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William Optics GT81 + 6AII FF Troubles

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#1 kdesrosier

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Posted 11 January 2019 - 08:00 PM

I've got the most recent iteration of the WO GT81 (link) and just received the WO 6AII Field Flattener (link) in the mail. The sales page for the FF shows an image of the compression ring removed from the focuser tube and the FF taking its place (w/ M63 threading). I've tried unscrewing the ring with no luck. There also seems to be three small hex screws holding the compression ring in place. I've tried unscrewing them, but none of my hex keys fit. However, I'm not sure the screws are holding the ring in place.

 

Has anyone else struggled with this who can maybe lend me some advice? Pics of the compression ring can be found here: https://photos.app.g...JjWiRK5cFqUiXj9

 

Thank you.



#2 Luna-tic

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Posted 11 January 2019 - 08:24 PM

All hex keys to fit the GT81 are metric, those little ones are probably 1.5 or 2 mm. I couldn't find anything in the pdf files about removing the compression ring, but surely it must come off somehow. Rather than booger it up, why not email customer support for WO and ask them? I'd like to be able to remove the compression ring on my 20th Anniversary model GT81 and be able to thread the FF in place, but I've resigned myself to just clamping its sleeve with the three compression screws. It's a firm fit, but threading is better if you can do it.



#3 tonyt

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Posted 11 January 2019 - 10:03 PM

The hex screw does look like a locking screw. You just need to get the correct size wrench to loosen it. I bought a wrench set with lots of small imperial and metric sizes for just such occasions.



#4 kdesrosier

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Posted 13 January 2019 - 10:57 PM

William Optics got back to me and explained you do indeed need to loosen the 3 hex screws on the compression ring before it can be unscrewed from the focuser tube. I was able to do this with a 1.5mm hex key.

 

I had to buy a new hex key set because my current set is older and has rounded edges and therefore could not conform to the inside of the hex screws.



#5 Christian-UAE

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Posted 14 January 2019 - 01:25 PM

Hi.

I would appreciate if you could let me know your experience with the performance of your scope and the reducer as I am currently looking into this set too.

Thank you
Christian

#6 Bluephoton

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Posted 11 February 2019 - 05:52 PM

I've got the most recent iteration of the WO GT81 (link) and just received the WO 6AII Field Flattener (link) in the mail. The sales page for the FF shows an image of the compression ring removed from the focuser tube and the FF taking its place (w/ M63 threading). I've tried unscrewing the ring with no luck. There also seems to be three small hex screws holding the compression ring in place. I've tried unscrewing them, but none of my hex keys fit. However, I'm not sure the screws are holding the ring in place.

 

Has anyone else struggled with this who can maybe lend me some advice? Pics of the compression ring can be found here: https://photos.app.g...JjWiRK5cFqUiXj9

 

Thank you.

I am going through the exact same exercise. I believe I have an older model GT81 from around 2008. I thought I was missing some kind of adapter but it looks like my compression ring has a single slotted screw on the bottom. I am off to try that.

The link for your pictures did not work for me.



#7 kdesrosier

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Posted 11 February 2019 - 06:12 PM

I am going through the exact same exercise. I believe I have an older model GT81 from around 2008. I thought I was missing some kind of adapter but it looks like my compression ring has a single slotted screw on the bottom. I am off to try that.

The link for your pictures did not work for me.

Probably your best bet. Sorry about the pictures, I think I deleted them from my Google Photos.



#8 kdesrosier

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Posted 11 February 2019 - 06:20 PM

Hi.

I would appreciate if you could let me know your experience with the performance of your scope and the reducer as I am currently looking into this set too.

Thank you
Christian

Christian,

 

The scope is really well made. The optics are sharp and the focuser feels really smooth. It's less important, but it's also a looker. Turns a lot of heads from my neighbors when I have it in my front yard.

 

As for the reducer/field flattener, I can't really say yet. I'm having a lot of trouble getting the FF to eliminate the curvature. It's a matter of getting the right backfocus between the FF and my imaging sensor. I also may have tilt in my system. I currently have an ongoing thread to report my progress in this endeavor: https://www.cloudyni...1-curved-field/



#9 Bluephoton

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Posted 11 February 2019 - 06:22 PM

Probably your best bet. Sorry about the pictures, I think I deleted them from my Google Photos.

The compression ring won't move. Did you have to use tools to thread it from the scope? It sure would be nice if they supplied some installation instructions.



#10 kdesrosier

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Posted 11 February 2019 - 06:45 PM

The compression ring won't move. Did you have to use tools to thread it from the scope? It sure would be nice if they supplied some installation instructions.

I did not. After I removed the hex screws (1.5mm), I was able to unscrew it from the draw tube with not much effort.

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#11 Bluephoton

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Posted 11 February 2019 - 09:36 PM

OK I am an idiot LOL. According to WO support my older GTF-81 5 element APO already has a flattener as part of the scope and does not accept the 6AII.

 

I just can't seem to reach focus with any camera I have tried. My Nikon in prime focus with or without the 2" nose extension will not focus. Which is why I bought the Focal reducer.

 

I said I would try one more time and then send it to their US office for testing.



#12 OldManSky

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Posted 12 February 2019 - 10:46 AM

OK I am an idiot LOL. According to WO support my older GTF-81 5 element APO already has a flattener as part of the scope and does not accept the 6AII.

 

I just can't seem to reach focus with any camera I have tried. My Nikon in prime focus with or without the 2" nose extension will not focus. Which is why I bought the Focal reducer.

 

I said I would try one more time and then send it to their US office for testing.

Do you know if you need more focuser travel or less to reach focus?

I mean...with the focuser racked all the way in, and moving to all the way out, are you getting closer to focus or further away?

If you're getting closer, an extension tube might take care of it.

If you're getting further away, and all the way racked in won't focus, then I've got nothing...except let WO have a look. :(



#13 Bluephoton

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Posted 12 February 2019 - 05:51 PM

Do you know if you need more focuser travel or less to reach focus?

I mean...with the focuser racked all the way in, and moving to all the way out, are you getting closer to focus or further away?

If you're getting closer, an extension tube might take care of it.

If you're getting further away, and all the way racked in won't focus, then I've got nothing...except let WO have a look. frown.gif

It approaches focus as I move the focuser out.

During the recent eclipse I set up in the afternoon and used a 1-3/4" extension tube on the end of my DSLR. I was able to focus on some trees about 100' away so I thought I had the problem solved. During the eclipse I wasn't able to bring the moon in focus using the same setup. I guess I am close and I should try a 2" extension.

Thanks for the feedback.




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