Log Book Entry No.174

Created: 30 Nov 2018 11:33:15

Last Revised: 30 Nov 2018 13:47:54

HughSpackman

PH3010 Solar Limb Darkening Data

• Dome entered 10am. Present: MA, JC, HS, supervised by Dr. DB
• Telescope cover removed, solar filters put on
• camera and colour filters were already attached to telescope. setup checked just to be sure
• Telescope setup reviewed+approved by DB
• Dome doors opened, telescope turned on

• Moon was still visible in sky - dome doors moved to allow viewing of it
  • Moon used for focus (coarse and fine), took a couple of images of nice craters
  • Moon found by (roughly) lining it up with the telescope, then with the finder scope, then with the camera image
• Dome doors moved to allow viewing of sun, telescope slewed to find sun
  • telescope shadow aligned on wall behind telescope
  • telescope moved to bring the two rows of knobs into alignment (i.e. telescope pointing at sun)
  • Using camera feed, approximate equator of sun found at one edge
  • Test images taken
• Moon and test sun images stored in focus_images folder

• Colour image sets taken.
  • All image sets performed by pointing telescope ahead of suns motion and switching to terrestrial mode - motion of sun across sky then carries sun across the frame of view.
  • All image sets taken over 3 minutes 10 seconds. This time determined by timing a test run of the method.
  • 1 image per second taken for the length of the image set.
  • Used maximum gain for all image sets. Exposure determined by manually slewing across the sun and trialling different exposures. Aim was to get as close to having maximum pixel values in the image, without actually having any maxed out pixels
• Where necessary, solar eclipse glasses were used to directly view sun e.g. to determine if clouds were obstructing the sun, or just the area around it

• Clear Filter 1:
  • Gain 799, exposure 1/1000 seconds
  • trees obstructing parts of image set - produces obvious errors in dataset
• Clear Filter 2:
  • Gain 1023, exposure 1/4000 seconds
• Blue Filter 1
  • Gain 1023, exposure 1/154 seconds
  • Some obstruction of sun by clouds
• Blue Filter 2
  • Gain 1023, exposure 1/154 seconds
  • Still some clouds, but far fewer than with Blue Filter 1
• Green Filter 1
  • Gain 1023, exposure 1/308 seconds
  • Lots of clouds
• Green 2
  • Gain 1023, exposure 1/308 seconds
  • Even more clouds
• Red 1
  • Gain 1023, exposure 1/1241 seconds
  • A few false starts (so the file indexing is messed up), but managed to get a good run of images

• Was not able to perform another run with the green filter, due to increasing cloud cover
• Dome doors repositioned above door to roof and closed.
• Solar filter removed and lens cap replaced. Filter stored back in its home.
• Telescope returned to 0h0d

• NOTE: Minor mix-up with imgae file names. All image sets are stored in the appropriate folders / .zips for the colour filter used, but the some image sets use the wrong colour name in the individual image filenames. Recommend handling image sets carefully / renaming appropriately when used.