ZWO OAG connection problems

[WbRaDy]

Evening everyone..

I have received my new ZWO OAG today to connect with my 1600mm and filter wheel and at that end with spacers all seems good until i attach the OAG to my skywatcher 0.85 reducer on my ED80, at this point when the reducer is screwed onto the OAG body the thread from the reducer catches the prism stalk to a point where its not only impossible to use the focus it also will not fully attach for that same reason, its only a mm or two but thats enough to ruin the day, im sure i need some sort of spacer/washer  between the reducer and OAG but wouldn't this ruin the 55mm spacing needed for focus? also the OAG in the box is different to whats on the box and found on the net so not sure if its updated or wrong full stop but as it came from a ZWO dealer im assuming an upgrade?

Im just after some advice before i go through the process of returns ☹️

If you look at the image my OAG does not have the 4 screws to change the face plate from item 5 to item 6,in fact i do not have item 6 in the box hence possible update to the item.

Thanks all, very much appreciated.

Wayne

[cjdawson]

Can you upload a photo of the setup, and where things are catching?  In this case a picture will save a million words.

[RayD]

I would have thought you would need some additional spacing with this configuration anyway?  Assuming you are using the mini FW then we have:

FW  = 20 mm

OAG  = 16.5 mm

ASI1600MM  = 6.5 mm

Total  = 42.0 mm

If we allow 1 mm for filters, this means you would still need a spacer of 14 mm to make up your 56 mm required to the sensor for your FF (including the 1 mm for the filter). 

Obviously we don't know the connection methods you are using, but the adaptors should only affect things by a few mm at most I suspect, so adding 2 mm of delrin spacers shouldn't be a problem?  Perhaps a 10 mm spacer with 2 mm delrin each end to prevent binding.

If you got the OAG from FLO it might be worth dropping them a line as to why it is different from the image shown.

[souls33k3r]

Funny timing, saw this from ZWO this morning

https://astronomy-imaging-camera.com/faq/best-back-focus-length-solutions-55mm.html

Hope this helps

Hope this helps

[RayD]

20 minutes ago, souls33k3r said:

Funny timings, saw this from ZWO this morning

https://astronomy-imaging-camera.com/faq/best-back-focus-length-solutions-55mm.html

Hope this helps

Hope this helps

Good find that man, so additional spacing is needed 

[souls33k3r]

18 minutes ago, RayD said:

Good find that man, so additional spacing is needed 

Cheers mate, as long as it works for the OP

[WbRaDy]

Thanks for getting back all, much appreciated, the problem i have isnt the spacing for the camera to reducer, at the moment i have the 55mm needed, if i remove the 16.5 spacer and replace with the OAG that is the complete spacing needed or so im told, its when the whole setup connects to the reducer...

agreed cjdawson..sorry minds slipping

Current setup before OAG..

My problem is if you look in the stalk hole to the left is the thread from the reducer "overhanging" the stalk hole by around 2mm when the reducer and oag body is tightened up

This is how it looks when the prism stalk is fitted..the reducer is slightly undone so its off the stalk and the prism is free to move for focusing, as mentioned it looks like i could get away with some sort of washer in there to let me nip it up but thats not the way and two im sure that will just add to my 55mm needed unless i reduce somewhere else....im sick of spacers already and dont need to purchase more ?

Thanks again all

Wayne

[WbRaDy]

6 hours ago, RayD said:

so adding 2 mm of delrin spacers shouldn't be a problem?

My thoughts too Ray

[RayD]

I would say that the OAG needs to snug up against the FW, and the other spacer/adaptor that is in there needs to be made up as a spacer between the FF and OAG.

[WbRaDy]

So move that 10mm "I think" forward, hoping it has a smaller length of thread....sounding good..will get back to you?

[RayD]

Just now, wayne11 said:

So move that 10mm "I think" forward, hoping it has a smaller length of thread....sounding good..will get back to you?

That would be my thought, Wayne.  That looks like a particularly long thread on the FF, and it is better for the OAG to be closer to the camera for adjusting focus.

[WbRaDy]

Sound plan Ray but no go...the 10mm spacer is T2...whereas the reducer and OAG is M48...the 16.5 spacer is T2 to M48 extender..i hate spacers...but the worst part is the spacers do have less thread and would of worked i think..im going to try a nylon washer in there and give it a go with focus....i have a week to return if needs be...Thanks again for your help

[RayD]

33 minutes ago, wayne11 said:

Sound plan Ray but no go...the 10mm spacer is T2...whereas the reducer and OAG is M48...the 16.5 spacer is T2 to M48 extender..i hate spacers...but the worst part is the spacers do have less thread and would of worked i think..im going to try a nylon washer in there and give it a go with focus....i have a week to return if needs be...Thanks again for your help

Ah man that's a nuisance!  I wonder how others who have used this with the SW FF have done it then?  Very odd.  My Atik OAG and my SX ones all screw directly to the FW so it seems odd that the ZWO one has a 10mm spacer between.  I wonder how that affects getting both the main and OAG cameras in focus?

As you say, try a 2mm delrin and see if it works, you never know.

[WbRaDy]

Just for future reference a reply from ZWO regarding the connection to the Reducer may save someone a lot of head scratching.....?

The thread of reducer is too long, we provide 5mm, but the reducer need 7mm. 

In this case, I think you need two customized adapters. one is M48 female ring, about 3mm thinkness, like the 11mm ring on camera. screw it on reducer. So that the thread won't stucked by prism.

Second one is 9mm M42 extender, replace the 11mm ring and T2-T2 adapter, between OAG and EFW.

[Waldemar]

If you are handy with tools, you can mark what needs to get out of the way and file it away or use a Dremel tool.
not so much work... Better than Delrin, for you need the right distance.