ASI120MC vs 120MM Long-Exposure Noise

I decided to order a 120MM to compare the monochrome version of the ASI camera with the color version. The color version generates significant noise with longer exposures. This noise, can be reduced by adding an external peltier (as demonstrated in a an earlier post). Below are two images comparing the noise of the 2 imagers with an approx 17-second exposure.

ASI 120MC at 19.3 degrees C and 17 second exposure

ASI 120MM at 22 degrees C and 17 second exposure

As you can see, there is a marked difference in noise levels. I have read that the MM version if also 4 times more sensitive than the MC, with a significant improvement in QE. I will be returning the MC and will order a filter wheel shortly. I'm looking forward to doing some deep sky imaging with the MM!

AR1861 on 10-14-2013

Here's another pic of AR1861, looking a little quieter today, although still capable of X-Class flares. The PST-DS also captured some dark filaments around the spot complex.

Test Shots of the Moon tonight (10-13-13)

Here are a couple of test shots of the moon taken tonight with the ETX 125 (no Barlow). These images were a test of the ASI camera and it looks pretty good. The shots were actually taken through the intervening leaves of my neighbor's tree! Click on each image for a larger pic.

The Sun on October 12, 2013

Here are some pix of the sun taken today. I've focused primarily on the AR 1861-1865 complex as it has the potential to release X-Class flares. Seeing was poor/fair, with lots of water vapor in the air. The images also show some comparisons between the old Lifecam and the new ASI imager.

This image was captured with the LifeCam and 1280x720

The LifeCam image at 1280x720, 30 FPS gives a good chunk of the whole disk. For the ASI, I had to use a Barlow to get good focus. In addition, I had a hard time getting a good framerate, so I captured at 640x40 @47 FPS. The first image, after processing, is a zoomed in view of the active area.

AR 1861 Complex with ASI

Finally, here's one more shot (not as cropped, but with some additional de-noising and sharpening:

AR 1861 Complex

There was also a rather nice prominence visible, too:

I have noticed some artifacts on the ASI images after output from Registax--a pattern of dots. I'm not sure what they are (artifacts of the Bayer Matrix?), but de-noising seems to remove them:

Grid Pattern after Registax Wavelet

ASI 120MC and Peltier--An Experiment

The ASI 120MC is a truly flexible camera. It can do planetary imaging as well as deep sky. However, like all uncooled cameras, it produces significant amounts of noise. While dark frame subtraction can take care of much of this noise, cooling the chip can greatly reduce noise and minimize processing. It also makes it easier to see deep sky objects as you monitor the exposure.

The camera's metallic case is a good conductor, so I decided to experiment to see how much cooling I could get by surface mounting a peltier cooler. I bought a very inexpensive (less than $5) 93-watt peltier and a $15 PC heatsink and fan.

The Alpine 64 has low vibration and 90 watts of cooling capacity

I then mounted the peltier to the heatsink (the heatsink has a conveneint adhesive thermal pad).

The peltier mounted on the heatsink

All that remained was to add a 12v power supply, place it on the imager, and turn the contraption on!

The working device!

The results are very interesting. The following images are captures showing chip temperature and the resultant image noise for a 17-second dark field exposure (click for a full-size image where all the noise will be visible).

Initial image. The original chip temp was 22 C. In a few seconds, it had cooled to this value.

The final image was taken at 0.5 C, about 5 minutes after turning the device on. As you can see, the noise is much reduced.

Significant noise reduction at 0.5C

However, the peltier and fan proved a little too demanding for my 13.8v, 6 amp supply (I knew I was pushing it) and it died rather horribly before I could continue cooling any further. However, the experiment was a success. The heatskink will be attached to the imager with rubber bands or bungies and powered with a more capable supply (like a car battery). For less than $25, this mod makes deep sky imaging a little easier for this fine camera. I appreciate very much the websites and forums that helped make this project possible.

Niches Land Trust at Walnut Ridge

This is a late write up, but on September 21st, the local chapter of Niches Land Trust held an event at Arbor America, West Point, IN. Walnut Ridge Observatory is located at Arbor America and 20-30 people came to the stargazing event.  We were fortunate to have what was the best night of the year so far for seeing and transparency and the views of objects, from the Moon and Neptune to the Dumbell, M31, M13, the Ring Nebula, Alberio and other deep sky objects, was superb.

In the video below, I took a quick pan from the west to the east at sunset. The sky is showing a fine example of the Girdle of Venus, surrounding us in a pinkish glow (called an anti-twilight arch). The dark layer visible especially in the east, separating the pink glow from the horizon, is the shadow of the earth itself.

Panning from the sunset sky to the east. 

Luminaries light the way to the observatory

New Camera!

Here's an image of the cloudy skies over my home taken yesterday night with my new ZWO Optical ASI 120MC. The image is a 30-second exposure. The Summer Triangle stars Vega (top right), Deneb (top left) and Altair (bottom) are clearly visible. You can also see from the treeline why I had to build Walnut Ridge Observatory--there's not a lot of sky visible through the foliage!

The camera comes packed in a pleasing box and has a really useful accessory--a removable 180 degree all-sky lens (which I used to take the picture above).

The Camera Box

The Camera and Fisheye Lens

The camera has a very respectable QE of 55, is capable of high framerates at reduced resolutions (up to 65FPS) and can handle single exposures of up to 1024 seconds. The I120 is not cooled, which means long exposures can be noisy. However, I plan on adding a removable peltier cooler to the back of the case. For less than $25 extra, I'll get very superior performance. The camera also comes in a monochrome version. While the monochrome camera has some advantages (no Bayer Matrix and slightly higher sensitivity), the cost of adding a filter wheel was prohibitive, so I opted for the color version, which will do pretty much everything I need in a single shot. I'll post more on the mods, as well as more images (when the inevitable clouds clear).