Try increasing gamma if dark sections aren't distinguished

Try increasing gamma if dark sections aren't distinguished

Thursday, June 20, 2013

sun and moon for summer solstice

 this is the year of the solar maximum--maximum sunspot activity in the 11 year solar cycle.
10 pm pacific today 6/20/13 is the summer solstice.
what better time for solar images?

here are two images of the sun taken at about the same time with different filters. 

first up, the sun in "white light", using a filter that blocks out 99.999% of the sun's light
you can see a few dark sun spots (which are still blindingly bright without filters), a slightly granular appearance, and a few lighter areas.  this is the photosphere which is basically the surface of the sun.

the second image is the sun imaged with a hydrogen alpha filter that allows all of the sun's light at a specific frequency, which corresponds to absorption and emission of light due to hydrogen.  this shows the chromosphere, a thin layer above the photosphere dominated by hydrogen emissions.  it usually can't be seen as it is overwhelmed by bright emissions from the photosphere.  the hydrogen alpha filter allows us to see the chromosphere's wavy filaments and prominences.
you can still see hints of sunspots, but there's much more going on. 

next i colorized the image and then lightened it dramatically to show the faint prominences (things shooting off the disk around the rim).  since this overwhelmed the central detail, the original darker image was superimposed to maintain some of the surface detail.  bear in mind the prominences seen at the edge are much more faint than the central detail.  the dark line upper right across the face is called a filament.  it's basically the same phenomenon as a prominence, but coming off the surface towards the viewer rather than occurring at the edge. 

last up is the full moon, which happens to be the same size as the sun, which is convenient for things like eclipses
and finding something to do with your solar rig at night. 
this was taken with the same scope and camera as the first image, leaving off the filter. 
why do astrophotographers rarely image the full moon? 
the sunlight is shining straight down on the face which washes out the detail of landscape. 

the sharp eyed viewer will note better contrast at the extreme bottom portion of the image
where a few shadows are cast enhancing detail in this moon that was 6 hours away from full. 

have a good summer