Friday, March 15, 2013

Cassegrain prime focus test

Yesterday I have received and email that looked very interesting: apparently we had anything in place to use our 50 cm Cassegrain also in prime focus. Looking at the weather I had no hope of seeing the CCD camera in prime focus operation anytime soon, but after I saw the comet (which was also hopeless just a few hours before), I stayed at the institute so test the setup.

It's rather easy: one has to remove the secondary mirror from its place and then uncover the corrector lens, fixing the camera into its place. The only problem is that the power cables were too short, but there's really nothing that some duct tape won't fix :D

As soon as I was reaching focus, David Muelheims join me for observations; we did not plan at the time to stay until 7 am the second day!

When we first saw our focusing frames our jaws dropped: the level of intricate detail with an exposure time of 1s was absolutely brilliant!! (we used M42 as a target for focusing)

Our next target was the Horsehead - Flame nebulae area. Unfortunately, as they were already quite low when we started, there was not much time to make a nice color image, so only about 60 minutes of H-alpha data are stacked below. After fiddling a bit with it I got this: 

Can't wait to get a proper color version of it!...

We then took some images for Cone nebula (I'll show that when it's nice and in colour) and we switched to the Leo triplet: M65, M 66 and NGC 3628. With the camera mounted in the Cassegrain focus, to get such an image would of  taken more than 110 hours!! This is the result of only 4 hours of data acquisition plus about two for post processing:

Processing the Leo Triplet image was a nightmare because it's very difficult to get good calibration frames with this telescope; the flats match the images badly. One can only get rid of this by exposing and dithering a lot more than we did. Maybe also observing in only one filter per night might help, I have the impression that the filters don't go back precisely the way they were before changing to some other one. 

   Besides all of this, I've made also some video meteor observations, but about that in another post :)

All images in this post have been taken jointly by me and David; data processing was only my task.

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