Sky-Watcher 5mm Planetary UWA Eyepiece (58°, 1.25 inch)

The Sky-Watcher 5 mm Planetary UWA is an eyepiece for high magnification: 5 mm focal brandpoint, five multi-coated lenses, 58 degrees apparent field of view and 16 mm eye distance. That eye distance is the difference with classic short eyepieces, where you have to look through the glass.

Does this eyepiece fit your telescope?

Yes, if your telescope has a 1.25-inch eyepiece holder, or a 2-inch eyepiece with the 1.25-inch adapter that comes standard with it. The magnification is the brandpoint of your telescope divided by 5. The brandpoint is the second number on the tube: at 130/650 it is 650 mm.

The focal point of your telescope	Magnification with this eyepiece
400 mm	80x
500 mm	100x
650 mm	130x
700 mm	140x
750 mm	150x
900 mm	180x
1000 mm	200x
1200 mm	240x

Whether that magnification is usable depends on the aperture: the highest meaningful magnification is approximately twice the aperture in millimeters (70 mm: 140x, 130 mm: 260x, 150 mm: 300x). Due to the air above the Netherlands and Belgium, the limit in practice is usually between 150 and 200x. On a telescope of 650 or 750 mm, this eyepiece remains below that limit with 130x to 150x; at 1200 mm (240x) it is above that limit; there it is only usable on the best nights.

What does it do?

The actual field of view is 58 degrees divided by the magnification: at 650 mm the brandpoint is 0.45 degrees (the moon at 0.5 degrees does not fit quite right), at 750 mm it is 0.39 degrees (about three-quarters of the moon), at 1200 mm it is 0.24 degrees (about half of the moon). On Jupiter you see the two main bands at 130x to 150x and during a transit the shadow of a moon on the planet; on Saturn the ring is detached from the planet and at calm air and from 150 mm aperture the Cassini separation. The planet remains small, even at 240x. In turbulent air (seeing: the blurring of the image due to layers of air), the image becomes blurred at 150x more often than at 108x or 125x with the 6 mm eyepiece; therefore, this is the eyepiece for calm nights.

Key data

6 mm, 5 mm or 2.5 mm?

The series also has a 6 mm and a 2.5 mm Version with the same construction. On a f/5 Dobson of 650 or 750 mm (f/5 is the brandfocal length divided by the aperture), 5 mm gives 130x to 150x, usable on calm nights; 6 mm gives 108x to 125x and is more often usable; 2.5 mm (260x to 300x) is almost never usable there. On a telescope of 1200 mm, 6 mm (200x) is the highest step that works regularly; 5 mm (240x) only on the best nights. Choose 5 mm if your telescope has a brandfocal length of 400 or 500 mm: that gives it 80x to 100x, and 6 mm at 67x to 83x remains on the low end for planets. If you’re unsure between 6 and 5 mm, choose 6 mm: in turbulent air it is often more useful.

Frequently asked questions about the 5 mm Planetary UWA

• Is 5 mm better than 6 mm on a telescope of 1200 mm? Usually not: 240x is only usable on the best nights, 200x more often.
• Does it fit a 2 inch telescope? Yes, with the 1.25 inch extension adapter that comes with every 2 inch telescope.
• Do I see Saturn with color and detail? The ring detached from the planet and a light yellow tint; the Cassini separation only at calm air and from an opening of 150 mm. The planet remains small.
• Can I screw on a moon filter? Yes, the eyepiece has a standard 1.25 inch filter thread.
• Can I use it with a 2x Barlow lens? Only on a telescope with a 400 or 500 mm brandfocal length (160x to 200x). At 650 mm and longer, it becomes 260x or more, too much for the air above the Netherlands and Belgium.

Specifications

Shipping and assistance

Which eyepiece fits which telescope is stated in the eyepiece explanation; more eyepieces of this merk type are available Sky-Watcher brand page. Orders with multiple items are shipped from multiple warehouses and may arrive in parts; each package will have its own tracking number. Help choosing: WhatsApp or call on business days from 9:00 to 17:00. 30-day return period.