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Installing Dovetail Bar on Evolution 8" OTA

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#1 jjhart827

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Posted 20 March 2017 - 09:39 PM

So, I just received my new CGEM DX mount that I am eager to use with my Evolution 8" OTA. To that end, I also purchased the Celestron D-Style Dovetail bar (I think this used to be call the CG-5 dovetail bar. It is the anodized orange bar that Celestron sells for 8" OTAs). 

 

At any rate, I can't seem to figure out how to install the dovetail bar on my OTA. The bar came with three thumbscrews that are too long to mount the dovetail securely to the OTA, and the three screws that I had to remove from the OTA to place the dovetail in the correct spot are far too short to be used for installing the dovetail. I'm at a complete loss.

 

What am I doing wrong? Any thoughts? 

 

Clear skies.

 

 



#2 leveye

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Posted 20 March 2017 - 09:56 PM

Use longer screws? I've even had to custom cut the lengths sometimes.



#3 jjhart827

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Posted 20 March 2017 - 10:04 PM

Use longer screws? I've even had to custom cut the lengths sometimes.

But doesn't that seem odd for a Celestron dovetail that is made specifically for this Celestron OTA to come with hardware that doesn't work?



#4 jallbery

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Posted 21 March 2017 - 12:43 AM

The cg5 is the vixen dovetail.  The cge is the "D" style.

 

Rather than replacing the dovetail, i would either replace the saddle (to a dual) or buy an adapter like https://www.amazon.c...r/dp/B003D3LYAQ

 

Why give up using the Evo for visual?



#5 lenrabinowitz

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Posted 21 March 2017 - 05:06 AM

Are you sure you are putting it on the right part of the optical tube?


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#6 junomike

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Posted 21 March 2017 - 03:12 PM

See the first pic here and the forth pic here for proper Dovetail orientation.

 

Mike



#7 jjhart827

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Posted 21 March 2017 - 07:47 PM

OTA Zoom.JPG

See the first pic here and the forth pic here for proper Dovetail orientation.

 

Mike

Actually, it would appear that the proper dovetail location on the Evo 8 is on the "side" of the OTA, across from the Vixen/CG-5 dovetail that comes pre-installed on the tube (for use with the Evo mount). It works out rather well, as when the OTA is installed on the DX mount, the old vixen dovetail sits directly atop to OTA, situated perfectly for a guidescope or other accessories. 

 

 



#8 xHarry

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Posted 26 March 2017 - 02:57 AM

jjhart827: Actually, it would appear that the proper dovetail location on the Evo 8 is on the "side" of the OTA, across from the Vixen/CG-5 dovetail that comes pre-installed on the tube (for use with the Evo mount). It works out rather well, as when the OTA is installed on the DX mount, the old vixen dovetail sits directly atop to OTA, situated perfectly for a guidescope or other accessories.

 

That's one of the things I'm considering - I just got the same mount and have the same scope. How did you manage with the screws?

 

Harry



#9 carver2011

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Posted 26 March 2017 - 11:02 AM

There are no screw holes for a dovetail bar on the sides of the optical tube. There are screw holes for a rail on the opposite side of the tube 180 degrees from the factory installed rail. The other holes to the sides of the present rail position are for accessories. 



#10 jjhart827

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Posted 26 March 2017 - 08:23 PM

There are no screw holes for a dovetail bar on the sides of the optical tube. There are screw holes for a rail on the opposite side of the tube 180 degrees from the factory installed rail. The other holes to the sides of the present rail position are for accessories. 

Depends on what your definition of the "side" is. -- On the Evolution mount, there is a single vixen-style saddle that attaches to the side of the OTA. On the opposite "side", (i.e.: 180 degrees away), is where I installed the Losmandy-style plate. Of course, when you move the OTA from a single-fork Alt-Az mount to an EQ mount, the OTA must be rotated 90 degrees -- which means that the "sides" are now the top and bottom. 



#11 jjhart827

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Posted 26 March 2017 - 08:34 PM

 

 

That's one of the things I'm considering - I just got the same mount and have the same scope. How did you manage with the screws?

 

Harry

Hi Harry, 

 

Actually, I ended up using some screws that happened to come with some other gear I already had. However, I did a little bit of primary research at a local home improvement store and was able to determine that one of the two different sizes of screws needed is 10-24 x 5/8". I didn't take the other size with me, as I had already identified some screws that worked. 

