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Finally made an R/C Collimation adapter

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#1001 Mert

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Posted 19 February 2024 - 03:41 AM

@James: do you have your camera fixed on the scope or like me mount everything every time you setup??

#1002 nateman_doo

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Posted 19 February 2024 - 10:22 AM

I have a semi portable pier, that I NEVER move. Its an EQ6 that sits in my driveway, all steel, welded, the works.  The RC lives there when it isnt on the road.  If I am at a place where I will be there a few days like a star party or a long weekend observing I will drag the RC, so it does move a few times a year, but it mostly stays.  The weather hardly cooperates around here.  It will endure 1900 mile drive from NJ to Texas for the Eclipse.  For my fellow Europeans, that is like driving from the Western most part of Portugal, to the Eastern most part of Poland (as the crow flies). and it will be sitting in the back of my pickup for the drive.  It will be a great test.  

e980NEal.png

 

 

 

 

 

So here is where I was last night.  I tapped out before zenith.

 

B9JXhPs.png

 

7KfCuZM.png

 

8RH3lru.png


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#1003 Mert

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Posted 19 February 2024 - 10:35 AM

That's absolutely amazing, extremely well adjusted!

#1004 nateman_doo

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Posted 19 February 2024 - 11:31 AM

I have trouble wrapping my head around it as well.  



#1005 wizzlebippi

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Posted 25 February 2024 - 06:16 PM

I finally installed my collimation adapter on my TS Optics 8" RC.  Not hard, or time consuming.  Probably spent more time driving and looking for a transfer punch set than actually working on this.  

 

8in RC with Collimation Adapter.jpg


Edited by wizzlebippi, 25 February 2024 - 06:17 PM.

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#1006 sparkyht

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Posted 03 March 2024 - 02:47 PM

Got the 10" kit on Friday, the work on the decoupler is beautiful. I installed it yesterday, and then used a Glatter laser to center the focuser and secondary within a few minutes. It was clear enough to start collimating the primary doing star tests. I got close, but nudging the primary takes a lot of time because of having to move the on-axis start back to center every time a screw is turned. This is when I wish I had a keypad for my Mach 2! 

Great work and thanks for providing such a game-changing product for us RC users!

Here's a pic of the beast!

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#1007 PFitzhorn

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Posted 13 March 2024 - 02:17 PM

Although I received the 10" kit 6 or so weeks ago, this is the first I've had a chance to start collimating it due to  a last-minute trip that came up. Just got back and spent the morning working on the scope. As others have commented, the decoupling ring is a serious piece of mechanical science and artwork. I couldn't be more pleased. I've attached a photo showing the scope on a table with the decoupler attached and a red plastic rapid-prototyped cap on it. I'll be doing preliminary collimation on the table here. First step - calculate backfocus numbers that include the decoupler:

 

* 10" GSO RC with 250mm total BF to focus

* 10" nateman_doo decoupler (25mm) -- replaced GSO collimation ring (18mm)

* Planetary imaging train with ZWO ASI662MC (12.5mm); adapter (7.5mm); filter drawer (18mm); ZWO OAG (16mm)

* DSO imaging train with ZWO ASI 2600MC (12.5); ZWO EFW (20mm); ZWO OAG-L (22.5mm)

* Blue Fireball rotator (13.5mm)

* Feather Touch FTF3015 focuser (169.5mm + drawtube focus length F)

* M100x1 50mm spacer ring (50mm)

* nateman_doo 10" decoupler (25mm) - replaced GSO collimation ring (18mm)

 

Since last I collimated before getting the decoupler, I replaced the Feather Touch 2" compression ring with an M48x0.75 ring because the compression ring seemed to generate a bit of inconsistency from collimation attempt to collimation attempt. Fortunately, I found both my Takahashi collimation telescope and Hotech laser chesire have those screw threads.  So now I'll collimate by using the Hotech first (screwed onto the focuser) to align focuser with center circle on the RC secondary. Then I'll adjust secondary to return the laser dot to the center of the Hotech. Then I'll screw on the Takahashi for a check and alignment of the primary.

 

Anyway, did all the BF calculations and all looks well. For those interested, I've attached my 10" RC backfocus worksheet calculating expected focuser drawtube focus length, and necessary spacing with my 2x Barlow and 0.67x telecompressor. (Forgot to update with today's date - done now.) With the DSO imaging train I should have a drawtube focus length of 12mm, and with planetary a length of 13mm. I would prefer shorter lengths for stiffness but I'm happy about those numbers. I can also still use both my 2x Barlow and 0.67x CCDT67 by adding a 50mm spacer / removing the 50mm spacer respectively. So - the upshot of all this is that preliminary back focus calculations show that it will all work appropriately with the 7mm (25mm-18mm) added back focus of the nateman_doo decoupling ring.

