Smaller-Sized Filters with Baader UFC-System :

We've been asked a few times recently on how to set up the Baader UFC for use with a DSLR and a range of wide-field imaging refracting telescopes. So we thought we would write a short blog on some ways this can be done.

Let us start from the telescope side first.

All the enquiries we have had, the wide field refractors have 2" barrel focusers, so there is our starting point. The telescope side of the UFC Base (to which everything else in the UFC system is connected to) uses Baader's S70 dovetail adaptors to allow the UFC to fit to telescopes.

Looking at the UFC main diagram above Baader do a UFC Telescope-Adapter S70a to 2"/SCTi – Optical height: 1 mm (#2459128 , € 25,- ) that allows 2"/SC male-thread accessories to be used. More about our UFC Telescope Adapters can be found in our blog: The UFC telescope-side adaptors.

It may appear, at first glance, that the Baader Planetarium Universal Filter Changer (UFC) is for use with larger 2″/50mm sized filters. Not so! You can use popular, and more often used smaller 1.25″, 31mm unmounted or 36mm unmounted filters too. So how can the filter slider drawer made for use with larger sized filters be used with smaller filters? Simple – with a step-down adaptor. Baader call these step-down adaptors AUX Filter Holders.

Apart from the UFC Base, and the associated telescope- and camera-side adaptors for your telescope/camera combination, you will need UFC Filter Slider D50 (for round filters Ø 50mm to 50.5mm) (#2459113 , € 45,- ) . It is to this particular filter slider that any of the AUX step-down adaptors attach to.

We offer three AUX step-down filter holder adaptors for use with the D50.4mm slider:

• UFC Filter Holder 1¼" AUX (requires #2459113) (#2459153 , € 11,- ) : This adaptor is (female) threaded to accept the standard 28.5mm filter cell threads.

• UFC Filter Holder 31mm AUX (requires #2459113) (#2459151 , € 11,- ) : This adaptor comes with three Allen-key socket screws and washers to securely clamp a 31mm unmounted filter in the AUX filter adaptor holder.
• UFC Filter Holder 36mm AUX (requires #2459113) (#2459152 , € 11,- ) : As with the above AUX filter holder, this adaptor comes with three Allen-key socket screws and washers to securely clamp a 36mm unmounted filter in the AUX filter adaptor holder.

The 31mm and 36mm unmounted AUX holder have a small narrow “shoulder” on the inside of the unit to support of the filter once the filter is in place (otherwise the filter would drop or fall straight through the holder!).

The AUX filter holder is simply inserted into the UFC filter slider's circular opening and then it is secured in place using the three Allen key hex-screws that come with the filter slider. As with the 31/36mm AUX filter holder, the D50.4mm slider also features a small “shoulder” in the “base” of the filter opening to support the AUX holder in place (as well as to support 50.4mm unmounted filters when the AUX holder is not used).

The 1.25″/31mm/36mm filters can be inserted, removed or exchanged with the AUX holder either in place or with it removed from the UFC filter slider – its personal preference.

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