This is a brief self-service howto for the Hotech ACT.
The HOTECH Advanced CT Laser Collimator uses 4 parallel laser beams to help align a Schmidt Cassegrain type telescope’s optics (CT, SCT, SN Mak, RC).
Its product page is at


  1. Test the collimation of the Hotech ACT
  2. Adjust a laser to collimate the Hotech ACT
  3. Repair a loose laser unit on the Hotech ACT
  4. Further tune the Hotech ACT at 16 meters using a mirror

1. Test the collimation of the Hotech ACT

Here's a simple method to test the collimation of the Hotech ACT unit itself.

Make a plain paper photocopy of the front of the unit, or mark the exact positions of the center laser and the 3 outer lasers on a piece of paper if you don't have a copier. Place the photocopy up at several meters distance. I used 8 meters which works well for me. (I increased this to 16 meters lateron in ch.4) Project the center laser with the crosshairs and the 3 outer lasers and align the center laser and its crosshairs as good as possible.

The 3 outer laser dots should now perfectly align with those of the photocopy. If they do then congrats your unit is collimated well and you can use it to collimate a telescope. There's no need to continue reading this page.

If they do not then you may want to align them. Like in this projection the lower right laser is clearly quite off its target.

2. Adjust a laser to collimate the Hotech ACT

The caps on the back of the 3 laser units unscrew just like the one of the battery unit. You have to cut through their safety stickers though which may void your warranty so check with Hotech if this is a problem for you.

The laser unit is in the aluminium colored cylinder. It is held in place at its back with 3 grub screws in the red colored cylinder. These grub screws can be adjusted with a hex key (I used 1.25 mm) like this:

After adjustment mine looked like this :

If you're content with this result then you're done with the alignment.

3. Repair a loose laser unit on the Hotech ACT

I wanted to align the lower left laser as well, it's off by only a tiny bit. When I started the collimation of this unit I saw that the laser dot moved several centimeters on the target when I just inserted the hex key in one of the grub screws. The red colored aluminium cylinder was loose. After a mail to David from Hotech I received the instructions on how to fix this; unscrew the two silver set screws on the back of the laser collimator at 9 and 3 O'clock position. This will release the front target panel and you will find the three laser silver caps at 12, 8, and 4 O'clock position. The front of the laser with the silver cap looks like this :

The red and black wires pass from the PCB board to the back end of the laser unit through the holes with which the silver cap is screwed onto the black safety cylinder at the back end of the unit.

Be very careful with these wires. They break easily at the solder points, both on the PCB side as well as on the laser unit backend side.

I think the easiest way to tighten the silver cap/black safety cylinder combination is to hold the silver cap in place with a tool as you do not want to adjust the place of the wiring while screwing the black safety cylinder at the back side tight. This way you do not have to disassemble the whole unit.

This is not what I did as I wanted to see how the entire thing was held together. Totally unnecessary of course but I'm curious and already got this far in. So I disassembled a whole unit. First desolder the wires from the PCB, and get them to the other side. Then use a tool to unscrew the unit.

The red cylinder holds the laser units with two nylon rings at the front that allow for some tilt adjustment at the back with the grub screws. Nice system.

Next I put it all back together and as you can see the laser unit still works. At this point both wires broke off at the laser unit side. But they're easy to solder back in place if you have a soldering iron with a fine tip. After assembly the wires were better aligned for the other solder point so I happily made use of them. Great PCB design.

Next is using the grub screws to properly adjust the laser, from :

To the perfect-to-me result :

I think this is an awesome device. Thanks Hotech for making it, and making it serviceable.

4. Further tune the Hotech ACT at 16 meters using a mirror

After getting quite good but still not optimal results on collimating an RC I decided to revisit the collimation of the collimator itself. And for that I needed more sensitivity, meaning an even greater distance to the target. The earlier effort with a paper photocopy of the ACT at a larger distance was not easily possible in my house, and I also did not want to again repeatedly walk between the source and the target to see the result of a very tiny adjustment of a grub screw. So I used a mirror that was also reflecting on the back side (so that the beam does not pass any refracting glass) that I had still lying around for another project and doubled the beam distance from 8.1 to 16.2 meters.

This worked really well. While the paper target at 8 meters showed all was fine the result at 16 meters was quite different :

And the adjustments were so much easier to do, no more walking to the target to see what the adjustment result was but instant feedback right at the source. Why did I not think of this before ? So much easier and more sensitive.

At 16 meters distance the dotted crosshairs are becoming small diagonal lines and the laser dots become big oval shaped blobs. I was happy with the following result :

Last page update : 2023-08-30T21:02Z -- Hans Lambermont