Triplet lens benefits

Often viewed as a complicated hobby, astrophotography can actually be quite simple using just a standard DSLR camera and a telescope. For best results though, the scope should be apochromatic, bringing all the colours of light to equal focus. To achieve this desired standard, the 70EDT-F uses three lenses, including one made of Ohara S-FPL53 ED glass, which is noted for having a refractive index close to that of natural fluorite – without fluorite’s drawbacks. In practical terms, this means that you can use a one-shot colour camera, DSLR or CCD/CMOS, without filters, and the stars will appear tight, true to their natural colour, and without unwanted coloured haloes. To confirm the apochromatic nature of the 70EDT-F we took a few random colour images from our image datasets, separated them into individual red, green, and blue channels, and then compared star sizes at pixel level. On a good telescope, all channels produce similarly sized star images, and the images we checked from the 70EDT-F were excellent in this regard.