Announcement
Baader Planetarium Narrowband Filters
for SBIG Cameras
June 15, 2007
Updated: July 14, 2008

SBIG is pleased to offer a custom set of Baader narrowband filters for the ST and STL cameras effective as of this announcement.  SBIG and Baader Planetarium, Mamendorf, Germany, have enjoyed a longstanding relationship.  Some accessories for the ST and STL cameras have been made by Baader for SBIG over the years, including the UV/IR cut filter that we supply with every single-shot color camera for optimum color balance.  Now, this relationship translates into incredible savings for SBIG customers.  Baader Planetarium has developed a set of narrowband filters in in 1.25" and 2" sizes.  The 2" filter is specifically made for the STL series cameras in the 50.8mm (2" unmounted) size for the STL filter carousel.  These drop in both the 5 position and 8 position filter wheels for the maximum clear aperture in a 2" filter for our large 11000 CCDs.  Moreover, these new narrowband filters are the same thickness as our standard 50.8mm LRGBC set making them all parfocal for the STL models.   Each filter is made of high quality substrate, polished to yield 1/4 wave flatness or better, with hard multiple anti-reflection coatings on both sides.  The narrowband filters are available in a 7nm wide H-alpha filter, 8nm wide H-beta filter, 8nm wide OIII, and 8.5nm wide SII.  In addition, there are some specialty filters such as an IR pass filter and a U filter ("Venus" filter), and a lower cost wider passband (35nm) H-alpha Pass filter.  The narrowband filters typically have around 90% peak transmission at the design wavelength.  Unlike earlier Baader narrowband filters, no separate IR blocking filter is required because the IR blocking is built into the filter coatings.   Out of band transmission is measured at less than 0.8% to less than 0.1% from 300nm to 1100nm depending on the filter and wavelength.  These filters are also available in 1.25" sizes for ST series cameras, in threaded cells for the CFW8A, CFW9 and CFW10 filter wheels.  Note, however, that due to the different thickness of the smaller 1.25" RGBC filters the narrowband filters are not parfocal in the smaller size at this time.  The remarkable news is that a set of the 3 most commonly used narrowband filters (H-alpha, OIII, SII) is available for under $400 for the ST cameras (1.25" size), and under $900 for the STL camera (50.8mm size)!    

The IR-Pass filter blocks wavelengths below  670 nm.  At these longer wavelengths, planetary images are less disturbed by wavefront distortions in the atmosphere.  By  combining a luminance image taken with the IR-Pass filter, along with  RGB frames, overall image sharpness is significantly enhanced.  Some of the world's best amateur planetary images have been taken with this technique.  This filter is available only in 2" OD threaded cell (48mm threads).  List price $165.

The latest coating technologies permit the Baader U Filter (Venus Filter) to transmit from 300nm to 400nm, with a peak transmission of 80%!  The filter completely blocks the rest of the region from 200nm to 1500nm, through the use of a complex 20 layer dielectric coating stack, on top of a special UG-11 substrate.  Up till now, Amateur efforts typically relied upon deep violet colored filters, or combinations with simpler interference filters, which do not provide the high transmission and efficient rejection outside the important spectral region from 320nm to 390nm.   Given the poor transmissions of many optics in the UV and the lower sensitivity of some CCDs to this wavelength, high filter efficiency and complete rejection at longer wavelengths becomes paramount to recording good contrast at reasonable exposures.  The same high optical quality and features as the other Baader filters ensures the highest contrast and sharpest images possible.  Interestingly, the solar Calcium K-Line is also within the pass band of this filter.  This opens up the exciting possibility for recording flare structures on the solar disk or edges.  This filter is available only in 2" OD threaded cell (48mm threads).  List price $259.

Baader's innovative new designs and features, together with the very latest thin film coating technologies, result in outstanding performance, efficiency, and image quality.   Baader filters are unique, in that they utilize true optically polished flat substrates.  Ultra-thin precision cells deliver the maximum clear aperture and minimize vignetting.   Ion beam hardened coatings ensure your filter will withstand real-world use and repeated cleaning - they are tough enough to survive boiling water! 

Baader Planetarium filters are made from striae-free substrates, and actually fine optically polished flat to within 1/4 wave p-v over the entire surface, plane parallel to within 30 seconds of arc.  This important and unique custom step adds cost - but the result is a filter that maintains the full wavefront quality of the telescope without double images or ghosting, even at high magnifications.   Critical to maintaining this level of flatness are Baader's carefully balanced coating designs, which prevent coating surface stresses from warping the substrate.   Such high flatness enables Baader filters to be used far in front of the focal plane, ahead of star diagonals.

Durability has always been a hallmark of Baader Planetarium.  The multi-layer dielectric coatings are plasma assisted and Ion beam hardened using the latest technology (the coatings are harder than the glass substrate itself!).  Baader filters withstand repeated real-world exposure to the elements and physical cleaning.  Users need not leave their precious filters dull and dust encrusted to avoid cleaning - Baader filters may be used and cleaned without fear.   Baader Filters will truly last lifetimes.

Baader's special filter cell design offers unique features that enhance their reliability and usability.  Though difficult to produce, the ultra-thin filter cell results in the maximum possible clear aperture, in order to minimize vignetting (1¼" Filter clear aperture is 27mm!).  The special threading has been designed to fit the wide variety of eyepieces and accessories (there is significant variation between the 1¼” filter threading used by eyepiece and accessory manufacturers).  The front 'crown' of the filter incorporates milled notches which make handling and threading the filter a more secure operation in the dark. 

Despite the high quality and advanced technology, Baader Planetarium filters are affordable.   By leveraging high volumes across all filters in the Baader family, these filters can be offered at very reasonable prices.

Update: July 14, 2008:  Baader Planetarium reduces prices on narrowband filters for STL cameras.
For the latest prices see our current Price List:

Baader 1.25" UV / IR Blocking Filter

The Baader UV / IR blocking filter is essentially a luminance filter.  It is included with ST-2000XCM color cameras to improve the color balance of the single shot color CCD by blocking the near IR light.  It is shown here along side the optional T-ring with filter threads for use on any ST cameras.  It can be placed behind a camera lens adapter and used to block the out of focus near IR light that causes stars to look bloated with using a typical 35mm camera lens to shoot wide field images.  Click here for current prices.

For the latest prices on Baader Planetarium filters, see our current Price List

Revised: August 11, 2008 09:07:20 AM.
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