First Light

Unbelievably last night the weather cleared up long enough for me to try out the new mono camera from ZWO, I decided to to image M101 the Pinwheel galaxy in Ursa Major, two reasons for selecting this target, first its high overhead at this time, secondly its very a faint object and a bit of a first test for the camera. As it turned out the seeing was fairly bad bordering on misty at times, but I pressed on anyway eager to see what the results would be like.

ZWO 1600mm first light

I ran the guide camera through the 1600mm Pro’s USB hub using one of the short USB2 cables supplied with the camera, eliminating a USB to laptop lead and it connected up first time I also started the 1600mm camera cooling and set it to -20C. Once I had done a 3 star alignment of the EQ6 Pro mount I slewed to Arcturus ( the brightest star in the constellation of Bootes ) to focus the camera using a clear focusing filter, once that was done I switched to a Luminance filter for imaging and double checked the focus with this filter, spot on. I then slewed the scope to the target for the evening, M101 and set the Gain on the camera to 139 and the offset to 21, these figures seem to be optimal for this camera according to the ZWO users forum but i’ll have to experiment with it. I got the Auto Guiding calibrated and set my first exposure to 300 seconds and clicked the start tab in APT, 300 seconds later my first image was on the screen, it was quite dark and all I could see was a few stars and they were quite dim so I opened the Histogram in APT  and did a screen stretch ( this brightens the image and allows details to be seen ) and there it was smack bang in the middle of the image. Thats when I noticed the hair on the brand new camera sensor, it had to be on the sensor because it was very sharply defined, had it been on the sensor chamber window it would of been blurred as further away from the sensor itself. Obviously this had got by ZWO’s quality control, anyhow I carried on to take 24 more images. I had to take Flat frames anyway and hopefully they would clean the image illumination up in processing.

First image of M101, Hair above green arrow

The hair showed more clearly on the flat frames as did the Dust Bunny on the outside of the sensor chamber window ( Doughnut on left of image ).

This camera outputs FITS files, unlike a DSLR that can output JPeg or Raw files. These FITS files can still be procced in Deep Sky Stacker ( DSS ) or program’s like MaximDL, Nebulosity and Pixinsight but these are not free programs so DSS it is, I had already captured the Dark and Bias frames. I loaded the Lights, Darks, Bias and Flat frames into DSS for registration, I then discarded the last 5 Light frames as they were too bad due to the misty atmosphere they were imaged through and when DSS had stacked and calibrated the image it was then processed in Photoshop CS5.

ZWO asi1600mm Pro first image
M101 The Pinwheel Galaxy

Not too bad for a first go with this camera.

As for the hair on the sensor, I removed the sensor chamber cover by undoing the four small screws on the front of the camera, there is a large pink rubber “O” ring that seals the chamber from outside moisture and four desicant tablets on the underside of the cover itself to dry the chamber ( these tablets can be replaced or cooked in an oven to reuse ). On the sensor itself there is a protective cover glass and the small hair was on the outside of this protective glass ( Phew ), a couple of puffs with a bulb blower got rid of it and I quickly closed the chamber again after making sure there was not a spec of dust anywhere inside the sensor chamber.  

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