365Astronomy 1.25" Deluxe 4-Element 5X Apochromatic Barlow
This is a HIGH QUALITY 4-element, 5x Apochromatic Barlow lens from 365Astronomy.
We buy these directly from the factory, hence the very competitive price.
High quality Deluxe 5x Barlow lens with practically no false colour and in full metal construction.
Due to the medium length construction it is recommended for use with refractors, Maksutovs and Schmidt-Cassegrains.
This might be too long for Newtonian telescopes. (We'll have to came back about this after some tests and feedback...)
Four element apochromatic construction provides excellent field correction and practically chromatic aberration free image.
Optical structure: quadruplet
Brass compression ring
Size: 31.7mm, 1.25"
Overall length: 88mm
Optical length: 58mm (might be too long for Newtonians)
Filter thread: YES (M28.5 filter thread to attach standard 1.25" filters directly to the Barlow)
General info about Barlow lenses.
The aim of a Barlow lens is to prolong the telescope's focal length, so e.g. a 2x Barlow doubles the focal length of the telescope, so when we divide the doubled focal length of the telescope with the focal length of the eyepiece we got twice the magnification obtained. This is a popular amateur complementary tool, because with the help of a Barlow lens we can achieve a wider magnification range with the same telescope without having to obtain additional eyepieces.
When we want to achieve high magnification, we would choose an eyepiece with a short focal length, but the aperture is usually smaller and the eye relief is shorter for eyepieces with shorter focal length (higher magnification eyepieces), thus these are less comfortable. With a Barlow lens we can achieve the same magnification but by using a more comfortable, longer focal length eyepiece.
Barlows are so good that they are being used even in more expensive wide-angle eyepieces where the Barlow is simply integrated into the construction of the eyepiece.
The Barlow lens is always being used between the telescope lens and the eyepiece.
However, there is a trick we will teach you now. If you use a refractor telescope, Maksutov or Schmidt-Cassegrain with a star diagonal, you would usually us the Barlow between the star diagonal (diagonal mirror) and eyepiece, thus achieving its nominal magnification, e.g. 2x.
Now, if you use the Barlow between the telescope and the diagonal, then you'll gain a different magnification, i.e. 2.75x for a 2x Barlow, thus further increasing the number of achievable combination of magnifications with just one Barlow and a set of eyepieces...
Barlow lenses will fit in a 31.7 mm or 50.8 mm eyepiece holder barrel.
This particular one will fit in a 1.25" holder barrel.