1308 replies to this topic

[nateman_doo]

a concentric laser is the most important part of the process.  I mailed my farpoint astro laser back to the factory and they sent it back collimated.  Verified in a V-block and lathe.  

[nateman_doo]

Does anyone know where to get a replacement dust cover for the 8" scope? 3d printed or otherwise?  or has an stl file? 

[wizzlebippi]

I decided to follow nateman's advice and take another look at my secondary since I adjusted it.  This turned out to be disappointing because I discovered that my Farpoint laser isn't as well collimated as I thought.  Rotating it in the clicklock makes it trace a circle about the same size as the donut center mark on the secondary.  After some messing around I adjusted my focuser alignment so that it's roughly tracing the outline of the donut and my secondary is reflecting the unsilvered donut's shadow centered on the laser's emitter through an entire rotation.  This led to more adjustment of the primary (without touching the secondary), and a better collimation.  I'm hesitant to work too much more on this without a good starting point, and I'm hoping Farpoint can finetune my laser.  

 

[slagrim]

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!

Open the link https://www.precisep...main/index.html. On the bottom of the page two drop down menus. Choose ZWO in both and click "Next". In the left drop down menu choose "ZWO OAG M48 (or any other you prefer) for focuser side. In the right drop down menu choose "ZWO ASI120mini camera" (this is small threads for HOTECH). In the center "Adapter Effective Length" choose " mm" radio-button and in the box type "14" or any other adapter heights (I have done 14mm adapter). Click "Build" button and on the next page you will see adapter drawing and animated image of it. The image does not look like what you want but drawing showing exactly what you going to order. Click "Add to Cart" and "View Cart" then follow to check out.

Hope it helps. At least when I got this adapter, I have repeatable results at multiple laser installations.

[slagrim]

Does anyone know where to get a replacement dust cover for the 8" scope? 3d printed or otherwise?  or has an stl file? 

One more cheep choice: https://www.amazon.c...10-catcorr&th=1

[DavesGalaxy]

Does anyone know where to get a replacement dust cover for the 8" scope? 3d printed or otherwise?  or has an stl file? 

The original cap that comes with the scope falls off too easily.  I purchased a "shower cap" like cover from AstroZap.  The nice thing about that one is that it is made of fabric and is breathable to let moisture out while keep dust out as well.  Slides easily over a dew shield as well.

[nateman_doo]

I decided to follow nateman's advice and take another look at my secondary since I adjusted it.  This turned out to be disappointing because I discovered that my Farpoint laser isn't as well collimated as I thought.  Rotating it in the clicklock makes it trace a circle about the same size as the donut center mark on the secondary.  After some messing around I adjusted my focuser alignment so that it's roughly tracing the outline of the donut and my secondary is reflecting the unsilvered donut's shadow centered on the laser's emitter through an entire rotation.  This led to more adjustment of the primary (without touching the secondary), and a better collimation.  I'm hesitant to work too much more on this without a good starting point, and I'm hoping Farpoint can finetune my laser.  

 

ASTAP_3-17-24.jpg

I emailed farpoint and they took it back and fixed it for free.  Made a world of difference.  It got me my best collimation.  

[nateman_doo]

Trying the cloth cover.  It really is such a fickle piece of plastic.  It always falls out.  Surprised no one 3d printed a new cover.  If i had a 3d printer I would probably try to make one.  Im afraid it rolled down the driveway into the street one night and I didn't notice.

[DavesGalaxy]

Trying the cloth cover.  It really is such a fickle piece of plastic.  It always falls out.  Surprised no one 3d printed a new cover.  If i had a 3d printer I would probably try to make one.  Im afraid it rolled down the driveway into the street one night and I didn't notice.

I tried even using extra felt on my cover that came with the scope but it looks like after the scope front metal ring gets cold, it expands while the plastic lid doesn't so it is easy to fall off when I bring the scope inside.  So now I just use the fabric shower cap from AstroZap and now I can leave the dew shield on as well and not worry about any of my dog's hair getting on my primary mirror LOL!

 

https://astrozap.com...t=8240244293676

 

FYI not my scope, image from AstroZap's Website :-)

Edited by DavesGalaxy, 18 March 2024 - 08:34 AM.

[lambermo]

...
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.

