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William Optics
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William Optics ZenithStar 73mm ED APO Refractor
Colour Available : RED
66000 + 18% GST
Zenithstar 73 APO Red Telescope Zenithstar 73 APO Blue Telescope
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Zenithstar 73 APO Gold Telescope  
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The William Optics ZenithStar 73 is an extremely well crafted and compact refractor, an ideal instrument for wide-field deep-sky imaging with DSLRs or dedicated astronomy cameras with APS-C and full-frame sensors. It’s also a great tool for visual observation of a wide range of celestial objects from the moon and planets to nebulae and star clusters and brighter galaxies, as well as for terrestrial observation.

The William Optics Zenithstar 73 f/5.9 apochromatic refractor features an air-spaced multicoated doublet objective lens and the premium mechanics and finish that’s typical of William Optics scopes. The objective features Ohara FPL-53 ED glass for superb control of false color and sharp, high-contrast images. When paired with a William Optics field flattener (sold separately), the scope features a flat field across the entire 43.3mm diagonal of a full-frame sensor.

With a focal ratio of f/5.9 and focal length of 430nm, the WO Zenithstar 73 is the perfect instrument for imaging extended objects such as the California Nebula, the Rosette Nebula, the Veil Nebula, the Sword and Belt of Orion, and the Andromeda Galaxy. Yet the scope is compact enough to work with nearly any medium-duty equatorial mount. It weighs just 2.5kg (5.5lbs) and measures 310mm with the dew shield retracted, portable enough for travel and small enough for carry-on luggage with most airlines. 
  • Premium 73mm apochromatic refractor for astronomical and terrestrial imaging and visual observation
  • Apochromatic f/5.9 doublet objective with FPL-53 glass
  • Large image circle for imaging with APS-C and full-frame sensors
  • Compact form factor and light weight ideal for transport and travel
  • Includes patented clear Bahtinov mask cover, dual-speed 2.5” focuser, mounting rings, soft carry case, dovetail rail, all color matched for an attractive appearance
Ohara FPL-53 vs FPL-51 ED Glass
The dispersion properties of ED and SD glass elements are important in determining the overall colour correction. The abbe index is used to quantify the 'partial dispersion' of a particular glass. Pure Fluorite offers the highest partial dispersion at around 94.99 V, Ohara FPL-53 glass is very close to Fluorite at 94.93 V and is often referred to as Synthetic Fluorite.  FPL-53 is also noticeably better than Ohara's lower spec' FPL-51 glass which offers an abbe index of 81.54 V.
Heavy-Duty Focuser, Rings, Soft Case and Accessories
The William Optics ZS73 features a patented objective lens cover that doubles as clear Bahtinov focusing mask. This makes it a snap to achieve sharp focus when setting up for astrophotography.

The ZS73 also features a heavy duty 10:1 dual-speed 2.5” rack and pinion focuser with tension screws to securely hold camera and accessories without slipping or image shift, even during longer exposures. One focuser knob even includes an integrated thermometer to help you track small temperature changes that might affect focus during your imaging sessions.

A convenient CNC-machined carrying handle mounts on top of the dual mounting rings. A dovetail in the handle accommodates an additional set of rings for a guide scope (guide scope rings and guide scope sold separately). On the bottom of the mounting rings is a reversible dovetail with a Vixen rail on one side and an Arca Swiss mount on the other for mounting the scope to a camera tripod for grab-and-go terrestrial and astronomical observation.

A soft carry case is now also included with this telescope.
Fast Optics with a Wide Field of View
Thanks to its fast optics (F/5.9), this refractor collects a lot of light in a short period of time. Image exposures of 2-3 minutes at ISO 1600 are likely all you will need to capture deep details of your target.

If you have ever struggled with framing up a large target such as the North America Nebula or Andromeda Galaxy, the Z61 is a breath of fresh air. The ultra-wide 360mm focal length means collecting photons on HUGE areas of the night sky in a single frame.

Even with a crop sensor camera like the Canon T3i/600D, the focal length of 576mm is still more than wide enough for the big targets.
Highly portable and Lightweight
A high-quality refractor at this size is the perfect travel scope. When combined with a portable camera mount, you’ve got a very capable deep-sky imaging rig that can pack up into a backpack or travel container.

A collapsible carbon fiber tripod, the iOptron SkyGuider Pro, and the Z61 is probably the most portable deep sky astrophotography setup you can have.
Deep Sky Imaging with the Zenithstar 61 APO
If you are new to deep sky astrophotography but have dabbled in tracked night sky shots including the Milky Way – this is likely the best possible next step for you.
An Affordable Imaging Refractor
The William Optics Zenithstar 61 currently retails for Rupees 50000.00.  The price includes the telescope only, as you can add a number of extras to your order. This includes everything from a color-matched dovetail plate to the photo adapter for your DSLR camera.
  • Z73 Doublet Air-Spaced APO with synthetic fluorite FPL-53 extra low dispersion glass
  • 2.5" Rack & Pinion focuser with 10:1 micro adjustment
  • Mounting Rings
  • CNC Handle Bar with Vixen style quick release or guidescope
  • Vixen style dovetail bar
  • 2" to 1.25" adapter with brass compression ring
  • Retractable lens shade
  • FREE WO patented Diffraction Spikes Bahtinov Mask Cap
  • FREE high quality soft carrying bag
    Astrophotography Performance in Compact Package
    The Ohara FPL-53 ED Glass is a top of the line material found only in the best apochromatic refractors. This makes the Zenithstar 73 an excellent choice for those looking for a primary imaging telescope. This APO doublet captures sharp, high contrast images free of false color.

    The Z73 is very compact and portable. It weighs only 5.5 lbs, which means that you don’t need a large equatorial mount with a heavy payload to use it for astrophotography.
    Ultra-Portable Telescope
    It is often said, that the best telescope is the one you use most often. With a retracted length of 330mm and convenient mounting options, you’ll have no excuse not to deploy the Z73 for a night of deep-sky astrophotography on a moment’s notice.
    Impressive Features
    The built-in star-spikes Bahtinov mask makes focusing your DSLR camera through the telescope quick and easy. Simply point the telescope at a bright star, and position the central spike evenly between the “X”.

    The telescope is held securely inside the mounting rings and can be adjusted back and forth to improve balance if necessary.
    The Perfect F-Ratio

    The William Optics Zenithstar 73 APO has an f-ratio of F/5.9. The focal ratio of a telescope represents its light gathering ability, and the Z73 hits the sweet spot. In my experience with the Z73, the combination of 430mm at F/5.9 was just right for collecting long exposure astrophotography images of the Butterfly Nebula and Heart Nebula.

    Although it is small, the 73mm objective is more than enough to gather impressive long-exposure deep-sky images. The wide field of view is particularly effective on large targets such as the Andromeda Galaxy, The North America Nebula, and the Heart Nebula.

    Optical system Air-spaced doublets with 1 FPL-53 fluorite element
    Aperture 73 mm
    Focal length 430 mm
    Focal ratio f/5.9
    Image circle

    Full frame corrected field with Flat73A, Flat73R

    Resolution 1.83 arcseconds
    Limiting magnitude 12.9
    Light gathering power 109x
    Tube material Aluminium
    Tube construction Full tube
    Focuser Dual Speed Rack and Pinion
    Gear reduction 1:10 Fine movement
    Tube clamps Yes
    Dew Shield Yes
    Carrying handle Yes
    Series ZenithStar
    OTA length

    330 mm (fully contracted)
    420 mm (fully extended)

    Recommended For Advance Users
    Weight 2.83 kg
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