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New adapter to decouple focuser from mirror for 10"+ RCs

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#1 tolgagumus

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Posted 28 July 2016 - 07:38 PM

I am super excited about this adapter. Finally Ron from Moonlite finished my adapter to separate the focuser from the mirror. The weight of the camera puling on the mirror has always been a problem with these GSO RCs. No matter how tight I made the collimation I always noticed a shift through the night. This was because of the weight.  These scopes are sold under different names like TPO, Astrotech, Highpoint, Mallincam. GSO realized their mistake and corrected the issue in the new truss tube versions but the older ones and even the new carbon fiber or steel closed tubes scopes still suffer from this problem. 

 

The adapter is not plug and play. It requires some work from the user. The rear cell has to be removed and drilled using the adapter as a template. Moonlite includes an o 'ring to center the adapter around the existing threads. I simply pressed the adapter on the o'ring, marked the holes using a drill. Next step is to remove the mirror cell by unscrewing the pull screws, remove the mirror and nut and bolt the adapter. Good news is, the adapter has the same 117 mm threads as the original back so I can continue using my old imaging train. It was only $250. I must do a warning tho it is not for someone who can't handle using a drill and not comfortable taking the scope apart. And the scope definitely has to be re collimated once put back together.

 

I tested it with a laser before and after installation and using about 20 pounds and the laser stood still. I am extremely happy. 

 

I also tried the upcoming Moonlite Nightcrawler focuser but it's not 100% ready.

Attached Thumbnails

  • 20160728_124512.jpg

Edited by tolgagumus, 29 July 2016 - 12:49 PM.


#2 Adam E

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Posted 29 July 2016 - 09:19 AM

That's really awesome and kudos to Ron and Moonlite!



#3 tolgagumus

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Posted 29 July 2016 - 06:02 PM

Yes Adam, really a big kudos for Ron. This has been bothering me for a long time. There are many of these scopes out there that can be picked up fairly cheap. This is a great way to improve their performance. 



#4 tolgagumus

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Posted 01 August 2016 - 12:18 AM

Here is the video of the installation process

 

 

https://youtu.be/GOIYVJfHxsQ

 

[video=youtube;GOIYVJfHxsQ]http://www.youtube.com/watch?v=GOIYVJfHxsQ[/video]


Edited by tolgagumus, 01 August 2016 - 12:27 AM.


#5 akulapanam

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Posted 01 August 2016 - 01:44 AM

Great upgrade! 



#6 Rick-T137

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Posted 01 August 2016 - 08:02 AM

Very well done video! I am assuming that the primary's orientation was preserved when it was removed and the rubber "O" ring is no longer needed? Is that correct?



#7 tolgagumus

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Posted 01 August 2016 - 08:13 AM

Very well done video! I am assuming that the primary's orientation was preserved when it was removed and the rubber "O" ring is no longer needed? Is that correct?

Hi, yes video doesn't show it but I also marked the mirror orientation before removing it. I am not sure it matters since the whole thing should be recollimated anyways but it may be easier to do. The rubber o'ring serves two purposes. One it holds the flange in place tightly as you mark the holes and two it centers the flange around the optical axis. Once the holes are drilled it's not longer needed. The gap allows the primary mirror to move freely within the flange. 



#8 nemo129

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Posted 02 August 2016 - 05:44 AM

Wow, way to go Ron! This is great news for the folks with the solid tube RC's but I looked at my truss tube model (AT10RCT) and it does not appear this particular solution will work on those as there are many more connections from the mirror cell to the truss assembly and the fans look like they would interfere with the flange installation as they are installed closer to the opening on the rear plate.



#9 akulapanam

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Posted 02 August 2016 - 03:53 PM

Wow, way to go Ron! This is great news for the folks with the solid tube RC's but I looked at my truss tube model (AT10RCT) and it does not appear this particular solution will work on those as there are many more connections from the mirror cell to the truss assembly and the fans look like they would interfere with the flange installation as they are installed closer to the opening on the rear plate.

In your case you need the Teleskop express mod.



#10 tolgagumus

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Posted 02 August 2016 - 05:18 PM

Wow, way to go Ron! This is great news for the folks with the solid tube RC's but I looked at my truss tube model (AT10RCT) and it does not appear this particular solution will work on those as there are many more connections from the mirror cell to the truss assembly and the fans look like they would interfere with the flange installation as they are installed closer to the opening on the rear plate.

What is the distance from the center of the OTA to the edge of the fan? This flange is 5 7/8" 


Edited by tolgagumus, 02 August 2016 - 05:21 PM.


