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Tips for Deforking an RCX400 16 inch

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#1 jt_3232

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Posted 25 June 2020 - 07:20 PM

Hello all,

 

I am looking to defork an RCX400 16" which is on a specially made pier mount made for our latitude.

 

I am hoping to replace the pier with a different one and place the assembly on an iOptron CEM120 mount. It has a payload capacity of 115lbs which I believe will be more than enough for the RCX400 16" OTA, a feathertouch focuser, a Meade Series 5000 ED80 guide scope, and a camera (feel free to check my math).

 

I was curious about how feasible you all think this will be. I am hoping to make this scope be able to accurately guide to take long-exposure astrophotography (5-minute images or longer) and possibly variable star research. I want this scope to be very easy for anyone to learn on and fall in love with the hobby.

 

I am not with the scope, it is 70 miles away currently. How do I attach a dovetail to it? I recall there being one to hold the guide scope, but not any other ones. It has been a while since I've seen this scope.

 

How does focusing work? It is currently an electric focuser, that you focus with the Autostar II handbox. Although I have an external one, I use both to be able to easily focus between eyepiece and camera settings.

 

Thanks guys! I am very new and hope to not break anything or waste money.

 

JT


Edited by jt_3232, 25 June 2020 - 07:20 PM.


#2 jt_3232

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Posted 25 June 2020 - 08:11 PM

I found a picture guys. I hope it will help you all to understand the situation better.

 

JT

Attached Thumbnails

  • telscope.jpg


#3 555aaa

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Posted 25 June 2020 - 08:18 PM

What is it with the present fork mount that you believe the new mount will fix? I have the current generation 16" ACF but before I talk about that let's hear about this mount and telescope and what needs to be improved.
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#4 jt_3232

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Posted 25 June 2020 - 10:01 PM

Basically, I want to make this scope good enough for DSO and easy for new-to-telescope people to use.

 

This scope is at a small public university. I want new students to be able to enjoy the hobby without all the frustration people before me and I have had to deal with.

 

This scope does not track well. It has severe backlash in the DEC motor, the RA acts weird when going in one direction (it likes to keep going for a tad bit after it should have stopped), and it cannot be easily polar aligned as it is nearly impossible to turn it azimuthally with precision. Also, the mind of the scope (the mount) is a bit crazy at times and dealing with that is always a bit of a hassle.

 

I have toyed around with disabling the DEC motors in one direction to no avail. I have tried several different combination of settings on guiding. I've tried an OAG and a guide scope. I have fought oh so much with this scope. 

 

Without complaining too much more, this scope does fine for observing sessions, I personally want more out of the scope.

 

Thanks



#5 carolinaskies

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Posted 25 June 2020 - 10:05 PM

Hello all,

 

I am looking to defork an RCX400 16" which is on a specially made pier mount made for our latitude.

 

I am hoping to replace the pier with a different one and place the assembly on an iOptron CEM120 mount. It has a payload capacity of 115lbs which I believe will be more than enough for the RCX400 16" OTA, a feathertouch focuser, a Meade Series 5000 ED80 guide scope, and a camera (feel free to check my math).

 

I was curious about how feasible you all think this will be. I am hoping to make this scope be able to accurately guide to take long-exposure astrophotography (5-minute images or longer) and possibly variable star research. I want this scope to be very easy for anyone to learn on and fall in love with the hobby.

 

I am not with the scope, it is 70 miles away currently. How do I attach a dovetail to it? I recall there being one to hold the guide scope, but not any other ones. It has been a while since I've seen this scope.

 

How does focusing work? It is currently an electric focuser, that you focus with the Autostar II handbox. Although I have an external one, I use both to be able to easily focus between eyepiece and camera settings.

 

Thanks guys! I am very new and hope to not break anything or waste money.

 

JT

I have a 2004 LX200 GPS 16".   The RCX400 is mainly a juiced up LX200 with focus shifting of the corrector plate. 

