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Astrodon Filters - An Overview

Click here to se the Astrodon Website with tons more information

Astrodon Imaging offers products that simplify astrophotography. We began in 2002 to serve the interests of the CCD astronomical imaging community for both pretty picture imaging and scientific research. We strive to make the best performing products available. We shall invest in product improvement based upon feedback from our customers. We will be accessible and responsive to our customers and prospective customers. We will continue to innovate and bring new products to the imaging community that again, simplify astrophotography.

PRODUCTS

Astrodon Tru-Balance filters simplify RGB imaging by equalizing the flux for general classes of CCD detectors, that allows you to combine your RGB color data with nearly equal weights. This allows you to take your color images and their corresponding dark frames with the same exposure time, while achieving a G2V white point balance for correct star colors and balanced OIII teal color in emssion objects.

Astrodon narrowband filters for H-a, OIII and SII provide the highest performance available for bringing out structure in emission objects, and allow you to image when the moon is up and image from light polluted environments.

Astrodon research grade Sloan (u',g',r',i',z') and Johnson/Bessell (UVBRIc) all-dielectric-coated filters provide the highest performance and durability available for photometric research.

Astrodon off-axis guiders allow you to guide your telescope in the same optical path as your imaging camera, thereby eliminating the cost for a separate guide scope and the potential for differential flexure.

Astrodon remotely-controlled camera rotators allow you to frame your object exactly the way you want and help to find guide stars.

Designed for astrophotographers by astrophophotographers.

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Astrodon Filters and Cleaning

We have had a number of problems where customers have used inappropriate methods to clean their Astrodon filters.

We recommend all customers read the following cleaning procedure as we will not be replacing or repairing any filters that have been inappropriately cleaned or not cleaned using these methods

Please click here to see Astrodons recommended method of cleaning

Furthermore -

We would add that it is critical to use disposable wipes and not microfiber clothes that get dirty fast. Astrodon uses Kimwipes and then dispose of it and use another one for the next filter. They suggest placing several wetted areas on one wipe and not go over the same area twice.

Kimwioes can be purchased via this link.

Use an eyedropper and NEVER put anything in the isopropyl alcohol bottle that would contaminate it.

If the filters appear not to clean up, dispose of the Isopropyl Alcohol in the eyedropper, rinse and add new IPA. Some stores carry 70% IPA, but it has too much water and may leave spots after the alcohol evaporates. Do not use the more complex mixtures that you hear about on the web.

For European customers who may not have access to KimWipes, locate disposable lint-free lab wipes.

Lastly, make sure your desk or cleaning area is clean before putting the KimWipe down. Unless you have proper clean room facilities with filtered air, dust and fibers will likely settle on the filter almost instantly after cleaning. There is no sense blowing the filter off at this point. You should do that after you mount the filters in the filter wheel just before closing the lid and covering the entrance before taking it out to the scope.

Astrodon 31mm Filters

31mm Filters for the dedicated QSI 31mm Iternal Filter Wheel

Astrodon E Series Gen 2 LRGB Filters

Astrodon Tru-Balance RGB filters have revolutionized CCD imaging. Their popularity is due to ease-of-use, high optical throughput and great resulting color for galaxies, star clusters and nebulae. There are two varieties of Tru-Balance filters - E-Series and I-Series.

E-Series filters are designed to approximately equalize the flux of Kodak's full-frame (E-Series) CCD detectors, including compensation for the solar photon flux. This means that your RGB color combine weights will be approximately 1:1:1 within perhaps 10%. This can never be perfect, but it does allow you to take equal time exposures for your RGB data and also just one corresponding dark exposure time.

Introducing Generation 2 Tru-Balance filters (LRGB2) in April, 2008 in all sizes. This is the first change in Astrodon filter design and fabrication since their inception. We listened to your requests.

Technical Specs:

•1.25" mounted, 49.7 mm dia., 49.7 mm square
•~1:1:1 color combine weights for G2V white-point for Kodak Full-Frame (E) detectors
•Best choice for backthinned and Sony detectors
•Equal RGB exposures and one dark time
•Better color separation (spectra)
•Better color rendition for galaxies based upon color theory
•Significant reflection and star halo reduction (see Alnitak image)
•Enhanced contrast for HII regions in galaxies
•Spectral "gap" to minimize effect of light pollution
•Highest efficiency blue filter with less UV
•Correct "teal" OIII color for planetary nebula
•More parfocal - thickness 3+/-0.025 mm*
•Parfocal with Astrodon's high-performance narrowband and near-IR filters
•Striae-free 1/4 wave fused silica substrates
•30 arcsec parallelism
•Ultra-hard and durable sputtered coatings
•Proudly made in the U.S.A.

Astrodon Narrow Band Filters

Narrowband (NB) filters enhance contrast of emission objects by accepting only a narrow range of wavelengths around the emission lines of hydrogen (H-a, 656 nm), oxygen (OIII, 501 nm), sulfur (SII, 672nm) and others.

They can be used to image when the moon is up, thereby extending imaging time. They can be used in light-polluted locations.