#11 nemo129

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Posted 03 August 2016 - 06:32 AM

 

What is the distance from the center of the OTA to the edge of the fan? This flange is 5 7/8" 

 

 

I measure 2.75" from center of OTA to the edge of the fans, so the flange would cover part of the fans.



#12 nemo129

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Posted 03 August 2016 - 06:44 AM

In your case you need the Teleskop express mod.

 

 

 

Thanks for your input, but if you are talking about this one, it includes a new 3" TS focuser and after the Euro conversion and shipping (minus VAT) is about $600USD. I already purchased a motorized Moonlite focuser for the OTA, so I am not keen on the TS solution. Buying a $250 flange that works with my current focuser is attractive, the TS solution is not.



#13 akulapanam

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Posted 03 August 2016 - 03:04 PM

 

In your case you need the Teleskop express mod.

 

 

 

Thanks for your input, but if you are talking about this one, it includes a new 3" TS focuser and after the Euro conversion and shipping (minus VAT) is about $600USD. I already purchased a motorized Moonlite focuser for the OTA, so I am not keen on the TS solution. Buying a $250 flange that works with my current focuser is attractive, the TS solution is not.

 

Email them and Altair Astro. Ok betting one of those two can help you get only what you want.



#14 jamesprovi

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Posted 11 August 2016 - 07:37 PM

Ordered the focuser decoupler for my 12" AstroTech RC last week and it arrived this week.  My brother and I installed it by following the instructions given by the video).  We didn't run into any significant surprises, the adapter fit and the screws/bolts cleared the mirror mount assembly and fans.  The adapter is very beefy and I can see that it should definitely hold anything I mount on my feather touch focuser.  Installation is pretty straight forward and really does not involve much more than what one would deal with in cleaning the mirror (removing the mirror assembly from the OTA metal tube).  The adapter is a very snug fit and took some effort to fit it over the o-ring supplied but it did go on.  

 

We aligned the mirror/secondary using a Takahashi collimator and will do final alignment (star) once the weather clears up.  I have a guide scope ready to go and will see how well the scope can guide with it.  In the past I could not guide more than 5min without seeing some star elongation due to flexure.  

 

James



#15 tolgagumus

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Posted 12 August 2016 - 01:56 PM

Ordered the focuser decoupler for my 12" AstroTech RC last week and it arrived this week.  My brother and I installed it by following the instructions given by the video).  We didn't run into any significant surprises, the adapter fit and the screws/bolts cleared the mirror mount assembly and fans.  The adapter is very beefy and I can see that it should definitely hold anything I mount on my feather touch focuser.  Installation is pretty straight forward and really does not involve much more than what one would deal with in cleaning the mirror (removing the mirror assembly from the OTA metal tube).  The adapter is a very snug fit and took some effort to fit it over the o-ring supplied but it did go on.  

 

We aligned the mirror/secondary using a Takahashi collimator and will do final alignment (star) once the weather clears up.  I have a guide scope ready to go and will see how well the scope can guide with it.  In the past I could not guide more than 5min without seeing some star elongation due to flexure.  

 

James

Hi James,

Your star elongation maybe due to differential flexture. I would highly recommend using an OAG instead of a guide scope with this OTA



#16 jamesprovi

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Posted 13 August 2016 - 07:39 PM

 

Ordered the focuser decoupler for my 12" AstroTech RC last week and it arrived this week.  My brother and I installed it by following the instructions given by the video).  We didn't run into any significant surprises, the adapter fit and the screws/bolts cleared the mirror mount assembly and fans.  The adapter is very beefy and I can see that it should definitely hold anything I mount on my feather touch focuser.  Installation is pretty straight forward and really does not involve much more than what one would deal with in cleaning the mirror (removing the mirror assembly from the OTA metal tube).  The adapter is a very snug fit and took some effort to fit it over the o-ring supplied but it did go on.  

 

We aligned the mirror/secondary using a Takahashi collimator and will do final alignment (star) once the weather clears up.  I have a guide scope ready to go and will see how well the scope can guide with it.  In the past I could not guide more than 5min without seeing some star elongation due to flexure.  

 

James

Hi James,

Your star elongation maybe due to differential flexture. I would highly recommend using an OAG instead of a guide scope with this OTA

 

I agree that the OTA likely was the cause of the differential flexure.  However, after this modification, I am hoping the differrential flexure issue will be greatly reduced or eliminated.  Once I do some imaging runs with the guide scope, I will report back with my results.  I do have a ONAG device and it does work well and I don't get any elongated stars using it.  However, I do struggle finding guide stars on some DSO's.  Using a guide scope, I do find many guide stars so hoping I can also use the guide scope at times when I need it.

