Astronomy – what astronomy?

It is many months since I last used the telescope.  We had week after week of cloud last year followed by several weeks of below freezing night temperatures.  It is difficult to get motivated when, by the time all the equipment is set up, you are frozen to the marrow and your fingers won’t work.  Also, during this time Mars completely disappeared and Jupiter is now so faint that I can’t expect to get any half decent pictures.  Of the planets only Venus is currently photographable with my modified webcam.  Venus is a featureless, crescent moon shaped, white blob so not that interesting.  But – Saturn will be visible in the Eastern skies towards the end of February so will make an effort to see that.  As 2009 is the International Astronomical Year I would like to do something related to that.

Telescope modifications

Somewhat disappointed with the quality of the astronomical images I’ve captured so far I searched for information on why this might be. I found a web site about our particular telescope, a Meade LX90, which went into some detail about improvements which can be made.

Apparently the main problem in achieving good images is getting the focus spot on. It seems that the focussing system used on our telescope is subject to backlash. This makes it difficult to be certain that you have homed in on the optimum focus point. Two ideas to help came out of my investigation.

The first cost money. This is a kit with precision ball bearings which, when fitted to the focussing control, takes out most of the slack which causes backlash. The kit came from America and cost me $32, around £17. Interestingly I found the same kit sold by an online UK astronomy shop for £29! The kit was ‘reasonably’ easy to fit and resulted in a much smoother focussing.

The second was free. It consists simply of a mask which fits on the front of the telescope. The mask has two holes in it. The idea is that when the image is not in focus it splits into two images. To ensure accurate focussing it is simply necessary to merge the two images. Here is a picture of the mask I made:

Armed with the mask and improved focussing control I set up the telescope last night to see what I could achieve. Unfortunately Mars and Saturn have moved away so I couldn’t photograph them. My modified webcam is not sensitive enough to photograph star clusters, galaxies or nebula so I spent some time trying out the mask and improved focussing using an eyepiece. At 11.30pm I was delighted to see Jupiter appear. It was very low so I didn’t expect great results but I just look at my first attempt. I’m delighted.

Can’t wait for Jupiter to get higher in the sky and out of the heat haze. I think by the end of July I should be getting even better pictures.

The Moon

I thought I would have a go at photographing the moon using the telescope and modified webcam. Quite an easy subject – large, bright – but the size actually causes a problem.

The webcam can only see about 5% of the moon’s surface so the technique is to take many pictures trying to make sure that all the visible surface has been captured. This proved harder than it sounds so I finished up with some shots which overlapped by 50/60% and some which only just made it.

The images were then pasted as transparent images into PaintShopPro. A bit tedious but surprisingly successful. Some touching up was necessary particularly extending the black background. And this is the result:

I’m really pleased – much more satisfying than my pictures of Saturn!

Yes, I know!!

Yes, I know, there is no real difference between  the original and ‘improved’ image of Saturn.  Every one’s told me and I can only agree.

I have been searching for clues as to why my images are worse than those obtained by others using much the same equipment.  The most likely culprit is poor collimation of the telescope optics.  Put simply it ensures that the two mirrors are accurately aligned.  Apparently this is a simple adjustment which should be checked every time the telescope is used.  Next time the weather is kind I will see what can be done.  If better images result I will, of course, put them on the blog and boast a little.

Improved photo of Saturn

I’ve been trying to improve the image of Saturn.  I use a program called Registax with which it is possible to selectively sharpen the image and adjust contrast and brightness.  The image below is the result of applying Registax’s image improvement features.

Registax was specially written for astronomical imaging.  It accepts individual .jpg images or .avi video consisting of hundreds of frames.  The first run through of the program sifts out the best images and ignores the unusable images.  An area of the image is then defined and a second run through ensures that all the images are aligned.  This is necessary because astronomical imaging is subject to atmospheric effects – the twinkling star effect – which blurs the image.

The sorted and aligned images are then stacked.  This is a statistical averaging procedure which doesn’t increase the brightness but is utilised to eliminate random noise.  The final operation is to sharpen the image to bring out the fine detail.  Sharpening is achieved by adjusting wavelets – no, I don’t understand what they are either – but it is surprising what can be achieved.  Finally the brightness and contrast are adjusted.

The image above probably represents the best I can achieve with my modified webcam.  My next target will be the moon.  This will have different problems because the camera cannot get the whole of the moon in one shot.  Apparently the technique is to take several images covering the whole of the moon and then using a program which ’stitches’ them together.  Watch this space!

First attempt at photographing Saturn

I have just spent the evening trying to get a decent picture of Saturn.  The picture below is the best yet – but I’m not really satisfied with it.  Seeing conditions were not ideal – plenty of haze and turbulance.

It was taken using a modified Philips Toucam webcam attached to our Meade 8″ LX-90 telescope.  The hardest part about capturing the picture is getting the telescope pointing in the right direction.

The telescope is initially set by using the sighting telescope followed by fine adjustment using the eyepiece.  The eyepiece is then replaced by the camera.  The field of view of the camera is somewhat less than the eyepiece so the chances of the image appearing in the right place is a bit hit and miss.

I also tried to get an image of Mars but it is now travelling away from us and has become a bit too small.  Maybe if we get better seeing conditions soon I’ll have another go.