The narrow range of wavelengths is defined as the FWHM (full-width at half- maximum intensity). Narrower filters decrease the background noise. However, narrower filters are more difficult to manufacture consistently, and are thus more expensive. Furthermore, it is difficult to maintain high transmission through the bandpass of the filter as it becomes narrower. If the peak transmission decreases as the filter is made narrower, the emission signal decreases and the gain in S/N (signal-to-noise) is not realized. Astrodon has achieved this goal of high transmission for narrower filters.

Astrodon has evolved its narrowband product line from 6 nm to 5 nm FWHM, significantly lowered the prices on all filters, and added the ultra-narrow 3 nm FWHM filters for H-a, OIII and SII. We added a Red Continuum filter (645 nm, 5 nm FWHM) that produces a star map without the H-a or SII emission in order to subtract stars from emission images. Astrodon NB filters are renowned for not producing halos around stars and not leaking NIR light.

The 3 nm FWHM filters are stocked and are not custom ordered. The 3 nm OIII filter provides the best protection from the effects of moonlight, producing half the background signal of a 90% T, 6 nm FWHM filter, resulting in an increase in S/N of ~21%. This will even be larger in comparison to wide 7 or 8 nm FWHM filters.

Technical Specs:

•28 mm dia (1.25" mounted)., 49.7 mm dia, 49.7 x 49.7 mm square unmounted
•65 mm square filters for SBIG STX NEW!

•36 mm dia. for SBIG ST-8300 NEW!

•28 mm dia. mounted in 31 mm insers for QSI cameras NEW!
•3 mm (+/-0.025) thick
•Parfocal to f/4 and parfocal with Astrodon LRGB depending on telescope optics
•H-a, OIII, SII, NII, Red Continuum
•5 and 3 nm FWHM filters guaranteed >90% transmittance (typically 92-97%)
•>4 O.D. (out-of-band blocking) 300 - 1150 nm
•1/4 wave, striae-free fused silica substrates
•30 arcsecond parallelism
•sides are blackened
•hardest available sputtered coating for durability
•3 nm filters can be used on systems to f/3
•designed to have lower blue spectral shift with faster (e.g. f/3) optics

Astrodon Filters for SBIG Cameras

A range of 36mm filters for the dedicated SBIG ST-8300 Filter Wheel and a range of 65mm filters for the SBIG STX Range of cameras.

SBIG recently announced its eagerly-awaited STX camera that houses the largest amateur imaging CCD detectors, such as the 16 megapixel 4096 x 4096 pixel Kodak full-frame KAF16803E that measures 36 x 36 mm with a 52 mm diagonal. The STX boasts many new features, such as fast USB2.0, full-frame image buffer, continuous imaging and guiding while downloading, better cooling to -50C, and many other advancements. Please see the link for more details.

SBIG continues its tradition of placing a guide detector inside the STX camera for their patented self-guiding. As a result, larger filters are required to cover both the imaging and guiding detectors. For this reason, SBIG will also introduce a filter wheel capable of housing 65 mm square filters that cover both STX detectors.

Astrodon Introduces 65 mm Square Filters for the STX

Astrodon introduces its latest Generation 2 E-Series LRGB imaging filters and 5 nm H-a (hyrdogen alpha) narrowband filter in 65 mm square size to support SBIG's introducton of the STX technology.

The E-Series is designed for the red-sensitive Kodak full-frame detectors with the goal of equalizing the fluxes, and hence, the signal-to-noise, for the red, green and blue filters. This simplifies your imaging, because it allows you to take the same length exposure for each color and only one dark frame exposure time. You will appreciate this since each 16803 FITS file is ~32MB in size. Within ~10% your color combine weights based upon a G2V (sun-like) star white point should be 1:1:1, making processing much easier.

Astrodon I Series Gen 2 LRGB Filters

Astrodon Tru-Balance RGB filters have revolutionized CCD imaging. Their popularity is due to ease-of-use, high optical throughput and great resulting color for galaxies, star clusters and nebulae. There are two varieties of Tru-Balance filters - E-Series and I-Series.

I-Series filters are designed to approximately equalize the flux of Kodak's Interline CCD detectors, including compensation for the solar photon flux. This means that your RGB color combine weights will be approximately 1:1:1 within perhaps 10%. This can never be perfect, but it does allow you to take equal time exposures for your RGB data and also just one corresponding dark exposure time.

Introducing Generation 2 True-Balance filters (LRGB2) in April, 2008 in all sizes. This is the first change in Astrodon filter design and fabrication since their inception. We listened to your requests.

Technical Specs:

•1.25" mounted and 49.7 mm diameter
•~1:1:1 color combine weights for G2V white-point for Kodak Interline detectors
•Equal RGB exposures and one dark time
•Better color separation (spectra)
•Better color rendition of galaxies based upon color theory
•Significant reflection and star halo reduction (see Alnitak image)
•Enhanced contrast for HII regions in galaxies
•Small spectral "gap" to minimize effect of light pollution
•Highest efficiency blue filter with less UV
•Correct "teal" OIII color for planetary nebula
•More parfocal - thickness 3+/-0.025 mm*
•Parfocal with Astrodon's high-performance narrowband filters
•Striae-free 1/4 wave fused silica substrates
•30 arcsec parallelism
•Ultra-hard and durable sputtered coatings
•Proudly made in the U.S.A.