HIGH RESOLUTION SOLAR OBSERVATIONS USING COMMERCIAL FILTERS AND SMALL APERTURE TELESCOPES

Patrick Stoker

BASIC FILTER TYPES

FRONT MOUNTED FILTERS

CORONADO – Ha & CaK

SOLARSCOPE – Ha

•Type of filter used by most amateurs

•98% use the Coronado Filters due to availability and price

•Available as either a 0.7Å or a 0.5Å bandpass filter•Both Companies use a tilt tuner at the back of the etalon for viewing some types of Doppler shifts and to facilitate tuning•Both filters are a Fabry-Perot design centered at 656.28nm but neither are designed for viewing in the wings of H-alpha•Etalon design of Coronado filters uses a spacer which creates a central obstruction of 2% to 5%. Solarscope filters are a classic Fabry-Perot airspace design with a clear aperture and no central obstruction•Used with small aperture and short focal length refractors

•Effective focal length increased with barlows

REAR MOUNTED FILTERS

DAYSTAR – Ha, CaK, CaH & Sodium D

SOLAR SPECTRUM –Ha, CaK & All Visible Light

•Most amateurs purchase the H-alpha filters in bandwidths of 0.3Å to 0.8Å

•Filters can be moved off band about 1Å into the wings of H-alpha

•Used with larger 4” to 6”aperture refractors, f/8 or slower

•Effective focal length increased with telecentrics

WHITE LIGHT FILTERSOnly used to observe the Photosphere

FILM OR GLASS

•Type used by most amateurs. Can be used on any type of telescope

HERSCHEL WEDGE

•Considered dangerous in the past, however new safety features have been added

•Can only be used with a refractor telescope

CAMERAS

•HIGH SPEED IMAGING CAMERAS - UP TO 60 fps

Camera of choice for most who are imaging the planets, moon and sun because it helps overcome the effects of poor seeing conditions. Cameras that fall into this classification include:

-Lumenera & DMK High Speed Cameras – 60 fps

-Modified Web Cams – 5 to 10 fps

-Monochrome Video Cameras – 30 interlaced fps

•COOLED CCD CAMERAS – Best choice for steady seeing; need at least 1/1000 sec exposure capability

•DSLR AND FIXED LENS DIGITAL CAMERAS

IMAGE PROCESSING

How do you get from something like this……

To something like this?

CONCLUDING REMARKS

•MANY AMATEURS AROUND THE WORLD CURRENTLY TAKING DAILY HIGH RESOLUTION SOLAR IMAGES, AND ALSO NEW AMATEURS STARTING TO CONCENTRATE EXCLUSIVELY ON THIS AREA OF ASTRONOMY

•RESULT IS AN EXISTING AS WELL AS AN EXPANDING RESOURCE FOR HIGH QUALITY PHOTOGRAPHIC SOLAR DATA

•CREATES AN OPPORTUNITY TO ACCUMULATE DATA THAT CAN BE USED FOR RESEARCH, BUT CURRENTLY THERE IS NO MECHANISM IN PLACE TO TAKE ADVANTAGE OF THIS OPPORTUNITY. ANY INITIATIVE TO CAPITALIZE ON THIS WILL HAVE TO COME FROM THE PROFESSIONAL RESEARCH COMMUNITY.