Welcome to

SPECTRAL OPTICS

Web Page

The Patent Pending DG Spectrum Products Page

Using our DG Filters and our software tools, you will be able to see some of the individual elements that make up a star and you will be able to actually identify some of these elements, plus you will be able to determine how fast the star is moving toward or away from us (you will need to accurately calibrate your system to do Red Shift calculations - there is a tutorial on our CD that tells you how you can do this and there are Red Shift tools included on the CD to help do the math for you.) With our DG Filters it will also be possible to determine some of the chemicals present in a comet's tail as well as the chemicals present in a planet's atmosphere (to determine chemical spectrums you will need a spectral reference book.)

1. Type A:

The Type A filter is designed to be inserted inside the empty lens well of a CCD camera. It is held in place by friction between the device and the lens well wall of the camera. In some cameras additional friction is sometimes needed. In those cases a small toothpick, or similar item, is usually used to gain the needed friction.

As this device is held in place by friction it will need to be adjusted each time it is used as the depth and position angle will change somewhat each time it is inserted into the camera.

2. Type B:

The Type B filter is designed to be mounted onto the filter threads on the end of the CCD camera. It has a small protrusion that fits down into the empty lens well of the camera.

The advantage of the Type B filter over a Type A filter is that a Type B filter is always positioned at the correct angle and depth eact time it is used, so its ready to go as soon as it screwed to the camera's filter threads.

3. Type D:

Our Type D - DG Filters incorporate Two Protective Glass Cover disks and Two PVC Seals on either side of the grating material. This protects the large grating area from dirt and contamination. While this does make the unit water resistant from splashes it does Not make it water proof.

Our Type D filters can be screwed directly to the filter threads on a standard 1.25" eyepiece as well as the filter threads on a standard CCD camera. The Type D1 and D2 units were designed especially for use with cameras. The Type D2 Filter isn't normally recommended for CCD photography unless the camera has a filter wheel/tray, where it can be placed in close proximity to the CCD chip, like SBIG's CFW-8, Celestron's NexImage camera or Meade's DSI PRO and the DSI II Pro.

We also make our Type D - DG Filters to fit film cameras and camcorders as well as 2" (48 mm) size for telescopes. To order these go to our Accessory Page.

Our Type D3 - DG Filter was specifically designed for visual use with eyepieces. They use a Low Dispersion grating that can accomodate the longer separation distances generally associated with eyepieces. The D3 Filter uses a very special grating that makes it difficult to miss seeing a spectrum. The D3 Filters do not have the resolution that the D1 Filters do but the D3 Filter produces bright spectrums in four planes while the D1 Filter only produces spectrums in one plane. The D1 Filter is better at seeing spectral lines and the D3 Filter is better at seeing/finding spectrums.

Visual views with the Type D3 - DG Spectrum Filter through a 20 mm to 40 mm eyepiece are Absolutely Breathtaking! One young woman, at a Star Party, looking through a small scope equipped with a D3 Filter, at a star field, Exclaimed - "WOW! With this you don't need drugs to Hallucinate!"

Visual Use and Cylindrical Lenses

Cylindrical lenses are used to defocus/spread the spectrum perpendicular to its axis to make the spectral lines in the spectrum are more easily visible. These lenses are expensive and very generally quite inefficient and you need a lot of different ones to cover different combinations of stellar magnitudes, eyepieces (yes, you need to match it to your eyepiece) and telescope sizes (see the FAQ page for more details). There are other more cost effective ways to achieve the same result without using a cylindrical lens, for this refer to our How to Focus FAQ Question.

Type D - DG Filters do not come with a cylindrical lens, as is supplied with similar products from competitors, as it drives the price up. Additionally, no visual spectrum filter made by any manufacturer, no matter what they might say, will produce spectrums of dim stars. For visual observations, when a spectrum filter is combined with a cylindrical lens the spectral image becomes so dim that 3 rd magnitude stars become the limiting magnitude, when using an 8" to 10" telescope.

Even with a cylindrical lens its very difficult to actually see any of the spectral lines present much less identify any of them. Without a cylindrical lens you can see the spectrums of stars one to two magnitudes dimmer then is possible when using a cylindrical lens.

There is a Major Misconception about using Cylindrical Lenses - a single cylindrical lens works for all. Nothing could be further from the truth. The old GOTO Star Spectroscope, which is what All visual star spectroscopes are judged against today, came standard with three different cylindrical lens units. Todays manufacturers Only offer a Single Cylindrical Lens with their products as if to say 'This will do it All for you'...