Hi, just FYI the V-block method to collimate a laser unit does not work with the Hotech SCA units.
The reason is simple: the V-block method is designed for laser units that are made out of 1 piece of metal, the Hotech SCA is made out of 3 pieces that screw together and two of these pieces are not intended to be aligned with the laser in the first piece (they're just to hold the battery).

This is described in detail on this Hotech page : https://www.hotechus...tegory-s/58.htm
 
If you want to test the Hotech SCA collimation then use something like a big ball bearing setup like here https://stargazerslo...-tilt-test-jig/ that holds just the laser attachment piece.

[nateman_doo]

And thats one reason I will always recommend the farpoint astro for this process.  Hotechs 1.25" to 2" adapter already introduce tolerances.  Farpoint is a single machined part that has 1.25" in the front, and 2" in the back.  No need for adapters, and you can check it in a V-block.  Not saying you cant get good results with the hotech (I made my own 1.25 to 2" adapter for mine) but I think the farpoint can introduce less error.  I also found their laser had a finer point.  but that just could be mine.

 

As for measuring tilt with that reflected laser, Its possible for that to work, but the guy is using a piece of wood, and ... muffler clamps?  I think its a good proof of concept, but not something you should do at home.  The precision one would need would have to be machined, vs some gadget you made at home.  If you dont own any machine tools like a granite surface plate etc I think you may do more harm then good.  

Edited by nateman_doo, 18 March 2024 - 01:08 PM.

[PFitzhorn]

But the Farpoint Astro laser, like the Howie Glatter, must be installed in an 1.25" or 2" compression ring, resulting in some error there. Or am I missing something with the Farpoint Astro? The Hotech has M48 screw threads on their 2" adapter, and I've taken some advice and ordered an adapter with M48 threads on one side to screw onto my focuser, and threads on the other side to screw the Hotech 1.25" adapter into. No more compression rings to worry about. The wooden "v-block" handmade and shown in the video from this Hotech page :https://www.hotechus...tegory-s/58.htm doesn't fill me with confidence. I'm talking about a machinist's steel v-block locked onto a granite surface plate, like the photo shown below. Rotating the 1.25" adapter (with knurled ring fully tightened, shows the same ~5mm error over 5 meters that the battery holder had. When I get the screw adapter I'll fit that into the v-block and rotate, but I'm not expecting significant difference in error.

Edited by PFitzhorn, 18 March 2024 - 02:12 PM.

[nateman_doo]

Farpoint is a tiered adapter.  

https://farpointastr...pg?v=1625071524

 

The front end is turned to an OD of 1.25, and then further down is turned to 2".  Goes right in your focuser.

[nateman_doo]

Their cheshire is the same way.  2" and goes right into your focuser.  its just a center drilled hole on a reflective surface.  no weird crosshairs.  Sticking that in, and getting the same amount of the spider vane holders in the corners of the cheshire were the magic bullet for me. (as well as having them re-adjust the laser after a few drops)

 

I swear by them. 

https://farpointastr...t-carrying-case

[slagrim]

Hi, just FYI the V-block method to collimate a laser unit does not work with the Hotech SCA units.
The reason is simple: the V-block method is designed for laser units that are made out of 1 piece of metal, the Hotech SCA is made out of 3 pieces that screw together and two of these pieces are not intended to be aligned with the laser in the first piece (they're just to hold the battery).

This is described in detail on this Hotech page : https://www.hotechus...tegory-s/58.htm
 
If you want to test the Hotech SCA collimation then use something like a big ball bearing setup like here https://stargazerslo...-tilt-test-jig/ that holds just the laser attachment piece.

I have Starlight Instruments SI-LC2-635 Single Red Beam 2" Laser Collimator - one of the best on the market. I have used it on my 8" RC and collimation process was quite tricky but with good result. After I got and installed nateman_doo collimation adapter I could easily point laser beam on secondary mirror center but I could not see reflected beam location. So, I got Hotech laser and found that with this laser I could not have collimation repeatability because of all rubber rings and movable part of the laser. Focuser compression can contribute in shifting laser body too. I removed 2" part and found threads inside 1.25" part of the laser matching 1.25" filter housing threads. First, I removed rubber rings and placed this side (I mean just 1.25" side of the laser) on metal V-block made for tool makers. Carefully rotating the Hotech on the block I found the laser was not perfectly collimated. After I got custom made laser-to-focuser adapter I unscrewed compression part of the RC focuser and installed TS-Optics Adapter from M63x1 to M48x0.75. Now, I could screw imaging train and Hotech laser directly on the focuser and not worry about wobbling assembled parts with different compression forces for different shooting or collimation sessions. After I collimated Hotech, as I described in the post #1023, I screwed it on 8" RC focuser to check if the red dot is on the center of secondary mirror as I previously set it with Starlight laser and it was right on. Even more, to my surprise, laser beam reflected right into the hole of the Hotech laser (I can see, where it lands now) and it made collimation of secondary mirror (with all custom parts) a piece of cake. What I am trying to say is any methods are acceptable if it giving you satisfying results and you feel comfortable with it.  
 