What do you think you will gain by moving from the fork system to a CEM120?   The weight of the 16" with accessories pretty much negates using the CEM120 for serious long exposure.  CEM/GEMs are great for up to 14" systems, but at 16" unless you are using a full ring support system the weight of the OTA is going to have stress at the riser blocks that attach the OTA to a Losmandy dovetail.  

pVOnnYWiHNlv_620x0_kWXURFLk.jpg



Unlike smaller telescopes, the LX200 and the RCX400 16" telescopes are well supported by the two massive fork arms of the system.  Even if the onboard system has failed, there are even aftermarket remedies to control the drives, so I wouldn't give up on the fork arms thinking the CEM120 is up to the task. 

As for capability.  A well maintained fork armed RCX400 is completely capable of long exposure imaging whether thru off axis guider or a guide scope externally mounted.  

The picture you shared of the system as it is currently configured is perfectly acceptable and since you are within 70 miles of the current location you can easily shim the base of the pier for the new location.  

I would seriously reconsider deforking it. 

Have you joined the Groups.io LX200 16" group?    The issues you seem to be having sound more like a system in need of a good cleaning and tuneup.  For what you're willing to invest in a new mount, you should for far less be able to get this one back in good working order. 


Edited by carolinaskies, 25 June 2020 - 10:23 PM.


#6 jt_3232

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Posted 25 June 2020 - 10:42 PM

I have a 2004 LX200 GPS 16".   The RCX400 is mainly a juiced up LX200 with focus shifting of the corrector plate. 

What do you think you will gain by moving from the fork system to a CEM120?   The weight of the 16" with accessories pretty much negates using the CEM120 for serious long exposure.  CEM/GEMs are great for up to 14" systems, but at 16" unless you are using a full ring support system the weight of the OTA is going to have stress at the riser blocks that attach the OTA to a Losmandy dovetail.  

pVOnnYWiHNlv_620x0_kWXURFLk.jpg



Unlike smaller telescopes, the LX200 and the RCX400 16" telescopes are well supported by the two massive fork arms of the system.  Even if the onboard system has failed, there are even aftermarket remedies to control the drives, so I wouldn't give up on the fork arms thinking the CEM120 is up to the task. 

As for capability.  A well maintained fork armed RCX400 is completely capable of long exposure imaging whether thru off axis guider or a guide scope externally mounted.  

The picture you shared of the system as it is currently configured is perfectly acceptable and since you are within 70 miles of the current location you can easily shim the base of the pier for the new location.  

I would seriously reconsider deforking it. 

Have you joined the Groups.io LX200 16" group?    The issues you seem to be having sound more like a system in need of a good cleaning and tuneup.  For what you're willing to invest in a new mount, you should for far less be able to get this one back in good working order. 

You have a beautiful scope. If I could fix the mount for cheaper, I would love to. I suppose it never occurred to me that the RCX400 and LX200 were practically identical scope setups. I'll go check out some of the posts over there. 

 

I'm so sick of dealing with the mount that I'd love to just have one purchase and no longer have issues. 

 

If I can get the scope to track within, say, 1 arcsecond RMS, I would be THRILLED. I just recall it going +/- ~7 arcseconds. 

 

You say shimming the mount would work well, but how about turning it azimuthally? Shimming only helps in the up and down direction :/ (I think)

 

Thank you so much for posting, I'm back at another brick wall of decisions to make.

 

JT


Edited by jt_3232, 25 June 2020 - 10:42 PM.


#7 rgsalinger

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Posted 25 June 2020 - 10:53 PM

Not being a Meade expert I may have confused the OP on what to do about his conundrum. 

 

I tried to guide with the system he has about 2 years ago and frankly it became obvious that it has some mechanical issues. RA and DEC were jumping around no matter how I tried to tame it. I suggested at the time sending it into Meade for an overhaul (do they do these?) as that's what I would do.

