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Mak 127mm visual back replacement

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#1 Nissaire

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Posted 03 January 2020 - 08:54 PM

I’ve recently obtained a used SkyWatcher 127mm Mak. I’m planning on using it for lunar and planetary visual from home in the city. I already have a selection of 2” eyepieces I use on other scopes, and plan on using them on the Mak. I’ll be mounting the scope on my Vixen Porta II mount.

The visual back that came with the scope supports 2” diagonals, but has no compression ring. I’d like to replace it with something as short as possible (just long enough to hold a 2” diagonal), but solid enough to support the diagonal and heavy 2” eyepieces. I want it to have a compression ring to hold the diagonal.

The visual back seems to be attached with the SkyWatcher Mak-specific thread. I’ve measured it to around 65mm in diameter on the scope. I’ve searched this forum and found references to an adapter that would convert that thread to the SCT standard thread:

https://agenaastro.c...-telescope.html

 

My understanding is that this would allow me to attach a 2” visual back such as this one:

 

https://agenaastro.c...r-acc-0003.html

 

Is that correct? I’m unsure the adapter is the correct part I need. The diameter of the thread on the back of my Mak is bigger than the diameter of the SCT standard thread, but the adapter seems to make the thread diameter bigger.

 

I’ve also found a reference to this visual back:

 

https://www.teleskop...teckhuelse.html

 

This seems to be exactly what I want in one single part. But I’ve failed to find a North American distributor for it.

I’d like some input on how to achieve my objective of replacing the visual back that came with the scope with one that can hold my 2” diagonal firmly. I’m open to other options.



#2 jeremiah2229

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Posted 03 January 2020 - 09:33 PM

If your 127 is threaded with the standard SCT threads then all you need is this.  LINK

Then just use your 2" diagonal in it.

 

 

Peace...



#3 dwmedic

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Posted 04 January 2020 - 10:58 AM

I know scopestuff makes an adapter that works with the Orion and Skywatcher brand 127mm mak.



#4 Nissaire

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Posted 04 January 2020 - 11:14 AM

If your 127 is threaded with the standard SCT threads then all you need is this.  LINK

Then just use your 2" diagonal in it.

 

 

Peace...

My Mak is not threaded with the standard SCT thread. The diameter of the ring on which the provided visual back is mounted is around 65mm (close to 2 1/2"), which is bigger than the SCT thread, which measures around 50mm (or 2"). Indeed, if I could convert this to a standard SCT thread, I could use an SCT visual back like the one you mention. I'm just unsure if the adapter (MCT thread to SCT thread) I mentioned in my original post is the proper one.



#5 Nissaire

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Posted 04 January 2020 - 11:32 AM

I know scopestuff makes an adapter that works with the Orion and Skywatcher brand 127mm mak.

I found a reference to what you mention on their website:

 

http://www.scopestuff.com/ss_smsa.htm

 

It seems similar to the adapter I mentioned in my original post. They mention it's for a 44.5mm thread. This looks too small for the thread on my Mak.

 

Attached is a picture I took of the thread on the back of the scope. It shows the thread to have a diameter around 65mm.

 

Seems to me like it's bigger than the thread shown on the 127mm Mak on ScopeStuff's web site.

Attached Thumbnails

  • MAK127.jpg


#6 Rock22

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Posted 04 January 2020 - 12:13 PM

Is there already an adapter on it?

The ScopeStuff adapter #SMSA and the #ADT3 combo should work. If you are not comfortable buying, send an e-mail to ScopeStuff, they will confirm. I used the combo on my 180mm Orion mak, and still have the #SMSA adapter on it for the Crayford focuser I put on. Ask Jim at ScopeStuff. They are very helpful. I purchase from them and communicate with them all the time.

Edited by Rock22, 04 January 2020 - 12:15 PM.


#7 junomike

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Posted 04 January 2020 - 12:21 PM

Interesting that SW used a proprietary VB for this.

If nothing compatible can be found I'd head down the the hardware store and grab some plastic/delrin screws to replace the metal one's.

I did this with my XX16G and find I like it better than compression as there's no hang-ups.



#8 Nissaire

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Posted 05 January 2020 - 07:45 PM

Plastic screws could be an alternative, but I'm afraid they won't hold the diagonal solidly enough, especially with heavy 2" eyepieces. Thanks for the suggestion, I'll consider it if I don't find a replacement solution for the visual back.

 

There doesn't seem to be an adapter. I tried turning the threaded part but was not able to. There are two small holes on it (one can be seen on the picture, the other is hidden by my finger), but no screws in those holes. Could be they are used for a special tool that places the threaded adapter when they assemble the scope.

 

I'll try contacting ScopeStuff, see if they can help.


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#9 Nissaire

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Posted 12 January 2020 - 12:09 AM

Jim from ScopeStuff thinks the threaded part that holds the actual visual back seems like the "factory" back, and thus not an adapter. He says he's never seen an adapter this big on a Skywatcher 127mm Mak. He did suggest permanently adding a 2" to 1.25" twist lock adapter, but that would imply purchasing a 1.25" diagonal, something I don't really want to do. Very nice of him to help me out, though.

 

Looks like I'll be searching for plastic set screws at the hardware store, then. undecided.gif



#10 Rock22

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Posted 12 January 2020 - 12:30 AM

Sincerely sorry to hear you aren’t able to find a work-around. Like someone mentioned earlier, it’s weird that your visual back seems to be a proprietary one.

Plastic screws work okay. I prefer the compression rings, but I use the plastic screws, too.

ScopeStuff sells the plastic screws, so you might want to ask them which ones you need. I buy all my plastic screws from them.

#11 Nissaire

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Posted 12 January 2020 - 10:06 AM

Not a big issue. This is my third scope, and I intend to use it from home for quick grab&go for planets and the moon. I'll also be trying Reflectix insulation with it, as I intend to do this as well for my CPC 1100 main scope.

 

I just find it weird as I haven't found any reference to a 127mm Mak with a similar back online. I seem to be the only one with such a scope. 


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