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Not a good day for focus? ES ED80, ZWO ASI071, 3" FF :(

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#1 azastronomer

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Posted 17 September 2020 - 02:17 AM

I was able to add the 3" Explore Scientific Field Flattener/Reducer along to the ASI071 with the Explore Scientific ED80mm. That's around 50mm + 17.5mm if I'm not mistaken. I tried without using the FF and just M42 extension adapters to get close to 45mm backfocus, 55mm, and in between. No focus or proper visibility in daytime and nighttime. I tried the recommended arrangement from the ZWO ASI071 manual. frown.gif

 

What magic combination worked for you Explore Scientific ED80mm owners who used it with ZWO cameras?

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Edited by azastronomer, 17 September 2020 - 02:45 AM.


#2 maxsid

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Posted 17 September 2020 - 04:01 AM

You need to add 21+16.5 mm rings (included with the camera) between the camera and the reducer. I believe.



#3 johnoelliott

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Posted 17 September 2020 - 06:19 AM

With my 294MC I have to add the 11, 16.5 and 21 mm between the camera and the flattner.

 

If I use my filter wheel, I have to remove the 21 mm.



#4 azastronomer

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Posted 17 September 2020 - 10:45 AM

So 55mm between the flattener and camera, and 55mm between the flattener and telescope?

 

My ZWO camera covers 17.5mm on its own too, so I'm counting that into my 55mm backfocus. Hope that's correct. 

 

Anyway, if we take out the flattener for now (assuming I should still be able to focus in the center), which I just did, I have 55mm backfocus and set my focuser such that I have 480mm overall focal length. I still don't get focus and I moved things around individually to no luck.

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Edited by azastronomer, 17 September 2020 - 10:46 AM.


#5 tlmotorsport

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Posted 17 September 2020 - 11:19 AM

It should be 55mm between the camera and the flattener, on my ED80 I have to use 1 of the extension tubes that came with the scope before the flattener to reach focus which i think is about 50mm, but that's not a critical dimension as long as you have enough to get in focus within the adjustment range of the focuser itself.



#6 johnoelliott

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Posted 17 September 2020 - 11:44 AM

It's 55 mm from the flattener to the sensor

 

For your camera that would be 55 - 17.5 = 37.5 mm

 

You shouldn't need any spacers if you are just connecting the camera to the scope, I don't need any when using just my camera or camera/filterwheel



#7 azastronomer

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Posted 17 September 2020 - 11:58 AM

I use the Explore Scientific 3" FF that's 50mm length by itself. It's a weird flattener to use with my setup. I hope your suggestions account for that. I tried varying length in 1-2mm increments... no difference.



#8 azastronomer

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Posted 17 September 2020 - 12:01 PM

It's 55 mm from the flattener to the sensor

 

For your camera that would be 55 - 17.5 = 37.5 mm

 

You shouldn't need any spacers if you are just connecting the camera to the scope, I don't need any when using just my camera or camera/filterwheel

I do want to first get the focus with just connecting the camera to the scope (no flattener), and even after accounting for the 17.5mm (and getting my perfect 55mm)and 480mm overall length, I don't seem to get any focus. I've read other forum about the ES ED80 causing such issues and tried those suggestions as well but this ASI071 + ED80 combo just seems unlucky at this point.



#9 tlmotorsport

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Posted 17 September 2020 - 12:44 PM

So using my ED80 as an example, I found that when I didn't have the flattener in place I had to use both extension tubes that came with the scope (the ones that that go between the  clamp joint and the focuser).  When I added a flattener, I have the Orion FF for short refractors, it was approximately the same length (i think a bit longer) as one of those extension tubes which I subsequently had to remove.  I'm guessing you need to add about 50mm in the area circled here:

 

 

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#10 azastronomer

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Posted 17 September 2020 - 02:34 PM

Thanks! I was able to achieve focus on objects 15m away. Looks like the more extension tubes I put, the farther the objects I can focus on... I hope that logic works for stars that are far far away.



#11 johnoelliott

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Posted 17 September 2020 - 04:40 PM

I just realized you are saying you have the 3" flattener. I didn't think you could connect that to the 80 mm which is only 2" and it's not supposed to work with F6 scopes.

 

With my 2" Hotech Flattener, I have my click lock adapter connect directly to the scope with no extensions, the Hotech plugs into the click lock, then I have the 21 mm extension connected between the flattener and my filter wheel that is 20 mm and the adapters to connect to the filter wheel total 6.5 mm

 

I was wrong earlier...when I don't have the flattener installed, I need both of the extensions, unless I have the diagonal installed in which case, no extensions are needed.




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