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36 mm dia. Unmounted Astrodon 3 nm SII for 671.6 nm

36 mm dia. Unmounted Astrodon 3 nm SII for 671.6 nm

Brand: Astrodon
Item Number: OIII3_36R

Regular price $960.00 $748.00 On Sale

  • Estimated Arrival: Between Oct 04 and Oct 19. * ETA for USA only

    Shipping & Returns: Free Shipping with $100 purchase. Easy Returns. Simply ensure that the item is returned in its original product packaging within 30 days of purchase.

    H-? (hydrogen-alpha) at 656 nm (nanometers) is deep red in color and the most popular narrowband filter. Hydrogen is ubiquitous in the cosmos and is present in emission nebula (North American, Pelican), planetary nebula (Dumbbell, Ring), Wolf-Rayet objects (Crescent, Thor’s Helmet) and supernova remnants (Veil). Many imagers like to present just a black-and-white H-? image of an object. It is has a beauty all by itself, like an Ansel Adams photo. However, most imagers blend their H-? data into their red RGB data to enhance structural detail while maintaining a “natural” look. Therefore, the H-? filter should be your first narrowband addition to your LRGB filters. The basic imaging set of 5 filters becomes LRGBH-?.

    Astrodon H-? filters have a center bandwidth of 656.3 nm If you want the look of Hubble Space Telescope (HST) images, such as the famous “Pillars of Creation” (the Eagle Nebula, Messier 16), then the next filter to consider adding to your collection after H-a and OIII is the SII (es-two) or sulfur filter. The SII filter, like H-a, is a deep red filter near 672 nm. H-a, OIII and SII filters provide that Hubble look for many emission nebula. Again, tri-color narrowband imaging with these three filters can be done with the moon up, so your equipment is not sitting dormant for several weeks.

    Astrodon SII filters have a center bandwidth of 671.6nmBring Out The Faint Structures In Nebulae
    Astrodon Narrowband filters set a new bar of performance and durability for imaging and research. We offer 5 nm and ultra-narrow 3 nm bandwidths.Astrodon Narrowband filters set a new bar of performance and durability for imaging and research. The narrow 5 and 3 nm bandwidths enhance contrast of emission targets by lowering your background signal. The guaranteed >90% transmittance at the emission wavelength provides you with the highest signal available. This guaranty is expensive to manufacture for such spectrally narrow filters, but it assures you in writing on each filter box that you will get what you paid for. These two factors combine to provide you with the highest contrast available. Our latest narrowband filters are typically achieving >95-98% transmittance. Astrodon Narrowband filters are renowned for minimizing halos around bright stars, even for long exposures of 30-45 minutes typical of narrowband imaging in astrophotography. Lastly, Astrodon Narrowband filters are coated to the edge of the part and are edge blackened. This is critical to minimize stray light for a filter that blocks most light except for the narrow bandpass.

    Astrodon Narrowband filters for imaging are all about contrast. What do we mean by this? Contrast brings out faint features by reducing the background – the narrower the filter, the better. The problem is keeping the signal (%T at the emission line) constant as the filter becomes spectrally narrower. This is why our >90%T guarantee is so important, even though it becomes very costly to manufacture. But, this assures you that you can take advantage of the improved contrast with our narrower filters compared to the much less expensive 7- 8.5 nm filters on the market. You can see the increase in contrast in the sequence of equal-exposure images of the Crescent Nebula (NGC 6888) taken on the same system and on the same night. As the bandwidth becomes narrower, the nebula “pops” out of the background, as does the faint surrounding nebulosity. Actually, the >90%T is a legacy specification, since new production technologies employed over the past 3-4 years routinely produces 97-98%T at the emission wavelengths.