For a cylindrical lens to spread a line spectrum out, so that you can see the spectral lines, the Cylindrical lens needs to satisfy four criteria: 1. Its focal length needs to be matched to the size of the scope (light gathering ability), 2. It needs to be matched to the FOV and Focal Length of the eyepiece it is to be used with (so you can see the spectrum), 3. Its focal length needs to be selected for the magnitude of the star being observed (so the spectrum will be bright enough to be seen), and 4. Its size much be matched to the size of the exit lens on the eyepiece it is to be used (so you can find the spectrum).

For one particular telescope using three different 1.25" eyepieces you should have at least six different cylindrical lens units. None of the manufacturers offer such options so they all act like "one lens will do it all". Without the proper cylindrical lens you won't see much of anything much less any spectral lines. Refer to our FAQ question on cylindrical lens selection.

Compact Version:

Our Compact version is Extremely Easy to Use and it allows both the object (zero order) as well as its spectrum (1st order) to be photographed at the same time. This makes wavelength measurements, calibration, and alignment extremely easy.

The Compact Version works with both 1.25" threaded eyepieces, CCD cameras and CCD filter wheels/trays.

High Resolution Version:

We also offer a High Resolution version for professional astronomers that produces a spectrum so wide that an object and its spectrum can't fit on the CCD chip at the same time. Because the spectrum is spread out so wide much finer detail can be gained from this spectrum. This grating is more efficient then the grating used in our Compact version.

The high resolution grating has a cutoff at 1000 nm due to its very wide dispersion. Better than 80 % of all of its spectral light is concentrated in its first order image.

The High Resolution version is Only Recommended for Experienced users as it is not as easy to use as the Compact version.

Very Low Dispersion Version:

We offer a Low Dispersion unit especially designed to be used with standard 1.25" eyepieces. This grating produces a spectrum much shorter than those produced by our Compact units. This makes them well suited for eyepiece use.

These units also produce multiple spectrums in four planes, while our other two types of gratings only produce a single spectrum in one plane. This makes it extremely easy to use and much more visually appealing when used with eyepieces.

If you are looking for a visual experience and don't want to spend a lot of money this is your only answer.

The Low Dispersion version is Only Recommended for Visual Use with Eyepieces or as a Special Effects filter with film cameras.

We offer Three Different DG Spectrum Filters and we have two versions of spectral resolutions for each of these three DG Filters, making a total of Six Different DG Spectrum Filters designed just for CCD cameras. We actually have Seven different types of DG Filters but the Type D3 Filter was especially designed for visual use which requires a Low Dispersion grating, while CCD cameras require a High Dispersion grating.

Supported Camera Models:

1. Meade's LPI CCD Camera (Retails for $150.00 USD) - Works with DG Filter Types A1/A2 and B1/B2

2. Meade's DSI & DSI II Camera (Retails for $300.00 USD) - Works with DG Filter Types B1/B2

3. Meade's DSI Pro & DSI II Pro Camera (Retails for $400.00 USD) - Works with DG Filter Types D1/D2/D3

4. Celestron's CCD NexImage (Retails for $150.00 USD) - Works with DG Filter Types B1/B2 and D1/D2/D3

5. SBIG CFW-8 Filter Wheel when on a SBIG ST-xx camera - Works with DG Filter Types D1/D2/D3

6. SBIG ST-xx series CCD Cameras with T-thread to 1.25" Ring adapter - Works with DG Filter Types D1/D2/D3

7. SBIG ST-5 series CCD Cameras with T-thread to 1.25" Ring adapter - Works with DG Filter Types B1/B2 and D3

8. Starlight Express series MX/HX/SXV-H5/M9 with 1.25" threaded Nosepiece - Works with DG Filter Types B1/B2

9. Most Filter Wheel/Tray CCD Cameras that accept standard* 1.25" filters - Works with DG Filter Types D1/D2/D3

10. Philips TUcam using a 1.25" Threaded Nose Piece - Works with DG Filter Type D3

11. Most Threaded Web Cams that have a standard 1.25" Threaded Nose Piece - Works with DG Filter Type D3

* For Film Cameras, Camcorders and Filter Wheels/Trays that accept other sized camera filters, like the 37 mm camcorder filters, go to our Accessory Page where we offer our Types D1 and D3 - DG Filters in sizes from 28 mm up to 72 mm.

If you don't see your camera in our list then contact us, as we can custom make a DG Spectrum Filter to fit most cameras that either doesn't have any lens elements or has a removeable lens.

