Brilliant! Your video should be provided with every scope & FF/FR sold by WO. I purchased a WO GT81 last October, along with the WO FF/FR 6Alll (adjustable). Sure there were online diagrams, but like you stated, they were somewhat confusing, especially when some of the main resellers (no names will be provided) had documentation on their websites about setting all of this up; and it was incorrect! I contacted WO directly. They responded very quickly with online links and thorough explanation of how to do it. Just as you described. This hobby is daunting for the beginner and it amazes me how much gear is sold without really good documentation on how to set it up and use it properly. If it wasn't for UA-cam and folks like you, we would be sitting around with piles of gear just scratching our heads. Even the acquisition software, bought or free, can be a struggle. I applaud all of the people on UA-cam who have taken the time to share their experiences, their solutions to technical challenges, their images and many of the other little tidbits of information that allow each and every one of us to move ever so slowly forward with this amazing hobby. Cheers to you for being part of the solution!
Thanks my friend! I remember struggling with this when I first got my scope. I get great joy sharing what I've learned so the next person who is courageous enough to step into this hobby is less frustrated than I was. I had alot of support and help in the beginning and with each video I feel like i am paying back the community for its kindness to me which Also continues to this day. Thanks so much for commenting and hope we all get some imaging nights here soon!
@@3_Gold_Coins I like to use the flange side to put into the adjustment point since that part actually changes your backfocus. The ring is to just "lock" the flange side in place
Thank you! Another great video that answered my beginner question. “What should the backfocus be with Z73 and field flattener with ASI 533?” And you made it quite clear. Keeping camera with 55mm backfocus (allowing for filter drawer and OAG instead of the respective spacers) and setting the WO flattener to the recommended distance made it more straight forward than any of the diagrams. You helped me set up the ZWO EAF and OAG on the Z73 too. Now just need a clear night to get the guiding camera focused and away I go!
Thank you that clarified everything. This has always been one of the most asked questions on forums and everyone seemed to interpret it differently. Now I totally understand!🍷
Thank you very much for this video. I'm new in this field, and I have the z73 with the flattener plus the filter. I live in Miami Florida, I'm looking to see which Zwo Camera for deep space would work for me here with the light pollution. Thank you
Confused about your remarks at around 4:55 about the extra 0.2mm that makes the adjuster set-point 11.4 rather than 11.2mm as you'd guess by subtracting 66.2 - 55.0 for the Z73. If you put a glass filter in the optical path, say 1.0mm thick, its optical thickness would be about 1.5mm so you'd want to shrink the path by the extra 0.5mm from 66.2 to 65.7mm. If the filter were 2mm thick, then its optical thickness would be 3mm and you'd shrink the recommended distance from 66.2 to 61.2mm. But you are saying that putting a filter into the path would _increase_ the extra path by 0.2mm and therefore the adjuster setting from 11.2 to 11.4mm. Please explain. Thank you. BTW, otherwise, this video is brilliant and changes the WO WTF diagram into something understandable!
Hey I'm glad this helped out in someway and yes this diagram is crazy in so many ways lol. My remarks are speculative on my part. When you add a piece of glass to your imaging train that adds to your backfocus by a given amount based on how thick that piece of glass is. I had guessed that WO took that into account with the 11.4 mm adjustment suggestion for the flattner. Filter thickness ÷ 3 = additional backfocus.
@@astronotna Thanks so much for your reply. As I'd said, your video was VERY helpful. One quick think about filters in the optical path. Glass has a refractive index, n, of about 1.5. That means that every mm of glass is equivalent to 1.5mm of air. A 9.5mm optical path that already includes 1mm of glass has an 'optical path length' of 10.0mm -- 8.5mm of air plus 1.0mm of glass x n = 1.5mm. A 2mm thick glass filter adds 2 x 1.5 = 3mm of optical path. So, my 2mm thick light pollution filter effectively adds an extra 1mm to the optical path, which makes it necessary for me to shorten the path by 1mm to compensate for the extra mm due to the glass. All this is because light goes slower in glass than in air, by a factor of about 1.5. I hope this helps, although it does not explain the 0.2mm in WO's recommendation for the Z73 set-up. If you ever figure out that 0.2mm discrepancy, please let us know. Your videos are really great.
Thanks for the add here! And great point. I'm sure people will find this information helpful as well. I emailed WO about this awhile back but were unresponsive, maybe at some point! Again, thanks so much for watching this one!