Attached Thumbnails

  • rc.jpg
  • rc6.jpg

Edited by PFitzhorn, 13 March 2024 - 05:31 PM.

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#1008 PFitzhorn

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Posted 13 March 2024 - 02:26 PM

Here the 10" RC is with red nateman_doo decoupler, 50mm ring, Feather Touch focuser with M48 threaded end, Blue Fireball rotator, and Hotech laser Cheshire screwed on to the end. Laser is on and initial result is surprisingly good. Now to adjust the decoupler so that the laser dot is in the center of the secondary. Then adjust the secondary to return the dot to the center of the Hotech Cheshire.

 

When I last did this (without decoupler and with 2" compression ring on the focuser) touching the cheshire moved the laser dot. Now with the M48 threaded attachment, touching the Cheshire doesn't  change anything. That's an improvement right there.

 

The red decoupler ring sure looks nice!

Attached Thumbnails

  • rc1.jpg

Edited by PFitzhorn, 13 March 2024 - 02:40 PM.

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#1009 PFitzhorn

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Posted 13 March 2024 - 02:41 PM

Adjusted all 3 sets of 2 screws on the decoupler ring so that it sits flush and screws are all tight. Then backed out both sets exactly one turn and retightened to give me a bit of space to make decoupler adjustments to center the Hotech laser dot exactly in the center ring of the secondary.

 

Step 1:  Adjust decoupler to center Cheshire laser dot in exact center of secondary center ring.  Went pretty quickly after I took an embarrassingly long time to figure out which adjusting screw made what change on the location of the laser dot. All decoupler screws retightened.  I then unscrewed the Cheshire off the focuser, screwed it back on, and rechecked. Same result. Another proof point showing that the Feather Touch 2" compression ring results in a lack of precision, even with the screw collar on the Hotech Cheshire.

 

Step 2: Adjust the secondary to put laser dot in center of Cheshire. That only took a few minutes.

 

So far I have excellent, repeatable results on both focuser and secondary without a ton of work and iteration. I think I'll take it all apart and do it again to see what happens. OK, removed 50mm ring, focuser and Cheshire and reinstalled. BAM. Still right on. Laser dot in center of secondary, and laser dot returning to center of Cheshire. No muss - no fuss.

 

I couldn't get a reasonable photo of the laser dot in the center of the secondary, but here's a photo of the result on the Cheshire. The photo is washed out, and isn't taken straight down to the dot rings, but I could tell tiny secondary adjustments moved the dot off the center of the Cheshire. Pretty good in my opinion.

 

Next - remove the Cheshire and replace with the Takahashi. I'll need to remove the ring baffles from inside the RC in order to set the primary so that the secondary's spider vanes all line up. Then, since it's on the table and I'm having fun, I'll remove it all and start over to see if it's still repeatable.

Attached Thumbnails

  • rc2.jpg

Edited by PFitzhorn, 13 March 2024 - 03:38 PM.

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#1010 PFitzhorn

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Posted 13 March 2024 - 03:14 PM

OK - here's a photo of the 10" RC with a Takahashi collimating telescope attached. You'll notice it has the optional 2" end ring to use with 2" compression rings, but (thankfully), the end of the 2" end ring is machined with M48x0.75 threads so screws directly onto the M48 rotator, screwed directly onto the M48 threads on the end cap of the focuser.  Initial sighting down the barrel confirms that the Takahashi center dot is in the center of the secondary center ring - so that's good!

 

The second photo shows a crap iPhone photo down the barrel of the Takahashi. The next step will be to align all four secondary spiker vanes from outside in, using he primary mirror adjustment screws. Notice that I've unscrewed the interior baffle tube and it's laying in the bottom of the tube (top of picture). The collimation is pretty good right now (a serious surprise) but I think I can do better. So time to fiddle with the primary.

Attached Thumbnails

  • rc3.jpg
  • rc4.jpg

Edited by PFitzhorn, 13 March 2024 - 11:33 PM.

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#1011 PFitzhorn

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Posted 13 March 2024 - 03:56 PM

Here's my setup for primary adustment. The Takahashi is screwed into the focuser imaging train, and the scope is pointed at an old 8mm video projector screen illuminated by a flashlight. I back out all three small adjustment screws, then iterate on the larger primary adjustment screws until the spider vanes are aligned. Then (assuming I recall in time), I'll screw the baffle tubes back in place and call it good. Well, actually, call it better than any of the collimation attempts I've done in the past!

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  • rc7.jpg

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#1012 PFitzhorn

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Posted 13 March 2024 - 04:10 PM

So here's a crap photo of the adjusted primary, and you can (hopefully) see the two sets of four spider vanes aligned inside and outside of the black ring. I've tightened the small screws so that the primary is now fully held in place. Table top collimation is now done. However, since it took longer to photograph and post here, I think I'll take it apart and do it all over again, see if I get repeatability. I have my fingers crossed. Weather looks terrible for awhile here so don't know when I'll have it back on its mount and pier outside.

