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OAG L and 1.25 inch filter wheel

ZWO OAG-L ZWO ASI174MM Mini Equipment Guiding
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IrishAstro4484 avatar
IrishAstro4484 avatar
Has anyone else purchased the OAG L and realised that it won't actually connect to the old 1.25 inch ZWO electonic filter wheel? 

If so, any thoughts on work arounds would be welcome.

I mostly bought it because I had been using the 174mm mini as a guide camera but the ZWO OAG clips most of the field so a good chunk of the sensor is actually wasted.

The OAG L provided a large FOV so looks like a better guiding solution when paired with the 174mm mini for my Edge HD.

​​​​​​
Matthew Proulx avatar
Matthew Proulx avatar
It doesn't work unless you make some custom adapter. Alternatives are Askar OAG, Celestron OAG or even QHY L.

Edit: I just got a celestron OAG and its the way to go, should have done it a long time ago. It does take up a lot of backfocus (45mm)
IrishAstro4484 avatar
IrishAstro4484 avatar
Matthew Proulx:
It doesn't work unless you make some custom adapter. Alternatives are Askar OAG, Celestron OAG or even QHY L.

Edit: I just got a celestron OAG and its the way to go, should have done it a long time ago. It does take up a lot of backfocus (45mm)

*** I suspect I may end up getting a custom adapter made. I don't want to buy another OAG and I'd like the OAG L to work with my 1600MM and electronic filter wheel on my Edge HD. ***
Steve Spring avatar
Steve Spring avatar
I was faced with the same conundrum. I have a Hyperstar with Starizona filter slider, but I also want to use my C8 at F10 or F7. I shoot with OSC and so only need two filters so I dont want a 7 position EFW for $400. I want to be able to swap filters between scopes including another 180mm scope and so have a Starizona Slider for each.

Inititially I bought a second M48 tilt plate, second hand for £20. Two of the holes in the tilt plate line up with two of the four mounting holes in the OAG-L. This could then be fitted to an M48 male to M48 male adaptor which could then be screwed to my Starizona filter slider. If your Filter Wheel has M42 threads then find an M48M/M42M adaptor instead.

I bought an M2.5 tap and accompanying drill. Using the two spare holes for positioning, I drilled and tapped two new threads in the tilt plate which gave me four fixings. This is fine for an SCT because there is back space to play with but may put you beyond the usual 55mm back focus, say on a refractor. It also means the guide camera needs an extra 5mm spacing to obtain focus, more on that later.

Having gone that far I plucked up the courage and drilled and tapped four holes directly into the Starizona Filter Slider. The two are bolted together and can be seen in the picture below. These are modular by design so I was able to take the top plate off and if I got it wrong, a new top plate can be purchased seperately.

ZWO do sell an adaptor plate to connect to the OAG-L without a filter wheel. It allows you to fit a filter but I didn't like the look of it as a solution. You would need to completely disasemble it to change the filter if I am looking at it correctly.

https://astronomy-imaging-camera.com/product/zwo-m54-adapter-replacing-efw

I am surprised they do not offer other solutions, ideally an adaptor with zero back focus.

Be warned if you are thinking of using the ZWO adaptor and then fitting your filter wheel to that. The distance between your camera sensor and the prism will then be so great that probably wont obtain focus in the guide camera so consideration should be given to that distance. The helical focuser holding the gude camera cannot be removed so you cannot add spacing between it and the OAG housing. In my case, I needed to add 2or 3mm and so slid a 5mm parfocal ring (very cheap) over the camera body which you can make out in the picture above the focuser threads.

***Disclaimer*** please don't blame me if you break your equipment, just wanted to share my thought process having gone through it 




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IrishAstro4484 avatar
IrishAstro4484 avatar
Steve Spring:
I was faced with the same conundrum. I have a Hyperstar with Starizona filter slider, but I also want to use my C8 at F10 or F7. I shoot with OSC and so only need two filters so I dont want a 7 position EFW for $400. I want to be able to swap filters between scopes including another 180mm scope and so have a Starizona Slider for each.