I also just received my z61 and flattener. I have no idea what I'm doing. Lol. I was able to image Andromeda but it's fuzzy and out of focus. At least I was able to find it and take a crappy pic of it. Next time I get out I'll try again now that my backfocus is set. Thanks. I subbed after I seen this. Thanks a bunch!
Is field flattener really required ( mandatory) for Z73 with Apsc sensor dslr? I'll be able to produce good images only right? Or i will get it down the line...maybe later...
It's worth it to get it at the same time. Not only will it correct for elongated stars at the edge of your photo but allows you mounting for your dslr and mounting for filters. It's possible to shoot without it but attaching the camera might be problematic. I suppose you could use a 1.25 to camera adapter but you might get some vinegetting there with a sensor that size. Of course everyone starts somewhere and building it little by little works too!
Thanks a lot. Just received the Z73 yesterday, and it was scary enough to unscrew these tiny grub-screws to install the 73A. I feel safer about what has to be done next, thanks to you. To check the focus/backfocus, can it be done at daylight focusing on distant mountains? I did that with my guidescope, after a big fail the 2nd night out - AsiAIR could not platesolve, guidescope with ASI120 was only showing an uniform gray image as I did not realize I had to extend the guidescope so much (1st experience with backfocus 😀).
Hello there glad this helped out! Focus is so tricky while you can roughly focus during the day to make sure things don't look fuzzy or blobby it's actually a good idea to do so, it won't be until you focus on stars will you know you are in good fiocus in space. You'll find the focus points a bit different there. I used my z73 a few weeks ago solid choice!! Have fun out there!
That's a great question. I don't own a 678 but since WO assumes a backfocus of 55mm to accomidate a astrocam I would assume you would be correct. I've never owned one so I can't say for sure.
Hi, thank you for the video. I have a question. My Sony adapter for the M48 is 37mm long (I haven't find nothing else). Is it maybe too long to compensate the right distance from the flattner to the sensor? Thank you
I don't have a Sony cam but if I am not mistaken the 37mm adapter would be what you need to achieve the proper back focus for Sony with the flattener Installed. On the flattener I would start with william optics suggestions and adjust it from there to get it right. I'm sure you should be pretty close if not right on.
I'm thinking about doing lunar and Planetary imaging with my Z61. I have the field flattener too. Can I / should I use a 2x Barlow ? new to this and thanks for your easy to understand videos!
Hi Angel! I haven't yet tried planetary imaging yet. Lunar has been great with these refractors but I've never tried a barlow so I'm afraid I can't give you sound advice. I'm glad some of these videos helped in someway. Good luck in your astro journey!
Hi William. Thanks for the really helpful backfocus video. I’m using the WO Z73 with the 73A field flattened. I set the backfocus to 11.4 as you suggested and the images look great. However, I have now added (screwed in) a 2” light pollution filter to the back of the 73A flattened (no filter drawer). Should I change the adjustment on the backfocus or leave it at 11.4? Thanks.
Hello and thanks for the video! It answered a lot of questions i had. But im still confused on one topic. I have the 61 and using it with a Sony a-mount dslr. The flange focal distance to my sensor is 44,5mm + the t-ring is 10mm + my filter is 0,7mm (2mm thikness/3) = 56,2mm. But what number do i take to substract this from? 1. A from the Flattener diagramm: 67,7 2. B from the Flattener diagramm: 69,2 3. Or the Backfocus-Number from the Z61 Manual: 67,9
Your welcome glad this helped in some way. Just a quick look at your measurements you should be within the zone for widefield and I would try it to see what the stars in the corners are like but the easiest frame of reference would be " A "
This was very helpful, thank you! I still have one question though. Would adding in a camera rotator in between the flattener and the telescope change anything? You mentioned how backfocus is measured from the last element of the flattener to the camera sensor, so it doesnt seem like the rotator would change anything but I want to make sure. My imaging train is WO Z73 --> WO Camera Rotator --> WO FLAT73A --> WO T-ring for Canon EOS --> Canon EF to EOS R Mount Adapter --> Canon EOS R I still adjust the ring on the flattener to 11.4 even though I also have the camera rotator? Thanks in advance
That's how I have my Z73 setup! No changes required. Just install your rotator and enjoy! I have a video on the rotator If your curious what mine looks likeua-cam.com/video/9iSk6CoYgfQ/v-deo.html
Do you need the reducer for these scopes to achieve focus if I did not want to buy it right away? I think you can. On the Skywatcher 72 - you cannot without the reducer.