 

Most large hardware and/or home improvement stores have test sockets for different sizes/threads of screws. Just take the screws that you'll need to remove from the OTA housing to your local hardware store, and find out what size threads are on them. Then, you may need to buy screws of that thread type of varying lengths, and see which works best. 


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#12 xHarry

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Posted 29 March 2017 - 02:33 AM

Just received my (94216) Celestron dovetail bar. The bar is beautifully made with 2 taped holes (for stand-offs?) and untapped holes that line up with the screw holes on the OTA.

Alas, no instructions and the screws don't fit.

 

Very frustrating. Would have been more frustrating but for Cloudy Nights.



#13 junomike

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Posted 29 March 2017 - 06:42 AM

Just received my (94216) Celestron dovetail bar. The bar is beautifully made with 2 taped holes (for stand-offs?) and untapped holes that line up with the screw holes on the OTA.

Alas, no instructions and the screws don't fit.

 

Very frustrating. Would have been more frustrating but for Cloudy Nights.

Apparently that Dovetail is made for the C8, are you sure you're aligning to the correct holes?

(Post #7 shows it attached to the C8)

Mike


Edited by junomike, 29 March 2017 - 06:43 AM.


#14 jallbery

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Posted 29 March 2017 - 08:29 AM

When I put a farpoint vixen style dovetail on my orange tube C8, the provided screws were incorrect as well.   It was easily addressed by a trip to the hardware store.  I just took the existing screws with me and got something a tad bit longer with the same threads.  I assume at some point Celestron changed the type of screws: I suspect that your screws probably would work on my OTA and vice versa...

 

As far as where to put the dovetail, the "side" of the Evo OTA where the existing dovetail would be the bottom of the OTA were it conventionally mounted on the original c8 double fork.   With the Evo (or the SE mounts), you end up with the dovetail on the left, the focuser underneath the visual back, and the finder on the top right.

 

With a vixen-saddle GEM like the AVX, the Evo vixen dovetail works fine:  you rotate the tube 90-degrees counter clockwise, and (with the GEM pointed north), you end up with the dovetail down, the focus knob to the right, and the finder to the top left  (the standard positioning for Celestron SCTs sold on GEM mounts).

 

By putting the CGE dovetail on the opposite side of the Evo's vixen, you'll end up with (when pointed north) with the focus knob on the left and finder on lower right, which strikes me as inconvenient, but I guess with a GEM you end up with inconvenient placing somewhere in the sky no matter what.   Nonetheless, I would opt for either an adapter, or changing the saddle to an ADM dual saddle that would handle either dovetail. On the other hand, the vixen dovetail on top could be utilized to piggback a small refractor when using CGEM DX...


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#15 xHarry

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Posted 29 March 2017 - 07:28 PM

CORRECTION: I was unaware that Celestron uses different screws in the front versus the back of the scope. Now that I have examined this carefully, I must report that the screws that I received are correct. Still instructions would have helped.

 

Harry 



#16 xHarry

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Posted 29 March 2017 - 07:34 PM

... On the other hand, the vixen dovetail on top could be utilized to piggback a small refractor when using CGEM DX...

Yes I'm thinking that a 65 mm AstroTech apo would be quite happy there.

 

Harry



#17 jjhart827

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Posted 29 March 2017 - 09:36 PM

 

By putting the CGE dovetail on the opposite side of the Evo's vixen, you'll end up with (when pointed north) with the focus knob on the left and finder on lower right, which strikes me as inconvenient, but I guess with a GEM you end up with inconvenient placing somewhere in the sky no matter what.   Nonetheless, I would opt for either an adapter, or changing the saddle to an ADM dual saddle that would handle either dovetail. On the other hand, the vixen dovetail on top could be utilized to piggback a small refractor when using CGEM DX...

You nailed it. Everything looks ****-backward, I can't get the Vixen style dovetail off, and it wouldn't matter anyway because the hole configuration on that side does not match a conventional CGE dovetail!

 

Clear skies!  



#18 Chris Johnson

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Posted 30 March 2017 - 07:18 AM

Does the existing dovetail have tapped holes? I converted my AVX mount to "D" plate style for the C11. My 6 and 8" scopes have tapped holes in their vixen dovetails so I bought a "D" plate and bolt it to the vixen dovetail on these scopes for use on the AVX.


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#19 jjhart827

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Posted 30 March 2017 - 09:24 PM

Does the existing dovetail have tapped holes? I converted my AVX mount to "D" plate style for the C11. My 6 and 8" scopes have tapped holes in their vixen dovetails so I bought a "D" plate and bolt it to the vixen dovetail on these scopes for use on the AVX.