 

If you have a GSO 10" RC, I wouldn't hesitate to contact nateman_doo to get and install his collimation decoupler.  Makes desktop collimation a breeze - especially with a Takahashi collimation scope and a 2" laser Cheshire. Three simple steps on the desktop.

 

For those who took the time to read these - thanks! If you see any errors or omissions, or ways to make this better, please let me know. I'm always open to learning. Doing a bang-on collimation is more important to me than ego!!! 

Attached Thumbnails

  • rc8.jpg

Edited by PFitzhorn, 13 March 2024 - 11:37 PM.

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#1013 Sonarlab

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Posted 14 March 2024 - 05:06 AM

Hello everyone,

Hello nateman_doo,

 

Nateman your work and the design is amazing !

I came across your post because I was looking for guiding improvement. I made the mistake of putting a guidescope and constantly having to throw away 60% of my subs. So I am finally get an OAG. Also as I need to clean the primary, so it would be stupid of me not to get one of your kit.

 

However, I tried to send you a message but can't because I didn't log in since a long time as the forum admin tells me. Could you send me a message so I can also step in your office :)

 

Great work !

 

thank you



#1014 Sonarlab

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Posted 14 March 2024 - 06:02 AM

Hello, again

 

Nateman, sorry can't even answer to your message.

 

I wrote three e-mails to this link 'Contact the community administrator' to tell them about this situation.. If one of them read this can they do something please.

 

Sorry Nateman



#1015 DavesGalaxy

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Posted 15 March 2024 - 07:52 AM

Hi All,

 

I finally wrapped up my M81 project and will posting more details in a forum post on CN and elsewhere.  Thanks again James for you ingenuity as without your adapter this project would have been a lot more difficult.

 

https://www.astrobin.com/q0fzhe/

 

gallery_406376_22923_9148698.png


Edited by DavesGalaxy, 15 March 2024 - 08:04 AM.

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#1016 nateman_doo

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Posted 15 March 2024 - 11:48 AM

 As others have commented, the decoupling ring is a serious piece of mechanical science and artwork. I couldn't be more pleased. 

 

I appreciate the kind words!   



#1017 nateman_doo

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Posted 15 March 2024 - 11:53 AM

Hi All,

 

I finally wrapped up my M81 project and will posting more details in a forum post on CN and elsewhere.  Thanks again James for you ingenuity as without your adapter this project would have been a lot more difficult.

 

https://www.astrobin.com/q0fzhe/

 

gallery_406376_22923_9148698.png

shocked.gif   That looks wild!  it has such depth!  


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#1018 BBryce

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Posted 15 March 2024 - 12:13 PM

Another one from Canada, for my AT8RC.

 

Beautiful piece of craftmanship, thank you James for the service, it defintely worth it, the RC8 just got value  !!

The red anodized parts fit so well with my optic train !

 

Easy peasy to install, way more robust than the former primary mirror retaining tiny screws system. Collimation is easy, steady and spot on. I use a cheshire or a TS TSRCKOLLI collimator with a dslr in front of it, baffle unscrewed, ready in 5 minutes tops.

 

I defintely recommend anyone with a GSO "like" RC scope to upgrade with this terrific decoupler, probably the last accessory you will ever need for this scope, get rid of anything else (tilt adapter, laser....etc).

 

Brice

 

decoupler
Album: AT8RC
2 images
0 comments

 
 
 
 

Attached Thumbnails

  • decoupler.jpg

Edited by BBryce, 15 March 2024 - 12:18 PM.

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#1019 nateman_doo

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Posted 15 March 2024 - 12:29 PM

Now that is just lovely!


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#1020 PFitzhorn

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Posted 15 March 2024 - 01:07 PM

And here's the 10"RC with nateman_doo decoupler with the entire DSO imaging train ready to go back on the mount and pier when the weather cooperates. I calculated all of the back focus contributions of each of the elements of the imaging train in post # 1007 above if anyone is interested. It's not light - from the OAG back to the camera is 3.5 kg, so there's a lot of weight hanging on the decoupler.

Attached Thumbnails

  • rc10.jpg

Edited by PFitzhorn, 15 March 2024 - 01:10 PM.

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#1021 wizzlebippi

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Posted 15 March 2024 - 07:12 PM

Major progress.  

 

My rig is more or less hardware complete.  I'm really liking the ~50lb weight which allows me to pickup the entire rig and carry it to my backyard.  The Electric Blue collimation adapter is pretty close to Pegasus Astro blue, though with just a tinge of green.  Could be brushed vs smooth aluminum. 