A lot of web cams and PC cams don't have removable lenses or standard 1.25" filter threads, as such our DG Filters will not work with them and we don't try to adapt our filters to them because of the cost involved in the conversion. In this case a Meade LPI camera can be purchased used for around $125, or less, on Astromart or ebay.

Type A1  Compact Spectrum Filter fits in the camera's lens well -     $ 99.95 
Type A2  High Resolution Spectrum Filter fits in camera's lens well - $124.95 
Type B1  Compact Spectrum Filter screws to camera's filter threads  - $159.95 
Type B2  High Resolution Filter screws to camera's filter threads  -  $184.95 
Type D1  Compact Spectrum Filter designed for CCD/Eyepiece use -      $134.95  
Type D2  High Resolution Filter designed for CCD use -                $159.95  
Type D3  Very Low Dispersion Filter designed for Eyepiece use -       $124.95  

There is an Additional Shipping Charge Required for All International Orders; Other than Orders to Canada and Mexico. If Your Order is an International Order follow these instructions: AFTER you have added your item(s) to your Shopping Cart and BEFORE you Checkout you need to click One of the Two ADD to CART Buttons Below to add the extra shipping cost to your purchase.

Airmail Letter Post: + $6.78

Global Express Mail: + $42.25

You have Two Options for International Shipping: Airmail Letter Post, and Global Express Mail. With Airmail Letter Post the package can't be insured or tracked, with Global Express Mail it can.

If you choose Airmail Letter Post and you don't receive your package contact us and we will Send you a Copy of the Mailing Receipt that will have your Destination Country, the package weight (in ounces) and the Customs Declarations Number, but We Will Not Reship Your Order a Second Time. If your package is lost You Will have to Replace Your Order and Pay for it All Over Again.

If you choose Global Express Mail your package can be tracked to where it was delivered if you do not receive it, and you will have $100 of insurance on your package. Plus We Will Re-Ship via Airmail Letter Post Another Package to you (At No Cost to you other than the money received from the package insurance) if your initial package is lost. The Re-Shipped Package will not have this insurance and will fall under the rules set out in the previous paragraph.

We hand test and inspect Every Single DG Filter, long before its shipped to a customer, at several different phases during the manufacturing process. Each unit undergoes a rigorous battery of tests to ensure each will preform as expected.

The units are all assembled in the United States from parts obtained from a variety of manufacturers who produce parts and sub-assemblies to our exacting standards. After we receive these parts and sub-assemblies each piece is checked to be sure it meets the tolerances ordered. Then during our final manufacturing process these pieces are again inspected. These tests and inspections include, but are not limited to, the following:

1. The number of defects in the grating material must be less than 5, and the defect area must not exceed 3% of the total surface area of the grating.
2. The grating must pass a continuous spectrum over 99% of its entire surface area without having any discontinuities in the central 90% of the grating area.
3. There must be no non-contiguous areas of the spectrum in the central 90% of the grating area.
4. The band within 2 mm of the outer edge of the grating area should have no more than 5 blemishes impeding the spectrum in that area.
5. The visible transmission of the grating material has to be in excess of 92% averaged across its central 90% area.
6. Impurities/marks from fastening or glueing of the grating to its holder will not extend beyond the 2 mm edge area.
7. There will be no finger prints or other permanent disfigurements in the central 90% of the grating area.
8. The central 90% portion of the grating must produce a flat linear spectrum without any bends or discontinuities.
9. Small scratches and or very small dust particles may be allowed as long as the total count of the particles doesn't exceed 20 and they do not interfere with the spectrum in any manner and they do not reduce the average transmission below 92%.
10. All external and internal surfaces of the grating holders are painted flat black to impede internal reflections.
11. Any chipped paint area on a housing will be less than 2% of the surface area of the side of the housing where the chip is located.
12. There will be less than 3 chips/chipping of the paint on a grating holder.
13. No single paint chip can exceed 4 square millameters in area.
14. All retaining rings will be tightened but not so tight that they can't be quickly loosened using the appropriate tools.
15. All glass surfaces are to be smooth, ripple free, clean and free of dirt and lint.

These stringent inspections take a toll on the units that are manufactured, plus the extra time required to preform all of the tests and inspections increases our cost. The DG Filters using the Compact Grating, 500 l/mm, average a 24% loss rate. The DG Filters using the High Resolution grating, 1000 l/mm, average a 36% loss rate. The DG Filters using the Low Dispersion grating, 200 l/mm, average a 50% loss rate.

