There has been a pretty impressive sunspot group (AR2192) which has been "passing" across the face of the sun. AR2192 is one of the largest active regions observed in the last 25 years. It is approximately the size of Jupiter. It was clearly visible while observing the solar eclipse "naked eye" on Thursday, October 25th. A few days after the eclipse I decided I needed to set up my telescope and take a few images of AR2192 while I had the opportunity.
The images were taken at Kings Norton Observatory.
Equipment:
Meade LX90 8" SCT
Nikon D300s
Meade Series 4000 f/6.3 Focal Reducer
Thousand Oaks Optical While Light R-G Solar Filter Part #RG-9750
Setup:
Set up the LX90 as you would for any observation session. I set up my telescope in the home position and estimate "north". I then follow the autostar setup menu and let the controller find the stars it wants to align to. I just accept both selected stars without even looking through the telescope. This is close enough for what I need for guiding as the autostar will NOT "go to" the sun (and for good reason). I will then attach the Thousand Oaks Optical White Light R-G Solar Filter on the telescope before slewing manually to the sun. The calibration should be close enough that once you have the sun in the field of view it will only need small periodic adjustments to keep it centered.
For Observation:
I have found that a 32mm eyepiece (62X) to be the eyepiece that gives the best view. A 26mm eyepiece while filling up the entire eyepiece at (77X) is good, the sun just seems to be more impressive at 62x.
For Imaging:
A Nikon T-mount Adapter and Meade #62 T-Adapter for Prime Focus were attached to the telescope along with the f/6.3 focal reducer. Without the focal reducer it is impossible to get a full frame shot of the moon.
See First Solar Image!
I focus the telescope while looking through the viewfinder of my camera and try to zero in on the penumbra (the lighter outer detail of the observed sunspot). I have also tried using the live view on the back of my Nikon D300s and zooming in on a sunspot. I think method this is a little tougher since there is some amount of delay in the image projecting on the rear display.
Images are taken with ISO200 with exposures ranging from
1/800 to 1/4000 of a second. The best images are typically 1/3200 and
1/4000 exposures.
I will take a 3 or so pictures varying the exposures by one stop through the settings mentioned above. I will then try to refoucs the telescope and take another set of images.... rinse and repeat 3 to 4 times. The idea of refocusing multiple times is the hope that at least one of them will be spot on!
