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!

11: Ray trace advanced

When I talked to my friend about optics and need of some ray tracing software he told me that he had found an addon for FreeCAD. All other I have looked at earlier was either too complicated or too simple, and they cost a lot of money too. If there is a free ray trace addon for FreeCAD that I'm already familiar with it will be a big bonus.

Install Optics:

Open Tools menu and click on Addon Manager. Search for optic and you find it. Install it and restart FreeCAD.

Ray trace of Pentax 645 300 mm f/4 lens:

The lens Pentax 645 FA 300 mm f/4 ED I have is a complicated 7 lens construction. I simplified it a lot, one front lens and one back lens. The lens tube is only 2D like a cut through of the lens. Even if it's simple it's much more advanced compare to what ray tracing I have done earlier. There is no problem with this lens and the full frame camera, just for practice.

Here is the view tilted to better understand how I have it setup. First a dew shield, a 70 mm diameter front lens normally at least a triple lens, then the back lens act as a field flatter. The back end of the lens act as a mask, and at most right the camera and its camera house.

Now I feel I can do all the thing I just dreamed about earlier.

Ray trace of TS130 f/7 APO and full frame camera:

Now it's time to do an analyze of my 130 mm f/7 APO with a 3 inch field flatter and full frame camera. Very simplified with only two lenses.

A side view, the bar left at top is a cut out of the dew shield.

Field flatter lens, adapter wall, off-axis adapter, camera house and full frame camera sensor. See what's happen: a lot of reflections at the end. Maybe this is what I see on my images when in high contrast, a couple of concentric rings. This is the part I can do things about to improve the image quality.

I have already before this analyze set in a mask to block unwanted light rays. It's good to have big image circles but it can cause problem like these, reflections. The reflections must be reduced and after the mask was inserted all the reflections is gone.

The camera's walls around the sensor is too close which cause vignetting with some optics. I have a spare camera, my plan is to remove the IR filter and the mirror from it. When I do that I will take a look if I can remove these walls.

Another view from behind to easier understand the setup. I have added another beam along the optical axis. Next time I put in my 3D-CAD drawings to do a full 3D ray trace. What's not included in this analyze is all the reflections from the optical surfaces of the lens's. But can't do that because I don't have any information of the internal optical lens construction.

Concentric reflection patterns:

This is how it looks like, the concentric reflection patterns. This is before I inserted the mask, after that they are almost gone. With this ray tracing analyzing tool I can do it even better.

3D modeling:

Here I have done it more advanced with 3D modeling of the tube and obstacles. It make it more difficult to study, it's hidden behind.

With the clipping tool the upper part is cut away. In the middle lower is the prism and outlet to the guide camera.

Rotate the tube 90 degrees and in this view I can see that the baffle (mask) is a little bit too narrow. But this isn't a precise model yet, I have to refine it a lot. Most important, now I have a tool where I can do ray trace simulation and have learned enough to do my first simulation.