1.Barlow magnifier (also known as Barlow magnifier, extended focus lens, barlowlens, etc.
In the 19th century, the British scientist Barlow added a concave lens in front of the eyepiece and found that the magnification of the telescope increased. Later, the Barlow mirror was modified by increasing the length of the lens barrel. So it is named Barlow Mirror after him. When it was first invented, the Barlow knowledge simply increased the magnification but blurred the view. Since then, the technology has improved a lot, and now the Barlow contains multiple high-quality coated lenses to reduce the loss of image quality. Good Barlow It will only lose 3% of the image quality, and it is a very cost-effective way to double the magnification of the eyepiece group with Barlow. The magnification is equivalent to 16mm, 13mm and 5mm eyepieces. Another benefit of the Barlow lens is that it increases the exit pupil distance while increasing the magnification. A high power eyepiece such as a 10mm eyepiece provides a small exit pupil distance, requiring the user to bring the eye closer to the eyepiece, while a low power eyepiece such as a 20mm eyepiece provides a smaller exit pupil distance. Large interpupillary distance, by combining 2X Barlow and 20mm eyepiece, you can get the magnification equivalent to 10mm eyepiece, and at the same time have a larger exit pupil distance, which makes any observer, children and users who wear glasses more comfortable while observing.
2.The principle and classification of Barlow mirror
Barrow of single concave lens: the most primitive one, in fact, it is also the direct application of Barrow's principle. It is to rely on the concave lens to synthesize a longer focal length than the original focal length. So if you have a concave lens handy, you can make your own Barrow.
Cemented lens or combined concave lens Barrow: It is an improved variety, which eliminates the effects of chromatic aberration and spherical aberration by combining lenses, and the imaging effect is better. Essentially a concave lens.
PM structure Barrow: It is a Barrow composed of a concave lens part and a convex lens field lens. This kind of Barrow belongs to the high-end products in Barrow, and it has the best effect so far. It has good performance in aberration, chromatic aberration control and flat field, and the focus position is close to the eyepiece, so it is easy to focus.
3. Usage details
When the 2x Barlow lens is placed between the eyepiece and the zenith lens, a 2x magnification can be obtained, while the barlow lens is placed between the telescope and the zenith lens, a 3x magnification can be obtained, but the higher The magnification does not always mean better image quality, higher magnification also amplifies the air disturbance and blurs the image, so it is necessary to constantly experiment and compare to find the most suitable match. (pictured)