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Services: OSI, Astrodon, OWL

Optical Structures provides a variety of services including:

  • Astrodon Professional Astrophotography Services. We offer advice, integration, and assembly to help you put together your complete dream astrophotography system. These services are available for individual customers as well as for large research and educational institutions.
  • Astrodon Filter Services. We offer custom filter orders and filter mounting services.
  • Optic Wave Laboratories (OWL) Services. We offer mirror coating, free mirror testing, mirror refiguring, and a wide variety of telescope services. More information at
  • Optical Structures offers robotic research telescopes, lightweight substrates and finished optics, LIDAR components, telescopes and scanners, and much more. More information at

For more information and prices, please email

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Authentic Astrodon Packaging

All Astrodon filters should arrive in Tamper-Proof packaging. There should be a seal on the envelope holding the filter(s) and a two seals on the filter box holding the filter(s) one on each side (so that the box can’t be opened by popping the hinge).  Please notify us immediately at if you suspect that your new Astrodon filters have been opened. Here is what the packaging should look like.

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36mm ring mount for Photometric Filters

Unlike other Astrodon filters, the Photometric filters (Johnson-Cousins and Sloan) do not come as 36mm of unmounted glass. For those who want 36mm round for use in a 36mm filter wheel, 27.5 mm of filter glass can be mounted in our 36mm adapter. Most people find the 27.5mm of filter glass more than adequate for single star photometry because only the center of the filter is used. Note that the 36mm ring adapter is 3mm thick (the same thickness as our Astrodon filters) but that the filter is raised 1mm above the top of the mount (total height of ring mount and filter is 4mm).

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Video of Astrodon Luminance filter blocking IR light from TV remote

Here is something you can try at home: Any cellphone camera or DSLR camera will allow you to see IR light from a TV or other remote. Best to use a DSLR like we did, so you can turn off the Auto-Focus (which uses IR). But even with a cellphone, you can adjust the angle to eliminate confusion from the Auto-Focus beam. But anyway, here is a video (without auto-focus) that clearly shows an Astrodon Luminance filter blocking IR light.

Click for Luminance Blocks IR video

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Most Astrodon Filters in stock!

Astrodon Photometrics UVBRI Filters_3

Astrodon Photometrics Sloan FiltersI just (July 31, 2018) finished updating the inventory numbers on the website and the stock is looking MUCH better than it ever has ever looked since OSI acquired Astrodon. Most (but not all) Astrodon filters are in stock, including the narrowband filters that everyone has been waiting for! So I think that we have really dug ourselves out of the deep hole that we were in and future wait times will be much more reasonable.


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Should I get Astrodon E-Series or I-Series LRGB filters?

Astrodon LRGB Gen2 E-Series Tru-Balance Filter Sets
Astrodon LRGB Gen2 I-Series Tru-Balance Filter Sets
Astrodon LRGB Gen2 I-Series Tru-Balance Filter Sets

A common question: Should I get E-Series or I-Series LRGB filters? The answer is that it depends on your camera sensor. Progressive Scan camera sensors ( including both Front Illuminated and Back Illuminated sensors) use the E-Series LRGB filters. Interline Transfer sensors should use the I-Series LRGB filters. Finding out what type sensor your camera uses can be difficult. This information is not often included in the specifications or even the manual. So it is best to check with the sensor manufacturer. If you absolutely can’t find out, then go with the E-Series and you will be fine.

FLI has put out a convenient list that specifies which type of sensor is in their camera. Since you usually know what sensor is in your camera (and different camera brands often use the same sensor) , this handy list can be used for other camera brands as well. But again, checking with your camera manufacturer and asking if their sensor is Front Illuminated, Back Illuminated, or Interline Transfer is your best bet.

For those who are interested in comparing the E-Series vs the I-Series Astrodon LRGB filters…Yes, we also sell the filters individually. The Luminance and Blue filters are the same in the E-Series and the I-Series. The Red and Green filters are different. So by buying one LRGB set (E-series for example) and then buying the Red and Green filters from the I-Series, you would essentially have both sets.




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2″ Lumicon Econoline OIII Filter Now $50

Lumicon 2 Inch Econoline Oxygen III Filter

We have halved the price of the Lumicon 2 inch Econoline OIII filter! Now only $50 with free shipping in the USA!

Lumicon 2 Inch Econoline Oxygen III Filter

Lumicon 2 Inch Econoline Oxygen III Filter, with an average peak transmission rate of 80%, is a bargain! Current mainline Lumicon OIII filters average greater than 90%, but at half the price, the Econoline provides solid performance. The Econoline is no slouch, it compares favorably with classic Lumicon filters of years ago. It was designed to vastly outperform “bargain brand” filters at only a slight increase in price over those low performance filters.

Oxygen III narrow band-pass filters isolate the two doubly ionized oxygen lines (496 and 501nm lines) emitted by diffuse, planetary and extremely faint nebulae. Thus, these faint objects become much more visible against the blackened background of space and produce near-photographic views of the Veil, Ring, Dumbbell and Orion nebula, among many other objects. This filter performs well under both light-polluted and dark skies.

More info and purchase here!

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What is the difference between Astrodon 1.25″ filters and Astrodon 31mm filters?

This is a common source of confusion. So…here we go. The glass portion of the filter is 27.5mm. So we take this 27.5mm of “naked glass” and mount it in one of two ways.

The first way is to put it into a 1.25 inch filter cell. This cell has threads, so it can screw into any 1.25 inch eyepiece or screw into many filter wheels.

The second way to mount the 27.5mm of naked glass is to glue it into a 31mm metal ring. There are no threads on this ring, so it is thinner than a 1.25″ filter cell. Most people prefer this thinner profile, so long as their filter wheel accepts 31mm filters and so long as they have no plans to screw it onto a 1.25 inch eyepiece or something. Depending on your equipment configuration, the 31mm filter may (or may not) reduce vignetting and/or allow you to use a faster scope.

Some people call 31mm filters mounted, some call them unmounted. Call it what you wish. But we refer to them as mounted because the 27.5mm of naked glass is mounted either in a filter cell or in a filter ring. But…nobody commonly sells 27.5mm of “naked glass”. We could, if someone actually has a filter wheel that accepts 27.5mm unmounted (I sold exactly ONE that way). Yes, 36mm and 50mm filters come unmounted. But 31mm is not “truly unmounted”. You just choose between filter cell or filter ring.

More confusion comes from the fact that if you take your calipers and physically measure the diameter of the 1.25 inch filter cell and the 31mm filter ring…they will both measure 31mm.