ZWO M42 2" Filter Drawer (Gen 2)

A slim 2" filter drawer for swapping one filter without a wheel

The ZWO M42 2" Filter Drawer (FD-M42-II) sits between your telescope's flattener or reducer and your astronomy camera and holds one 2" (M48) mounted filter in a pull-out holder. It has an M42 × 0.75 male thread on the camera side and an M48 × 0.75 female thread on the telescope side, so it suits ZWO cooled cameras with 4/3", 1" and APS-C sensors such as the ASI533MC Pro and ASI2600MC Pro. It's 70mm across and 21mm thick.

Key specs: holds one 2" mounted filter (M48 × 0.75) · 21mm optical thickness · M42 × 0.75 male (camera side) · M48 × 0.75 female (telescope side) · 70mm diameter · double magnets plus side lock screw · M48-to-M42 adapter included

When a filter drawer makes sense

• Color cameras: switch between a duo-band or tri-band nebula filter for emission nebulae like the North America and Heart nebulae and a UV/IR cut or light-pollution filter for galaxies and star clusters.
• Short imaging trains: at 21mm it's thinner than any ZWO 2" filter wheel, which helps with scopes that have little back focus to spare.
• Light travel rigs: no power cable, no USB, nothing to configure.
• Mono cameras: it works, but changing filters by hand each hour gets old fast. For LRGB or SHO, a ZWO 5-position 2" EFW is the better tool.

How it works

Thread your 2" filter into the holder, then slide the holder into the drawer until the magnets catch it. Tighten the small lock screw on the side to take up any gap. To change filters, pull the holder out by its knob and drop the next one in. With a spare holder for each filter, you don't have to unscrew filters at the scope at all.

Back focus: the drawer adds 21mm. Remember that a filter also pushes focus back by about one-third of its glass thickness, so a 2mm filter adds roughly 0.7mm.

Using a third-party filter? ZWO says its cell must be under 50.8mm in diameter and under 7.5mm tall, with an M48 × 0.75 thread no longer than 2.7mm.

What to add for the best results

• Extra 2" filter holders: keep each filter in its own holder for quick swaps.
• A 2" filter: the ZWO Duo-Band filter (choose the 2" size) or the Optolong L-eXtreme for nebulae from the city, and the ZWO IR Cut filter (2" size) for broadband targets.
• 1.25" to 2" filter adapter: lets you use 1.25" filters in the holder with smaller sensors.
• A camera: the ASI533MC Pro or ASI2600MC Pro.

Which ZWO filter drawer do you need?

All four take the same Gen 2 filter holder. See all filter wheels and drawers.

What's in the box

• ZWO M42 filter drawer with one 2" filter holder
• M48-M42F adapter

Filters and extra holders are sold separately.

ZWO M42 2" Filter Drawer FAQ

Filter drawer or filter wheel?

A drawer is the simple, low-cost choice when you change filters a few times a night, which is typical with a color camera. If you shoot mono and change filters every few subs, get a ZWO 2" filter wheel so the ASIAIR or N.I.N.A. can do it for you.

M42 or M54 drawer?

Choose the M42 drawer for cameras up to APS-C size with an M42 front thread. Choose the M54 drawer for full-frame cameras like the ASI6200 or any camera with an M54 front, where the wider opening helps avoid vignetting.

Will my old ZWO filter holders fit?

No. Holders from the Gen 1 drawer don't fit this Gen 2 drawer, and Gen 2 holders don't fit the Gen 1 drawer. The Gen 2 filter holder fits the M42, M54, Nikon and EOS drawers.

Can I use 1.25" filters?

Yes, with the ZWO 1.25" to 2" filter adapter. Keep it to smaller sensors such as the ASI533, since a 1.25" filter will vignette on APS-C.

Specifications