If you’re not completely new to astrophotography, you should probably quickly go back to your favourite search engine and perform another search, as it’s quite probable you know more about astrophotography than I do – so you won’t learn anything here.
OK, if you’re still reading, I guess you’re like me – extremely new to astrophotography. I’m a novice astronomer, with six months’ experience using my Sky-Watcher Explorer 130P telescope, and my photography experience is limited to pointing and clicking. Basically, I know virtually nothing about photography, and virtually nothing about astronomy.
The camera
My old digital camera had broken, so I asked my wife to buy me a new one for my birthday. As usual, the budget wasn’t huge, so I asked her to get a FujiFilm FinePix F200 EXR, which, although being a reasonably high spec compact digital camera is, at the end of the day, just a compact digital camera.
The reason I opted for this camera is because I knew it had a CCD (charge coupled device) sensor and, based on a bit of Internet research, I had identified that cameras aimed at astrophotography were often called CCD cameras.
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| FujiFilm FinePix F200 EXR Camera |
CCD cameras
In a digital camera, the sensor is the bit that converts light (entering the camera) into digital (electrical) signals.
To take photos in very low light situations such as photographing the night sky, you need a camera with a good quality sensor, and ideally one that is cooled to prevent the sensor from heating up too much during long exposures.
A CCD sensor is better for astrophotography than a CMOS sensor (which some digital cameras have), and the bigger the CCD sensor, the better.
Noise
In order to take photos at night, you need to use a long exposure time. One problem that this can cause though is that the sensor can start to heat up and cause ‘noise’.
So what is ‘noise’? Noise is apparent by the presence of colour speckles where there should be none. For example, instead of a blue sky, you might notice faint pink, purple and other colour speckles amongst the otherwise blue sky.
If you’re interested in knowing more about noise, here is a link to a good article on the subject:
http://www.photoxels.com/tutorial_noise.html
The adapter
In order to be able to attach your digital camera to the telescope, you need to use a camera adapter.
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| Camera Adapter |
Adapters such as the one shown here clamp onto the telescope, and allow the camera to be positioned in front of the eyepiece. They cost around £30, and can easily be found on the Internet if you do a search for ‘digital camera adapters for telescopes’ or something similar.
Setting up the adapter
1. Insert an eyepiece into the telescope and secure in position.
2. Using the telescope’s focus adjustment, focus on the object you want to photograph and, if your telescope allows you to, start to track the object.
3. Clamp the adapter to the eyepiece, taking care not to knock the eyepiece as this might cause the object to disappear from the telescope’s view.
4. Secure the camera to the adapter using the tripod socket. Again, take care not to knock the eyepiece.
5. Using the position adjusters on the adapter, move the camera so that the lens is aligned with the telescope eyepiece. Don’t position the camera too close to the eyepiece because you’ll need to leave enough space for the lens on the camera to extend when you’re using the zoom setting.
6. Switch on the camera.
7. If necessary, use the camera’s zoom adjuster to get the image to fill the camera’s LCD screen (more or less).
8. Take the photo (see below).
The telescope/adapter/camera setup should look something like:
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| Camera Adapter Setup |
Taking the photo
Having set up the camera and adapter as described above, you are ready to take a photo and, below, is my very first attempt at astrophotography.
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| My first attempt at astrophotography – the moon |
In fact, this was the best of five photos I took. It was very windy and I was finding it very difficult to keep the camera steady, even though I had set the timer on the camera to 10 seconds. If you look at the photo you’ll see that it is slightly out of focus, which I think was caused by very slight camera movement.
The camera was set to ‘auto’, giving a very short (probably about 1/100 of a second) exposure time – the moon is very bright after all !
I used a 25 mm eyepiece, along with a 2x Barlow lens, giving me a resultant magnification of 52x.
The camera itself takes photos at 12 megapixel, meaning that the photo was huge when I opened it in PaintShopPro. I then cropped it to give me the image shown above.
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My second attempt at astrophotography
- a full moon |
And here is my second attempt at photographing the moon, taken around 6pm on 1st January 2010.
As you can see, the photo is slightly overexposed – again I used the ‘auto’ setting on the camera, which made the exposure too long.
As with the previous photo, I took this photo using a magnification of 52x, and then played around with it in PaintShopPro.
Problems with this astrophotography setup
Update to this post: 23 April 2010. Having used the above telescope/camera/adapter setup for a few months now, I can see that it has a couple of limitations that I had not anticipated.
Firstly, you need to focus on the object before you attach the adapter and camera to the eyepiece. This is because when you view the object on the camera’s LCD screen, what you see isn’t as clear as when you look through the eyepiece. This makes it difficult to focus on an object by relying on the LCD screen. (I have updated the setup steps given earlier in this post to reflect this.)
Secondly, once you have attached the adapter and camera, it is difficult to keep the object in view on the LCD screen at magnifications above 50x. I have tried, and failed, a few times to photograph objects at 130x. I think the problem is that having located an object, it is very difficult to not knock the eyepiece slightly when you attach the adapter. This is not a problem at low maginifications, but certainly is at higher ones.
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