ZWO 2" M42 filter drawer - m48 to m42 adapter ring

[Rob-Minchinbury]

To all ZWO 2" M42 filter drawer owners (ZWO-FD-M42, example https://astronomy-imaging-camera.com/product/zwo-filter-drawer-m42).

The 3rd main image shows the m48 to m42 ring that screws into the drawer.

Does your drawer have some type of notch which prevents the m48 to m42 ring from screwing straight through and and hitting the actual filter?
I feel it should have some type of stopper to prevent that, and also so the threads on extensions can stop at a known point (to help with figuring out back focus).

Mine doesn't have any type of "wall" to stop the m48-m42 ring from simply screwing straight through the thread and dropping into the glass filter area.

It also means the drawer can easily rotate e.g. if there is a tight or heavy cable pulling the camera slightly off centre, the drawer could spin, affecting field rotation etc.

I hope that explains what I'm trying to ask?

[Finbar]

Hi Rob.
I have two of these drawers in different configurations for ready use as needed, and for simultaneous use on two scopes. Yes, it seems weird when trying to add that adapter as you described, and the solution is to screw in onto whatever 42mm piece is to be added. I can’t remember at the moment what my set up needs it for (away from home for the day), but recall screwing it on tightly to the other piece, then screwing it snugly into place in the drawer. It holds together without problem, but I also recall trying to separate them at some stage and having difficulty. That was when the perfect solution arose with a used but as new one coming up for sale here - jumped at it. Hence now the two permanent configurations so I needn’t reconfigure again.
I also found using a thin spacer ring useful to get the drawer oriented in the best position.
Hope this helps.
Barry

[Joshua Bunn]

Hi Rob,


Let us know how you go, I can machine you up something to solve these issues.


Cheers
Joshua

[evltoy]

Very easy! you screw the M48 to M42 ring to your male M42 adaptor, then screw the draw to the ring. The draw will stop and lock in place once it hits your M42 adaptor. This is just a common step down ring used in the EFW etc.




When you use the step down ring make sure the little notches are facing outwards from the adaptor its going to butt up against. If it locks up you can get a flat blade to help undo it.

[Joshua Bunn]

That makes it a lot easier if there are notches in the step down ring.

[Rob-Minchinbury]

Thanks guys, I'm not sure I've explained myself clearly.

Barry (Finbar) you said you've screwed your m48 to m42 onto your m42 piece and then screwed them into the drawer and they fit snugly.

I've uploaded a video to YouTube, is this how yours works?
About 40 seconds in is where my concern lies.

As you can see, the supplied m48/m42 ring screws right through to the filter area. I would expect a block to prevent that.

Without something for the m48/m42 adapter to stop against, there is a chance of breaking the glass filter or of the camera randomly rotating if a cable drag is strong enough.

In addition I can't guarantee how far in it's screwed, which can affect the overall length of the extenders and affect focus.

Is that how yours works? It feels like poor design or a manufacturing defect to me. Every other threaded connector I've ever seen has something to prevent the thread going straight through into a cavity.

https://youtu.be/sGSictVvzfg

[Finbar]

Hi again Rob.

Yes is easier to see what the problem is now. You do need another part that provides the stability, because whatever is attached onto the drawer needs a base wider the hole it is being screwed into.

I checked my two setups again to remember which needed what. I needed a 2" nose on my drawer, and since I already had a Bintel 2"-T2 one I threaded the given ring to it, then the nose could be used - I did that rather than track down an m48-2" nose.

These photos show my set up, but I'm not attaching extension rings as you are, but it may help see possibilities. I've not tried attaching photos here before, so we'll see how this goes.

Ring + nose.
297653

Ring starting to be added to the nose.
297654

Ring in place.
297655

Nose attached to the drawer and diagonal.
297656

You need something similar before whatever extensions you need, but I'm not sure what - it is easy to get muddled between the various possibilities, but hopefully the photos may help.

Barry

[edited - having worked out how to attach photos]

[Finbar]

Is this perhaps what you need?

https://www.testar.com.au/products/adapter-m48-male-m42-female-2-5mm

[Rob-Minchinbury]

Thanks Barry, now your setup makes sense about fitting snugly.
That's exactly the type of block I need, I just presumed ZWO would have built the blocking piece into the inside of the thread, not require a 3rd party adapter to go on the outside of the thread.

Barry, yes that seems to be exactly what I need if I can't find something from my other gear to do the job. Thanks for the link :)

And Joshua, thanks for your offer to custom build something. I might private message you next weekend ... I think I have another issue you could solve.