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Edited by slagrim, 18 March 2024 - 11:41 PM.

[DevonRob]

Sadly UK suppliers seem to be saying Farpoint aren't shipping any more (although US site still seems OK). I just lucked into a 2" Howie Glatter which hopefully will give me a similar option. There is also a Parallelizer HG offer too which I'm gonna give a test with my Baader 1.25" laser. The Baader laser is actually quite decent, but tricky to center perfectly. TBH, even if the Parallelizer works I may keep the HG laser too since they so rarely come up in stock for sale in UK.

Edited by DevonRob, 19 March 2024 - 10:25 AM.

[nateman_doo]

I could not have collimation repeatability because of all rubber rings and movable part of the laser. Focuser compression can contribute in shifting laser body too. 
 

This is why I stopped using the hotech.  I was not a fan of the moving parts, so I did as you did, but turned my own adapter on the lathe, but still I found the beam not as tight as the farpoint.  It could very well be that I bought it second hand?

[nateman_doo]

A buddy of mine came through.  

 

 

fits like a glove.  no worries about collimation knobs or anything...  and it WONT FALL OFF.  It also probably blocks way more light then the loose fitting factory one since it slides over the entire front end like the dust covers for refractors (havent tested it yet for that though).  If anyone is interested in replacing theirs, shoot me a PM and I will give you his name.  He is a fellow forum member. 

Edited by nateman_doo, 20 March 2024 - 07:40 AM.

[PeteM]

That is a great idea. I just got a large 3D printer so I could make things for up to a 14" telescopes. But that factory 8" RC cap is a pain and that will be my next print project.

As for the lasers. I have a Howie Glatter and it is out of collimation too. Sadly Howie isn't around anymore to recollimate it and Starlight Instruments that is making the lasers now have never replied to my multiple emails to send it in. Guess I will need to do it myself.

[DevonRob]

That is a great idea. I just got a large 3D printer so I could make things for up to a 14" telescopes. But that factory 8" RC cap is a pain and that will be my next print project.

As for the lasers. I have a Howie Glatter and it is out of collimation too. Sadly Howie isn't around anymore to recollimate it and Starlight Instruments that is making the lasers now have never replied to my multiple emails to send it in. Guess I will need to do it myself.

I'd be interested to know what process you use - just in case the HG unit I have on the way is either out of collimation, or I ever mess that up over time myself.

[lambermo]

Here's a followup of my question from 3 months ago

I assume its the same M117x1.0 as the 10"?

After a test with a paper version of the ring that nateman_doo sent me as PDF we found that the 12" truss model is quite different from the tube 10" model.
I did not want to ship my backplate to the US so instead looked for a local astro workshop that could help me build a collimation ring and found that at Astro Systems Holland.
This project was great fun ! Here's the TLDR version :
 


I'm very happy with the new collimation adapter. I have not yet used it to collimate anything but I'll let the new silicone glue harden properly first.
Here's more photos of the project: https://lambermont.d...tro/rc/surgery/ with many thanks to Herman ten Haaf of A.S.H.

And of course also to nateman_doo here for starting this entire project and helping (via private msg).

 

-- Hans

[nateman_doo]

That was a wild ride with all those photos!  That this is a beast!  Love it! 

[chrisjackson184]

Hi,

 

I have a RC 8 and am very interested in getting hold of the parts to upgrade. How do I order one?

 

Thanks!

[nateman_doo]

Step into my office.

[nateman_doo]

Finally after 2007 miles and I have arrived:

 

 

Eventually when the clouds disappear I will see how well the collimation held on the journey.