It doesn't take long for refractors. In cold weather it should be at proper temp by the time your rig is set up and polar aligned and dew heated. Within 30 minutes I suppose if I were to put a time on it. I haven't seen a difference between imaging right away vs waiting on a refractor. They are pretty low maintence. Just set up and enjoy
@@astronotna Thank you very much for your answer. Yesterday I received my first refractor, I come from a Newton family and I couldn't find an answer on Google or William Optics. Your videos are very good, thank you for sharing your experience! Greetings from Argentina 😊.
Hi, appreciate the video. I just purchased a Z73 scope and adjustable flattener/reducer. I'm assuming your setup is just flattener without focal reducing?? Reason I ask, is my flattener suggests an adjustment of 1.8mm for DSLR/Mirrorless, not 11.4mm. Thanks!
Getting ready to pull the trigger on the Z73, moving away from the SCT scopes for awhile, and WO's explanations completely confused me. Does the backfocus setup change with the .8 reducer/flattener or am I at still at 11.4 (using a 294MC filter drawer in lieu of one of the spacers). Also saw you have the EAF on the 73. Hard to install?
Hey William! Thanks for watching this vid and visiting my channel! With the reducer your back focus requirements should be the same (11.4mm swaping out the 21mm spacer if you use the ZWO drawer and the EAF was super easy to install. Just have to remove the knob on the thermometer side. I've been running my eaf for over a year now and I still love it. The Z73 is an awesome buy at the price just have to figure what color to get!! Hope you love yours like I've loved mine!!
Yes. So the ring on one side should fit your camera and the other side is a m48 thread to screw onto your flattner. I am assuming you will be using a DSLR /Mirrorless cam here.
@@astronotna Thanks, just got the right ring. But I can't reach focus with this back spacing, focuser is all the way in, just gets worse outwards. No adjustment to the flattener and I can reach focus. You know what the problem could be or am I missing something here? I have a Nikon DSLR
@Adolphus if you are using the z73 with Flat73 field flattner (NOT the reducer flattner) you should just be able to set the the flattner to 11.4mm and the focuser reaches focus with the Nikon DSLR around 26mm. All of my Nikon DSLR/Mirrorless cameras reach focus with that set up which includes my oldschool D70 all the way up to my Nikon Z6II. You might have something going on there and double check which components you have attached to your imaging train.
![Telescope Back Focus: The Ultimate Guide [TAIC Short]](/img/n.gif)
Brilliant! Your video should be provided with every scope & FF/FR sold by WO. I purchased a WO GT81 last October, along with the WO FF/FR 6Alll (adjustable). Sure there were online diagrams, but like you stated, they were somewhat confusing, especially when some of the main resellers (no names will be provided) had documentation on their websites about setting all of this up; and it was incorrect! I contacted WO directly. They responded very quickly with online links and thorough explanation of how to do it. Just as you described. This hobby is daunting for the beginner and it amazes me how much gear is sold without really good documentation on how to set it up and use it properly. If it wasn't for UA-cam and folks like you, we would be sitting around with piles of gear just scratching our heads. Even the acquisition software, bought or free, can be a struggle. I applaud all of the people on UA-cam who have taken the time to share their experiences, their solutions to technical challenges, their images and many of the other little tidbits of information that allow each and every one of us to move ever so slowly forward with this amazing hobby. Cheers to you for being part of the solution!
Thanks my friend! I remember struggling with this when I first got my scope. I get great joy sharing what I've learned so the next person who is courageous enough to step into this hobby is less frustrated than I was. I had alot of support and help in the beginning and with each video I feel like i am paying back the community for its kindness to me which Also continues to this day.
Thanks so much for commenting and hope we all get some imaging nights here soon!
I still am not sure which side of the adjustment ring to set my mark on. All I know is that it is at 7.1 for gt81.
@@3_Gold_Coins I like to use the flange side to put into the adjustment point since that part actually changes your backfocus. The ring is to just "lock" the flange side in place
This was really helpful. Clear, concise and to the point. Why can't manufacturers make to this straightforward? Thank you.
Hey thanks! Glad this helped. I'm not really sure either lol. I remember having the darn hard time understanding it myself when I got mine!
