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....
The current issue of Astronomy Technology Today introduces the UFC System - the tester was impressed:
What do you get if you cross an Erector Set with some giant metal washers, a plethora of variously-sized openings, a filter tray that slots in like a clip in a Glock, and, well, all sorts of other stuff? The Baader Universal Filter Changer, or UFC for short. And when Baader says “universal,” they mean it.
Read the Testreport ATT 1/2018 Baader-UFC . Mark Zaslove shows all wonderful things you can do with the Baader UFC (Universal Filter Changer).
Info about using quickchange-frontfilters with the UFC in combination with DSLR-cameras
There are no monochrome DSLR-cameras on the market, so a filter holder (e.g. the Baader-UFC) may seem quite useless for DSLR imaging, but if you take a closer look, there are indeed some interesting use-cases.
Many owners of DSLR-cameras remove the complete UV/IR-blocking filter and use this simple way to improve the sensitivity especially for H-alpha – but because of the costs, they decide not to add a new blocking filter with increased H-alpha-transmission.
But as a result, you have to find another way to block the IR- and UV-parts of the spectrum so that they will not decrease the image quality. You can use the UFC to mount such a UV/IR-cut filter in front of the camera - and to quickly replace it with another filter, without touching the camera.
Narrowband filters are not perfectly suited for a DSLR because of the Bayer-matrix, but especially a 35 nm H-alpha filter will show the emission nebulae better.
Especially in light-polluted areas the UHC-S-filter is very helpful. You can use the Baader-UFC to switch between several filters fast and easy. This way you can see which filter is the best for...
Off-standard single filter sizes from Baader - why not:
Quite often we receive requests for a single filter in an off-standard size. In all cases we are sorry that we must answer as follows:
Sorry (we know it would be so very much cheaper in production - and we would be so much more flexible to fill special requests) - but we have decided long ago to not cut or saw our filters from large plates because this would leave the coating stack open and mutilated (with microscopic cracks) all around, prone to aging and peeling.
Many times we had the chance to inspect our competitors filters after several years of use (due to our 30+years of servicing SBIG-CCD-cameras/and filter wheels) and we realized already 15 years ago how moisture and heat stress can deteriorate even most modern hard coatings, slowly peeling off from the carrying substrate over time, unless the coating stack is sealed all around the filter stack.
As a consequence - in order to create our filters to remain impermeable - we only offer all filter substrates already cut to final shape and run each substrate on an double deck auto-polisher to achieve perfect optical flatness and freedom from cone errors.
Then we do individually coat these substrates in 500 pc per run as minimum to fill a complete coating chamber, in a way that the coating stack (many times 50+ layers) applied onto each filter won't reach to the very edge of the round or square substrate, so that the coating stack remains completely sealed from all sides. In this way we can ensure that our filters will not age at all.
The sad effect is that we cannot offer other sizes unless the inquired production quantity were in the range of 250 to 500 pc (depending on size) and the tooling rings or square holders will be paid for, which serve to precisely center each individual filter substrate within the rotating calotte inside the coating chamber. Sorry - as explained above - we just will not coat onto large plates and cut any shape from them, also because such large plates cannot be polished optically flat in the same way we do it.
For your most urgent need and for single piece solutions we can only recommend to order the next larger size of our respective filter and have that cut to shape by an ophtalmologist locally. We can supply the round filters without the metal cell in such cases; square filters come without cell in any case.
Unmounted Filters – which side should face the telescope?
Question in Detail:
I just bought LRGB 36mm unmounted filters. I have question: which side of filter should be placed towards telescope? Is it better way of distinguish than "more shiny surface towards telescope"?
Always put the more reflective side towards the telescope side. To guide you we already put a small arrow on the filter rim, on those filters were the position matters. This arrow indicates which face of the filter should be directed towards the sky (telescope-sided). All cell-mounted filters are already oriented in a way that the most appropriate filter face is facing the sky when the filter would be mounted directly onto the front end of the nosepiece of a camera.
If you mount your filter the other way, any reflected light would have a short way to the camera sensor, resulting in a higher risk of getting some kind of back-reflections inside the camera field. Many sensors have highly reflective areas near to the light sensitive area, also the area with the bonding contacts is sometimes highly reflective.
But: this is true only for instruments without optical elements near to the focal plane. If you have f.e. a coma corrector, field flattener, focal reducer, focal extender (to a lower degree due to concave surface), or in extreme cases a whole lens group for more complex field corrections a few centimeters in front of the filter it could be useful to flip the filter against the rule from above (thus having the arrow pointing away from the telescope). Cause in such cases the likelihood of reflections from the sensor could be lesser then fort- and back- reflections from such glass-surfaces. If in doubt, it helps to make some test images from a star field with bright stars, using the filter in both ways for comparison.
Should you really have some reflections with both positions it can be more effective to add a spacer between filter and camera, eventually shifting the reflection out of the image field. With focal correctors having curved surfaces changing the filter-lens distance could help also.
Case for UFC filter slider as 3D-printable .STL file *
Our company exists now for more than 50 years. In this time, more than 15.000 Baader Planetariums (the first patented product of our company) help all over the world to give students an understanding of astronomical correlations. In our own manufactory, more than 500 observatory domes have been produced and delivered turnkey-ready. Instruments and telescope accessories from "Baader" are known for their high qualities by many astronomers and universities. We consider it our duty and obligation, not only to sell telescopes, but an indivdually selected telescope system, that brings you a lifetime of joy.