Inititially I bought a second M48 tilt plate, second hand for £20. Two of the holes in the tilt plate line up with two of the four mounting holes in the OAG-L. This could then be fitted to an M48 male to M48 male adaptor which could then be screwed to my Starizona filter slider. If your Filter Wheel has M42 threads then find an M48M/M42M adaptor instead.

I bought an M2.5 tap and accompanying drill. Using the two spare holes for positioning, I drilled and tapped two new threads in the tilt plate which gave me four fixings. This is fine for an SCT because there is back space to play with but may put you beyond the usual 55mm back focus, say on a refractor. It also means the guide camera needs an extra 5mm spacing to obtain focus, more on that later.

Having gone that far I plucked up the courage and drilled and tapped four holes directly into the Starizona Filter Slider. The two are bolted together and can be seen in the picture below. These are modular by design so I was able to take the top plate off and if I got it wrong, a new top plate can be purchased seperately.

ZWO do sell an adaptor plate to connect to the OAG-L without a filter wheel. It allows you to fit a filter but I didn't like the look of it as a solution. You would need to completely disasemble it to change the filter if I am looking at it correctly.

https://astronomy-imaging-camera.com/product/zwo-m54-adapter-replacing-efw

I am surprised they do not offer other solutions, ideally an adaptor with zero back focus.

Be warned if you are thinking of using the ZWO adaptor and then fitting your filter wheel to that. The distance between your camera sensor and the prism will then be so great that probably wont obtain focus in the guide camera so consideration should be given to that distance. The helical focuser holding the gude camera cannot be removed so you cannot add spacing between it and the OAG housing. In my case, I needed to add 2or 3mm and so slid a 5mm parfocal ring (very cheap) over the camera body which you can make out in the picture above the focuser threads.

***Disclaimer*** please don't blame me if you break your equipment, just wanted to share my thought process having gone through it 





*** Thanks Steve! Yes I'm aware ZWO has an adaptor but you need to screw in the filter if I understand correctly which wouldn't be very practical if I want to flip between RGB and narrowband in the same imaging session. I have the manual filter slot which allows you to quickly exchange filters if needs be but the OAG L doesn't work with it.

I Really have no idea why ZWO changed the design of the OAG connections for the OAG L. I can only assume they were hoping people would bin their old EFW in favour of the new one. The only difference really being that the 4 holes are drilled into the new EFW face plate as far as I can recall. 

I Don't particularly trust myself to be drilling holes into the filter wheel faceplate so looks like I'll need a custom adapter. I'm certainly not buying the new EFW just so I can screw in the OAG L.

Very disappointed with ZWO over this!


***
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Monty Chandler avatar
Monty Chandler avatar
I bought an OAG-L and afterwards found out it cannot be connected to the ZWO Filter drawer.  Very disappointing.  Had to put the Celestron on my RC8 at the cost of my pegasus rotator. Rotator, oag & filter drawer are just a bit too long and my backfocus is 270mm.  Requiring it be bolted to a filter wheel is silly.
Steve Spring avatar
Steve Spring avatar
It is  a shame they haven't opened it up to a wider market, I think a bolted connection is considered a better connectin tha a treaded one these days. Also, they need to fit these things into the limited 55mm back focus which is also a driver.

If you can get a custom adaptor made up then that's great. I didn't know where to or ho much it would cost. A second tilt adaptor with m ale to male adaptor cost me around £50

Good luck with it. Worth the effort though I think. The OAG-L coupled with the ASI174mm gives a great field of view and multi satr guiding at 1410mm on an OAG really helps the guiding
IrishAstro4484 avatar
IrishAstro4484 avatar
Steve Spring:
It is  a shame they haven't opened it up to a wider market, I think a bolted connection is considered a better connectin tha a treaded one these days. Also, they need to fit these things into the limited 55mm back focus which is also a driver.

If you can get a custom adaptor made up then that's great. I didn't know where to or ho much it would cost. A second tilt adaptor with m ale to male adaptor cost me around £50

Good luck with it. Worth the effort though I think. The OAG-L coupled with the ASI174mm gives a great field of view and multi satr guiding at 1410mm on an OAG really helps the guiding

*** I found a company in the US that makes custom adapters for imaging trains. You can specify when equipment is at the OTA and camera side of the adaptor and how thick you want the adaptor to be. 

