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Planning WO Z73 + ZWO setup and backfocus

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#1 ljoraanstad

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Posted 30 October 2024 - 01:31 PM

Would love to get some feedback on my working setup as I am planning in. I dont have the equipment yet but am planning to order everything in the coming days and weeks. The setup is attached here:
 

image (20).jpg

Does the attached diagram make sense from a functional standpoint? I am wondering about the 54mm backfocus. Unless I am missing something, it should be 55mm. Not sure If I am missing 1mm somewhere?

Any recommendations for the guide camera or imaging camera? I don't need top of the line equipment, just something that does great for its cost. I could go the mono route but not sure I want to spend that much more.
  • SCOPE - Williams Optics Z73
  • SCOPE CAMERA -  ZWO ASI533MC Pro USB3
  • FOCUSER - ZWO EAF
  • GUIDE SCOPE - ZWO OAG
  • GUIDE CAMERA - ZWO ASI120MM
  • CONTROLLER - ZWO ASIAIR Plus
  • FILTER WHEEL - ????
  • MOUNT - ZWO AM3

 

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  • image (20).jpg

Edited by ljoraanstad, 30 October 2024 - 01:36 PM.


#2 KTAZ

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Posted 30 October 2024 - 01:35 PM

Don't forget that the chip sits 6.5mm back from the front of the camera body. Also remember to balance space between the exit of the OAG and the camera. Your guide cam may not be able to focus if you are too far back; it will focus at the same distance from the prism as your primary.


Edited by KTAZ, 30 October 2024 - 01:38 PM.


#3 ljoraanstad

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Posted 30 October 2024 - 01:39 PM

Don't forget that the chip sits 6.5mm back from the front of the camera body.

Good call out! Definitely was missing that. That leaves me with needing a 11mm spacer somewhere in there...which I think the WO 73R reducer actually has integrated, right? To set to 11.4. Now this makes sense, I think



#4 ljoraanstad

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Posted 30 October 2024 - 01:43 PM

 Also remember to balance space between the exit of the OAG and the camera. Your guide cam may not be able to focus if you are too far back; it will focus at the same distance from the prism as your primary.

Hmm... so you're saying I need 55mm spacing between the OAG and the Guide camera too then? That seems like a dumb question, I am new to the OAG concept. 



#5 ljoraanstad

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Posted 30 October 2024 - 01:46 PM

Updated, attempt 2

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#6 ShiftSix

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Posted 30 October 2024 - 02:10 PM

 

Would love to get some feedback on my working setup as I am planning in. I dont have the equipment yet but am planning to order everything in the coming days and weeks. The setup is attached here:
 



Does the attached diagram make sense from a functional standpoint? I am wondering about the 54mm backfocus. Unless I am missing something, it should be 55mm. Not sure If I am missing 1mm somewhere?

Any recommendations for the guide camera or imaging camera? I don't need top of the line equipment, just something that does great for its cost. I could go the mono route but not sure I want to spend that much more.
  • SCOPE - Williams Optics Z73
  • SCOPE CAMERA -  ZWO ASI533MC Pro USB3
  • FOCUSER - ZWO EAF
  • GUIDE SCOPE - ZWO OAG
  • GUIDE CAMERA - ZWO ASI120MM
  • CONTROLLER - ZWO ASIAIR Plus
  • FILTER WHEEL - ????
  • MOUNT - ZWO AM3

 

Great setup.  Almost identical to what I built.  

So here was mine.  Currently selling it because I had a RedCat on back order and don't need both, but I was rocking the Flat73A and the single filter drawer from ZWO and all it took to reach backfocus was the16.5mm spacer.

I never had a chance to play with the OAG or the .8 reducer though so no experience there.

53262786968_9bc783c85f_b.jpg

 

I'm still a noob when it comes to astrophotography but if you have any questions about the gear I'm happy to try to help smile.gif


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#7 ljoraanstad

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Posted 30 October 2024 - 02:42 PM

 was rocking the Flat73A and the single filter drawer from ZWO and all it took to reach backfocus was the16.5mm spacer. I never had a chance to play with the OAG or the .8 reducer though so no experience there.

I think the reducer may change the backfocus, but even if not, as someone else pointed out the ZWO ASI camera may include a removable 11mm spacer that is optional so in my diagram that main imaging camera could technically be 17.5mm vs what I am showing as 6.5mm which would eliminate some more extension requirements. 