Great video!!! Both videos on the Zenths helped clear up so much. Thank you
Oh man! You welcome so glad this helped out!!
thanks a lot, I own also a Z61, the video helps a lot, wish you clear sky
Glad it helped
Keep up the good work, man. Your videos are super helpful. I can see this channel growing pretty quickly if you keep uploading.
Thanks Ethan! I'll try my best to not disappoint! Thanks for checking out the channel! Glad I could be helpful to you!!
I totally agree
Thank you! Another great video that answered my beginner question. “What should the backfocus be with Z73 and field flattener with ASI 533?” And you made it quite clear. Keeping camera with 55mm backfocus (allowing for filter drawer and OAG instead of the respective spacers) and setting the WO flattener to the recommended distance made it more straight forward than any of the diagrams. You helped me set up the ZWO EAF and OAG on the Z73 too. Now just need a clear night to get the guiding camera focused and away I go!
Sweet !!! Dude I am so happy for you! Glad these videos helped you out! Wishing you clear skies soon!
Thank you that clarified everything. This has always been one of the most asked questions on forums and everyone seemed to interpret it differently. Now I totally understand!🍷
It has been confusing hasn't it! Glad this helped out
Amazing!! Best video on setting up backfocus. Took me many nights to figure out mine with Z61+Nikon. WO should use this as official video guide.. 😀
It is a confusing subject isn't it? Lol. Glad you thought so and thanks for watching this one.
Thank you so much for this video which really solved the hassles I have been having trying to solve this with my Z61.
Glad this helped you out! 🙏
Thank you very much for this video. I'm new in this field, and I have the z73 with the flattener plus the filter. I live in Miami Florida, I'm looking to see which Zwo Camera for deep space would work for me here with the light pollution. Thank you
Glad this helped!!
thank you - I'm going to agree with people in the comments saying WO needs to just point people to your video.
Thanks Danette! So glad this helped you out! Enjoy and clear skies!!
Excellent Job! You have a new subscriber.
Thanks Ron! And I am glad this helped in some way!
Exactly what I needed, thanks!
Awesome glad this helped out!!
Well presented video and very informative. Thank you
Glad this helped out!!
What a legend! Great video!
Confused about your remarks at around 4:55 about the extra 0.2mm that makes the adjuster set-point 11.4 rather than 11.2mm as you'd guess by subtracting 66.2 - 55.0 for the Z73. If you put a glass filter in the optical path, say 1.0mm thick, its optical thickness would be about 1.5mm so you'd want to shrink the path by the extra 0.5mm from 66.2 to 65.7mm. If the filter were 2mm thick, then its optical thickness would be 3mm and you'd shrink the recommended distance from 66.2 to 61.2mm. But you are saying that putting a filter into the path would _increase_ the extra path by 0.2mm and therefore the adjuster setting from 11.2 to 11.4mm. Please explain. Thank you. BTW, otherwise, this video is brilliant and changes the WO WTF diagram into something understandable!
Hey I'm glad this helped out in someway and yes this diagram is crazy in so many ways lol. My remarks are speculative on my part. When you add a piece of glass to your imaging train that adds to your backfocus by a given amount based on how thick that piece of glass is. I had guessed that WO took that into account with the 11.4 mm adjustment suggestion for the flattner. Filter thickness ÷ 3 = additional backfocus.
@@astronotna Thanks so much for your reply. As I'd said, your video was VERY helpful. One quick think about filters in the optical path. Glass has a refractive index, n, of about 1.5. That means that every mm of glass is equivalent to 1.5mm of air. A 9.5mm optical path that already includes 1mm of glass has an 'optical path length' of 10.0mm -- 8.5mm of air plus 1.0mm of glass x n = 1.5mm. A 2mm thick glass filter adds 2 x 1.5 = 3mm of optical path. So, my 2mm thick light pollution filter effectively adds an extra 1mm to the optical path, which makes it necessary for me to shorten the path by 1mm to compensate for the extra mm due to the glass. All this is because light goes slower in glass than in air, by a factor of about 1.5. I hope this helps, although it does not explain the 0.2mm in WO's recommendation for the Z73 set-up. If you ever figure out that 0.2mm discrepancy, please let us know. Your videos are really great.
Thanks for the add here! And great point. I'm sure people will find this information helpful as well. I emailed WO about this awhile back but were unresponsive, maybe at some point! Again, thanks so much for watching this one!
You're a life saver.
