Astromodified Canon EOS cameras (450D and 1000D) from only £220
Cheap Astrophotography introduces its more versatile camera. Two different models; canon 600D and 700D are now available with the all-in-one modification: astronomical, daylight, UV and infrared photography as well as wildlife-night vision . A very powerful and capable device at an affordable price. You can now diversify your interests and use your camera even when the weather isn't that great.
How does it work?
A typical digital camera is designed to block all that valuable infrared and ultraviolet light, since when left uncontrolled it pollutes the visible light reaching the RGB sensor. In astrophotography, unless we are interested in specstroscopy, the infrared light can cause bloated stars and chromatic aberration.
In normal daylight photography, both infrared and ultraviolet wavelengths will degrade the quality of our photos. This is the reason why typical camera sensors are fitted with a hot mirror (which cuts IR light) and an anti-aliasing filter (which cuts UV and IR light as well as blurring the image to avoid moiré).
We already know that the hot mirror, also blocks that part of the visible radiation produced by emission nebulae (Hydrogen alpha wavelength) thus our interest in removing it to achieve high quality astrophotos.
Now, the infrared spectrum from about 700 nanometers (the longest wavelength red we can see with our eyes) to around 1000 nm (the longest wavelength to which our camera sensors are typically sensitive) — is full of interesting opportunities. Gray skies turn into cinema-worthy masterpieces, foliage pops and separates itself from surrounding rocks and buildings, and everyday objects can take on an otherworldly aspect. Also, the ability of the naked sensor to capture infrared radiation can make the camera suitable for night vision and wildlife nocturnal photography. Wouldn't it be nice if we could modify the camera in a way that it can be used for all these functions?
Full Spectrum conversion
We can achieve this flexibility by doing a conversion to threespectrum (UV+Visible+IR). That conversion involve removing the infrared filter and replacing it with a similarly-sized Astronomik specially coated clear glass filter. This allows you to pick and choose which parts of the spectrum your camera captures depending on which screw-in filter you use in front of your lens. You can even tweak which portion of the IR spectrum you photograph by selecting specifically-rated blocking filters (e.g. 650nm, 720nm, or 760nm.)
One downside to this more flexible approach is that you’ll almost always need to use a filter of some kind in front of your lens. If you don’t use any filter at all, having both IR and visible light hit your sensor will typically result in a muddy image. Also, it has already been mentioned that IR light can produce star bloating in your astrophotos. Another shortcoming of a full spectrum conversion is that when you are recording infrared, you won’t be able to see through the viewfinder — as visible light is blocked at the lens filter. For that reason, this conversion is available in models that have LiveView.
The transmission shown in red below is that allowed by the hot mirror filter.
When combined with the OWB clip in filter, the wavelengths blocked out match very closely to what many original lowpass filters do. There is slightly less light available to the sensor than on a stock camera (about 1/5 of a stop), but the transmitted wavelengths are the same, and in the same proportion.
The result is an astrocamera that can also be used for infrared like a normal full spectrum conversion, but provides a very accurate color rendition for visible photography on a converted camera anywhere. It also can use as a night vision system or a night camera to video or photograph wildlife with an infrared torch. The removal of the anti-aliasing filter also produces sharper images.
For astronomical use, this camera need an infrared filter if used with refractors or lenses. A good solution is to use a light pollution filter with IR protection such us the Astronomik CLS CCD clip filter or the IDAS D1 light pollution suppression filter..
For daylight photography, again, an UV-IR filter such as the OWB clip in filter would be a good solution.
Stock unmodified camera (Auto White Balance)
IR-UV & two clear glass mod (Auto White Balance)