While this is expensive it is worth it in the long run as our customers will be assured of getting a DG Filter that will work right out of the box, under a variety of conditions, and perform perfectly each time.

We not only give you great discounts but we also give you a Great Money Back Guarantee on all our products. If one of our products doesn't perform as advertised, when used on its supported camera, simply send it back in Good Resellable Condition (this means the grating hasn't been damaged in any way), with your original sales receipt, within 30 days and we will issue you a full credit for the item, less shipping and handling charges. What more could you ask for?

All of our DG Filters are warrantied against defects in manufacturer for a period of 30 days from the date of purchase. Mishandling, general wear and tear, aging, modifications, finger or oil smudges or dirt on the grating surface, chipping paint, use on non-intended cameras, accidental damage and other use incidents are not covered by our warranty.

We don't Warranty or Guarantee our DG Filters or our Accessories to work on cameras they are not intended to be used on or in conjunction with, or in Not Recommended assemblies. This means if you have a supported camera, like a TUcam, and you buy a D2 DG Filter to use with it don't expect the D2 Filter to work as advertised with it as the TUcam was not included in the D2 drop-down selection list.

NOTES:

1. Our DG Filters produce the advertised results when used at the Prime Focus of a telescope. Using Barlows and or Reduction lenses, etc. may significantly affect performance, for better or worse, due to scattering and absorption by these extra optical elements.

2. All of our DG Filters will allow standard 1.25" filters to be screwed onto either the camera or the DG Filter itself depending on the filter type.

3. Type A and Type B - DG Filters will not work with any camera that has a non-removable lens.

4. Type D - DG Filters will work with any filter wheel that accepts 1.25" filters, most eyepieces and cameras that have standard 1.25" threads on it.

5. All units are shipped USPS First Class Mail. Shipping and Handling charges are in addition to the price of the DG Spectrum Filter.

6. All orders for a DG Filter will also receive our UCC Copyrighted 200+ Meg. CD as set out above. On orders for multiple DG Filters only one CD will accompany the shipment. If additional CDs are desired then place separate Filter orders and a single CD will be included with each order. If you have already placed a multiple DG Filter order and would like an additional CD go to our Accessory Page where you can order additional CDs.

An Absolute Transmission graph shows you how much light is available for your camera.

With this grating over 92% of an objects spectral energy is concentrated in the 1st order.

This grating has 2.5 times better resolution then does our 200 l/mm visual grating.

This grating has an overall average transmission of 94.3% when the grating is facing the source - this is the orientation used when assembling DG Filters.

This grating has an overall average transmission of 93.5% when the grating is facing away from the source.

The average transmission of the 1st order spectrum is 34.9%.

The average transmission of the 1st order spectrum in the visible region is 34.6%.

Maximum transmission, for the 1st order, is 47.2% at 425 nm.

The average transmission of the 2nd order spectrum is 2.9%.

The average transmission of the 2nd order spectrum in the visible region is 3.2%.

Maximum transmission, for the 2nd order, is 3.9% at 650 nm.

The 2nd order spectrum ends at 986 nm.

The average transmission of the 3rd order spectrum is < 0.1%.

An Absolute Transmission graph shows you how much light is available for your camera.

With this grating over 93% of an objects spectral energy is concentrated in the 1st order.

This grating has twice (2x) the resolution of our 500 l/mm grating.

This grating has an overall average transmission of 93.3%.

The average transmission of the 1st order spectrum is 37.3%.

The average transmission of the 1st order spectrum in the visible is 49.4%.

Maximum transmission, for the 1st order, is 69.1% at 400 nm.

The average transmission of the 2nd order spectrum is < 0.1%.

An Absolute Transmission graph shows you how much light is available for your camera.

With this grating over 88% of an objects spectral energy is concentrated in the 1st order.

This is our Visual Grating which produces Stunning Visual Spectrums with Eyepieces.

This grating has an overall average transmission of 93.7%.

The average transmission of the 1st order spectrum is 31.7%.

The average transmission of the 1st order spectrum in the visible is 27.3%.

Maximum transmission, for the 1st order, is 43.2% at 900 nm.

Maximum transmission in the visual, for the 1st order, is 37.3% at 400 nm.

The average transmission of the 2nd order spectrum is 3.7%.

The average transmission of the 3rd order spectrum is 0.3%.

The average transmission of the 4th order spectrum is < 0.1%.

This grating produces multiple spectrums in four different planes while the other two gratings, the 500 l/mm and the 1000 l/mm gratings, only produce a single spectrum in one plane.

