Baader Universal Filter Changer (UFC): Part 2 - The UFC Base

Baader Universal Filter Changer (UFC): Part 2 - The UFC Base

In the first part of this series of blogs about the Baader Universal Filter Changer (UFC), we gave a general introductory overview of the UFC system. You can read that first introductory blog >>here<<. In this second part, we will look more closely at the main component of the system - the UFC Base - and outline its features. In the UFC overview diagram below, the UFC Base is the component in the middle (between the two red arrows).

Baader UFC Overview

Baader UFC general simplified overview

The UFC Base is also known as, and sometimes referred to, as the UFC filter chamber. For the purposes of this and future blogs in this series, we will refer to the UFC Base as just the "Base". The Base has a number of functions or purposes. It allows:

  • The range of Baader UFC telescope-side adaptors and spacers to be attached allowing the UFC to be connected to a telescope.
  • The Baader camera-side adaptors to be attached so that cameras can be connected to the filter system.
  • The filter slider, which holds your filters, to be easily inserted and removed, and also to be held securely when in place (thus allowing the filter to be used for its imaging or visual purpose).

In the box

**Please note: the photographs of the Baader UFC Base and other UFC components in this series of blogs are of a working model and as such there are some minor marks on them due to real-life in-the-field use of the product. Furthermore, as the parts are anodised in a black matte finish, dust and other marks become more obvious, especially under certain lighting conditions.

The box containing the Base clearly identifies the name of the product and also has the important Baader product code number (for ordering) clearly visible.

Baader UFC Box and contents

Baader UFC Base box and contents

Inside the box there is the Base and a bag with six (6) small hex-screws and two different sized Allen keys. The hex-screws are used to hold the telescope-side adaptor in place (see below) and the smaller of the two Allen keys are used for these screws. The larger Allen-key is used to secure a camera-side adaptor plate.

UFC Base and screws and Allen keys

UFC with screws and Allen keys

The "Bare" UFC Base

The Base is made out of a single block of aluminium and anodised black. It measures ~88mm/3.5" in diameter, is 13mm in thickness/optical length and weighs approx. 55g.

It may be confusing at first glance which side of the Base is the camera-side and which is the telescope-side. For reference, the camera side of the chamber is the side that has two sets of four tapped holes and a distinctive shape. The telescope side is "featureless".


Sticking with the telescope side, there are six threaded holes around the Base's edge, spaced equally at 60° around its circumference. The hex-screws that are supplied with the Base are for these holes, with the smaller of the two Allen keys being used to insert/remove and tighten/loosen them. These six screws together clamp Baader's proprietary S70 dovetail telescope adaptors and spacers securely in place. We will cover more about the telescope-side adaptors (and attaching them to the UFC Base) in detail in a later blog.

Baader UFC Telescope-side

Baader UFC Base Telescope-side. The locations of the 6 holes for the screws can be seen.

An edge-on view of the UFC Base

An edge-on view of the UFC Base showing one of the six holes (at the bottom nearest the camera) that secure a Baader S70 dovetail telescope-side adaptor


On the camera side, there are two sets of four threaded holes on the Base's face plate. The range of Baader camera side adaptor plates (discussed in a later blog) are attached to this side using eight hex-screws that are supplied with each camera adaptor and using the larger Allen key supplied with the Base unit.

The image below shows the camera-side of the Base and there are a number of "features" highlighted that we would like to mention.

UFC Base with parts labelledUFC Base with features marked 

    • Magnet (-): The location of the magnet is shown in the image above and a close up of it can be seen in the image below. The purpose of this magnet is to keep the filter slider securely in place once the slider has been fully inserted into the Base (the filter slider also has a magnet - see later). The filter slider (and therefore the filter being used) can be accurately re-positioned so that flat field frames do not have to be taken every time the slider is removed and replaced.

UFC Base showing the magnet.

 UFC Base magnet

    • Spring-loaded ball bearings (-): Near the top of the Base there is a milled-out narrow section which matches the outline shape of the filter slider. On each side of this narrow section there is a spring-loaded ball bearing. Working together, these two ball bearings essentially "grab" on to the (narrow) end of the filter slider to provide additional support. 

UFC Base Ball Bearings

Close-up of one of the UFC Base's spring-loaded ball bearings (the other is opposite the one that can be seen). The filter slider locating hole can also be seen to the right of the ball bearing.

    • Locating Hole (-): The "end" of the filter slider (i.e. the end opposite the filter slider handle) features a brass pin. When the filter slider is inserted in the Base the brass pin goes through this hole helping the slider to be seated correctly. Once fully inserted, the brass pin "sticks out" of the locating hole, which also serves another main purpose. Rather than pulling on the filter slider handle to remove the filter slider, which may potentially disturb the position of your telescope, you gently push on the brass pin to "eject" the slider away from the Base magnet. You then simply, and easily, pull the slider out without disturbing the telescope!


    The Baader UFC Base (Filter Chamber) is the central "core" part of the UFC system. It is the part to which all other UFC components (i.e. telescope- and camera-side adaptors and filter slider) are attached to. The telescope-side adaptors are held in place with 6 equally spaced hex-screws with the camera-side adaptors being secured using 8 hex-screws. The filter slider is easily inserted and removed by a gentle press of a brass pin that sticks out of the side of the Base unit when the slider is fully in place and the slider is held in place using two magnets.

    Although we will discuss the filter slider in the next blog, to demonstrate the Bases' features mentioned previously in this blog we present the three images below. These show the UFC Base, but without the camera side adaptor attached, in order to show clearly the Base chamber as the filter slider is inserted.

    Top view of the UFC Base with filter slider partly inserted

     Top view of the UFC Base with filter slider partly inserted:

    Here, above, you can see the filter slider partly inserted as viewed from above the camera side of the Base. The filter slider's handle is at the bottom and its brass pin can be seen at the top. 

    Side view of the UFC Base with filter slider partly inserted showing the magnet

    Side view of the UFC Base with filter slider partly inserted showing the magnet

    A side view of the filter slider being partly inserted into the Base unit (above) clearly shows the (round silver) magnet on the edge of the slider. The magnet that is installed in the UFC Base can be seen near the "0" of the item's product code. When the slider is fully inserted in the Base, the two magnets keep the slider securely in position. 

    Side view of the UFC Base with filter slider fully inserted

    Top-view of the UFC Base with filter slider fully inserted. The brass pin can be seen sticking out of the locating hole.

    With the Slider fully inserted into the UFC system - image above - it is just about ready for use (when the camera- and telescope-side adaptors and filter slider are attached of course). The locating pin can be seen at the top which is used to help eject the filter slider (by a gentle press) without pulling on the slider which can potentially move the telescope.

    Baader UFC with camera side adaptor and filter slider in place

    UFC Base with filter slider slider fully inserted into the Base and the camera-side adaptor plate attached (camera side adaptors to be discussed in a later blog).

    The image above shows what the Base looks like with the filter slider installed and the camera-side adaptor plate has been attached. The image below shows the UFC being held to give a general idea of its size.

    UFC System being hand-held.

    In part#3 of the series next week, we will look at the telescope-side connection adaptors for the UFC Base.

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