Sky-Watcher Quattro 200P Imaging Newtonian 8" (203 mm)

Fast f/4 Optics With a Parabolic Mirror

The f/4 focal ratio is very fast and lets faint galaxies and nebulae show detail with limited exposure time. The primary mirror is parabolic and the secondary is flat, both of low-expansion borosilicate glass, which gives near-zero thermal expansion and shorter cool-down times.

The Quattro also gives nice visual images even without a coma corrector. No eyepiece is supplied: many astrophotographers already have eyepieces, so Sky-Watcher chose not to charge for one.

Full-Offset Secondary Mirror

The 70mm secondary mirror is mounted full offset, so the spider vanes look off-center when you look in through the focuser; this is normal. The fully illuminated field is 44 mm.

Coma Corrector and Back Focus

A high-quality coma corrector is an essential accessory for wide-field astrophotography, and it is left out of the box so you can choose the best fit. Sky-Watcher's F4 Coma Corrector (4 lenses, enlarged T2 thread) is one option.

The standard back focus is 55mm, and the drawtube extends up to 75mm from its base. The 75mm of travel is not 75mm of free back focus, so test your camera, filter wheel and guider combination.

2-inch Dual-Speed 10:1 Linear Power Focuser

Four precision ball bearings support the drawtube, giving stability and zero image shift with a heavy eyepiece or camera. A roller moves the drawtube instead of a rack and pinion.

Focus with the main knobs until the image is nearly sharp, then with the 1:10 knob until it is sharp. The focuser also has:

• Tension adjustment: a large thumbscrew below the focuser; correct tension lets you focus smoothly without the imaging train moving under gravity.
• Focus lock: a thumbscrew on top locks the drawtube; loosen it to focus and tighten it when a heavy load is attached.
• T2 plate: the 1.25-inch adapter is a tube screwed onto a T2 (42x0.75mm) plate; unscrew the tube to use the plate with your T2 accessory adapter.

Knife-Edge Baffles and Thin Secondary Vanes

The tube is lined with nine internal knife-edge baffle rings: they cut down stray light entering the tube and help improve image contrast. The tube weighs 9.5 kg (20.9 lb) and is 71.1 cm long and 23.5 cm in diameter.

The secondary sits on 0.5 mm ultra-thin vanes, which limit heat build-up and reach thermal equilibrium quickly. A pair of tube rings and a V-style dovetail plate are included.

Collimation and Focuser Parallelism

The mirrors are aligned at the factory; check the alignment on a bright star, which should look symmetrical.

If it does not, loosen the primary's blocking screws, make small corrections with the large adjustment knobs, and lock them again. For heavy misalignment the secondary should be aligned too, and an optional laser collimator is recommended. If stars in the four corners of a wide-field image look different, the focuser may need realigning with its push-pull screws; this is a delicate operation, so check for other causes first.

Balancing a Heavy Imaging Train

The tube weighs 9.5 kg (20.9 lb) and comes with tube rings and a V-style dovetail plate, so choose a mount with a Vixen-style saddle and a payload rating that covers the tube plus your camera and accessories.

A heavy imaging train on the side-mounted focuser unbalances the tube. Sky-Watcher's solution is to rotate the tube so the imaging train points vertically to the ground; it warns that gravity is then your enemy, so secure every accessory to the focuser and set the focuser tension.

Cool-Down and Refocusing

The low-expansion borosilicate mirrors give shorter cool-down times, and the manual notes the image usually needs fine refocusing over time as the temperature changes.

Finder Alignment

To focus the finderscope, look at an object at least 500 meters away, loosen the knurled ring, turn the front lens holder until sharp and lock it with the ring. Then center that object in the main telescope's eyepiece.

Use the finder bracket's adjustment screws to center the crosshairs on the same object. The image in the finder is upside-down, which is normal.

Solar safety: Never look directly at the Sun with the telescope or the finderscope, and never use an eyepiece-type solar filter.