A light pollution filter will block some of the mercury light that is given off from some street lights. To show this I took two pictures of a street light, one without the filter, and one with, to show how much the filter blocks I took the pictures of the light its self. If you look at the picture on the right you will see the full light coming from the bulb without a filter. The picture on the left has the filter added to the camera. You can clearly see the light from the bulb has halved. These pictures are taken of the bulb its self, when you look at an object in the night sky the only light you will have to stop is the glow in the sky.
Ever looked up into the night sky and wondered where the planets are, I did and I bought myself a telescope. The views of saturn were amazing, looking at the planet with it’s rings I thought I need a picture of that. So off I went on youtube to learn how to go about it. As always there is an expensive way which will most probably get a nice image or a cheap way of getting an image that to me is good enough for now.
I looked for a decent webcam to place into the eyepiece and hooked it up to my laptop. I found that there are two kinds of webcams, one has a sensor called a CMOS image sensor and the other is a CCD [ charge-coupled device ]. What I found out is the ccd sensor is supposed to pickup more light than the cmos sensor, so I went for the ccd one. I got one from Ebay for about £25, and started looking at the night sky. I was hoping that I would start seeing the planets nice and clear, and was very disappointed with the results. After more research I found that I had to record the video and place it into image stacking software. The software will run the video taking snapshots through out the file and stack them together to get the picture. The stacking software is called Sharpstack.
The pictures to the left of Saturn and Jupiter are image stacked using software, the pictures are not fantastic, but not bad using a webcam. You can make the pictures better quality, but that will mean stacking a lot more pictures using the software, but it can only get as good as the video that was recorded. Pictures taken using the webcam are limited in what you can do, but it was a start, and I got some images.The telescope I used was a Helious 6 inch 1400 refractor.
The best way if you have a good slr [single-lens reflex]camera is to attach the camera to the telescope using an adapter like the ones above, you will have to get one for your make of camera. This way you can use the manual mode to capture the images. If you have live view on your camera it will make things a lot easier. You will have to turn up the iso setting before you start getting something in the view finder. The image will be very small so you will have to use your view finder to zoom in to magnify the image. You will then have to set the lens to manual focus and, looking at the zoomed in image make very slight changes to the focus until you are happy with the image. It will also help if you can set a delay time on your camera before it takes the shot so that any movement given with you pressing the shutter button will settle down. I use 4 seconds, but you put in what your happy with, even using a shutter control remote the mirror opening will shake the camera a bit.
The way to get a closer view is to use a Barlow lens. These come in different magnifications. These go into the telescope eye piece first, and then the camera or use both Barlows at once, but remember that the higher the magnification the faster the image will go from view. Unfortunately the best times for taking good pictures are on very cold winter nights, and when the object is high in the sky, this is because there is no heat coming up from the ground, and with the object being high up there is not as much atmosphere to look through, both will hinder a good image.
light pollution filter
The filter comes with different price tags, I only have a 1.25" filter from Ebay that cost about 40 pounds so I cannot comment on the higher priced filters. The other name for this filter is a "Nebula filter", and as the name says the filter is very good for viewing Nebulas. I have used this filter for viewing and photographing planets. But Before you buy one you should really visit astronomy forums and find out what filters they use. I have found that there are different filters being used to help with removing sky glow that also help in other ways as well. It might be worth spending that little bit extra to get a better filter, but please do your homework as there are a lot to look at.