Overview of the Baader UFC-System
The Baader Universal Filter Changer (or UFC for short) is a very versatile simple system for using, mounting and changing (or swapping) filters in and out of a light path. The UFC can be used for imaging where you may want to swap different filters (e.g. LRGB) between a camera and a telescope but do not want the bulk, or expense, of a filter wheel. The UFC can be used between a camera and a Celestron RASA 11/14(36) or a Starizona Hyperstar system where the overall size and shape of a filterwheel causes issues. You can also use the UFC for visual purposes where you can easily switch between different colour filters between a telescope and an eyepiece.
The image below shows the standard "exploded" diagram of the parts that make up the Baader UFC. We've colour-coded it to highlight the main different parts (see below). At present there are 30+ parts to the whole UFC system in total. The large number of components may seem somewhat overwhelming at first glance, and can lead to some confusion, and that the system is complicated. However, we hope this series of blogs will help show how simple, and effective, the UFC is.
Baader UFC Base (Filter Chamber)
The Baader UFC is really quite simple. Although looking at the diagram above it looks complicated and crowded....you will only really need.....four (4)....main parts! We have colour coded each section in the diagram above to make it easier to understand. To put it simply, you will need: a camera-side adaptor (part #1) and a telescope-side adaptor (part #2) in addition to the core part of the system called the UFC Base unitpart #3) sand then a sliding filter drawer for your filter (part #4)
UFC 2" Filter slider (#2459112) with mounted Filter - showing both sides
UFC D50.4mm Filter slider (#2459113) with mounted Filter - showing both sides
Application Image: UFC 50x50 Filter slider (#2459114) with mounted Filter - showing both sides
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The Baader-UFC is the priceworthy answer to an ever growing problem. New camera-models come to market in ever increasing speed. Spacers between 
telescope and camera don´t support the correct distance or are subjected to torsion due to their flimsy design and heavy cameras. And the owner may want to change the telescope - or use several OTAs, but does not want to purchase new filters and filter sliders all the time. The Baader-UFC is a (seemingly) simple answer to a complex problem. It is made in the typical Baader-way, trying to connect each and everything in the most elegant and flexure-free manner.
The filter chamber (UFC-Base) is the core part, which up to now does accept three different kinds of filter sliders for 2"/ for 50 mm round and for 50x50 mm filter sizes. The filter sliders are kept in place by means of an adjustable magnet, to adjust the retaining force and to assure exact repositioning of the filter for repeatable usage of flats. A brass-pin mounted onto the far side of the filter-slider. This pin is sticking out at the opposite side of the filter chamber. The pin enables an easy eject of the filter slider without pulling on the filter slider, to not endanger the precise telescope position during exchange of filter sliders.
Versatile application – for almost any telescope / camera
UFC with 50x50 filter slider, SP54 adapter, Straylight flange as well as DT-Ring SP54/M62 and Stepper Ring M62/M72 for Adaption on DSLR camera lense
The camera-side of the UFC-Base (the filter-chamber) remains open towards the camera - until the matching camera-adapter gets mounted directly onto the UFC-Base. The purpose of this is to have the filters mounted with minimum distance to the image sensor, avoiding additional vignetting.
The telescope-side of the UFC-base carries a receptor with 6 clamp screws in 60° spacings, to mount all the Baader-proprietory S 70-dovetail-adapters and spacers. A number of rigid UFC-S 70 spacer tubes is available in 5/15/40 mm length , as well as an ultra-stable S 70 VARI-LOCK spacer, engraved with Millimeter scale and being seamlessly adjustable from 15 to 20 mm. These four spacers will allow precise adaption with almost any backfocus situation, for both - back and prime focus - instrument configurations. Please accept the six tiny set screws, they are dearly necessary at times, when correct spacing becomes difficult. Each joint must be able to rotate, while requiring only a minimum of optical length.
Just one "click" onto the brass-pin releases the filter holder from the magnetic fixture. Afterwards it can be removed easily
1¼" extension with barrel, clicklock and UFC System for fast filter changing
Another set of telescope-adapters, with the male S70 dovetail facing the camera-side, completes the assortment, enabling the user to mount the UFC-assy onto almost any telescope firmly and flexure free. For the RASA-adaptation we even mill this RASA/S70 adapter plate from stainless steel, in order to provide the necessary stiffness while retaining the extremely thin flange tolerances required for the RASA-design.
For any telescope, for any camera - just replace the corresponding adapters on either side of the filter chamber when you change telescope or camera and want to keep on using your trusted set of filters.
As added benefit any camera lens can be used with the UFC. In this case, the UFC-Base will be fastened in front of the camera-lens with adding both the S70/SP54 adapter #2459134 and the retaining flange #2459121, as well as one of the many step-rings of the Hyperion-ring-system (#2958028 - 2958082) to be found here. Note that filters ought to be mounted in reverse order when using the UFC-filter changer in front of camera lenses.
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About the author: Lee Sproats
Dr. Lee Sproats has been interested in astronomy since watching Star Wars in 1977 and has appeared on the UK Sky at Night TV programme. He then went on to study Astronomy where he obtained a degree and then a PhD in the subject at University College London/Mullard Space Science Laboratory. He has worked in Australia in radio astronomy and used optical/infrared telescopes on Hawaii and La Palma and Lowell and Kitt Peak observatories in the USA. After working for the University of Surrey to promote the use of computers for teaching in UK higher education and then as an IT trainer for a stock market company, he went on to work for Greenwich Observatory Ltd where he ran their northern branch and then worked for David Hinds Ltd dealing with our and Celestron products. He is often involved in flight excursions that take passengers to observe the northern lights, has led trips to see the great USA 2017 eclipse near Hopkinsville and was lead astronomer onboard a specially chartered 737 to view the 2015 total solar eclipse at 38,000ft. Lee`s astronomical interests include Lunar observing, astrophotography, photometry and pro-am collaborations.
Since David Hinds stopped operation in December 2020, Dr. Sproats works for Baader Planetarium as our UK representative/consultant and is responsible for looking after our UK/Eire dealers, dealing with Baader Planetarium/PlaneWave/10Micron product support, writing articles and also is involved in our large telescope and observatory instrumentation projects.