Great in theory but I'm not paying $200 dollars for a custom part. 

I could probably mock up a drawing myself and get a local company to manufacture it for a fraction of the cost. Still annoying as hell I have to do this. 

***
Palmito avatar
Palmito avatar
Has anyone else purchased the OAG L and realised that it won't actually connect to the old 1.25 inch ZWO electonic filter wheel? 

If so, any thoughts on work arounds would be welcome.

I mostly bought it because I had been using the 174mm mini as a guide camera but the ZWO OAG clips most of the field so a good chunk of the sensor is actually wasted.

The OAG L provided a large FOV so looks like a better guiding solution when paired with the 174mm mini for my Edge HD.

​​​​​​

I think the new models of the 1.25" include the proper holes tapped.

So, perhaps, you may order the new EFW plate from ZWO.
Or else you may get your plate tapped by some machinist in your area, easy job for him.
IrishAstro4484 avatar
IrishAstro4484 avatar
Has anyone else purchased the OAG L and realised that it won't actually connect to the old 1.25 inch ZWO electonic filter wheel? 

If so, any thoughts on work arounds would be welcome.

I mostly bought it because I had been using the 174mm mini as a guide camera but the ZWO OAG clips most of the field so a good chunk of the sensor is actually wasted.

The OAG L provided a large FOV so looks like a better guiding solution when paired with the 174mm mini for my Edge HD.

​​​​​​

I think the new models of the 1.25" include the proper holes tapped.

So, perhaps, you may order the new EFW plate from ZWO.
Or else you may get your plate tapped by some machinist in your area, easy job for him.

*** I doubt they sell just the face plate. Probably quicker, easier and cheaper to get a local machinist to drill and tap the faceplate or to make up a custom adapter. Excellent suggestion, thank you ***
Gary Brown avatar
Gary Brown avatar
I adapted my OAG-L to my 1.25" filter wheel by adding a second $29 ZWO 48mm tilt adapter, as Steve stated above. I drilled and tapped holes in it to attach to the OAG-L. I then attached it to the filter wheel like any other 48mm device. With the ASI1600MM Pro the total back focus is 55.8mm. 

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Miguel avatar
Miguel avatar
Gary Brown:
I adapted my OAG-L to my 1.25" filter wheel by adding a second $29 ZWO 48mm tilt adapter, as Steve stated above. I drilled and tapped holes in it to attach to the OAG-L. I then attached it to the filter wheel like any other 48mm device. With the ASI1600MM Pro the total back focus is 55.8mm. 


*** I wonder how it all worked out. I have an OAG L coming this week and I have an M42 tilt plate to do the same with my EFW Mini. If you do not mind me asking: The half of the tilt plate with the most holes has a series of threaded holes equally spaced 30 degrees apart on a 62mm bolt circle. That is the same as what the drawing for the OAG shows. So my questions: Does the pattern on the OAG not match 4 of the holes on a 62mm circle on the tilter plate?  and do you have a 42 or 48 tilt plate? Thank you***
shenmesaodongxia avatar
shenmesaodongxia avatar
Has anyone else purchased the OAG L and realised that it won't actually connect to the old 1.25 inch ZWO electonic filter wheel? 

If so, any thoughts on work arounds would be welcome.

I mostly bought it because I had been using the 174mm mini as a guide camera but the ZWO OAG clips most of the field so a good chunk of the sensor is actually wasted.

The OAG L provided a large FOV so looks like a better guiding solution when paired with the 174mm mini for my Edge HD.