 

James



#17 tolgagumus

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Posted 13 August 2016 - 07:46 PM

 

 

Ordered the focuser decoupler for my 12" AstroTech RC last week and it arrived this week.  My brother and I installed it by following the instructions given by the video).  We didn't run into any significant surprises, the adapter fit and the screws/bolts cleared the mirror mount assembly and fans.  The adapter is very beefy and I can see that it should definitely hold anything I mount on my feather touch focuser.  Installation is pretty straight forward and really does not involve much more than what one would deal with in cleaning the mirror (removing the mirror assembly from the OTA metal tube).  The adapter is a very snug fit and took some effort to fit it over the o-ring supplied but it did go on.  

 

We aligned the mirror/secondary using a Takahashi collimator and will do final alignment (star) once the weather clears up.  I have a guide scope ready to go and will see how well the scope can guide with it.  In the past I could not guide more than 5min without seeing some star elongation due to flexure.  

 

James

Hi James,

Your star elongation maybe due to differential flexture. I would highly recommend using an OAG instead of a guide scope with this OTA

 

I agree that the OTA likely was the cause of the differential flexure.  However, after this modification, I am hoping the differrential flexure issue will be greatly reduced or eliminated.  Once I do some imaging runs with the guide scope, I will report back with my results.  I do have a ONAG device and it does work well and I don't get any elongated stars using it.  However, I do struggle finding guide stars on some DSO's.  Using a guide scope, I do find many guide stars so hoping I can also use the guide scope at times when I need it.

 

James

 

This is a very typical issue going from a guide scope to an OAG. This adapter is more for collimation staying put as you slew across the sky. Before this I could see visually. I also need to test it out yet. 

 

I am actually thinking about another upgrade for this OTA. I want to get a 300 mm ring, put it about 2/3 of the way to the front, somehow bolt it to the dovetail and loosen the front bolts. Because what good is a CF tube if the two metals parts of the scope is tied together with a piece of aluminum? This is just an idea. I don't know if I will do this yet. 



#18 jamesprovi

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Posted 14 August 2016 - 06:29 PM

 

 

 

Ordered the focuser decoupler for my 12" AstroTech RC last week and it arrived this week.  My brother and I installed it by following the instructions given by the video).  We didn't run into any significant surprises, the adapter fit and the screws/bolts cleared the mirror mount assembly and fans.  The adapter is very beefy and I can see that it should definitely hold anything I mount on my feather touch focuser.  Installation is pretty straight forward and really does not involve much more than what one would deal with in cleaning the mirror (removing the mirror assembly from the OTA metal tube).  The adapter is a very snug fit and took some effort to fit it over the o-ring supplied but it did go on.  

 

We aligned the mirror/secondary using a Takahashi collimator and will do final alignment (star) once the weather clears up.  I have a guide scope ready to go and will see how well the scope can guide with it.  In the past I could not guide more than 5min without seeing some star elongation due to flexure.  

 

James

Hi James,

Your star elongation maybe due to differential flexture. I would highly recommend using an OAG instead of a guide scope with this OTA

 

I agree that the OTA likely was the cause of the differential flexure.  However, after this modification, I am hoping the differrential flexure issue will be greatly reduced or eliminated.  Once I do some imaging runs with the guide scope, I will report back with my results.  I do have a ONAG device and it does work well and I don't get any elongated stars using it.  However, I do struggle finding guide stars on some DSO's.  Using a guide scope, I do find many guide stars so hoping I can also use the guide scope at times when I need it.

 

James

 

This is a very typical issue going from a guide scope to an OAG. This adapter is more for collimation staying put as you slew across the sky. Before this I could see visually. I also need to test it out yet. 

 

I am actually thinking about another upgrade for this OTA. I want to get a 300 mm ring, put it about 2/3 of the way to the front, somehow bolt it to the dovetail and loosen the front bolts. Because what good is a CF tube if the two metals parts of the scope is tied together with a piece of aluminum? This is just an idea. I don't know if I will do this yet. 

 

My AstroTech 12" RC is aluminum tube and luckily comes comes with OTA rings for mounting.  I agree with you that rings will likely reduce the flexure issues over using a dovetail to mount the OTA.  Im hoping this week, ill get a break in the weather so I can test out the guide scope tracking.  The guide scope i plan to use was purchased from Astro-Physics and comes with a solid mounting system to reduce flexure at the camera end.

