Webcam settings

WHEN BEST TO OBSERVE : The best time to image planets is when there has been a few days of high pressure sitting over the country and has created a haze. And the very best seeing for planets is when a mist has come down and just before that mist turns into fog that is when you have the best chance of that perfect shot.

Of course this sounds crackers who in their right minds would want to image in these sort of conditions certainly not the deep space crowd, I am sure they would all be at home in front of the telly, but it is a fact, this is when the air is at its most stable for planetary imaging

Webcam settings vary from user to user you just have to experiment until you find what suits you the best. As a general guide though I use the following. And please do remember if the seeing conditions are poor no matter how hard you try you will NEVER get a decent image.

GAIN: as low as possible remember more gain more grain. You must still make sure though that the planet remains reasonably bright but not saturated.

BRIGHTNESS: 50%

SATURATION : 80 to 100%

GAMMA: 0-20%

FPS: 5 when the seeing is good but usually 10 but no more than 15. The higher the frame rate the more likely you are to capture that fleeting glance of a perfect seeing and the easier it is to focus. But due to compression on USB 1 cameras 5 fps yields the best quality. But with such poor weather and pollution in the U. K. you will find that more often than not you will be using 10 fps.

SHUTTER SPEED: 1/25 or 1/33of a second- Which by the way is nonsense as when the camera is in  manual mode it is the frames per second that govern the shutter speed e.g. at 5 frames per second the shutter speed is 1/5 of a second and at 10 frames per second it is 1/10 of a second

NUMBER OF FRAMES: This again is up to the individual but as a guide line aim for about a 1000, so when the bad frames are taken out you will be left with around 300 or 400. But watch your capture time, for planets with fast rotation like Jupiter (10 hrs) do not go above 2mins or your image may blur, but the Moon, Venus, and Mercury you can almost shoot to your hearts content. Do bear in mind that video eats up huge chunks of hard drive. A 2min video could be as much as 600mb, but this is not so much of a problem with today's computers with such enormous hard drives.

COLLIMATION: Correct collimation in a telescope is critical for planetary imaging if the telescope is even a fraction out it will affect the final image, especially if your telescope is portable, and it is moved from the house to the observing site.   you need to check it every couple of weeks to see if it is still in collimation or not, or if you want you can check it every time you move it.  Tips on collimation and its affects can be found at http://legault.club.fr/collim.html

THERMAL COOLDOWN: Thermal cool down means allowing the optics of the telescope to cool to the ambient temperature of the night air this can take several hours depending on the thickness of the mirror, and in telescopes of large aperture of 12in upwards this can be a long wait sometimes they will not cool till the early hours of the morning especially if their mirrors are enclosed such as in some newtonian reflectors and things really get bad if they are housed in domes they may never cool to the outside air temperature, which is why most planetary imagers  keep their telescopes either in a run off shed, or they take their telescopes outside when needed. Some even install a fan at the back of the mirror to help them to cool to down. Refractors are less affected by thermal currents in the tube as they are sealed as is the SCT but they still require a cool down period of an hour or so

FOCUS

Focus is always tricky, it seems that most of the time you are trying to image under six foot of water and you can be there hours fiddling about never really happy with it, but it is critical that you get your target as sharp as possible and this is where an electric focuser will help by minimising any shake that may come about by focusing manually. When imaging Saturn focus on the Cassini division and when on Jupiter there is usually a moon in view you will have to turn bring the gain up until you can see the moons, but do remember to bring the gain back down again after focusing, to a level where the planet is not saturated. Mars is quite easy as it has areas of high and low contrast to help you focus.

CAMERA SOFTWARE

Now you have gone out and bought your webcam what software do you need to run it? The answer is the software that it comes with will be enough to do the job for you but if you want full control over the camera settings I suggest you download K3CCD which is a program that can handle all your cameras needs, it is free for the first month on a trial basis after that you will have to pay a small fee.

K3CCD http://www.pk3.org/Astro/ when on website go to " my software".

PROCESSING YOUR IMAGES

Processing images is an art and can be quite complex, you will often find that the same image can be processed with totally different results. For this reason I am not going to include the way I Process mine. What I will tell you though is that in my mind the best image processing software you can get is Registax and best of all it is free.

http://registax.astronomy.net/

If you need some guidance on how to use it try the following.

http://www.starizona.com/ccd/software/soft_proc_registax.htm

http://registax.astronomy.net/controls.pdf

This is a PDF file and you may have to wait a minute or two before anything appears on the screen.

You can also use a program such as Photoshop to finalise your image.

Phil Reed

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