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Mounting an ETX-90 RA to EQ mount

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#1 Spammy

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Posted 28 December 2017 - 10:28 AM

I came across and ETX-90 Astro M that I could not pass up. I am wanting to de-fork it and mount to an Orion Skyview Deluxe that I currently have a ST-80 on. I have a couple questions I could use some advice on.

 

1. What size rings to I need to use for the ETX-90 tube? I've been unable to find anything on the outside diameter of this scope online.

2. has anyone ever mounted two small scopes side by side on the same EQ mount? Is that possible? What would I need to do that with the ETX and ST-80? 

 

Thanks in advance for your wisdom. 


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#2 Augustus

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Posted 28 December 2017 - 10:37 AM

You don't necessarily need rings - a dovetail will attach to the 1/4 20 hole on the bottom of the OTA.


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#3 deSitter

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Posted 28 December 2017 - 10:45 AM

I have the same, you don't need any rings, just a dovetail bar to attach to the finder shoe. I got this one..

 

https://www.amazon.c...e/dp/B0000XMYFQ

 

You need to make sure it doesn't rotate once attached, so needs to be firmly screwed down. You could drill another hole in it for the second hole in the shoe.

 

Related - it's better to use the back port because the collimation is set for that - you need these parts - then you can use the top port + a diagonal as a finder!

 

ETX male to SCT male, for the back port

https://agenaastro.c...sct-thread.html

 

SCT female 1.25" visual back

https://agenaastro.c...-back-e-15.html

 

I used this setup for the eclipse in August. I have a similar one-armed mount.

 

-drl


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#4 deSitter

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Posted 28 December 2017 - 11:02 AM

Be careful deforking, there are little plastic tangs here and there that must be properly disengaged.

 

-drl


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#5 Spammy

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Posted 28 December 2017 - 12:03 PM

I have the same, you don't need any rings, just a dovetail bar to attach to the finder shoe. I got this one..

 

https://www.amazon.c...e/dp/B0000XMYFQ

 

You need to make sure it doesn't rotate once attached, so needs to be firmly screwed down. You could drill another hole in it for the second hole in the shoe.

 

Related - it's better to use the back port because the collimation is set for that - you need these parts - then you can use the top port + a diagonal as a finder!

 

ETX male to SCT male, for the back port

https://agenaastro.c...sct-thread.html

 

SCT female 1.25" visual back

https://agenaastro.c...-back-e-15.html

 

I used this setup for the eclipse in August. I have a similar one-armed mount.

 

-drl

Do you have pics of your setup? I'd like to see how you mount the dovetail to the "finder shoe" on the scope.



#6 James Ball

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Posted 29 December 2017 - 09:38 PM

I made a solar filter for mine by cutting the end out of a 4" PVC pipe cap for the solar film, using the normal diameter to slide over the tube and it fits fairly snugly,one rubber band  around the tube was enough to make it fit tightly.  If using rings, you would probably want to use 4" rings(102mm). I believe that is the actual outside diameter of the tube.


Edited by James Ball, 29 December 2017 - 09:39 PM.


#7 Spammy

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Posted 29 December 2017 - 10:16 PM

Thanks, I was able to mount it today to my EQ mount with the same adapter I use with my ST-80. Did’t realize the scope had that 1/4 20 hole on the bottom. 

 

Are you saying for visual it’s better to use a diagonal in the back port instead of the one built in to the scope?



#8 RAK on Tour

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Posted 30 December 2017 - 02:26 PM

I, too, have a de-forked ETX-90 RA that I'm thinking might work better using the rear port and diagonal. When using the flip mirror, the image is mis-collimated. Would a flip mirror that doesn't set at exactly 45 degrees introduce that collimation problem?



#9 deSitter

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Posted 30 December 2017 - 06:02 PM

Thanks, I was able to mount it today to my EQ mount with the same adapter I use with my ST-80. Did’t realize the scope had that 1/4 20 hole on the bottom. 

 

Are you saying for visual it’s better to use a diagonal in the back port instead of the one built in to the scope?

Yes, and if you use a diagonal in the top port with a long eyepiece you get a correct image finder as a bonus. Warning, do not attempt to collimate it, you cannot improve on the factory setting.

 

-drl




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