Don't be afraid of collimating an RC telescope

A short introduction and experience report

I am often asked how I approach the collimation of my GSO RC telescope without much previous experience and without expensive equipment.
In fact, I was a bit worried before purchasing my telescope. The positive sides of an RC telescope are obvious: the focal length, the compactness of the telescope with a relatively low weight and the ability to work with reducers make an RC telescope interesting for astrophotography.
However, you always read about the difficulty of adjusting an RC telescope.

In fact, I tried several methods, such as using a laser or camera adjustment. Unfortunately, I had no success with this. The stars were terrible and if it was OK in the center it would be hard to look at the edges of the images even though I did collimation.
However, then I came across the TS collimator for RC telescopes. It consists of a precisely fitting socket, a little hole to look through, circles inside and white and red LEDs.
The LEDs are used for lighting during the adjustment; no laser point or similar is used.

I rate the instructions on the internet as quite complicated and my attempt to copy them unfortunately failed.
This can be clearly seen in my image of the planetary nebula M57. Although I was able to use various methods to ensure that the center of the image was completely fine, it was also clear from the out-of-focus stars that the accuracy of the representation quickly decreased towards the outside, even though I had a fairly small sensor with the ZWO ASI 533 have used.

After several attempts, I found out that I should not pay attention to the rings shown on the collimator, as described in the instructions, but rather that the screw connections of the struts of the secondary mirror can be seen centrally and evenly at the edge of the image. In addition, care is taken to ensure that the center marking can be seen in the center.
When collimating, it is also important that the collimator is firmly clamped so that nothing can tilt.
The adjustment process must first be carried out on the secondary mirror and then on the primary mirror. The process must be repeated 2-3 times.
The telescope is now fundamentally adjusted.
Now when you are in the field, you look for a bright star and set it out of focus. Now several rings can be seen. If these are not yet concentric, you can improve your adjustment with minimal changes to the secondary mirror.

With this simple procedure I can adjust my RC telescope within 5 minutes and so precisely that I can also use larger sensors.
My pictures of the bubble nebula and that of Melotte 15 shows the result of this five-minute adjustment after complete misalignment (after moving). The edges are not perfect, but that is probably due to an incorrect backfocus to the reducer. The adjustment was also fine in the corners.

I can therefore only recommend RC telescopes; there is no need to be afraid of collimation.