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Does this filter have a positive function with a 127/1200 achromatic telescope in a herschel wedge visual/photographic usage ? If yes, should it be directly screwed on the eyepiece/camera or stacking ND and solar continuum on the wedge is fine?
Question by: Firat Cingi on Jul 10, 2022 10:20:00 AM | 1 Answer(s)
- Description
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Details
1¼" and 2" Baader Fringe-Killer Color Correction-Filter
Planeoptically polished with Phantom Group Coating
Baader Fringe KillerThe Fringe-Killer (Fringe = colour fringing) blocks unfocused light in the red part of the spectrum (IR) uo to 100% - but above all suppresses over 50% of the interfering stray light in the blue spectral range - without changing the colour impression of the image.
The most delicate details of lunar craters and planetary surfaces can be seen with a much higher contrast.
The Baader Fringe-Killer Color Correction-Filter prevents unwanted colour fringes in both the blue spectral range and in the NIR above 700 nm! The visual impact initially corresponds to a minus violet filter, as opposed to this but the image colour remains broadly balanced. In itself a contradiction in terms? It can only be implemented by applying modern DWDM plasma assisted coating technology, which allows the application of approximately 100 individual layers on a flat-optically polished face surface perfectly and reproducibly without compromising visual quality. This fine optical precision tool also allows inexpensive China-refractors to reach the promised imaging performance. The reduction of chromatic aberration corresponds to what is achieved by corrections-lens systems, which usually cost 20 times more.
Example of Sirius with and without the Fringe Killer
For comparison please clickThe Baader Fringe Killer Overview
Facts and Figures
- Is due to its construction both visually and photographically a very valuable aid
- Removes blue fringing as well as red fringing above 700nm.
- Forms in the range between 450 to 480 nm with a plateau at around 50% transmission rate, the coating becomes more complex to produce than even the narrowest Nebula filters.
- Achieved in the passband the highest transmission of all previously available colour fringe, whether filter or correction lens. From 486-656 nm all relevant deep sky wavelengths are completely transmitted. Visually this is enough light for even high magnifications.
- Above of 656 nm (H-alpha), at 660nm, the transmission sinks very fast. In the NIR at 670nm, transmission is already down to 50%, and at 690nm it is already close to zero. The NIR is fully blocked up to 1150nm. This way, details on planets are shown much clearer when using CCD/CMOS-cameras, too.
The clearly visible colour correction of the Baader Fringe Killer. For comparison please clickThe Highlights of the Baader Fringe Killer Color Correction-Filter
- Provides the brightest image of all industrially produced colour error correction systems. Thus the Fringe Killer is a must for even the smallest telescopes.
- Removes blue fringing as well as red fringing above 700nm.
- Cancels the devastating intensity of the disturbing purple fringing in a new form, which was never implemented to date in astronomical filters
- Even weak nuances remain clearly visible in the planet due to the excellent colour balance.
- In conjunction with an RG-610 Red Filter produces a narrowband Ha-pass filter with an only 70 nm wide windows and 95% light transmission - at an incredibly low price!
- The combination with the Neodymium Skyglow Filter (with Phantom-Group-Coating) results in a balanced, breathtaking contrast to the observation of fine lunar and planetary details.
- Planeoptically polished for perfect sharpness, even when the filter is assembled well before the focal point (or binocular digital camera insert).
- No deterioration of resolution with high magnification - as would happen with flame-polished (raw polished) glass, commonly used for all sorts of filters!
- Hight Quality Coating: Plasma-enhanced dielectric coatings result in hard, scratch-resistant and waterproof filters. Almost 50 layers on either side, carefully positioned as not to impair the optical quality of the substrate surface
- Makes the performance of a simple f/8 economy refractor look like a classic f/15 Fraunhofer achromat. See it to believe it!
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Information about Baader Filters and Filtercells
About Baader Filters The variety of uses for filters in amateur astronomy has considerably increased during the last decade, enabled by both more accurately manufactured optical accessories, and, above all, by the “digital revolution“. In the old days, colour filters for visual planetary observations were not screwed in the front part of the eyepiece, but were simply placed between the eyepiece and the eye. Plane-parallelism of these filter glasses was not important, because they were not in the optical path of the telescope. Today, filters are placed in the optical path of the telescope, even well in front of the focal plane. This definitely requires some degree of plane parallelism and accurate production of the filter glasses. Every single cell mounted filter delivered to our customers is cut as a round or square disc in the according size (1¼", 31mm, 36mm, 2", 50,4mm, 50x50mm, 65x65mm), and then is polished plane to a quarter wavelength on both sides on a computer numerically controlled polisher. After that, the polished blanks are submitted to the costly coating procedures. This sequence is also used for all unmounted filters. We deliberately avoid cutting filters from larger sheets, because the coating layers can be damaged at the edges and suffer from microscopic...
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HALOS – viewed without prejudice
The moment you insert any type of filter into the optical setup, which consists of your specific camera, the appropriate flattener/reducer or coma corrector and the telescope, the filter becomes part of this unique optical system. And every optical system is different because many products from different manufacturers are involved. All optical surfaces interact with each other in some way. One possibility is that coatings of the camera reflect unwanted light back into the telescope and onto all optical elements in front of the filter. If there is no other optical surface that will reflect the light back to the filter a second time, then it is perfect. There are no halos other than residual halos or scattering, which are unavoidable, depending on the filter design. That's what we mean by our slogan "no halos, no ghosting, no reflections" on our product pages. A filter rarely produces halos itself, which are created inside the filter by internal reflections (this happened to us once in 2015, but we replaced all of these filters). Because the moment there are other surfaces near the filter, it is much more likely that light will be reflected from one of those surfaces, creating halos that...