😇!!! Glad this helped!
that was very informative! i just recently got my Z61 lens and the field flattener and this video is exactly waht was i looking for, thank you 😊
Nice!! Glad this helped you out!! Thanks for checking out my channel!!
I also just received my z61 and flattener. I have no idea what I'm doing. Lol. I was able to image Andromeda but it's fuzzy and out of focus. At least I was able to find it and take a crappy pic of it. Next time I get out I'll try again now that my backfocus is set. Thanks. I subbed after I seen this. Thanks a bunch!
@@1dragonracing Glad this helped in someway! Its so fun figuring all these things out. Wishing you clear skies and awesome pics!
thanks for your vids!! that help me a lot! one question: is this 61A flattener a reducer too? I tried to find that info, but I can´t find it. Thanks
Your welcome! The fla61 is just a field flattener they do make a flattener reducer though as well!
Is field flattener really required ( mandatory) for Z73 with Apsc sensor dslr? I'll be able to produce good images only right?
Or i will get it down the line...maybe later...
It's worth it to get it at the same time. Not only will it correct for elongated stars at the edge of your photo but allows you mounting for your dslr and mounting for filters. It's possible to shoot without it but attaching the camera might be problematic. I suppose you could use a 1.25 to camera adapter but you might get some vinegetting there with a sensor that size. Of course everyone starts somewhere and building it little by little works too!
Thanks a lot. Just received the Z73 yesterday, and it was scary enough to unscrew these tiny grub-screws to install the 73A. I feel safer about what has to be done next, thanks to you.
To check the focus/backfocus, can it be done at daylight focusing on distant mountains? I did that with my guidescope, after a big fail the 2nd night out - AsiAIR could not platesolve, guidescope with ASI120 was only showing an uniform gray image as I did not realize I had to extend the guidescope so much (1st experience with backfocus 😀).
Hello there glad this helped out! Focus is so tricky while you can roughly focus during the day to make sure things don't look fuzzy or blobby it's actually a good idea to do so, it won't be until you focus on stars will you know you are in good fiocus in space. You'll find the focus points a bit different there. I used my z73 a few weeks ago solid choice!! Have fun out there!
@@astronotna If I am replacing the ASI533 (backfocus 11+6.5 = 17.5) with the ASI678 (backfocus 12.5), I will need to buy a 5mm spacer, correct?
That's a great question. I don't own a 678 but since WO assumes a backfocus of 55mm to accomidate a astrocam I would assume you would be correct. I've never owned one so I can't say for sure.
Great video!
Thanks and thanks for watching this one!
Hi, thank you for the video. I have a question. My Sony adapter for the M48 is 37mm long (I haven't find nothing else). Is it maybe too long to compensate the right distance from the flattner to the sensor? Thank you
I don't have a Sony cam but if I am not mistaken the 37mm adapter would be what you need to achieve the proper back focus for Sony with the flattener Installed. On the flattener I would start with william optics suggestions and adjust it from there to get it right. I'm sure you should be pretty close if not right on.
I have a flat a and zenithstar 61mm telescope, a 2 inch optolong filter. What dimensionyshould I set? Thanks
You would divide the filter thickness by 3 then add that to your stock backfocus
Perfect!!!! Thank you
You're welcome glad this helped!
I'm thinking about doing lunar and Planetary imaging with my Z61. I have the field flattener too. Can I / should I use a 2x Barlow ? new to this and thanks for your easy to understand videos!
Hi Angel! I haven't yet tried planetary imaging yet. Lunar has been great with these refractors but I've never tried a barlow so I'm afraid I can't give you sound advice. I'm glad some of these videos helped in someway. Good luck in your astro journey!
Yes you can use it, Just put the flattener behind the barlow.
Hi William. Thanks for the really helpful backfocus video. I’m using the WO Z73 with the 73A field flattened. I set the backfocus to 11.4 as you suggested and the images look great. However, I have now added (screwed in) a 2” light pollution filter to the back of the 73A flattened (no filter drawer). Should I change the adjustment on the backfocus or leave it at 11.4? Thanks.
Yes all you need to do is get the thickness of the filter glass and divide it by 3. T/3 = additional backfocus to add to your set up.
Hello and thanks for the video! It answered a lot of questions i had.
But im still confused on one topic.
I have the 61 and using it with a Sony a-mount dslr. The flange focal distance to my sensor is 44,5mm + the t-ring is 10mm + my filter is 0,7mm (2mm thikness/3) = 56,2mm.
But what number do i take to substract this from?
