Trial and Error

Mostly Error

I'm continuing to explore solar imaging with a new ZWO ASI 1600 camera. The first picture below shows my Lunt 100mm solar telescope with the camera attached to a tilt adjuster and 3X Barlow lens.

Observing conditions on March 28th were fairly comfortable with diminishing thin clouds, little wind, and temperatures in the mid 50's. Since there were no significant features on the solar disc, I tried to capture relatively dim spicules and prominences along the limb. The first image below was made using a 30.7 ms video frame exposure time with gain and gamma set at 50.

I then decided to overexpose the featureless disc it in order to enhance the limb. The frame exposure time was changed to 29.7 ms, gain increased to 123, and gamma changed from 50 to 24. This camera setting combination made limb features show up clearly on the preview screen where they had been previously invisible. The next image is a 3-panel mosaic made with camera settings mentioned above. It shows a variety of features around the limb with the overexposed portion blacked out. (Click on the image for a larger view.)

Although I captured enough individual images to include the entire rim circumference, construction of a full circle mosaic was impossible. None of the software tools I use to patch individual images together into mosaics would handle overexposed, featureless disc areas. It was also impossible to darken the yellow glow surrounding the Sun without simultaneously darkening limb details I purposely set out to capture. 

Next, I tried cooling the camera to zero degrees C. I could see no significant reduction in background level. A yellow glow still accompanied limb features. I tried a frame exposure time of 27.2 ms, gain of 100, and kept gamma at 24. Once again, it was impossible to make a mosaic. The last image below shows the largest prominence and other nice limb details in the midst of the yellow haze. (Click on the image for a larger view.)

Lots of time was spent stumbling through new software menus and features. The latest version of Firecapture is required to operate the camera. I also installed the latest version of Photoshop Elements to process and enhance the images. Operation of my new camera has still not settled into an efficient, comfortable routine.