At the beginning of 2000 I completed my Audine camera. This is a fantastic astronomical CCD-camera designed by a group of French amateurs amateurs led by Christian Buil. I am using this camera with a 13cm F/11,5 Schmidt-Cassegrain made by Opticon on a Vixen GP-DX mount in my back garden. It is shown in the picture at the left.
The camera can be set to different resolutions, the picture below was made at the highest resolution. (768 x 512 pixels of 9 x 9Ám each = 0.009 mm). To center an object on the CCD without having to remove the camera everytime to replace it with an eyepiece I'm using a Meade flip-mirror. When the knob is turned the mirror can be flipped up so the light falls onto the CCD. In the low position the light is directed towards the eyepiece. This is surely one of the most usefull accessories I ever bought! On the picture on the right you can see (from left to right): the Audine camera, the flip-mirror and the backside of the Opticon 13cm SCT. The aluminium knob on the flip-mirror is used to flip the mirror in the desired position. This mirror has to be adjusted once to be sure that an object that is seen in the middle of the eyepiece ends up in the middle of the CCD chip as well. Then the focus for the CCD has to be adjusted and after that the focus for the eyepiece without using the focussing knob on the telescope. The focus position for the eyepiece can then be locked making it very much easier to focus the next time! Focussing of the CCD is achieved with the aid of artificial diffraction spikes, generated by temporarily putting a small bar acros the telescope opening. When the spikes are turning from double to single spikes, without a doubt the point of best focus is found. You only have to remember to put the mirror in the "up" position before starting an exposure, otherwise you need extreme exposure times...
At the moment I am having difficulties with the cooling of the camera, for it is working too well... Because of this the water vapour inside the camera housing settles on the window of the CCD-chip as frost. Despite all this I managed to take some nice pictures on August 29 in binning 2 x 2 mode which simulates 18 x 18Ám pixels by putting the information of 2 x 2 pixels together. The resolution decreases but the sensitivity increases!
These images of galaxy NGC7331 in Pegasus were made on Augustus 29 2000 and both consist of 17 exposures of one minute each. Because the telescope mount wasn't aligned at the celestial pole, the exposures had to be short. And a few of the exposures had to be discarded because they were not sharp enough. The picture on the left has a logarithmic greyscale and has a quite natural look. The right image has been treated with "Digital Darkroom Processing". The image below left shows what happens if you make a long exposure with a poorly aligned telesope mount. It consistst of a sequence of 24 exposures of one minute each made directly after eachother. By registering and adding together only the best of these images you can still produce a nice image despite a seamingly hopeless tracking error. These images were added and processed with the help of the freeware Iris software package.
The object in the picture on the right is "Stephans Quintet" a beautyfull little group of galaxies quite near NGC7331. The biggest member of this group is called NGC7320 and is a bit up and left of center. These are 20 of the 24 images of the terrible image on the left added together by Iris. The various bright stars are easily found back in the left image. The parts that were not on all exposures were discarded (cropped). Four exposures were not used because they were not sharp.
Naturally it is better to perfectly align the mount with the pole, in that way the sharpness is much better and you don't lose so much of the edges.
Next time I am going to use the PEC (Periodic Error Control) feature of my mount as well to get even better results.
The following images were made on October 6th 2000. The CCD chip doesn't freeze over any more because I sealed a lot of openings in the camera like the connectors. NGC891 (left) is a combination of 40 single 30 second exposures. By using such short exposures there was no need to guide during exposures to get nice round star images. Click on the small images to see them full size. The Ring Nebula M57 is a combination of 16 images of 30 seconds each. This combined image was treated with the Lucy-Richardson command (5 iterations) in the Iris software.
This picture of M51 is a combination of 20 exposures of 30 seconds each. On the left the addition of 20 images, on the right the same image displayed with Digital Darkroom Processing (DDP in Iris) Due to the short exposures, steaks are formed from the core of the galaxy when the CCD is read! This can be avoided if you use a shutter.
Combination of 15 exposures of 2 minutes each, treated with a crude flat-field and Unsharp Mask. Due to using PEC, the exposure time per frame could be increased from 30seconds to 2 minutes. Usually 4 out of 5 frames are quite good. Since the total exposure time has increased, there is less noise in this picture. On the right a false-colour version to show the background texture. A satellite trail is visible, a cosmic ray impact (below right) and a small background galaxy (top right).