Hi Chris,

 

Yes, the vixen dovetail does have tapped holes...and I was thinking about doing what you describe -- bolting a D plate to it for use with my new guidescope, that came with D-style clamps. 

 

However, there is a small steel plate covering about half of the vixen dovetail bearing the Celestron Evolution branding. Of course, it covers one of the screws that I would need to replace in order to attach a D plate. 

 

So, yes, I had considered the same approach as you, but I can't get that darn branding plate off!

 

Thanks for letting me know I'm not entirely barking up the wrong tree!

 

Clear skies.



#20 Chris Johnson

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Posted 31 March 2017 - 08:11 AM

I don't understand why you can't remove the vixen bar. It should be mounted with standard socket head screws. Does the nameplate cover the screws? The vixen bar is mounted in the standard position for a Celestron sct. When mounted in a gem or fork mount the focuser is at the right. The evolution mount places the focuser at the bottom. You should find the same mounting holes for the d plate under the vixen bar.



#21 jjhart827

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Posted 31 March 2017 - 08:49 AM

I don't understand why you can't remove the vixen bar. It should be mounted with standard socket head screws. Does the nameplate cover the screws? The vixen bar is mounted in the standard position for a Celestron sct. When mounted in a gem or fork mount the focuser is at the right. The evolution mount places the focuser at the bottom. You should find the same mounting holes for the d plate under the vixen bar.

Hi Chris,

 

You are correct. The name plate covers the front screw of the vixen rail. 

 

Additionally, as far as i can tell, the mounting holes will not accommodate a D-style dovetail. I'll post a couple of pictures later today to illustrate. 

 

Thanks for your interest!



#22 jallbery

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Posted 31 March 2017 - 11:54 AM

 

I don't understand why you can't remove the vixen bar. It should be mounted with standard socket head screws. Does the nameplate cover the screws? The vixen bar is mounted in the standard position for a Celestron sct. When mounted in a gem or fork mount the focuser is at the right. The evolution mount places the focuser at the bottom. You should find the same mounting holes for the d plate under the vixen bar.

Hi Chris,

 

You are correct. The name plate covers the front screw of the vixen rail. 

 

Additionally, as far as i can tell, the mounting holes will not accommodate a D-style dovetail. I'll post a couple of pictures later today to illustrate. 

 

Thanks for your interest!

 

It would surprise me that the Evo OTA would not have the same mounting holes as the standard OTA.   If memory serves me right, the top and bottom mounting holes are the same, except that holes are switched: on the top of the OTA (assuming it is sitting with the focus knob on the right) the rear cell has one screw and the front cell has two, while the bottom has two screws to the rear and one on top.

 

But I've been surprised before...



#23 xHarry

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Posted 01 April 2017 - 05:54 PM

Another issue with the C8 on the CGEM Dx is that the StarSense camera cable is now too short. Especially in the upside down position. This is another annoyance with a DIY solution but Celestron should at least offer these cables for sale.


Edited by xHarry, 01 April 2017 - 09:29 PM.


#24 jjhart827

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Posted 03 April 2017 - 10:17 PM

 

 

I don't understand why you can't remove the vixen bar. It should be mounted with standard socket head screws. Does the nameplate cover the screws? The vixen bar is mounted in the standard position for a Celestron sct. When mounted in a gem or fork mount the focuser is at the right. The evolution mount places the focuser at the bottom. You should find the same mounting holes for the d plate under the vixen bar.

Hi Chris,

 

You are correct. The name plate covers the front screw of the vixen rail. 

 

Additionally, as far as i can tell, the mounting holes will not accommodate a D-style dovetail. I'll post a couple of pictures later today to illustrate. 

 

Thanks for your interest!

 

It would surprise me that the Evo OTA would not have the same mounting holes as the standard OTA.   If memory serves me right, the top and bottom mounting holes are the same, except that holes are switched: on the top of the OTA (assuming it is sitting with the focus knob on the right) the rear cell has one screw and the front cell has two, while the bottom has two screws to the rear and one on top.

 

But I've been surprised before...

 

Here are the pictures I referred to. Again, as far as I can tell, there are no holes that are properly spaced on either end of the OTA that would accommodate a D-style dovetail -- either with or without the V-style dovetail attached. Also, note the metal "Evolution" plate that covers one (or more screws) on the factory installed dovetail...

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