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Baader Universal Filter Changer (UFC): Part 3 - The UFC Filter Slider

Baader Universal Filter Changer (UFC): Part 3 - The UFC Filter Slider

In this, our 3rd part of the Baader Universal Filter Changer (UFC) system, we will look a little more closely at the UFC filter sliders. Below is an updated simplified diagram of the Baader UFC system. To catch up, you can find the first part of the series - a general introduction here, and the second part about the UFC Base here. Today in this blog we are dealing with the items in yellow.


Baader UFC - simple diagram

Baader UFC simplified diagram

The image below shows the three UFC filter slider models available. More about these are individually discussed later.

All three Baader UFC Filter Sliders together

Baader UFC Filter sliders: from the left: 2"/M48 mounted filter slider; 50.4mm diameter unmounted filter slider ; 50x50mm square filter slider. 

All the UFC filter sliders feature

  • a knurled (removable) aluminium handle for holding the slider. This allows the slider to be easily held, inserted and removed from the UFC base.
  • a 4mm long x 3mm diameter brass pin : The brass pin allows the slider to be seated correctly in the UFC Base. Once the filter slider is fully inserted, the brass pin "sticks out" of the locating hole in the UFC Base. The brass pin also serves another main purpose. Rather than pulling on the filter slider handle to remove it, which may potentially disturb the position of your telescope, you gently push on the brass pin to "eject" the slider away from the UFC Base magnet. You then simply, and easily, pull the slider out with the aluminium handle and without disturbing the telescope!
  • a round 4mm diameter magnet. The purpose of the magnet is to keep the filter slider securely in place once the slider has been fully inserted into the Base which also has a magnet - see part 2 of our blog. 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.

The filter slider is made from a single piece of aluminium and anodised black. Each slider is ~101mm long (from handle to brass pin), ~75mm wide and ~9mm thick and the weight is approx 55g. 

There are three versions of the UFC filter slider which accommodate three different types/sizes of filters.

  • 2" / M48 (#2459112) : has a large thread central hole for use with 2"/M48 mounted filters. The filter simply screws into the hole.

Baader UFC Filter slider for 48mm mounted

 The 2"/M48 Filter Slider

  • D50.4mm diameter (#2459113): for use with 50.4mm/2" round unmounted filters. The filter is laid flat into the central opening and there is a smaller diameter edge/shoulder at the bottom of the opening for the filter to "rest on" (otherwise the filter would drop straight through the opening!). There are three small threaded holes (see left image below) on the outside edge of the filter slot opening 120 degrees apart to allow the unmounted filter to be securely held in place using the hex-screws and washers supplied with the slider (see right image, below) . This filter unit can also be used with smaller-sized filters using optional Baader Auxillary Filter Holder adaptors. See later for more details.

Baader UFC Filter slider for 50.8mm unmounted

Filter slider for 50.4mm round unmounted filters

  • 50x50mm square (#2459114): For 50x50mm square type unmounted filters this filter slide is required. It comes with 4 hex-screws and washers to secure the square filter in place  in the middle of each of the filter's four sides (see mage below, right).

Baader UFC Filter Slider 50x50

 UFC 50x50mm square filter holder. Left:empty holder with four filter securing screws. Right: filter in place.

As mentioned previously, if you already have, or want to use smaller sized filters, you can use them with the UFC system. Use of these smaller filters is achieved using an appropriate optional Auxillary (Aux) Filter Holder (a "drop-down filter size adaptor") in conjunction with the 50.4mm diameter filter slider (#2459113). There are three "sizes" of Aux Filter Holder available:

  • for 1.25" mounted filters (#2459153)
  • for 31mm round unmounted (#2459151)
  • for 36mm round unmounted (#2459152)

All three Aux Filter Holders have the same outside diameter and simply drop in to the 50.4mm unmounted filter slider, with the AUX holder being secured in place using three hex screws (i.e. the AUX holder "takes the place" of an unmounted 50.4mm filter).

The images below show how each of these adaptors look and how they are used with the 50.4mm filter slider. 

Baader UFC 1.25" filter insert

The 1.25" mounted Aux filter holder (left) and D50.4mm filter slider with Aux holder in place. 

In the image above the Aux filter holder for 1.25" mounted filters is shown on the top left. The image on the top right shows the holder in place in the filter slider with a 1.25" mounted filter attached. The filter simply screws into the Aux holder (either before the Aux holder is secured into the filter slider or after). The image on the bottom left and right shows the underside of the Aux holder and the underside when it has been attached to the filter slider (bottom right).

Baader UFC 31 and 36mm unmounted insert



The images above and the following description applies to both the 31mm round- and 36mm-round unmounted Aux filter holders. The image on the top left shows what the Aux holder looks like along with the supplied 3 hex screws and washers for securing the filter in place in the holder. The image on the top right shows the Aux holder in place in the UFC filter slider with an unmounted 31/36mm filter in place. The image on the bottom right is the underside of the filter slider with the Aux holder and filter in place. 

Next time we will look at the camera-side adaptors.

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