 

Just today this all resurfaced and I suggested that if the OTA weighed 67 pounds as specified, then it could be deforked and put on (with rings of course) to a CEM120 as the least expensive alternative that's likely to work. It seemed to me that on THIS forum there would be someone who might know about how to overhaul one of these or who would have instructions about how to do it. 

 

So, one key item to ascertain is the weight of the OTA. The manual says 140 pounds but on the Meade website a new 16" RC is shown to have a weight of 67 pounds. Big difference. I have 70 pounds on my CEM120 and it handles it perfectly. I would put 10 pounds or so more on the mount and not worry about performance. On the other hand I would not put 100 pounds on it despite it's rating. 

 

To me the issue is can it be re-conditioned and, if not then what does the OTA - which seemed very well collimated actually weigh!

 

Rgrds-Ross



#8 555aaa

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Posted 26 June 2020 - 10:10 AM

I think this scope is a lot heavier than the current production 16.

#9 SkipW

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Posted 26 June 2020 - 11:12 AM

Here are some additional things to think about before deforking an RCX400-16. 

 

Our club has an RCX400-14 permanently mounted in our observatory, and I've become one of the de facto experts on this telescope and its operation since our previous long-time operator died a few years ago. I'm still not a true expert with it, but learned a lot about its operation pretty quickly.

 

Presuming the 16 is similar to the 14, the collimation and internal electronic focus are accomplished with three motors moving the corrector plate. Control of these motors is integrated into the Autostar system. If the OTA is detached from the base, you will almost certainly lose that functionality.

 

Focusing without Autostar  could be accomplished using your Feathertouch focuser, but you will want to set the internal focusing so that focus can be reached for your desired configurations (visual or imaging) using only the feathertouch (and perhaps some extender tubes), diagonals, etc., before splitting it. Collimation will be another issue - you will have to devise some method to control the three motors (which could also be set up for coarse focusing again), or bypass them; neither of these will likely be trivial to do.

 

As far as long-exposure astrophotography is concerned, remember that the FL of that instrument is probably in excess of 3 meters. It will be very sensitive to even small errors in guiding and any shake. I suspect that it will be far from simple to use for beginner-level deep sky imaging unless the mount is extremely robust, well aligned, precisely controllable, and has a well-tuned guiding system in place. It should be outstanding for lunar and planetary imaging, however - our 14 certainly is! Perhaps you could devote the 80 mm "guide scope" for deep-sky imaging and the 16 for guiding, at least for novices.

 

For polar aligning your current setup in azimuth, how is the flange at the bottom of the tubular pier attached to the foundation? How far is it off in azimuth? If it uses three or four bolts, could the holes in the flange be enlarged or be extended into short arcs so the whole thing can be rotated, then use something like screw or hydraulic jacks braced against the wall and the fin(s) to rotate it by small amounts?


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#10 555aaa

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Posted 26 June 2020 - 10:12 PM

You can correct the error in azimuth by shimming one side of where the mount base connects to the top of the pier. Have you adjusted how the worm meshes on the dec drive? A further option is to fully replace the drive electronics.

#11 Michael Covington

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Posted 26 June 2020 - 10:43 PM

I think that fixing up the existing mount is the right way to go.  Besides the electronics involved in focusing, there's the sheer size of the telescope.  I think you would be looking for an observatory-class mount, not a CEM120, if you remounted it.  There must be lots of ways to improve the existing mechanism.



#12 jt_3232

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Posted 27 June 2020 - 06:50 PM

Guys I posted several pictures on this dropbox.

 

I believe we are going to attempt to fix these issues on the current mount in the meantime and choose not to defork it.

 

The OTA with the little fork arms does not weigh 67lbs. I am thinking somewhere near the 120lb mark. It was extremely heavy to put back on after we took it down.

 

I hope this gives a better idea about the situation. I think we are going to purchase the Buck's precision gears kit and replace the gears.

