Inside a Rear Mounted Ha Filter
After passing through the ERF,
telescope and Telecentric lens the light rays are properly prepared to enter the filter.
Here is the description used by permission from
DayStar Solar Filters:
"At the heart of rear mounted
DayStar style filters is a Fabry-Perot etalon crystal. We actually coat
the Mica crystal to use the perfectly parallel surfaces of fine grade
Mica. So the very thin 0.010 - 0.030mm cleaved crystal is its own,
stand-alone etalon. The crystal grows in the ground naturally with
perfectly flat layers measuring 10Å thick. We cleave the crystal.
That-is cause it to split between its layers to generate a perfect,
untouched surface. This is a delicate process, because the material
often splits across a layer boundary and causes a steppe.
This steppe in material causes a
10Å jump in transmission at that point. We can also only use crystal of
the highest natural homogeneity. Non-homogeneous mica crystal will
cause slight variants in the transmission wavelength through different
areas of the filter aperture. These fluctuations usually range at
0.02-0.05Å, if present. Only mica crystal with perfect natural
homogeneity is used for University(PE) grade etalon crystals. Most
observers can't discern a 0.02 - 0.05Å fluctuation across the aperture.
However, in academic studies or in photographic tiling, these uniformity
issues can be critical.
They are then coated using a
protected process in an optical thin film coating process, then tested,
qualified and mounted in BK-7 glass using a special optical couplant. The solid spacing of the etalon crystal with no air gap allows it to
maintain structural integrity and uniformity needed for rear mounted
applications. "
For more
information see:
http://www.daystarfilters.com/introduc.shtml
Why Ha? |
The View |
What you see |
The Chromos |
Ha Emission |
Bandwidth |
Main Designs |
Ha Components | Rear Filters |
The Etalon |
Front Filters |
Coronado filters |
DayStar Filters |
Solar Spectrum Filters