Type A1 - DG Filter - Patent Pending:

Design: Type A1 is our smallest, least expensive and is our most popular filter. It produces a Compact Spectrum allowing both the object and its spectrum to be seen at the same time.

The Type A1 DG Filter is designed to slip into a camera’s lens well. It is held in by friction between the wall of the lens well and the outside of the filter itself.

Open Grating Area: 11 mm in Diameter, will fully illuminate chips up to 28 mm across.

Compact Spectrum Design: This version spreads the visible spectrum between 11.5 and 20.5 degrees (400 nm to 700 nm).

Transmission: Our Type A1 DG Spectrum Filters have a transmission > 93% across the visual spectrum including the near IR.

Grating: The grating used in the Type A1 DG Spectrum Filter is a transparent plastic film with grating on one side and a protective plastic covering on the other side.

Grating Fineness: We use a high quality plastic diffraction grating in the Type A1 DG Filters.

Its grating has 500 line pairs per millimeter (mm) finely ruled into the grating side of the grating material.

Spectral Line Resolution: 0.1 nm (1 Angstrom) at 500 nm (with full illumination).

The Resolution can be extended down to 0.1 Angstroms, or better, over selected portions of a spectrum, with proper calibrations and processing.

Spectral Band Pass: 390 nm to 890 nm.

Select Your CCD Camera Meade LPI Type A1 - Patent Pending: $ 99.95

Type A2 - DG Filter - Patent Pending:

Design: The Type A2 DG Filter is designed to slip into a camera’s lens well. It is held in by friction between the wall of the lens well and the outside of the filter itself.

The only difference between the A2 and the A1 versions is the spread of the spectrum produced.

Open Grating Area: 11 mm in Diameter, will fully illuminate chips up to 28 mm across.

High Resolution Grating: This version spreads the visible spectrum between 23.6 and 44.4 degrees (400 nm to 700 nm).

This grating produces a spectrum so long that only the visible portion of the spectrum and part of the near IR (from 390 nm to 765 nm) will fit on the CCD chip at one time. Unless the camera’s IR Blocking Filter is removed the CCD chip won’t see much beyond 650 nm.

Transmission: Our Type A2 DG Spectrum Filters have a transmission > 93% across the visual spectrum including the near IR.

Grating: The grating used in the Type A2 DG Spectrum Filters is a transparent plastic film with grating on one side and a protective plastic covering on the other side.

Grating Fineness: We use a high quality plastic diffraction grating in the Type A2 DG Filters.

Type A2 is our High Resolution Design. Its grating has 1000 line pairs per millimeter (mm) finely ruled into the grating side of the grating material.

Spectral Line Resolution: 0.05 nm (0.5 Angstrom) at 500 nm (with full illumination).

The Resolution can be extended down to 0.1 Angstroms, or better, over selected portions of a spectrum, with proper calibrations and processing.

Spectral Band Pass: 390 nm to 890 nm.

This grating has a Red end cutoff at 1000 nm due to its very wide dispersion, and better than 80 % of all of its spectral light is concentrated in its first order image.

The A2 Filters are Not Recommended as your Initial Purchase as they are more difficult to use than the A1 Filters for dim objects where the spectrum can't be seen on the monitor.

Select Your CCD Camera Meade LPI Type A2 - Patent Pending: $124.95

Type B1 - DG Filter - Patent Pending:

Design: The Type B1 DG Filter fits down in the lens well of the CCD camera but unlike the Type A1 DG Filter it is held in place using the filter threads on the front of the camera lens well.

The main difference between the B1 and the A1 filters is that the B1 filter is not held in by friction and therefore fits the camera much better with no movement or play.

Open Grating Area: 10 mm in Diameter, will fully illuminate chips up to 28 mm across.

Compact Spectrum Design: This version spreads the visible spectrum between 11.5 and 20.5 degrees (400 nm to 700 nm).

Transmission: Our Type B1 DG Spectrum Filters have a transmission > 93% across the visual spectrum including the near IR.

Grating: The grating used in the Type B1 DG Spectrum Filters is a transparent plastic film with grating on one side and a protective plastic covering on the other side.

Grating Fineness: We use a high quality plastic diffraction grating in the Type B1 DG Filters.

Type B1 is one of our most popular filters. It produces a Compact Spectrum. Its grating has 500 line pairs per millimeter (mm) finely ruled into the grating side of the grating material.

Spectral Line Resolution: 0.1 nm (1 Angstrom) at 500 nm (with full illumination).