 

JT

 

Dropbox:

https://www.dropbox....UMhywMg_sa?dl=0

 

 

P.S. Can we put a Polemaster where a guide scope mounts on the scope, aim the scope at Polaris, and use that instead of drift alignment?


Edited by jt_3232, 27 June 2020 - 06:50 PM.


#13 555aaa

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Posted 27 June 2020 - 08:23 PM

You can clamp the polemaster to any rigid part of the fork. All it has to do is rotate with the polar axis. It doesn't have to be on the scope or precisely parallel to the ra axis. I use a woodworking clamp to hold it on
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#14 Christopher Erickson

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Posted 28 June 2020 - 08:21 PM

The LX200-16 OTA weighs 75 lbs and the upper fork assembly with OTA weighs 125 lbs. The entire scope with Meade's giant field tripod weighs 285 lbs. The RCX400-16 should be very close to that.

 

Getting 1 arcsecond RMS tracking from any Meade mount is very optimistic. Somewhere around 20-30 with PEC turned off would be typical. 5-10 with PEC turned on and everything carefully-optimized is more realistic. Under 5 would be incredible. This isn't an Astro-Physics mount, after all.

 

The CEM120 tripod and/or mount would not be capable of handling the RCX400-16. An Astro-Physics 1600GTO or 1100GTO or a used 1200GTO would be much more appropriate. 

 

The 16" Meade LX/RCX scopes are way different internally than their smaller LX/RCX brethren.  Be cautious with any advice/knowledge coming from the smaller models.

 

It is my understanding that Meade has abandoned the entire RCX product line. No repairs, no parts and very limited technical support.

 

The RCX400 electronics have always been problematic. There is a fellow that was selling an electronics repair package for the RCX scopes named Charlie Trump. I don't know if his kit is still available or if it will even work on the 16" model.

 

The biggest problem I have seen with the RCX models is the failure of the electronics controlling the three focus/collimation motors. I believe Charlie's kit was primarily to solve that problem.

 

Deforking a RCX is a bit of a big deal because of the collimation/focus motors in the OTA. Adding a motorized focuser to the RCX works. Collimation can be converted to a manual process where the shafts of the three collimation motors can be extended out the back of the scope, where they can be manually manipulated for collimation and focus preset. This is NOT a trivial project.

 

These scopes like to be balanced in both axes. When the clutches are released, the scope should stay put, wherever it is pointed. Or at least somewhat close to that.

 

A big problem with all of the Meade 16" scopes is the worm block assemblies. The mounting bolts become loose very easily. Loctite them in place. Use the non-permanent stuff. The worm block tension springs are too weak. Replace them. The worm block play limit set screws usually aren't set at all and allow the worm gear teeth to ride up and sometimes completely out of the worm wheel grooves. Set the limit screws so there is only a very tiny amount of play. Use non-permanent Loctite on the set screws so they don't drift.

 

Regreasing the worm drives while everything is apart is always a good idea. I use a two-part formula for worm drives A 3:1 blend of Lubriplate 105 and Nye Fluorocarbon Gel 868H. The 868H is rather expensive and hard to come by. I mix up batches of this worm grease for use in my day job and if you are interested in getting some, contact me off-list. 

 

Do a careful PEC training run after the worm blocks have been dealt with and the balance has been improved on both axes.

 

You will want to use off-axis or on-axis guiding with this scope to get decent pics. Piggyback scopes for guiding will only lead to tears. A focal reducer will help significantly with getting good images. The really-long focal length of these big compound scopes makes everything more challenging.

 

I hope this helps.


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#15 carolinaskies

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Posted 28 June 2020 - 09:06 PM

The LX200-16 OTA weighs 75 lbs and the upper fork assembly with OTA weighs 125 lbs. The entire scope with Meade's giant field tripod weighs 285 lbs. The RCX400-16 should be very close to that.

