickness — glass shifts focus by about a third of its thickness. Using filters of the same thickness in a drawer keeps this negligible.

Is a drawer light-tight?

Good designs are, with a sprung or magnetic closure. It is worth checking with a test frame after installation, since a light leak here shows up as a gradient rather than an obvious flare.

How much back-focus does it use?

Typically considerably less than a motorized wheel, often around 20 mm or less depending on design. We will include the exact figure in the spacing calculation we supply.

Simplifying your imaging train?

Send us your camera and corrector and we will spec the drawer and spacing. Ships from our Canadian warehouse.