    Random tests of a competitor’s low-cost 7 nm H-? filter showed %T values ranging from 86% down to 71%. Random selection of 5 nm Astrodon filters measured %T values at the H-? emission wavelength of 93, 98, 97 and 98%. You will never know that you are using their 71% filter compared to a 97% Astrodon filter because they do not guarantee this important performance parameter. They recently came out with a 3.5 nm H-? narrowband filter and those results are even worse, ranging from 3-70% at the emission wavelength. Similarly, analysis of different 2016 lots of Astrodon 3 nm H-? filters measured 97, 97, 97 and 96%T. Yes, our filters are more expensive, but you always know what you are getting with Astrodon Narrowband filters – the best performance in the market – guaranteed. Our recent blueshift data show that Astrodon 3 and 5 nm filters can be used with nearly all systems as fast as f/3.5 with virtually no loss in emission signal, so you do not need to buy custom “upshifted” filters if you have both fast and slow systems.

    Step up to the quality and performance of Astrodon narrowband filters.

    Astrodon Narrowband filters currently are provided off-the-shelf for:

    Sulphur SII 671.6 nm 5 and 3 nm
    Hydrogen-alpha H-? 656.3 nm 5 and 3 nm
    Nitrogen NII 658.4 nm 3 nm only
    Red Continuum RedCon 645 nm 5 nm only
    Oxygen OIII 500.7 nm 5 and 3 nm
    Other emission lines, bandwidths and sizes upon request
    When we refer to bandwidth, we are referring to the spectral width of the transmission region at 50% of the peak transmittance (FWHM – full width at half maximum).

    1.25? mounted, mounted in 31 mm rings (for QSI), 36 mm unmounted, 49.7 mm diameter and square unmounted (36 mm filters will not exceed 36.1 mm dia.)
    3 +/- 0.025 mm thick (5 nm); 3+/-0.05 mm thick (3 nm) substrate prior to coating
    Parfocal with all other Astrodon filters (depending upon telescope optics)
    Peak transmittance guaranteed >90% at the emission line (97-98%T typical) f/10 to f/3.5 for both 3 nm and 5 nm
    >90%T at the emission wavelengths for 5 nm OIII and H-a at f/3. >80%T for SII at f/3
    >90%T for 3 nm OIII at f/3
    Steep spectral profile minimizes halos around bright stars
    >4 OD (out of band blocking) 300 – 1150 nm
    Single, striae-free 1/4 wave fused silica substrate
    30 arcsecond parallelism
    Durable hard-oxide sputtered coatings with a 5-year limited warranty against delamination
    All filters are coated to the edge and edge-blackened to minimize stray light contamination that can come though the uncoated “rim” in other brands
    Please read our detailed Astrodon Narrowband Filters_FAQ (Frequently Asked Questions) by clicking on the link. We cover such issues as what is a narrowband filter, filter selection guidelines, contrast, bandwidth, out-of-band blocking, fast optics, effect of moonlight, separation of NII and H-a, etc.

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    To request your partial refund simply e-mail us a link to the same product on our website, or on our competitors website within six months from the date of your order and we will process the credit accordingly.

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    Order Shipment If your order is received, the inventory is in stock and your credit card information matches the information, In most cases, we can ship within 5 business days. We will send you tracking information within 24 hours of your order leaving the warehouse to the e-mail address your provide when checking out.  If you do not receive tracking information from us within six business days of your order please email us at info@skygazeoptics.com.

    Miscellaneous Shipping Information

    • We cannot ship to PO boxes.
    • Non-standard shipping surcharges will apply to isolated service areas, such as remote areas, areas not readily accessible by a delivery vehicle, islands, etc., as defined by the shipper. These circumstances occur less than 1% of the time.

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    Processing time is the time it takes from when you submit your order to when the product leaves the warehouse. The "Ships Within" time frame listed with each of our products on the website applies to this time frame. For example, if your order a product that reads "Ships Within: 2 Weeks", this means that the product typically leaves the factory within two weeks. If there will be any additional time required to process your order, we will notify you immediately to confirm the delivery period. This time is needed for products that are shipped to you directly from our manufacturers. The manufacturers need this time to fulfill your order. In some cases, the items are custom built.  Shipping time is measured when your order leaves the warehouse to when it arrives at your address. Actual shipping time can vary between 2-5 business days. Contact our helpful customer service experts at (888-264-2244)  for more information.

     

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