The included spectral transmission chart indicates the transmission measured
for the filter you received.
LIGHT POLLUTION
IMAGING FILTER, RASA 8
#93 614
PARTS LIST
Light Pollution Imaging Filter in Filter Cell
Spectral Transmission Chart
Plastic Case
The Light Pollution Imaging Filter for the Rowe-Ackermann Schmidt Astrograph
(RASA) 8 improves image contrast by selectively blocking wavelengths of light
strongly emitted by certain sources of light pollution. These sources include
high and low pressure sodium-vapor streetlights, mercury-vapor streetlights,
and natural airglow caused by oxygen in the atmosphere. The filter only blocks
narrow sections of the spectrum instead of wide regions; this helps to retain
image brightness and color balance. Specific emission lines from nebulae, such
as H-α (656nm), H-β (486nm), OIII (496nm and 501nm), and SII (672nm), are
highly transmitted, so emission nebulae won’t be dimmed.
INSTALLING THE FILTER IN RASA 8
The Light Pollution Imaging Filter replaces the R ASA 8 optical window. This
maintains optical performance, as no extra piece of glass is added to the fast
optical system. The optical window is removed along with its cell, and the filter
is installed using its own cell.
WARNING : When removing the optical w indow and installing the filter, avoid touching optical
surf aces or you may leave fingerprints. Handle the filter and optical window by their cells only.
1. Carefully grasp the knurled edge of the optical window cell within the R ASA
8 lens group cell, and begin rotating it counter-clockwise. If the edge of the
optical window cell cannot be grasped initially because it is too recessed, use
the notches in the knurled surface of the cell to begin rotating it. Completely
unthread and remove the optical window cell. The optical window can be
stored in the filter case when the filter is in use.
2. Install the Light Pollution Imaging Filter by threading its cell into the lens
group cell of the astrograph. The notches in the edge of the filter cell should
be facing outward. Do not over-tighten, the filter cell should only be threaded
until it stops turning.
Notches on filter
face outward
CARE AND CLEANING OF THE FILTER
Avoid touching the optical surfaces of the filter. Handle the filter by its cell only.
Keep the filter stored in its plastic case when not in use. If the filter remains
installed on the astrograph, keep the astrograph’s dust cover on.
Dust should normally be removed with a blower bulb or an optical cleaning
brush. If the filter must be cleaned, use optical grade tissue with a few drops of
optical cleaning solution applied to the tissue. Gently wipe one small area at a
time. Do not rub. Use a new tissue and solution for each wipe.
Filter Glass Schott B270
Glass Thickness 1.9 mm
Filter Diameter 46 mm
Clear Aperture 43 mm
Coatings Dichroic multi-bandpass and
multi-layer antireflection coatings
Filter Cell Aluminum, black anodized
CELESTRON T WO YEAR LIMITED WARRANT Y
Celestron warrants your telescope mount to be free from defects in materials and workmanship for two
years. Celestron will repair or replace such product or par t thereof which, upon inspection by Celestron,
is found to be defective in materials or workmanship. As a condition to the obligation of Celestron to
repair or replace such product, the product must be returned to Celes tron together with proof-of-purchase
satisfactory to Celestron.
This product is designed and intended for use by those 14 years of age and older.
© 2018 Celestron • All rights reserved
2835 Columbia Street • Torrance, CA 90503 U.S.A.
Telephone: 800.421.9649 • celestron.com
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