 

James



#19 Hawkdl2

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Posted 15 August 2016 - 07:13 AM

This is great news.  I had just started talking to a friend about machining my own adapter! Has anyone confirmed whether the adapter with work on a 10" truss tube?  

 

 

 

Larry



#20 tolgagumus

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Posted 15 August 2016 - 10:51 AM

This is great news. I had just started talking to a friend about machining my own adapter! Has anyone confirmed whether the adapter with work on a 10" truss tube?



Larry


Larry,
I can't confirm. Maybe you should call Ron and ask if you can try it out to see if it fits.

#21 Hawkdl2

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Posted 15 August 2016 - 12:11 PM

Tolga,

 

Thanks.  I will call Ron, but I'm in Ireland for business for the week and won't have time until I'm back in the States.  If I knew it would work, I'd order one today!

 

Once installed, is the collimation tilt adjuster ring needed any longer? I already am at the limit on backfocus.

 

Larry


Edited by Hawkdl2, 15 August 2016 - 12:13 PM.


#22 tolgagumus

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Posted 15 August 2016 - 12:13 PM

Tolga,

Thanks. I will call Ron, but I'm in Ireland for business for the week and won't have time until I'm back in the States. If I knew it would work, I'd order one today!

Larry


Larry
I don't have one to test it on. I looked at some pictures and that's about it. When you get back, give me a buzz and we'll take some measurements together.

#23 bigeastro

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Posted 24 August 2016 - 04:32 PM

I just found this thread.  I usually don't watch this catagory so I just saw the thread. 

 

​I want to congradulate Tolga and Ron for developing this.  I already installed one on my Aluminum Tube TPO RC10.  I have always been bothered by the collimation of the scope and the difficulty of trying to collimate the scope with the focuser attached to the primary mirror cradle.  Furthermore, the internal workings of the telescope was somewhat of a mystery to me.  Purchasing and installing this simple device removed the mystery of the scope and fixed the problem of having the focuser attached to the primary mirror. 

 

I can attest to the fact that the modification is incredibly easy to do and works well.  I think it took me from about 6:30 pm to about say 10:00 pm including a stop for dinner and messing around with other stuff on the scope, like CLEANING THE MIRRORS, to actually install. I bet you can install this in an hour or two at most.

 

I don't know what else to say except that it gave me great piece of mind on being able to handle the relatively heavy Moravian 16200 on the back of the scope with no deflection of the primary mirror.  I think this modification is a must do for those owning the older RC 10 Metal Tube scopes.

 

All I can think of is what where they thinking when they attached the primary mirror cradle to the focuser. 

 

This fixes the issue. 



#24 bigeastro

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Posted 24 August 2016 - 04:46 PM

One other thing,

 

If you own a Moonlite focuser, you don't have to purchase a separate collimation ring which deducts from available back focus.  I now own Starlight Instruments focusers as well as one Moonlite focuser.  The focuser on the RC is a Starlight Instruments Focuser, a fine focuser for sure with massive lifting capacity, but it needs a separate collimation ring.  It does take away from back focus but it still works well and I can focus with the RC10 at native F8

 

However, the need for an additional collimation ring will take up back focus affect the maximum amount of reduction you can attain from an AP 27PVTH.  Utilizing the recommended separation from the AP site on this reducer leaves you with the inability to focus, because of the inability to rake the focuser in enough with or without the extra collimation ring.  I called AP and they were not surprised, and indicated that I would just have to live without being able to get the maximum reduction.  Having to install the separate collimation ring necessary with the SI focusers takes more way from the maximum reduction.  I have not tried it yet, but expect that I may only be able to eeek out .8 or .85 reduction instead of the .75 as advertised on the AP27PVTH.  You have to reduce the recommended separation between the chip and the reducer to get focus and that reduces the amount of reduction you can get from the AP27PVTH.



#25 Hawkdl2

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Posted 25 August 2016 - 07:32 PM

Just an FYI for those with truss RCs.  I've been corresponding Ron about whether the current adapter will work on a truss RC and the answer is NO.   The current adapter is too shallow to clear the 117mm threaded piece extending out of the back of the truss's visual back.  He is in the process of machining one that will work.  It will have to cover a small portion of the fan holes, but not much and it shouldn't have much of an impact on air flow. I may get to test this for him, so I will post when I get one and how it works. I may get to test a prototype for him, so I will post when I get one and see how it works.  I think taking apart the truss will be a bit more complicated than the tube RCs. 

 

 

Larry




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