The Resolution can be extended down to 0.1 Angstroms, or better, over selected portions of a spectrum, with proper calibrations and processing.

Spectral Band Pass: 390 nm to 890 nm.

Select the appropriate DG Filter to fit your camera, for a Type B - DG Filter made for one camera may Not fit any other camera; ie: A DG Filter made for a Meade DSI (or DSI II) camera WILL NOT fit in Meade's LPI camera.

BEFORE you order a DG Filter for a Starlight Express CCD camera read our FAQ about Starlight Express options versus DG Filter bandpass FIRST! There is a bandpass table at FAQ - Starlight Express listing the DG Filter bandpass of different combinations of DG Filters and Starlight Express hardware and cameras. You need to choose the right DG Filter for your camera and hardware based on your intended use.

Select Your CCD Camera Starlight Express + Nosepiece Meade DSI II Meade DSI Meade LPI Celestron NexImage SBIG ST5 + T-Ring Adapter Type B1 - Patent Pending: $159.95

Type B2 - DG Filter - Patent Pending:

Design: The Type B2 DG Filter fits down in the lens well of the CCD camera but unlike the Type A2 DG Filter it is held in place using the filter threads on the front of the camera lens well.

The only difference between the B2 and the B1 versions is the spread of the spectrum produced.

The main difference between the B2 and the A2 filters is that the B2 filter is not held in by friction and therefore fits the camera much better with no movement or play.

Open Grating Area: 10 mm in Diameter, will fully illuminate chips up to 28 mm across.

High Resolution Grating: This version spreads the visible spectrum between 23.6 and 44.4 degrees (400 nm to 700 nm).

This grating produces a spectrum so long that only the visible portion of the spectrum and part of the near IR (from 390 nm to 765 nm) will fit on the CCD chip at one time. Unless the camera’s IR Blocking Filter is removed the CCD chip won’t see much beyond 650 nm.

Transmission: Our Type B2 DG Spectrum Filters have a transmission > 93% across the visual spectrum including the near IR.

Grating: The grating used in the Type B2 DG Spectrum Filters is a transparent plastic film with grating on one side and a protective plastic covering on the other side.

Grating Fineness: We use a high quality plastic diffraction grating in the Type B2 DG Filters.

Type B2 is our High Resolution Design. Its grating has 1000 line pairs per millimeter (mm) finely ruled into the grating side of the grating material.

Spectral Line Resolution: 0.05 nm (0.5 Angstrom) at 500 nm (with full illumination).

The Resolution can be extended down to 0.1 Angstroms, or better, over selected portions of a spectrum, with proper calibrations and processing.

Spectral Band Pass: 390 nm to 890 nm.

This grating has a Red end cutoff at 1000 nm due to its very wide dispersion, and better than 80 % of all of its spectral light is concentrated in its first order image.

Select the appropriate DG Filter to fit your camera, for a Type B - DG Filter made for one camera may Not fit any other camera; ie: A DG Filter made for a Meade DSI (or DSI II) camera WILL NOT fit in Meade's LPI camera.

The B2 Filters are Not Recommended as your Initial Purchase as they are more difficult to use than the B1 Filters for dim objects where the spectrum can't be seen on the monitor.

BEFORE you order a DG Filter for a Starlight Express CCD camera read our FAQ about Starlight Express options versus DG Filter bandpass FIRST! There is a bandpass table at FAQ - Starlight Express listing the DG Filter bandpass of different combinations of DG Filters and Starlight Express hardware and cameras. You need to choose the right DG Filter for your camera and hardware based on your intended use.

Select Your CCD Camera Meade DSI II Meade DSI Meade LPI Starlight Express + Nosepiece Celestron NexImage SBIG ST5 + T-Ring Adapter Type B2 - Patent Pending: $184.95

Type D1 - DG Filter - Patent Pending:

Design: A Type D1 - DG Filter is mounted in a standard filter cell and is meant to be used in the filter wheel/tray of a CCD camera like SBIG's CFW-8. Type D1 Filters are designed to be used in CCD filter trays unlike Types A1 and B1 Filters which are designed to be connected to the CCD camera directly.

It can also screw into the filter threads on the bottom of eyepieces, while they were not designed for visual use they will work reasonably well for this use, as long as the eyepiece body isn't very long and the focal length isn't too short (refer to our FAQ page for details on different eyepieces). For longer eyepieces the Type D3 Filter should work much better, but the Type D1 Filter has much better resolution than does the D3 unit.

