A lot to take in

Unless you dedicate your setup solely to imaging, eyepieces are a vital part of any astronomer’s toolkit.

They come in a variety of designs including Orthoscopic, Kellner, Erfle, Plössel, Nagler and more.

Each have advantages and disadvantages depending on what you plan to observe, with some more suited to low magnification work and others to high.

Plössel eyepieces are often included in telescope packages and have an apparent field of view of around 50°, useful for a good range of astronomical objects, including deep-sky and planetary.

The apparent field of view of an eyepiece has steadily increased over time, giving the user a more enhanced viewing experience. Today, Nagler style eyepieces offer an astonishing 100° field of view.  Indeed, when first designed and introduced by Al Nagler, the views were often compared to walking in space!

In our November issue, Pete Lawrence reviews the Explore Scientific 9mm 120° eyepiece. A 120° field of view! Wow!

In discussions with manufacturers and suppliers, the general consensus is that 120° may be the practical usable limit, although a 140° and 160° field of view may be a possibility.

If design limitations can be overcome then perhaps so but cost may well be the deciding factor – for the price of the Explore Scientific 9mm 120° eyepiece you could buy a good, Rich Field refractor.

As to the usefulness of such a wide view, some argue that you only really look at its centre. But I like to compare it to looking out of your window. You don't just look straight ahead, you enjoy the whole view – even if you can't take it all in at once!

Meanwhile, Steve Richards has also been very busy reviewing the new imaging kit from Starlight Xpress. Check out his review of the Trius H814 CCD and the SX Mini Filter Wheel & OAG in the latest issue of BBC Sky at Night Magazine.


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