​​​​​​

In fact, the 8mm*8mm of oag is enough to find the guiding star
Gary Brown avatar
Gary Brown avatar
I used a 48mm tilt plate.  The OAG-L is designed to mount to the 2" filter wheel using 4 screws 90 degrees apart. I drilled and tapped matching holes in the 48mm tilt plate. The holes fall just outside of the foam gasket on the plate.  I then attached the tilt plate to the 1.25" filter wheel using the T2 adapter provided. You have to make sure that the tilt plate rotation allows you to mount the OAG-L with the focuser assembly clearing the filter wheel. After the tilt plate is attached, I screwed the OAG into the four holes I added. Once its attached you reinstall the tilt plate provided with the OAG-L and you're ready to mount it to your OTA. I hope this makes sense.
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Miguel avatar
Miguel avatar
Gary Brown:
I used a 48mm tilt plate.  The OAG-L is designed to mount to the 2" filter wheel using 4 screws 90 degrees apart. I drilled and tapped matching holes in the 48mm tilt plate. The holes fall just outside of the foam gasket on the plate.  I then attached the tilt plate to the 1.25" filter wheel using the T2 adapter provided. You have to make sure that the tilt plate rotation allows you to mount the OAG-L with the focuser assembly clearing the filter wheel. After the tilt plate is attached, I screwed the OAG into the four holes I added. Once its attached you reinstall the tilt plate provided with the OAG-L and you're ready to mount it to your OTA. I hope this makes sense.

*** Gary, thank you for the response. Yes, I realized after I posted that my T2 t​ilter has the 62mm hole pattern that is different hole patten than the M48/2". The holes are spaced all around at 30* apart which using one hole every 4 gives me same 90* you mention. So hopefully it will fit  ***
Miguel avatar
Miguel avatar
Hello,

For those looking for solutions and like me with no means to drill and tap accurately ​​​​​​I wanted to confirm that if you have a ZWO EFW Mini ( 5 positions 1.25/31mm filters) that has a T2/M42 x . 75 threaded ports and wanted to install the ZWO OAGL without having to drill and tap new holes the way to go is buying what ZWO lists as New T2 Tilter. That has the hole pattern that would fit the 4 holes on he camera side of the OAGL.

The 55mm +:filter glass thickness correction spacing can also be accommodated assuming you are using a camera that has 6.5mm of sensor backfocus.

This is all reversible for all the parts to go back to factory state. No modification required. 

Hope this help
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Ryan Heuer avatar
Ryan Heuer avatar
Miguel:
Hello,

For those looking for solutions and like me with no means to drill and tap accurately ​​​​​​I wanted to confirm that if you have a ZWO EFW Mini ( 5 positions 1.25/31mm filters) that has a T2/M42 x . 75 threaded ports and wanted to install the ZWO OAGL without having to drill and tap new holes the way to go is buying what ZWO lists as New T2 Tilter. That has the hole pattern that would fit the 4 holes on he camera side of the OAGL.

The 55mm +:filter glass thickness correction spacing can also be accommodated assuming you are using a camera that has 6.5mm of sensor backfocus.

This is all reversible for all the parts to go back to factory state. No modification required. 

Hope this help

I can confirm this works!

I have an ASI 533 with 1.25" 8 position EFW.  I Bought the OAG-L and the New T2 Tilter.  I first screwed the Tilter into the EFW, then I screwed the OAG-L onto the tilter without a problem. You cannot screw the OAG and T2 Tilter onto the EFW at the same time as the OAG will collide with the EFW- you gotta do one at a time. No drilling or any other modifications needed.

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AstroLancer01 avatar
AstroLancer01 avatar
Ryan Heuer:
Miguel:
Hello,

For those looking for solutions and like me with no means to drill and tap accurately ​​​​​​I wanted to confirm that if you have a ZWO EFW Mini ( 5 positions 1.25/31mm filters) that has a T2/M42 x . 75 threaded ports and wanted to install the ZWO OAGL without having to drill and tap new holes the way to go is buying what ZWO lists as New T2 Tilter. That has the hole pattern that would fit the 4 holes on he camera side of the OAGL.

The 55mm +:filter glass thickness correction spacing can also be accommodated assuming you are using a camera that has 6.5mm of sensor backfocus.

This is all reversible for all the parts to go back to factory state. No modification required. 

Hope this help

I can confirm this works!

I have an ASI 533 with 1.25" 8 position EFW.  I Bought the OAG-L and the New T2 Tilter.  I first screwed the Tilter into the EFW, then I screwed the OAG-L onto the tilter without a problem. You cannot screw the OAG and T2 Tilter onto the EFW at the same time as the OAG will collide with the EFW- you gotta do one at a time. No drilling or any other modifications needed.


I’m in the same situation, I have OAG L and want to get a filter wheel, does it work with the mini and are you able to explain or provide more pictures please. I’m having a hard time comprehending it thanks 😁