 

Getting 1 arcsecond RMS tracking from any Meade mount is very optimistic. Somewhere around 20-30 with PEC turned off would be typical. 5-10 with PEC turned on and everything carefully-optimized is more realistic. Under 5 would be incredible. This isn't an Astro-Physics mount, after all.

 

The CEM120 tripod and/or mount would not be capable of handling the RCX400-16. An Astro-Physics 1600GTO or 1100GTO or a used 1200GTO would be much more appropriate. 

 

The 16" Meade LX/RCX scopes are way different internally than their smaller LX/RCX brethren.  Be cautious with any advice/knowledge coming from the smaller models.

 

It is my understanding that Meade has abandoned the entire RCX product line. No repairs, no parts and very limited technical support.

 

The RCX400 electronics have always been problematic. There is a fellow that was selling an electronics repair package for the RCX scopes named Charlie Trump. I don't know if his kit is still available or if it will even work on the 16" model.

 

The biggest problem I have seen with the RCX models is the failure of the electronics controlling the three focus/collimation motors. I believe Charlie's kit was primarily to solve that problem.

 

Deforking a RCX is a bit of a big deal because of the collimation/focus motors in the OTA. Adding a motorized focuser to the RCX works. Collimation can be converted to a manual process where the shafts of the three collimation motors can be extended out the back of the scope, where they can be manually manipulated for collimation and focus preset. This is NOT a trivial project.

 

These scopes like to be balanced in both axes. When the clutches are released, the scope should stay put, wherever it is pointed. Or at least somewhat close to that.

 

A big problem with all of the Meade 16" scopes is the worm block assemblies. The mounting bolts become loose very easily. Loctite them in place. Use the non-permanent stuff. The worm block tension springs are too weak. Replace them. The worm block play limit set screws usually aren't set at all and allow the worm gear teeth to ride up and sometimes completely out of the worm wheel grooves. Set the limit screws so there is only a very tiny amount of play. Use non-permanent Loctite on the set screws so they don't drift.

 

Regreasing the worm drives while everything is apart is always a good idea. I use a two-part formula for worm drives A 3:1 blend of Lubriplate 105 and Nye Fluorocarbon Gel 868H. The 868H is rather expensive and hard to come by. I mix up batches of this worm grease for use in my day job and if you are interested in getting some, contact me off-list. 

 

Do a careful PEC training run after the worm blocks have been dealt with and the balance has been improved on both axes.

 

You will want to use off-axis or on-axis guiding with this scope to get decent pics. Piggyback scopes for guiding will only lead to tears. A focal reducer will help significantly with getting good images. The really-long focal length of these big compound scopes makes everything more challenging.

 

I hope this helps.

The RCX issues always were around controlling those three focus motors on the smaller RCX models and that plastic gear issue common to many scopes of that era. The OP issues didn't include any mention of focusing/colimation issues.  The general issues seem related to what we're more familiar with happening to the LX200 models in pointing/control accuracy. 

I think he could do well with a tune-up per your suggestions, and seeing the pictures he has shared the RA & DEC look very good other than needing the regreasing and upgrades as mentioned

I would conjecture this 16" has likely seen very little overall abusive usage by looks of those interior shots.  And a tune up is cheap by comparison of picking up a whole new mount especially if having to find if Charlie Trump still makes those upgrade boards!  



#16 bignerdguy

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Posted 10 July 2020 - 10:50 PM

The original RCX400-20" weighs around 150lbs so i know the 16" is not that far off.  It definitely isn't 67lbs like the newer units since they use newer materials in the current production models to save weight.  FYI, i know a guy who has the 20" here in the Dallas area and he uses an engine hoist and cargo straps to remove it and reattach it all by himself to his mount.  He has the MAX robotics mount or did last time i knew him, no telling what he has now.  Apparently he does something like attach the straps through the handles on the scope or some such, really i am not sure, but i have seen him in pictures with it on the ground with the hoist near by.  Believe it or not Meade GAVE it to him as he does a lot of their Beta testing and marketing sky shots, along with a few other people here in the USA. He said he is easily able to remove it and mount it with little effort.  Maybe something like that might help next time you have to remove yours from the pier?

