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Baader Planetarium Neodymium Moon & Skyglow Filter

Baader Trademark (19,559 bytes) Baader Moon & Skyglow filters (68,093 bytes) The Moon & Skyglow is a multi-bandpass filter transmitting a high percentage of light in the visual spectrum; it is among our most economical and versatile well made astronomy filters. The filter enhances contrast when observing brighter objects including the moon and planets. It also will suppress sky glow from artificial lighting and background glow reflected when the Moon is up. The filter has a mild effect of darkening the background of the night sky so that the fainter objects are more clearly seen contrasted against the blackness of space. This is the only filter suggested by Company Seven that has any positive effect when viewing galaxies and star clusters.

Right: Baader Planetarium Neodymium Moon & Skyglow 1.25 and 2 inch filters shown with provided plastic cases.(97,825 bytes).
Click on image for enlarged view (179,869 bytes).

What Does This Filter Do For Me?
The filter is made with a special Neodymium glass that effectively filters out selective wavelengths of low-pressure sodium and other manmade sources typically used in street lighting. Although it is not a nebula filter, it enhances the views of deep-sky objects by increasing the contrast of these objects against the background sky. While nebula filters transmit only a few select wavelengths corresponding to various atomic lines, this filter transmits a large portion of the continuous spectrum while blocking a few select lines of the more common manmade light. Neodymium provides a unique, selective, blocking feature in that this element greatly reduces glare without reducing important color and brightness variations.

It enhances contrast of all reddish details and so this filter can also be used for planetary viewing (the Great Red Spot on Jupiter), as well as of blue details (some surface and atmospheric details on Mars). A positive feature is that the image retains its natural colors in as opposed to the effect of conventional color filters.

It also works well for observing Mars when stacked with the yellow filter of the Baader Premium 1.25" Colored Filter Set, this brings out the surface features of the planet.

You can also use the filter on the deep sky, contrast is enhanced a little in bright planetary nebulae or other nebulous objects, like for instance the Great Orion Nebula. The observer with a broad range of interests will find their filter will be complemented by other bandpass Nebular filters including the Baader Oxygen III.

Very high light transmission exceeding ninety five (95) per cent of that light some the portions of the spectrum - while blocking unwanted skyglow and many street light emissions. The filter has a notable effect at enhancing contrast when observing brighter objects including the moon and planets.

By rejecting most other light this will cause certain objects to appear more clearly against a blacker background of space. The visual effect is subtle to the less experienced observer. However with experience the differences of observing with and without this filter become easier to comprehend.

The filter is also suited for CCD imaging applications due to it's contrast enhancing properties and modest effect at darkening the objects.

Available in diameters of 1.25 (31.7 mm) and 2 inch (50.8 mm).

This is among the first few filters for lunar, planetary, and deep sky observing generally recommended by Company Seven to our customers who have a suitable telescope for the task.

    Filters take away but they can not add - diminishing some parts of the spectrum
    so that we might see what is otherwise obscured...

How Are These Constructed?
The filter is made with a disc of neodymium filter glass that has been ground to be plane parallel and then polished until very smooth. The glass undergoes a vacuum deposition multi coating process where numerous micron-thin coatings of various elements are applied one upon another in a precise order and thicknesses to improve light transmission and reduce possibility of ghosting or reflected images.

The filter element is housed in a machined aluminum cell, retained by a thread in retaining ring. The filter name, size and part number are in silver, and this mirror like print when combined with the fine print make this information difficult to read under dim red lighting. Company Seven recommends our customers keep these filters in well organized accessory cases, so that you know which filter is which. It helps to become familiar with how the elements appear too.

Incidentally, this BG-20 ionically colored glass was developed by Schott Glassworks for the Carl Zeiss company. Ionically colored means this is a colored glass that is constituted of a true solution of glass, ions of heavy metals or rare earths, which attribute to the the glass its coloration, absorption and transmittance properties.