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Unmounted Filters – which side should face the telescope?
For our CMOS-optimized filters we have created the following images showing which side of the filter should face the telescope.
LEGACY FAQ for older unmounted CCD-Filters without black outer rim
Question in Detail:
I just bought LRGB 36mm unmounted filters. I have question: which side of filter should be placed towards telescope? Is it better way of distinguish than "more shiny surface towards telescope"?
Answer:
Always put the more reflective side towards the telescope side. To guide you we already put a small arrow on the filter rim, on those filters were the position matters. This arrow indicates which face of the filter should be directed towards the sky (telescope-sided). All cell-mounted filters are already oriented in a way that the most appropriate filter face is facing the sky when the filter would be mounted directly onto the front end of the nosepiece of a camera.
If you mount your filter the other way, any reflected light would have a short way to the camera sensor, resulting in a higher risk of getting some kind of back-reflections inside the camera field. Many sensors have highly reflective areas near to the light sensitive area, also the area with the bonding contacts is sometimes highly reflective.But: this is true only for instruments without optical elements near to the focal plane. If you have f.e. a coma corrector, field flattener, focal reducer, focal extender (to a lower degree due to concave surface), or in extreme cases a whole lens group for more complex field corrections a few centimeters in front of the filter it could be useful to flip the filter against the rule from above (thus having the arrow pointing away from the telescope). Cause in such cases the likelihood of reflections from the sensor could be lesser then fort- and back- reflections from such glass-surfaces. If in doubt, it helps to make some test images from a star field with bright stars, using the filter in both ways for comparison.
Should you really have some reflections with both positions it can be more effective to add a spacer between filter and camera, eventually shifting the reflection out of the image field. With focal correctors having curved surfaces changing the filter-lens distance could help also.
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HALOS – viewed without prejudice
For our CMOS-optimized filters we have created the following images showing which side of the filter should face the telescope.
LEGACY FAQ for older unmounted CCD-Filters without black outer rim
Question in Detail:
I just bought LRGB 36mm unmounted filters. I have question: which side of filter should be placed towards telescope? Is it better way of distinguish than "more shiny surface towards telescope"?
Answer:
Always put the more reflective side towards the telescope side. To guide you we already put a small arrow on the filter rim, on those filters were the position matters. This arrow indicates which face of the filter should be directed towards the sky (telescope-sided). All cell-mounted filters are already oriented in a way that the most appropriate filter face is facing the sky when the filter would be mounted directly onto the front end of the nosepiece of a camera.
If you mount your filter the other way, any reflected light would have a short way to the camera sensor, resulting in a higher risk of getting some kind of back-reflections inside the camera field. Many sensors have highly reflective areas near to the light sensitive area, also the area with the bonding contacts is sometimes highly reflective.But: this is true only for instruments without optical elements near to the focal plane. If you have f.e. a coma corrector, field flattener, focal reducer, focal extender (to a lower degree due to concave surface), or in extreme cases a whole lens group for more complex field corrections a few centimeters in front of the filter it could be useful to flip the filter against the rule from above (thus having the arrow pointing away from the telescope). Cause in such cases the likelihood of reflections from the sensor could be lesser then fort- and back- reflections from such glass-surfaces. If in doubt, it helps to make some test images from a star field with bright stars, using the filter in both ways for comparison.
Should you really have some reflections with both positions it can be more effective to add a spacer between filter and camera, eventually shifting the reflection out of the image field. With focal correctors having curved surfaces changing the filter-lens distance could help also.
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Off-standard single filter sizes from Baader - why not:
Quite often we receive requests for a single filter in an off-standard size. In all cases we are sorry that we must answer as follows:
Sorry (we know it would be so very much cheaper in production - and we would be so much more flexible to fill special requests) - but we have decided long ago to not cut or saw our filters from large plates because this would leave the coating stack open and mutilated (with microscopic cracks) all around, prone to aging and peeling.
Many times we had the chance to inspect our competitors filters after several years of use (due to our 30+years of servicing SBIG-CCD-cameras/and filter wheels) and we realized already 15 years ago how moisture and heat stress can deteriorate even most modern hard coatings, slowly peeling off from the carrying substrate over time, unless the coating stack is sealed all around the filter stack.
As a consequence - in order to create our filters to remain impermeable - we only offer all filter substrates already cut to final shape and run each substrate on an double deck auto-polisher to achieve perfect optical flatness and freedom from cone errors.
Then we do individually coat these substrates in 500 pc per run as minimum to fill a complete coating chamber, in a way that the coating stack (many times 50+ layers) applied onto each filter won't reach to the very edge of the round or square substrate, so that the coating stack remains completely sealed from all sides. In this way we can ensure that our filters will not age at all.The sad effect is that we cannot offer other sizes unless the inquired production quantity were in the range of 250 to 500 pc (depending on size) and the tooling rings or square holders will be paid for, which serve to precisely center each individual filter substrate within the rotating calotte inside the coating chamber. Sorry - as explained above - we just will not coat onto large plates and cut any shape from them, also because such large plates cannot be polished optically flat in the same way we do it.
For your most urgent need and for single piece solutions we can only recommend to order the next larger size of our respective filter and have that cut to shape by an ophtalmologist locally. We can supply the round filters without the metal cell in such cases; square filters come without cell in any case.
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