Main telescope

The main telescope is the observatory’s most complete deep-sky imaging setup: a Sky-Watcher 200P Newtonian reflector (200 mm, f/5) on a HEQ5 equatorial mount, controlled by a ZWO ASIAIR Mini, with motorized focus, a filter wheel, a coma corrector and two ZWO ASI294 cameras, one color and one monochrome.

Capabilities

• Light gathering: with a 200 mm aperture, it collects about 16 times more light than the 50 mm of the Seestar S50 and about 44 times more than the 30 mm of the Seestar S30 Pro.
• Field of view: approximately 1.1° × 0.75°, with a scale of about 0.95″ per pixel (ASI294 sensor of 4144 × 2822 pixels of 4.63 µm at the 1000 mm focal length, not counting the coma corrector).
• Tracking: the equatorial mount follows the sky with a single axis, without the field rotation of alt-azimuth mounts, which allows long exposures.
• Automation: the ASIAIR Mini controls the camera, mount, focus and filter wheel, with autofocus and filter changes during the session.

Possibilities

This is the setup for the faintest objects and the finest details: emission and reflection nebulae, galaxies and clusters over many hours of integration. The color camera delivers color images in a single sequence of exposures; the monochrome one, used with filters, allows broadband (LRGB) and narrowband imaging, a technique that stands out under an urban sky like that of Rio de Janeiro.

The setup, component by component

Sky-Watcher Explorer 200P

Newtonian reflector with a 200 mm (8-inch) aperture and a 1000 mm focal length (f/5), with a parabolic mirror and a 2-inch focuser. It is the telescope of the setup: its aperture determines the amount of light and the level of detail in the images. Like every Newtonian, it needs periodic collimation.

Sky-Watcher HEQ5 mount

German equatorial mount with GoTo, with a payload capacity of around 15 kg. Aligned with the celestial pole, it follows the motion of the sky and lets you point at the target and keep the framing throughout the whole session.

ZWO ASI294MC Pro

Cooled color camera, with a Sony IMX294 sensor in 4/3″ format, 4144 × 2822 pixels (11.7 megapixels) of 4.63 µm. Cooling reduces thermal noise in long exposures.

ZWO ASI294MM Pro

Monochrome version of the same camera, with the same sensor and the same field. It works with filters, photographing each band separately, which yields more detail and makes narrowband imaging possible.

ZWO ASIAIR Mini

Compact astrophotography computer, operated through the ASIAIR app on a smartphone. It controls the camera, mount, focuser and filter wheel, performs autofocus and field position solving (plate solving), and runs capture sequences.

ZWO EAF

Automatic electronic focuser, attached to the telescope’s focuser. With it, focus is adjusted by the ASIAIR, including automatically throughout the night as the temperature changes.

ZWO EFW

Electronic filter wheel. It changes filters on command, without touching the telescope, and is essential for working with the monochrome camera.

Coma corrector

Fast Newtonians like this one distort stars at the edges of the field, giving them a comet shape. The coma corrector, installed before the camera, compensates for this effect and keeps stars round across the whole field.

Optolong 1.25″ filters

Broadband and narrowband filters that isolate the bands of light of each object and reduce the effect of light pollution and sky glow.

At the Astronomia no Telhado Observatory

This is the observatory’s main equipment. The sections below bring together the field-of-view simulator, the results processed in AstroFITS v2, ongoing projects, captured objects, recent captures and finished images.