Moon & Skyglow Filter Graph (134,493 bytes) Right: Baader Moon & Skyglow filter transmission curves in nanometers, with the transmission (permeability) given in per cent. The area under the curve is the spectral region which the filter transmits (161,131 bytes).

Features Of The Baader Filters:

  • The glass elements used to make the Baader Filters are free of striae, optically finely polished plane parallel to within 30 seconds of arc. This eliminates any double images or ghosting due to wedge errors in the glass. These filters tend to far supersede the quality of common color filter elements which are flame polished. The combination of their fine optical craftsmanship and a comparatively thin 2 mm profile allows these filters to be inserted anywhere into the optical path without introducing astigmatism or other noticeable defects into the image. For instance they can be installed in the front of a Binocular Viewer without degrading the image in any way.

  • All filters will thread into conventional slip fit eyepieces or accessories with the common 1.25 inch diameter x 42 tpi (28.5 x 0.6 mm) or 2 inch (50.8 mm) threading. These thread patterns have been tested and optimized to fit allmost all eyepieces on the market.

  • Stackable filters: each filter cell incorporates both a male and a female thread to allow stacking the filters to obtain even narrower passbands or special effects. For example, try adding the yellow filter from the Baader Premium 1.25 inch Color Filter Set to boost the contrast on Mars. When stacking filters on an eyepiece, be careful that the eyepiece barrel with the filters attached does not strike the mirror or prism of your diagonal.

  • The filter cells features the largest clear aperture of any 1-¼ and 2 inch filters on the market - for complete freedom from vignetting at any focal length. The front crown of the cell incorporates milled notches which makes handling and threading the filter an easy operation in the dark.

  • Multi-layer coatings on both surfaces - ultrahard and durable ion-beam hardened coatings, may be cleaned anytime without fear. Note: the 2 inch filter has a very hard, single layer MgF2 coating (Zeiss T coating).

  • For protection, each filter is provided with its own transparent plastic case. We are astonished however, that as outstanding as the filters are, plastic case latch tend to fail sometimes even when new. Company Seven therefore offer optional third party cases. And for the most discriminating clients, we even offer a custom made wood accessory case described below.

    Optional Wood Case
    optional wood case for Questar Color Filter Set. (52,803 bytes).

    Company Seven makes available to our customers an optional wood case that is foam lined with cutaway spaces for filters, eyepieces and other small accessories for your telescope. Please refer to our price list for current prices for the filter set and the optional case or contact Company Seven for more information.

    Right: optional wood box for Color Filter Set (52,803 bytes)
    Click on the image to see enlarged view (190,049 bytes).


      "Recently I have discovered the Skyglow works wonderfully when stacked with high transmission color filters to highlight details on Mars. My favorite combination for Martian detail is to stack the Skyglow with a Deep Yellow color filter... I find the Skyglow helps sharpen images that are otherwise negatively affected by slight haze (slight reduction in transparency). It's the best $ I've spent on astronomical accessories. T. R., VA

      "I purchased the Baader Moon & Skyglow filter a little over a month ago and would like to share I am very pleased with it. I've been using it in the mornings to view Mars with my 4" refractor. I'm a little nervous we'll get a major sandstorm this year so I've been trying to view every chance I get. Comparing to unfiltered views the Baader really makes the polar cap pop out! I'm also very pleased with the contrast it shows on the dark and lighter land features. It is a great planetary filter." M.S., Oregon

      "Recently I have been using it with Mars observation. No question the filter improves my view. Contrast is improved. Markings on the surface are more easily seen. The edge is sharper as is the south polar cap rim. The filter seems to improve the seeing condition. Glare is also reduced. On top of it all I find the color rendition it gives to Mars very pleasing." B.F., CT

      "Just a note to let you know how pleased I am with the 48mm Moon & Skyglow filter. It's a great Jupiter filter, makes the moon tolerable in my 18"and costs 1/2 of what a (brand deleted) 1.25" skyglow filter (my previous Jupiter filter) cost. There are no 48mm moon filters out there, so this was a great find -- I use it as one of four filters in my Astrosystems filter slide. You should advertise these things more to the big Dob crowd. You'd sell a lot of them. " MPD, MA