Each Type D - DG Filter incorporates Two Protective Cover Glasses and Two PVC Seals enclosing and protecting the grating material. While this will keep dust, dirt and fingerprints from contaminating the grating surface it isn’t water proof, but it is water resistant for splashes.

Open Grating Area: 25 mm Diameter, Much Wider FOV then Types A1 and B1.

Compact Spectrum Design: This version spreads the visible spectrum between 11.5 and 20.5 degrees (400 nm to 700 nm).

Transmission: Our Type D1 DG Spectrum Filters have a transmission > 78% across the visual spectrum including the near IR.

Grating: The grating used in the Type D1 DG Spectrum Filters is a transparent plastic film with grating on one side and a protective plastic covering on the other side.

Grating Fineness: We use a high quality plastic diffraction grating in the Type D1 DG Filters.

Type D1 produces a Compact Spectrum. Its grating has 500 line pairs per millimeter (mm) finely ruled into the grating side of the grating material.

Spectral Line Resolution: 0.05 nm (0.5 Angstrom) at 500 nm (with full illumination).

The Resolution can be extended down to 0.1 Angstroms, or better, over selected portions of a spectrum, with proper calibrations and processing.

Spectral Band Pass: 390 nm to 890 nm.

While the Type D DG Filters will screw into any eyepiece that has standard 1.25" filter threads these filters were designed to be used with cameras where the distance between the filter and the light sensor is generally under an inch, as such Type D1 - DG Filters lose a lot of the red portion of the spectrum when used on eyepieces with long bodies and or short focal lengths. The Type D3 - DG Filter was designed just for visual use with eyepieces but the Type D3 Filter doesn't have as good a resolution as do the Type D1 Filters.

This unit does Not come with any type of cylindrical lens. Cylindrical lenses are strictly used for visual spectrum observations of objects brighter than a 3rd magnitude star. Visual observation of spectrums of objects dimmer than a 3rd magnitude star is very difficult when using a cylindrical lens.

* BEFORE you order a DG Filter for a SBIG ST-xx camera read our FAQ about SBIG options versus DG Filter bandpass FIRST! There is a bandpass table at FAQ - SBIG listing the DG Filter bandpass of different combinations of DG Filters and SBIG hardware and cameras. You need to choose the right DG Filter for your camera and hardware based on your intended use.

Select Your Intended Use SBIG ST-xx + CFW-8 * SBIG ST-xx + T-Ring * Meade DSI Pro Meade DSI II Pro Other Filter Wheels Celestron NexImage Eyepieces Type D1 - Patent Pending: $134.95

NOTE: In Type D filters there may be seen small flakes of dust on the grating material. This is an unavoidable consequence of the manufacturing process and the fact that grating materials have very high electrostatic properties. These small dust flakes will not affect the performance of the filter.

Type D2 - DG Filter - Patent Pending:

Design: A Type D2 - DG Filter is mounted in a standard filter cell and is meant to be used in the filter wheel/tray of a CCD camera like SBIG's CFW-8. It can also screw into the filter threads on the bottom of eyepieces, but they were not designed or recommended for visual use as their dispersion is much too wide for most eyepieces.

The only difference between the D2 and the D1 versions is the spread of the spectrum produced.

Each Type D - DG Filter incorporates Two Protective Cover Glasses and Two PVC Seals enclosing and protecting the grating material. While this will keep dust, dirt and fingerprints from contaminating the grating surface it isn’t water proof, but it is water resistant for splashes.

Type D2 Filters are designed to be used in CCD filter trays unlike Types A2 and B2 Filters which are designed to be connected to the CCD camera directly. Because of their very wide dispersion they are not recommended for use with eyepieces.

Open Grating Area: 25 mm Diameter, Much Wider FOV then Types A2 and B2.

High Resolution Grating: This version spreads the visible spectrum between 23.6 and 44.4 degrees (400 nm to 700 nm).

Transmission: Our Type D2 DG Spectrum Filters have a transmission > 78% across the visual spectrum including the near IR.

Grating: The grating used in the Type D2 DG Spectrum Filters is a transparent plastic film with grating on one side and a protective plastic covering on the other side.

Grating Fineness: We use a high quality plastic diffraction grating in the Type D2 DG Filters.

Type D2 is our High Resolution Design. Its grating has 1000 line pairs per millimeter (mm) finely ruled into the grating side of the grating material.

Spectral Line Resolution: 0.25 nm (0.25 Angstrom) at 500 nm (with full illumination).

The Resolution can be extended down to 0.1 Angstroms, or better, over selected portions of a spectrum, with proper calibrations and processing.