 

With that said i am glad you didn't try to mount it to the GEM mount as it probably wouldn't have held and that would cause one EXPENSIVE accident.  frown.gif Hope you get everything working as that is one sweet scope!  Wish i could afford one of those and had a place to permanently mount it...



#17 Jeff J

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Posted 11 July 2020 - 09:42 AM

FYI, i know a guy who has the 20" here in the Dallas area and he uses an engine hoist and cargo straps to remove it and reattach it all by himself to his mount.

 

That RCX400-20" with the MaxMount is possibly - Jason Ware.

http://www.galaxyphoto.com/max.htm


Edited by Jeff J, 11 July 2020 - 09:42 AM.

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#18 jt_3232

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Posted 04 May 2021 - 12:57 PM

For those interested, Charlie Trump does indeed still make these kits. I contacted him by email and he would be able to make one for the 16" RCX400.

 

I noticed above that Mr. Jason Ware's RCX400 20" was attached to the MAX mount by a special cradle which was holding the scope. Is there anything like this for sale right now? The best thing I could find is this Software Bisque OTA ring set https://www.bisque.c...mounting-rings/. According to SB, the inside diameter of these rings is 17.54". I do not know what the RCX400 16" tube diameter is as I am 70 miles away from it.

 

JT



#19 jt_3232

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Posted 06 May 2021 - 08:06 PM

I found a guy who mounted his 16" RCX 400 using a single dovetail bar on the bottom. Craziness! I found a 16" and 20" RCX400 and Max Mount manual that states the 16" OTA weighs 140lbs. If you guys think it would work, I think there just 3 screws per end of the OTA to screw this dovetail into: https://www.admacces...-meade-16-otas/ .This only costs $170. I think the other option is to use these rings: http://www.parallaxi...html#ringprice2 which I believe the proper dimension would be the 20.7" rings. These cost $589. It might be worth trying the dovetail to buy an extra AP counterweight!

 

I'll keep you all updated on this project, it still is up in the air.

 

Jaxon



#20 bignerdguy

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Posted 06 May 2021 - 09:08 PM

For those interested, Charlie Trump does indeed still make these kits. I contacted him by email and he would be able to make one for the 16" RCX400.

 

I noticed above that Mr. Jason Ware's RCX400 20" was attached to the MAX mount by a special cradle which was holding the scope. Is there anything like this for sale right now? The best thing I could find is this Software Bisque OTA ring set https://www.bisque.c...mounting-rings/. According to SB, the inside diameter of these rings is 17.54". I do not know what the RCX400 16" tube diameter is as I am 70 miles away from it.

 

JT

Yeah, those wont work for the RCX since it isnt fully circular. it has flat sides.

 

 

I found a guy who mounted his 16" RCX 400 using a single dovetail bar on the bottom. Craziness! I found a 16" and 20" RCX400 and Max Mount manual that states the 16" OTA weighs 140lbs. If you guys think it would work, I think there just 3 screws per end of the OTA to screw this dovetail into: https://www.admacces...-meade-16-otas/ .This only costs $170. I think the other option is to use these rings: http://www.parallaxi...html#ringprice2 which I believe the proper dimension would be the 20.7" rings. These cost $589. It might be worth trying the dovetail to buy an extra AP counterweight!

 

I'll keep you all updated on this project, it still is up in the air.

 

Jaxon

A dove tail bar if sturdy enough might work.  Yeah Jason uses a custom mount for the RCX 20" but keep in mind his is a prototype unit that mead GAVE him.  Yup, he got it free from what i heard and all he needs to do is make a bunch or nice photos for their marketing department and participate in their development as a beta tester. #Jealous...




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