Estimated Arrival: Between May 16 and May 28. *ETA to USA Only
What about NII and H-a?
This is a bit complicated. It is not well known that most H-a filters pass both H-a and NII. H-a emits at 656.3 nm and NII emits most strongly at 658.4 nm (and weakly at 653.8 nm). These are very close together spectrally. Thus, most H-a filters are wide enough (e.g. 4.5 nm bandwidth and wider) to pass both emission lines as shown for the older Astrodon 6 nm filter above. Our 3 nm H-a begins to separate both emission lines and reduces the NII contribution significantly. In this example the 3nm filter only transmits 15% at the NII 658.4 nm wavelength, whereas the H-a remains unchanged. As mentioned earlier, some objects are enriched in NII, such as planetary nebula and Wolf-Rayet bubbles. The Dumbbell Nebula, M27, is a good example. The wispy clouds in the core of M27 are dominantly NII. A tricolor narrowband image is also shown below, mapping OIII to blue, H-a to green and NII to red to produce a beautiful color image. This information provides you with a choice based upon your light pollution, desire for more detail, or simply wanting all the photons you can get out
of your H-a filter.
Our NII filters have a center bandwidth of 658.4 nm. Bring 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.
We work very hard to ensure that we offer the absolute best prices online. If you find another online store that offers a lower price then us within six months of your purchase date please let us know and we will refund your original payment for the difference. We want you to feel confident that you are getting the absolute best price for the product you are ordering. If you find that our own website has a lower price for the same item you have ordered within six months of your purchase date will refund the difference as well.
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.
Our 100% Price Guarantee has some limitations:
- You must purchase the item from our website before requesting your Price Match Guarantee
- Promotions such as rebates and buy one, get one free offers are not eligible
- The item must be in stock on the competitors website
- The competitor must be an online store, they may not have a retail location
- The website can not be a discounter or auction website (ie; eBay, overstock, etc..)
- The competitor must be an Authorized Retailer of the product in question
- The Price Match Guarantee includes the item price and the shipping charges, it excludes sales tax
Order Confirmation As soon as you place your order you will receive an order confirmation e-mail. This means that we have received your order in our system and pre-authorized your credit card for the purchase. As soon as we receive your order we automatically reach out to our suppliers to confirm that it is in stock and available for immediate shipment. If your item is on backorder or unavailable we will void the pre-authorization and reach out to you via e-mail. If your item(s) are available for immediate shipment (within 5 business days) we will process the charges and submit the order for shipment.
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 email@example.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, Hawaii & Alaska etc., as defined by the shipper. These circumstances occur less than 1% of the time.
You can estimate the deliver time to your home or business by viewing the "Ships Within" information listed with every product. This refers to the time from when you place your order, to the time it leaves the warehouse. The total delivery time for your order is calculated from the time your order is placed, until you receive it. The diagram below shows how the total delivery time is broken down into pre-ship processing time and shipping time.
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.
Did your shipment arrive damaged or defective?
Please report damaged or defective merchandise to us immediately by email phone. Photos of the items and the packaging would be greatly appreciated. This will speed up our resolution process. We strongly recommend at the time of delivery, if your notice any cartons that look dented, crushed or just not right, open them immediately and inspect the contents. If the contents appear to be damaged, please notate it on the delivery ticket, refuse that item only and contact us as soon as possible for instructions.
Brands/Products that do NOT qualify for our 30 Day Return Policy:
APM products do not qualify for our 30 day return policy.
Additionally, items that are special ordered, customized, or engraved - cannot be returned or refunded under our 30 day return policy.
If your engraved item needs to be repaired within 30 days of purchase, please reach out to us and we will have the product repaired or replaced, re-engrave if necessary, and return it to you in new condition.
QUESTIONS & ANSWERS
Have a Question?
Be the first to ask a question about this.