Spectral Band Pass: 390 nm to 890 nm.

This grating has a Red end cutoff at 1000 nm due to its very wide dispersion, and better than 80 % of all of its spectral light is concentrated in its first order image.

While the Type D DG Filters will screw into any eyepiece that has standard 1.25" filter threads these filters were designed to be used with cameras where the distance between the filter and the light sensor is generally under an inch. The Type D2 - DG Filters are not recommended for eyepiece use at all because of their wide dispersion.

This unit does Not come with any type of cylindrical lens. Cylindrical lenses are strictly used for visual spectrum observations of objects brighter than a 3rd magnitude star. Visual observation of spectrums of objects dimmer than a 3rd magnitude star is very difficult when using a cylindrical lens.

The D2 Filters are Not Recommended as your Initial Purchase as they are more difficult to use than the D1 Filters for dim objects where the spectrum can't be seen on the monitor.

* BEFORE you order a DG Filter for a SBIG ST-xx camera read our FAQ about SBIG options versus DG Filter bandpass FIRST! There is a bandpass table at FAQ - SBIG listing the DG Filter bandpass of different combinations of DG Filters and SBIG hardware and cameras. You need to choose the right DG Filter for your camera and hardware based on your intended use.

Select Your Intended Use Celestron NexImage SBIG ST-xx + CFW-8 * SBIG ST-xx + T-Ring * Meade DSI Pro Meade DSI II Pro Other Filter Wheel Type D2 - Patent Pending: $159.95

NOTE: In Type D filters there may be seen small flakes of dust on the grating material. This is an unavoidable consequence of the manufacturing process and the fact that grating materials have very high electrostatic properties. These small dust flakes will not affect the performance of the filter.

Type D3 - DG Filter - Patent Pending:

This is our Visual Spectral Filter. With this unique grating you won't miss seeing a spectrum. Over 88% of an objects spectral energy is concentrated in its 1st order diffractions.

Design: A Type D3 - DG Filter is mounted in a standard filter cell and is meant to be used in a standard threaded 1.25" eyepiece or as a special effects filter on a camera.

The differences between the D3 and the D1 or D2 versions is the spread of the spectrum produced and the fact that Type D3 Filters produce multiple spectrums in four planes while Types D1 and D2 only produce a single spectrum in one plane.

Each Type D3 - DG Filter incorporates Two Protective Cover Glasses and Two PVC Seals enclosing and protecting the grating material. While this will keep dust, dirt and fingerprints from contaminating the grating surface it isn’t water proof, but it is water resistant for splashes.

Type D3 Filters are designed to be used in eyepieces for visual work or as a special effects filter with cameras.

Open Grating Area: 25 mm Diameter, Much Wider FOV then Types A and B.

Low Dispersion Grating: This version spreads the visible spectrum between 4.6 and 8 degrees (400 nm to 700 nm).

Transmission: Our Type D3 DG Spectrum Filters have a transmission > 78% across the visual spectrum including the near IR.

Grating: The grating used in the Type D3 DG Spectrum Filters is a transparent plastic film with grating on one side and a protective plastic covering on the other side.

Grating Fineness: We use a high quality plastic diffraction grating in the Type D3 - DG Filters.

Type D3 is our Very Low Dispersion Design. Its grating has 200 line pairs per millimeter (mm) finely ruled into the grating side of the grating material.

Blazing: The Type D3 - DG Filter is not blazed.

Spectral Line Resolution: 0.125 nm (1.25 Angstrom) at 500 nm (with full illumination).

Spectral Energy by Order: The first order spectrum contains 88.9% of the spectral energy, the second order contains 10.2% of the spectral energy leaving the third and fourth order spectrums less than < 1% of the total spectral energy.

Spectral Band Pass: 390 nm to 890 nm.

Type D units do Not come with any type of cylindrical lens. Visual observation of spectrums of objects dimmer than a 3rd magnitude star is very difficult when using a cylindrical lens.

Select Your Intended Use 1.25" Eyepieces Celestron NexImage SBIG ST-xx + CFW-8 * SBIG ST-xx + T-Ring * SBIG ST-5 + T-Ring Meade DSI Pro Meade DSI II Pro Philips TUcam Threaded Web Cams Most Other Filter Wheels Type D3 - Patent Pending: $124.95

NOTE: In Type D filters there may be seen small flakes of dust on the grating material. This is an unavoidable consequence of the manufacturing process and the fact that grating materials have very high electrostatic properties. These small dust flakes will not affect the performance of the filter.