New ZWO ASI 1600 Camera

First Light

The Sun continues sleeping through the current sunspot cycle minimum, but things will eventually change. When activity picks up I'll be ready to capture images with a new ZWO ASI 1600MM camera. This camera has a substantially larger chip than my ZWO ASI 174MM, so it will produce a wider field of view and require fewer panels for full disc mosaics. The 1600 chip has 3.8 micron pixels in a 4656 x 3520 array and measures 17.69 mm by13.38 mm. The 174 chip has 5.86 micron pixels in a 1936 x 1216 array that measures 11.34 mm by 7.13 mm. Here are front, side, and rear views of the new camera.

A cool, clear afternoon in the low 50's on March 17th was a good opportunity to try the new camera with my Lunt 100 mm solar telescope. I began with the camera at prime focus, and obtained the full frame image below.

The field of view above is 81.5 by 61.6 arc minutes, obviously more than enough to capture the whole Sun at once. I worried this large chip would have a slow video frame download rate, but the image above was created from a 400-frame video that took about 40 seconds to download. The camera's onboard 256MB DDR3 memory buffer probably helped speed downloads.

Next, I tried defining a region of interest including the whole Sun while eliminating empty surroundings. With this reduced region of interest the 400-frame video downloaded in only 20 seconds and produced the next image below.

Unfortunately, these prime focus images don't have the best resolution. They don't show the most pleasing amount of detail. Click on the image above and then compare the detail with better images below. Magnification is required for better quality images. So I next tried using a 2X Barlow lens. The magnified 2X image, seen below, was now too large to fit the entire Sun in one frame. The 2X Barlow field of view is 31.6 by 23.9 arc minutes. (On this day the solar diameter was 32.2 arc minutes.) If you look closely, you can see hints of a circular interference pattern below center. (The 2X Barlow image is also rotated compared to the prime focus images.)

Click on the image above to see it has much better detail than the prime focus image preceding it. From past experience I knew a 3X Barlow lens would yield even better results, but the first 3X Barlow view included intense, dark, circular interference rings. I installed a tilt adjuster between the Barlow and the camera, but it had little initial effect. When I rotated the camera plus tilt adjuster 90 degrees while leaving the Barlow fixed, the annoying interference rings completely disappeared! The field of view had now diminished to 26.5 by 20.1 arc minutes. I combined four separate 3X Barlow images to produce the following 4-panel mosaic.

Click on this image to see better detail, including small prominences along the limb. I don't know why I didn't take two more images to cover the whole disc. Now I wish I had done so! No truly impressive features are present on the disc, only one small dark filament and a small white active area below the filament. Three or four days later the small active area developed into flaring sunspot 2736.

The resolution of the 3X Barlow looks pretty good. I may always use this configuration in the future. It looks like it can produce nice, detailed, full-disc mosaics with only six component images! This is much better than the 40-panel mosaics I labored to construct in the past.

Finally, I tried the camera with a 5X Barlow lens. Circular interference rings were present again even with the tilt adjuster in place as you can see in the following grayscale image.

The field of view with the 5x Barlow is 16.5 by 12.4 arc minutes. Next is a cropped and enhanced portion of the previous image showing the two disc features.

Interference fringes are visible but the detail is respectable. I'll have to work on eliminating the interference effects and decide between the 3X and 5X Barlow for future imaging.

The new camera also includes a cooling system and fan for cooling the chip to reduce unwanted thermal signal. Thermal signal (dark current) probably doesn't have enough time to significantly develop during relatively short exposure times (roughly 27 milliseconds) used to capture individual solar video frames. Cooling will be more important if I ever try to use this camera at night to take long exposures of dim celestial objects. Nevertheless, in the future I will see if cooling has any noticeable effect on the quality of solar images.