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Telescopes > William Optics > FluoroStar > William Optics Apochromatic refractor AP 91/540 Space Gray OTA
Product no.: 69899

Apochromatic refractor AP 91/540 Space Gray OTA

$ 3,260.00 incl. VAT, plus shipping costs
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Product description

More about the series FluoroStar...

The Fluorostar's lens consists of three lenses with an air gap, which use FPL-53 ED special glass by Ohara, Japan as well as and lanthanum glasses. This extremely high-quality triplet design guarantees colour purity and image clarity which leaves nothing to be desired - a true high-end instrument!

Combine this apochromat with a suitable high-quality diagonal mirror from William Optics and you can see the stars with a level of clarity which other lens rarely provide. Binary stars separate and appear sharp, Jupiter's bright bands and zones reveal striking details and Saturn's rings appear as though they are flying past in a spaceship.

With its large aperture, without obstructions by the secondary mirrors required by reflectors, the wide world of Messier objects and ambitious deep sky objects is at your feet. Anyone who has ever looked through such a high-quality apochromat has been lost to the universe forever!

In the case of astrophotography, the large image circle provides illumination, even for full-frame cameras. Combined with the Flat6AIII flattener by William Optics, it produces an faster aperture ratio and a flat image field right to the edges. The flattener can be securely screwed on to the drawtube.

The drawtube has smooth, precise 1:10 reduction, a temperature display and a large adjustment range. It effortlessly supports heavy astrophotography equipment which can also be rotated to find the best position on the sensor.

A further special feature of the William Optics apochromats is the specially calculated Bahtinov focus mask:

These new focus masks made from optical acrylic glass provide 92% transparency.

The imprinted pattern provides a diffraction structure which is around three times brighter than classic metal masks. The acrylic glass masks, therefore, produce a clearer diffraction pattern and enables focusing with the help of fainter stars.

The FLT91's Strehl value is 0.95+ and it can be used with the following cameras for astrophotography:

  • Canon EF, RF
  • Nikon F, Z
  • Sony E
  • Pentax K
  • Fuji X

This high-quality triplet apochromat is also suitable for CMOS and CCD cameras!

The lens tube has a retractable dew cap and can therefore be converted to a practical size for transportation. Furthermore, at 4.16kg, it weighs almost nothing. The FLT91 is an ideal travel telescope.

Specifications

Optics


Type
Refractor
Type of build
Apochromat
Aperture (mm)
91
Focal length (mm)
540
Aperture ratio (f/)
5,9
Resolving capacity
1,52
Limit value (mag)
12,3
Light gathering capacity
170
Max. useful magnification
182
lens design
Triplet
Tube weight (kg)
4,16
tube diameter (mm)
100
Tube length (mm)
510
Coating
STM
Carrying length (mm)
441

Focuser


Type of build
rack and pinion
Connection ( to eyepiece)
2
Connecting threaded socket (camera-side)
T2
Gear reduction
1:10 fine focusing
Rotating
yes

Mount


Type of build
OTA
Mounting type
no mount

Included accessories


Deviating optics
no
Prism rail
Losmandy-Style
Carrying handle
yes
focusing help
Bahtinov focus mask
Carry case
yes
finder base
Vixen/Skywatcher Level

General


Series
FluoroStar
Colour
silver

Area of application


Astrophotography
yes (very good)
Moon & Planets
yes
Nature Observation
no
Nebulae & galaxies
yes
Sun
yes (Only with appropriate Sun filter)

Recommended for


Beginners
no
Advanced
yes
Observatories
yes

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*All prices include VAT plus shipping costs.

William Optics Apochromatic refractor AP 91/540 Space Gray OTA

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