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etx-60 to etx-70

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#1 go4broke

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Posted 09 February 2013 - 07:26 PM

So I have an old ETX-60, and it seems to me that it's the same scope as the 70mm with a smaller lens. Does anyone know if I can mount a 70mm lens in the 60mm tube?

#2 Jerry-rigged

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Posted 11 February 2013 - 11:58 AM

1- anything is possible if you are good at building things.

2- I have not used the 60/70, but they have the same focal length, so maybe if you got the entire lens/cell/tube shroud thingie it might be an easy swap. With a little time watching e-bay, you should be able to pick up a ETX70 with a dead mount/focuser/something else for under $50.
3- If you want to use a different lens set, make sure the FL is pretty close to the 350mm of the ETX60/70. Note most cheap 70mm objective sets have a FL between 700mm-1000mm. This would require a much longer tube and probably a different focuser. But then, refer back to #1.

Good Luck, and post up your project if you move forward.
Jerry

#3 Lynnblac

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Posted 12 February 2013 - 08:42 PM

I believe I made the first ETX-80 many years ago. I mounted a 80mm f/5 Surplus Shed lens in a plastic cell to the front of the existing 60mm cell. No vignetting, came to focus and well collimated. I used the threaded lens cap to attach the 80mm cell to the ETX-60. Works great.

#4 Lynnblac

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Posted 13 February 2013 - 06:05 PM

Homemade ETX-80

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#5 Lynnblac

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Posted 13 February 2013 - 06:06 PM

and

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#6 jimarshall

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Posted 20 February 2013 - 04:18 PM

I believe I made the first ETX-80 many years ago. I mounted a 80mm f/5 Surplus Shed lens in a plastic cell to the front of the existing 60mm cell. No vignetting, came to focus and well collimated. I used the threaded lens cap to attach the 80mm cell to the ETX-60. Works great.

Can you post more details on how the threaded lens cap was used to attach the 80mm lens cell to the ETX-60. I removed the original lens and placed a 80mm Surplus Shed lens on my ETX-60 and it fits very tightly with almost no wiggle room for collimation. The only way I could minimize the flare was to shim up the lens with a couple of pieces of black tape placed at the bottom of the lens cell to tilt the lens in the right direction. This helped but the collimation was still not spot on. Did you use the original Surplus Shed lens cell...mine has ribs for a dew shield? If you have a better method of mounting and collimating the 80mm lens I would appreciate the help.

#7 Lynnblac

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Posted 21 February 2013 - 01:23 PM

This was years ago, but I epoxyed the lens cap to the back of the lens cell, then used a hole saw to cut out the opening in the cap then screwed it on. Check that your flip mirror is at 45* when flipped in. If not the system will not be aligned.

#8 jimarshall

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Posted 23 February 2013 - 03:32 PM

Thanks, I can see the the OD of the lens cap is about the same as the telescope's tube so it should be a snug fit. I think I'll try that when I get a chance. The flip mirror alignment looked good with a Cheshire eyepiece and 60mm lens not so good with the 80mm.






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