Telescopes

Celestron at the Cutting Edge of Astrophotography

Celestron at the cutting edge of astrophotography

On 7 January 2013, Celestron announced the introduction of a new range of telescopes specifically designed for astrophotography. This included the new Advanced VX mount and the EDGE HD range of Schmidt-Cassegrain optical tubes (SCT). The Celestron Advanced VX 8 EDGE HD computerised telescope comprises the VX mount with an EDGE HD 8 inch SCT which offers an outstanding entry level astrophotography package.

The Advanced VX Mount

The Advanced VX mount offers the sophisticated aspects of more expensive German equatorial mounts (GEM) for smaller telescopes at an affordable cost and excellent value for money. Its simple set up is suitable for novice astrophotographers but also offers the required versatility for more advanced and experienced astrophotographers. It can be set up by one person and its compact size makes it easily transportable. It has been designed to easily support Celestron’s range of refractors, newtonian reflectors and Schmidt-Cassegrain optical tubes (SCT).

Celestron Advanced VX 8 EdgeHD Computerised Telescope

Celestron Advanced VX 8 EdgeHD Computerised Telescope

The VX mount offers a number of improvements over previous Celestron mounts. It is more rigid offering more stability for larger and heavier optical tubes as well as their accessories. New improved motors offer better compensation for optical tube and accessory imbalances.

One of the most significant improvements is the VX’s ability to accurately track objects through the night sky over large distances for a long duration. This allows for longer exposures for imaging deep sky objects. The mount has inbuilt Period Error Correction which underpins the improved tracking performance. The mount also allows for imaging across the meridian (imaginary line from the North celestial pole to the South celestial pole passing through the zenith) without the need for a meridian flip. This facilitates keeping the image in the field of view to allow for longer exposure times. Furthermore, there is a separate port for attaching an autoguider to keep the object in the field of view over exposures of several hours.

Although a standard polar scope can be used for the VX mount, the computerised hand control also makes available an “All Star” polar alignment function. This uses a bright alignment star, preferable one that is high in the sky and close to the meridian, to accurately polar align the mount for astrophotography.

The following Youtube video from Celestron provides further information on the Advanced VX mount.

 

The EDGE HD optical tube range

The EDGE HD series offers significant benefits for today’s astrophotographer compared to previous catadioptric SCTs. It is available in 8, 9.25, 11 and 14 inch SCTs.

The EDGE HD uses aplanatic optics which are designed to specifically reduce chromatic aberration and coma, typical of older SCTs. This is achieved by inserting field flattening lenses into the path of light travelling up and down the optical tube to maintain astrograph quality of images right to the edge of the field of view.  This combined with enhanced Starbright XLT coatings, typically used in Celestron optical tubes, results in a sharper and brighter image that is free of fringes of colour separating light and dark parts of the image (caused by chromatic aberration) and tails appearing on single point images such as stars (caused by coma).

In addition, mirror lock knobs support and minimise movement of the primary mirror while the optical tube moves around the mount that is an important feature when taking long exposure deep sky images.

The EDGE HD optical tube is compatible with the Celestron Fastar Optical System. This allows for fast imaging at a focal ratio of f/2 which allows exposure times 25x shorter than with the f/10 setup of the standard EDGE HD.  The Fastar system works by replacing the secondary mirror at the front of the optical tube with a flattening lens. A high quality focal reducer can also be purchased for the EDGE HD allowing imaging at f7.

Finally, the EDGE HD incorporates tube vents which allows air to be released from behind the primary mirror allowing faster thermal equilibrium.

Here is a link to a Youtube video that provides further information on EDGE HD technology

In summary, the new Advanced VX mount combined with the EDGE HD optical system offers outstanding potential for astrophotography, using up to date technology at an affordable price and is excellent value for money.

Article by Zoltan Trenovszki
www.365astronomy.com

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Posted on January 22nd, 2014.