It was brought to our attention that when the Celestron RASA 11" was combined with the Baader UFC (Universal Filter Changer) (various versions available) UFC System, reflections could be seen in the final images. After thorough investigation and troubleshooting, we found that the problem could not be located in the UFC System. To adapt the UFC system to the Celestron RASA 11" you will need our UFC Telescope-Adapter S70a to RASA 11" – Optical height: 3 mm (#2459126 , € 165,- ) .
What is it about?
Since the clear glass filter of the optical window must be removed when using the UFC system to take advantage of the maximum back focus of the Celestron RASA 11", or when using an additional filter, there is no natural aperture in the form of the mount of the pre-installed filter glass. This mount has an inner diameter of 68 mm, which is also the maximum aperture of the system with the built-in optical window. As this aperture is specified in the optical system by the manufacturer Celestron, the optical surfaces and lens edges are not sufficiently protected without this cover and therefore stray light is scattered into the image. This stray light can vary in intensity depending on the filter.
Our solution
3D printed rings as an insert in the lens group
To avoid this effect, we have published a set of 3D printable rings here or on the corresponding product page, with which this effect can be avoided to varying degrees. These are insert rings that are provided with a saw tooth to minimize reflections. We ourselves have subsequently coated our 3D prints with oven paint from a spray can, as this is readily available commercially, has a matt black surface and delivers very good results.
Test series
3D-printed rings with different clear apertures were tested
During testing we found that even the 68mm ring in this series of tests did not eliminate all stray light effects.
We have therefore produced an additional set of rings to reduce the field of view further until there are no more reflections. However, the optics are then slightly vignetted at the edges. With well exposed flat frames, this vignetting can be removed completely.
The images below show the results:
Conclusion and free 3D printing files
3D printed rings in several designs
From August 2024, Baader Planetarium will supply a 64mm diameter aperture ring with every UFC Telescope-Adapter S70a to RASA 11" – Optical height: 3 mm (#2459126 , € 165,- ) , as we have identified this diameter as the sweet spot between vignetting and low reflection. If you want to achieve even less reflection or vignetting, you can download the corresponding 3D printing files for free from our website.
The download files are subject to the Creative Commons Licence CC BY-NC-SA 4.0. You may distribute the files under attribution © Baader Planetarium GmbH as well as linking to the licence and indicating any changes. The files may not be used for commercial purposes. If the files are modified, they must be distributed under the same licence.
Further information
- Unfortunately, we do not have the manufacturing capacity to produce these adapters in large quantities. Custom manufacturing would be too expensive. We therefore have to decline requests to print these adapters in-house.
- If you have a 3D printer, you can print the download file directly.
- If you do not have a 3D printer but are still interested in a 3D printed ring, you can contact a 3D printing company. There are now many suppliers online - or perhaps you already have a 3D printing company you trust?
- If you have any problems or questions about the file, please feel free to contact us.
