Astro LPR Type I
Kenko Astro LPR Type I is designed mostly for visual astronomical observation of celestial bodies, stars and constellations.
This filter transmits only light spectrum that comes from celestial bodies, and cuts other light, thus enhancing contrast and clearness of the image. This filter is also modified to transmit the light that comes from two tails of the comet providing natural colors of the object. This modifications makes Kenko Astro Type I more demanded among astronomers.
Because of the color shift that may occur due to the wide spectrum of light cut by the filter, using Kenko Astro LPR Type I for photographic purposes is not recommended. Images will require serious post-processing work to correct color balance of the image. For photographing use we suggest using Kenko Astro LPR filter Type II that is designed for this purpose.
Note: Before using Kenko Astro LPR filter Type I we recommend to obtain basic knowledge about astronomic filters.
Why you need astronomic filters?
Often, long exposure images of the night sky are of low contrast or highlighted. This happens due to the light coming from nearest city or different sources of artificial light (for example, street lamps).
Astro filters depending on type and purpose of use can eliminate those unwanted lights thanks to the specific features of filter coating aimed to cut off unnecessary span of light spectrum.
 |
 |
Every astronomical filter has its own purpose of use and differs by specifications or light transmittance characteristics.
Light transmission
According to the graph below, Kenko Astro LPR filter Type I transmits only 3 main light spectrums that come from the comet - green, red and blue. Red graph reveals the light transmission of Kenko Astro LPR Type I. White graph shows light spectrum of the comet. As you can see, spans of spectrum that are transmitted by filter are covering the light peaks that are reflecting from the comet thus providing clear and natural view.
Blue line in the next graph shows the light spectrum of Nebula M42 (Orion constellation) and read - light transmission of Kenko Astro LPR Type I. You can see that 3 peaks of the light from nebula and those of Kenko Astro LPR Type I are coinciding with each other quite perfectly.
Coating technology
Kenko Astro LPR Type I adopts precision coating based on Ion Assisted Deposition technology. In order to achieve the desirable coating specification each coating layer is sprayed on the surface of the filter with the help of ion particles creating coherent multilayer surface more durable, more harder comparing with the common coating.
The filter transmits OIII, Hβ, C2 coma, HII, H alfa, CN and C3 factors thanks to its band-pass technology.
Limitations
Because of the color shift that may occur due to the wide span of light spectrum that is cut off by the filter using Kenko Astro LPR Type I for camera shooting is not recommended. Color balance has to be corrected by software that might be difficult and low performance routine. For camera shooting Kenko Astro LPR Type II can be used instead. Kenko Astro LPR Type II is modified for astrophotography and its coating prevents color shift.
Because of the color rampage that might occur in peripheral areas of the image due to the coating specifications, Kenko Astro LPR Type I is not recommended using with middle or wide angle SLR lens.
We recommend using Kenko Astro LPR Type I with SLR lenses focal distance of whose is 100mm or more (converting 35mm film).
Below are the examples shot with wide angle SLR lens (16mm) showing the result of color shift in peripheral areas of the image.
 |
 |
Sizes
Kenko Astro LPR Type I features 6 sizes: 1.25" (american size) for eyepiece, 48mm, 52mm, 67mm, 72mm, 77mm to screw on the objective lens of telescopes, SLR cameras and spotting scopes.
General care and handling of the photographic filter
- Use filter carefully and always keep it clean. When cleaning use cleaning tissue or cleaning cloth. But before that remove as much dust and dirt as possible from the lens with a blower or brush.
- Avoid unnecessary cleaning of your filter.
- Filter is made of glass. When it is broken glass fragments may injure.
- Do not disassemble filter by yourself.
- When the filter is not attached to the lens, store it away from sharp objects. They may damage the filter glass.
- Keep filter away from children.
- Keep filters in plastic hard-sided case or filter pouch.
- Keep filters dry and away from direct sun light.
- Avoid storage in high humidity environment. Moisture drops due to the high humidity or dew on the filter can burn the coating and create traces on the glass surface that can be hardly wiped off.