8in RC Mounted.jpg

 

I do have the TSRCRED 0.8x M68 reducer/flattener burried in the focuser, which is why I have an M68 light path to the filter wheel.  There is some light falloff, but no vignetting on an APS-C sensor (Player One Poseidon-M).  My pixel scale is just under 0.6"/px. 

 

I did a rough collimation with my Farpoint Astro laser, aligning the focuser with the secondary mirror first.  Then under the stars I centered a bright star and tweaked the primary and made a small tweak to the secondary.  It was getting late, and I should have tried getting my mini PC more setup before going outside in the cold and dark, but I was able to make significant progress in very little time.  

ASTAP_3-10-24.jpg

 

It's not perfect, but compared to my experience with a 6" RC two years ago, it's difficult to describe how much easier collimation is.  I suspect that most of my remaining tilt is at the camera since the light cone appears to be well centered on the sensor.  


Edited by wizzlebippi, 15 March 2024 - 07:13 PM.


#1022 nateman_doo

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Posted 15 March 2024 - 09:36 PM

Awesome!  anodizing is all about the texture.  A matte finish will have a completely different look over a machined/shiny surface. If you look at the bottom of your adapter it looks vastly different as the bottom is lapped with a very rough finish.

 

Glad its working out way better than before.  If I can make one suggestion, when you use the concentric laser to align the focuser with the secondary... dont ever mess with it.  No matter how tempted you are, you verified with a beam of light that these 2 items are perfectly aligned with the other.  All you have to do is mess with the primary.  You have to get it to play nice with the other 2.  Stand your ground.  Resist the temptation to move them.  


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#1023 slagrim

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Posted 17 March 2024 - 12:09 AM

Remark on the post #1009

"Step 1:  Adjust decoupler to center Cheshire laser dot in exact center of secondary center ring.  Went pretty quickly after I took an embarrassingly long time to figure out which adjusting screw made what change on the location of the laser dot. All decoupler screws retightened.  I then unscrewed the Cheshire off the focuser, screwed it back on, and rechecked. Same result. Another proof point showing that the Feather Touch 2" compression ring results in a lack of precision, even with the screw collar on the Hotech Cheshire."

 

Hi PFitzhorn,

 I did the same secondary mirror collimation with the same HOTECH laser collimator but... I removed biggest part (where 48mm threads are). 1.25" part of laser body threaded inside with 28.5mm which is size of 1.25" filter. I have ordered custom adapter from https://www.precisep...main/index.html. It cost ~$120+shipping.

Adapter 1.JPG Adapter 2.JPG

Now, the laser can be screwed on the focuser eliminating any wobble on outside rubber rings.

IMG_0938.JPEG

I placed red arrow to point on the cone shaped nut, which I could unscrew with hand. Unscrew and slide the nut off and you will see three small set screws. Use V shaped block (rotate laser on it) to check laser collimation. I did it in my garage on table-top small lathe projecting red dot on opposite wall and found the laser dot was making a circle instead of to be the dot. Stop the dot on top of the circle position, turn upper set screw in (very small angle) and turn opposite screws ~half angle out. Do it until the dot has no visible movement.  Do not over-tighten screws - laser dot will be de focused. Turn cone nut back on laser body and your HOTECH laser will be near perfect tool for secondary mirror collimation. It sounds quite complicated procedure, but it is not. I just wanted to share my experience on secondary mirror collimation.   


Edited by slagrim, 17 March 2024 - 12:13 AM.

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#1024 PFitzhorn

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Posted 17 March 2024 - 09:10 AM

What a great idea! Thank you for sharing. I will start to implement your idea for my own collimating. I have a granite surface plate and v-block so I think I'll check alignment of the Hotech today using your instructions.

 

Just went to the website - do you recall what values you entered for the adapter? I figure "generic M48x.75" for the input threads, but I don't find an output thread for 1.25" filters. What did you use there? Also, about 25mm in length do you think?

 

Thanks!


Edited by PFitzhorn, 17 March 2024 - 09:16 AM.

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#1025 PFitzhorn

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Posted 17 March 2024 - 11:29 AM

Checked the alignment of my Hotech laser dot per your instructions. Over a 5m distance, the dot drew an ellipse with major diameter about 30mm, so good to about 0.6%. That means over the 685mm round trip from Hotech to secondary mirror on the RC, back to Hotech, it could be off as much as 4mm. Removed the cone ring, put it back on v-block, then rotated till each adjustment screw was straight up, tightened or loosened the screw to draw the dot to center, then went to next... until all three screws were tight and barely drawing a circle, maybe about 4mm on major diameter so off by a max of 0.0008%. Now on telescope over 685mm it will be off no more than 0.5mm - that's within the dot radius. Cannot get any better accuracy because the three adjusting screws move the dot about that just when touched - so good enough!

 

Again - thanks for the tip.




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