My astronomy project:
TS130 refractor to Nikon D800 adapter

Content:

1. TS130 to Nikon adapter
2. Adapter prototype
3. Implement of a duo narrow filter
4. Preparing for first light
5. Aberration analyze
6. Shorten the adapter length
7. Adjust tilt and back focus
8. New bracket for guide camera
9. Baffles
10. Prism bracket
11. RayTrace advanced
12. To be continued

Note:
I take no responsibility or liability for what are written here, you use the information on your own risk!

8: New bracket for guide camera

The project continues and I have started some astro photographing. One thing that could be better is the bracket for the guide camera.

This is the old guide camera bracket, designed for the ZWO ASI120 camera. The camera has T2 threads but at that time I didn't know how to 3D-print that small threads. I made this solution instead, it squeeze around the camera body. Some drawbacks, it didn't lock the camera in exact position and the camera could fall off. I could use it even to my QHY5 camera.

Now when I master how to 3D-print even small narrow threads I have designed a new bracket with T2 threads (M42x0.75). I have also extended the length of the bracket with a couple of mm to better fit the new designed off-axis adapter.

The QHY5 camera and the new bracket, will the threads fit together? An exciting moment.

It fitted perfectly and now they sits very tight together. Enough friction between them to adjust the camera angle without a need of a lock screw.

Two M3 screws for focus adjustment and two springs that retard the camera when unscrew the focus' screws. One turn of the screws adjust the focus by 0.5 mm. It has an opening of 14x9 mm to the prism in the off-axis adapter for a future bigger guide camera sensor.

My calculations of the theoretical correct focus will be with a slit of 4mm between the off-axis adapter and the guide camera bracket. I use a 4 mm drill to adjust it to that, later I must fine adjust it.

To fine adjust it I first set the main camera at correct focus with the auto focuser. After that I move the focuser until I have the guide camera in correct focus, I judge that by looking at the SNR of the guide star. Example: if I have to move the focus 800 steps and know that each step is 0.001 mm. Then I have to turn the guide camera focus screws 0.8/0.5 = 1.6 turns to get both the main camera and guide camera in correct focus.

The ASI120 camera had its USB port on the side which was better, on the QHY5 camera the USB cable protrude far away to the side. Cons with this QHY5 camera is that it has a bigger sensor and a bigger pixel size. But not as sensitive that it should have been, it's on the limit to lock on the guide stars. The telescope in this case is a slow f/7.

The guide camera must sit at correct angle, in my case I screw it all the way in.