Jump to content
  • Join the online East Midlands astronomy club today!

    With active forums, two dark sites and a knowledgeable membership, East Midlands Stargazers has something for everyone.

Out of collimation Hotech Laser Collimator.


BAZ
 Share

Recommended Posts

I found out recently that my Hotech, which I trusted go be accurate as they are factory collimated, was way out of true. This has been sending the collimation of my Dob right out and I could never figure out what I had done wrong. I took it along to Ibbo's, who kindly offered to help me try and sort it out and it was then we discovered it was out.

I since then emailed Hotech andI have had a reply back off a chap called David, who advised me how to re-collimate it. So twenty minutes down the shed, the Hotech is accurate again and the cat is totally wired by the laser shining down the garden.

If anyone thinks they have a Hotech out of true, stick it in the focuser and leave it just tight enough to hold it, but leaving it free enough to rotate. Or  if the focuser is able to rotate, use that to keep it centred. It should remain in exactly the same spot, if it doesn't then it might need collimating. If it is out, then you can remove the bevelled cover between the battery tube and the viewing window tube. Behind this are three collimation screws. These can be adjusted to bring it back in. Here's what David says about it.

 

You can collimate the collimator in the focuser with a 0.005" hex key yourself to shorten the shipping time.  To access the alignment setscrews, you back out the cover between the target face plate tube and the battery tube.  Just unthread the cover with a jar-opener or a rubber grip.

 

Compress the SCA mechanism until the collimator has a snug fit without a lot of movement and yet you can slightly rotate the collimator in the focuser (with pressure registration on the opening).  You will do a quick rotation to get some idea of the center of the laser spot rotation (does not need to be center of the doughnut on the primary).

 

Adjust the corresponding setscrews to move the laser dot to the center of the rotation.  Do not over crank the setscrews which may damage the laser circuit.  Use the same adjustment technique on the secondary where you drive on down and let other two up.

 

If you need help, let me know. I am not sure about the five "thou" allen key though. But it is imperial.

Link to comment
Share on other sites

0.005" is 0.127mm. About the thickness of a hair. :)

 

I think you mean a 0.05" which is 1.27mm? 0.05" is a standard size for a hex key.

 

You must have got a friday afternoon model. I'm sure you've not been throwing it about. :)

Edited by Tweedledee
Link to comment
Share on other sites

I collimate them using a lathe. 

Put it in the chuck so the laser shines through the headstock tube onto the workshop wall. After a few feet of distance even the slightest misaligned is glaringly obvious. 

  • Like 3
Link to comment
Share on other sites

6 hours ago, Graham said:

I collimate them using a lathe. 

Put it in the chuck so the laser shines through the headstock tube onto the workshop wall. After a few feet of distance even the slightest misaligned is glaringly obvious. 

 

So did we, but had topoke the HDP out first :D

 

Edited by Ibbo
  • Like 2
Link to comment
Share on other sites

Yep lathe is the best way but not everyone has one, the el cheapo way is to lay it o table or desk with a known flat surface, turn it on pointing at a wall or sheet of paper, roll it sideways and if the beam flat lines its OK, if it describes a sine wave its out

  • Like 2
Link to comment
Share on other sites

16 hours ago, philjay said:

Yep lathe is the best way but not everyone has one, the el cheapo way is to lay it o table or desk with a known flat surface, turn it on pointing at a wall or sheet of paper, roll it sideways and if the beam flat lines its OK, if it describes a sine wave its out

 

Just love your Les Dawson quote! Ace! :D

Link to comment
Share on other sites

Well, since I am not likely to get a lathe anytime soon, it's time to have a think about the next best way round the problem of keeping the SCA (Self Centering Adapter) concentric and free to rotate. So with a good bit of mooching about down the shed I reckon I have got it licked. I have built an device to allow the whole assembly to rotate and remain centered while being able to easily adjust the Hotech.

So here we have a 5mm thick bit of angle iron, to this is bolted two further angle iron uprights to which identical bearings are mounted. I used a bit of 10mm studding and since it seemed a waste to cut it down, I have left it full length. Then all I did was machine out the internal seam of the pipe to make sure it stays correctly centered. Here's the result and it works well, very easy to rotate and it took minutes to get the Hotech bang on. I used an old target which is ideal to bring the beam to centre. To collimate another Hotech, I would centre the target with mine and then adjust the other one to it.

I will try it over a greater distance next time, this will make it even more accurate. Here's some pics.

 

20161022_145931_zpsvyahcrr8.jpg

 

20161022_145939_zpsa1tjghwq.jpg

 

20161022_145950_zpsmwnrpwf5.jpg

 

20161022_145939_zpsa1tjghwq.jpg

 

20161022_150021_zpshdvi5m20.jpg

 

20161022_150101_zpsbswxhppw.jpg

Link to comment
Share on other sites

Brilliant idea. You could sell some of those. :2thumbsup:

 

When the internal seam was machined out, did the inner diameter of your pipe just happen to be a perfect fit for the SCA? Or did you have to machine it on a lathe the make it fit?

Link to comment
Share on other sites

Not my rifle, it was a works day out shooting. Not bad, 25 yards open sights. I got 100% with the pistol on tin cans and pipes of different diameters. It is something I could get hooked on again, but I don't think so at the moment.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.