1. A from the Flattener diagramm: 67,7
2. B from the Flattener diagramm: 69,2
3. Or the Backfocus-Number from the Z61 Manual: 67,9
Your welcome glad this helped in some way. Just a quick look at your measurements you should be within the zone for widefield and I would try it to see what the stars in the corners are like but the easiest frame of reference would be " A "
@@astronotna Thanks! I will try it in the next clear night.
This was very helpful, thank you! I still have one question though. Would adding in a camera rotator in between the flattener and the telescope change anything? You mentioned how backfocus is measured from the last element of the flattener to the camera sensor, so it doesnt seem like the rotator would change anything but I want to make sure.
My imaging train is WO Z73 --> WO Camera Rotator --> WO FLAT73A --> WO T-ring for Canon EOS --> Canon EF to EOS R Mount Adapter --> Canon EOS R
I still adjust the ring on the flattener to 11.4 even though I also have the camera rotator?
Thanks in advance
That's how I have my Z73 setup! No changes required. Just install your rotator and enjoy! I have a video on the rotator If your curious what mine looks likeua-cam.com/video/9iSk6CoYgfQ/v-deo.html
Sweet! Thanks a bunch
Do you need the reducer for these scopes to achieve focus if I did not want to buy it right away? I think you can. On the Skywatcher 72 - you cannot without the reducer.
You can use it without not sure what type of camera you will be using Mounting could get creative.
Hello, how long do you have to let the Zenithstar 61 acclimatize?
It doesn't take long for refractors. In cold weather it should be at proper temp by the time your rig is set up and polar aligned and dew heated. Within 30 minutes I suppose if I were to put a time on it. I haven't seen a difference between imaging right away vs waiting on a refractor. They are pretty low maintence. Just set up and enjoy
@@astronotna Thank you very much for your answer. Yesterday I received my first refractor, I come from a Newton family and I couldn't find an answer on Google or William Optics. Your videos are very good, thank you for sharing your experience! Greetings from Argentina 😊.
Glad I could help and thanks for watching this one! Congrats on your new scope!! Wishing you clear skies!
Hi, appreciate the video. I just purchased a Z73 scope and adjustable flattener/reducer. I'm assuming your setup is just flattener without focal reducing?? Reason I ask, is my flattener suggests an adjustment of 1.8mm for DSLR/Mirrorless, not 11.4mm. Thanks!
Hi Mr. Lewis yes this is just the flattner with no reduction
Getting ready to pull the trigger on the Z73, moving away from the SCT scopes for awhile, and WO's explanations completely confused me. Does the backfocus setup change with the .8 reducer/flattener or am I at still at 11.4 (using a 294MC filter drawer in lieu of one of the spacers). Also saw you have the EAF on the 73. Hard to install?
Hey William! Thanks for watching this vid and visiting my channel! With the reducer your back focus requirements should be the same (11.4mm swaping out the 21mm spacer if you use the ZWO drawer and the EAF was super easy to install. Just have to remove the knob on the thermometer side. I've been running my eaf for over a year now and I still love it. The Z73 is an awesome buy at the price just have to figure what color to get!! Hope you love yours like I've loved mine!!
Z73 Field flattener doesn't fit my t ring? The thread on the field flattener seems to be too big?
Bummer.!! Not sure what your set up is but the flattner excepts the standard M48 threads
@@astronotna I think I have the t ring to t2 thread or what it is called, from what I understand I need t-ring to M48 right?
Yes. So the ring on one side should fit your camera and the other side is a m48 thread to screw onto your flattner. I am assuming you will be using a DSLR /Mirrorless cam here.
@@astronotna Thanks, just got the right ring. But I can't reach focus with this back spacing, focuser is all the way in, just gets worse outwards. No adjustment to the flattener and I can reach focus. You know what the problem could be or am I missing something here? I have a Nikon DSLR
@Adolphus if you are using the z73 with Flat73 field flattner (NOT the reducer flattner) you should just be able to set the the flattner to 11.4mm and the focuser reaches focus with the Nikon DSLR around 26mm. All of my Nikon DSLR/Mirrorless cameras reach focus with that set up which includes my oldschool D70 all the way up to my Nikon Z6II. You might have something going on there and double check which components you have attached to your imaging train.
Which would you recommend?
That's a really tough choice! I suppose if I had to choose it woould be the Z73 with a small chip sensor. Frames up many targets nicely!
I love you