Did you feel that auto-guiding was necessary? With a small FL and diameter, I wonder if its needed. Did you try without it? I wonder if the ASIAir and AM3/5 combo will be great enough to eliminate the need for AG.



#8 ShiftSix

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Posted 30 October 2024 - 03:06 PM

I think the reducer may change the backfocus, but even if not, as someone else pointed out the ZWO ASI camera may include a removable 11mm spacer that is optional so in my diagram that main imaging camera could technically be 17.5mm vs what I am showing as 6.5mm which would eliminate some more extension requirements. 

Did you feel that auto-guiding was necessary? With a small FL and diameter, I wonder if its needed. Did you try without it? I wonder if the ASIAir and AM3/5 combo will be great enough to eliminate the need for AG.

 

Unfortunately I never tried without it.  Basically picked this setup up to learn all of the basics as I was coming from a purely visual setup prior. Workflows in the ASI Air, polar aligning, guiding, etc.  Ultimately I only really used this scope in the live stack mode without saving off FITS to post process, but it was a wonderful grab and go kit for those spur of the moment nights with a break in some clouds.  


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#9 ljoraanstad

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Posted 30 October 2024 - 03:34 PM

I am trying to message you about buying your scope but it says I have exceeded the limit :) Perhaps you can start the conversation? 



#10 bobsdobs

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Posted 30 October 2024 - 04:24 PM

I have run my z73 with both the flattener and reducer. The ZWO filter drawer or equivalent spacer and the 16.5 mm spacer gets you sorted with both. It's hard to measure back focus exactly with the adjustable flattener/reducer so it's best to get it ball park and then look at individual subs to spot back focus issues. I spent ages trying measure .X of a millimetre on the reducer scale but when I analysed it in Hocus Focus it was out by about 1mm.

#11 Oort Cloud

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Posted 31 October 2024 - 01:15 PM

For around the cost of that doublet & the required flattener, you could get the much better Askar 65PHQ. I own both; the Askar was purchased specifically to replace the doublet. Also, the Askar doesn't require specific spacing, just attach your camera, focus, shoot. The convenience of this cannot be overstated.

#12 ljoraanstad

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Posted 01 November 2024 - 09:56 AM

This is what I landed on. All parts have been ordered! I am excited to try it out. If someone thinks I am missing something here, please let me know!

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#13 bobsdobs

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Posted 01 November 2024 - 05:00 PM

Your imaging train is identical to mine. I have been very happy with it. I'm one year in and still learning lots every image, but here's some pics I have taken with an identical optical setup - https://www.astrobin...ers/davidmason/
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#14 bobsdobs

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Posted 01 November 2024 - 05:04 PM

One thing you might want to add is a ZWO filter drawer. It gets lame real quick having to screw filters onto the flattener. It is a direct replacement for one of the spacers so your spacing doesn't change. Also if you don't already have one, you will need a UV/IR cut filter for the 533 when shooting broadband. Much easier to swap filters in/out of a filter drawer when you switch between broadband/narrowband.

I use a cheap Baader UV/IR cut filter for broadband and mostly an Optolong L-Extreme for narrowband.

Edited by bobsdobs, 01 November 2024 - 05:09 PM.


#15 ShiftSix

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Posted 01 November 2024 - 05:07 PM

Your imaging train is identical to mine. I have been very happy with it. I'm one year in and still learning lots every image, but here's some pics I have taken with an identical optical setup - https://www.astrobin...ers/davidmason/


Fantastic images! Easy follow on Astrobin 🍻
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#16 ljoraanstad

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Posted 04 November 2024 - 04:51 PM

Your imaging train is identical to mine. I have been very happy with it. I'm one year in and still learning lots every image, but here's some pics I have taken with an identical optical setup - https://www.astrobin...ers/davidmason/

Great photos! Can you identify your backfocus setup? Is what I have described above correct? I ordered an M42 to M42 21mm adapter and that doesnt seem to fit what I expected. It doesn't screw into anything. What am I missing here?


Edited by ljoraanstad, 04 November 2024 - 04:54 PM.


#17 ShiftSix

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Posted 04 November 2024 - 04:58 PM

Great photos! Can you identify your backfocus setup? Is what I have described above correct? I ordered an M42 to M42 21mm adapter and that doesnt seem to fit what I expected. It doesn't screw into anything. What am I missing here?


Mine had the 16.5mm out of the Flat73a, then the ZWO filter drawer, then the ASI533.
I think the 21mm takes the same place as the filter drawer.


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