EOS flange to M54 interface

w7ay

As most of you are probably aware, ZWO had a couple of months ago released a new (at least the third iteration now in the last 2 years) style filter drawer that finally has acceptable light leak.

The drawer two versions ago was practically unusable unless you are in a Bortle 1 area, and the fix for it (simply overlapping the curve plate of the filter carrier) was not much better.

This latest version insets the curve plate of the filter carrier so it is flush with the body of the drawer itself. I still won't recommend it for daytime solar use, but appears fine in a borderline Bortle 5 to 6 area at night.

There are two versions of the drawer -- one for 42mm and one for 54mm camera flange.

ZWO has also since released a new EOS adapter that incorporates the new drawer -- except, in their infinite wisdom, only sell the version with the M42 camera flange! They even showed a diagram to a full frame ASI6200 :-) :-). Do these guys actually use their own products? A M42 (hole aperture about 38mm) with a camera whose sensor diagonal is 44mm??! It would vignette horribly even with an f/16 lens.

After staring at diagrams and pictures, I decided to buy the newer EOS with drawer to experiment with. I aready have two of the new style M54 stand-alone filter drawers.

Sure enough, the subcomponents match.

Here is a picture showing the new style stand-alone M54 drawer and the new style EOS filter drawer with the M42 interface. The left is the stand-alone M54 drawer, and the right is the EOS-M42 drawer. Notice the hole sizes.

Here is another look, at the side view.

Notice the bolt holes of the first picture? Light-bulb above head :-).

So, I removed the camera flange (M54) plate from the stand-alone drawer, and replaced the flange plate of the EOS drawer with it :-).

Here it is on my Canon 100L/2.8 setup, with a ASI6200 at the camera end:

With an IDAS HEUIB filter, and a tree 70m away, the Canon lens's focus marking shows this (focused with a ZWO EAF):

So, if you can't wait for ZWO to release a more sensible M54 version of the EOS drawer, you can get these two parts and Frankenstein it yourself:

https://cloudbreakoptics.com/products/new-filter-drawer-for-eos-lens
https://cloudbreakoptics.com/products/new-2-filter-drawer?variant=43595031871737

Chen

AstroDude42

w7ay Nice rig, Chen! And thanks for sharing.

I just finished setting up my Samyang 135/2 with the ZWO EOS filter drawer (oh my! second generation), an IDAS NBZ filter and the 2600 MC Pro. Can't wait to test it out. I will have some duck tape ready at hand in case I need to fix some light leaks. 🙂

Olli

Clarky2

w7ay Just to add, I just tried this solution and it still works great as at Dec 2024

w7ay

AstroDude42 oh my! second generation

Yeah, the first generation leaked the most.

The leaks are hard to tame unless you electrical tape all around the removable part of the drawer (which negates the convenience of a filter drawer). I had been using a discarded lens heater to cover the entire drawer, making it easier to change filters.

They tried a lazy fix by extending the curve plate a little bit more, to overlap the hole more, apparent not realizing that the curved plate on top of the drawer shell is the root of the problem to start with. So, it fixed very little of the original problem -- they apparently don't test the stuff they draw on paper.

The third generation finally has the removable part inset into the body of the drawer, so light would need to enter through the equivalent of two baffles which are not lined up. Under extreme conditions, it will still admit some photons that got bounced around - the surfaces are still smooth -- a mistake they did not fix -- perhaps they will fix it in a 4th generation.

I bought one new drawer initially, and did some testing. After making sure that it does work better, I bought a second one, and the one that is integral to the EOS adapter. And needing to replace about a dozen filter holders.

Aloha, Olli.

Chen