      "Below is a mini-review I posted to the NexStar GPS Yahoo group: I have the 2" Baader Moon & Skyglow filter in for visual use and just leave it in all the time when I'm observing from the suburbs. It is awesome on planets improving contrast and detail while retaining the natural color. It also is a substantial help on DSOs, in particular galaxies and globular clusters. I had a 11/4" (brand deleted) filter prior, but wanted to go to a 2". After comparing the two filters spectral characteristics, they were so close that I couldn't justify spending an additional $150 on the (other brand)." C.S., CO

      "The filter enhances contrast on Jupiter, especially the GRS and gnarled details where there is white against rust or reddish colors. It's a great deal to have a 2" filter of this quality at this price. Unlike the filters in the ubiquitous multi-color sets, this filter takes off the edge without killing the image. I'm planning on keeping mine." G. N., New York

      "The Baader Sky Glo filter enhances the views of Jupiter in my AP 155MM f/7 very well. ( The views are already impressive to say the least without the filter.) On certain nights though, this filter aids in reducing unwanted glare, further embellishing the festoons, GRS (great red spot) and other interesting details of this gas giant. I highly recommend this filter when observing the moon past first quarter! Thanks for such a most needed addition to my observing arsenal." P. W., S.C.

      "I am most pleased with my 48mm Baader Moon and Skyglow filter and highly recommend it. I have found it to be a great filter to boost the contrast on Jupiter and bring out planetary details that are typically difficult to discern in my mediocre Northeast skies on most nights. Threading it into the nosepiece of my Maxbrite diagonal allows me to use multiple eyepieces without the need to remove and reattach the filter with each eyepiece change. I also use the filter when viewing the moon. It not only enhances contrast to help bring out lunar detail but it also cuts down some of the glare through the eyepiece when the lunar phase is nearing full." C.R., MA


    • PDF IconBaader Planetarium Professional Astronomical Filters one page color illustrated overview of several Baader specialized astronomical filters including the Moon and SkyGlow, Oxygen III Narrow Band, Contrast Booster, Color Filter Set, UV-IR Rejection, Fringe Killer, Solar Continuum, UHC-S High Transmission Nebula, and U-Filter. Includes filter transmission curve graphs. Publication content by Baader Planetarium, all rights reserved. From Company Seven's Archives (127,011 bytes in Adobe .pdf).

    • PDF IconBaader Planetarium Neodymium Moon & Skyglow Filter one page color illustrated overview of the Moon and SkyGlow filter. Includes filter transmission curve graph. Publication content by Baader Planetarium, all rights reserved. From Company Seven's Archives (265,190 bytes in Adobe .pdf).

    • Review: Baader Skyglow Filter 2 inch an illustrated evaluation of the filter written in October 2002 by Mr. Tom Licha. In this Mr. Licha demonstrates the value of this filter even for CCD imaging. Text and illustrations (with exception of the filter curve) 2002 by Tom Licha.


    1. It is best to protect the filter from sharp edges or any item that could cause a scratch or abrade the glass.

    2. When not in use, store the filter in a its provided rigid container, and it may help you to keep them organized in a fitted carrying case.

    3. Dew may form on the filters, if this happens do not store a wet filter into its airtight container for long periods of time; whenever possible let the filter "dry out" in order to reduce the potential for problems developing associated with Fungus, etc.

    4. Draw any large, loose bits of foreign matter from the surface of the glass with an air bulb or small vacuum. Stubborn particles can be removed with a soft camel's hair brush. Throughout the year, but especially in cold climates when static become more of a problem we particularly recommend the use of a Staticmaster brush.

    5. Place a few drops of an approved lens cleaning solution (by Carl Zeiss or Kodak) or mild soap solution of clear dish washing liquid diluted with distilled water onto a cotton swab. Then gently wipe in a circular motion with little or no pressure. The filter can be damaged if there are tiny abrasive particles on the surface which are pressed in by rubbing hard.

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