The GSO Dobsonian line is particular model serves a very clear purpose, to offer a large aperture and an excellent image quality at reasonable cost.
Set-up is as easy as you can imagine very simple assembly with the rocker box and put it on the ground, insert the telescope tube and put the springs in position and you're ready to go to navigates through the night sky by simply moving the tube up or down, or side to side, by hand.
All GSO dobsonian use optical quality BK7 glass, cooling fans built into the rear cell to decrease cooling times, also all dobs use a roller bearing on the azimuth surface providing dozens of support points for smooth swivel motion. The deluxe model comes with 2" Micro 10:1 Crayford style focuser and 1.25" adapter.
New design GSO truss tube 16" aperture, 1800mm focal length Dobsonian delivers amazing views of deep space and represents outstanding value!
Huge 16" f/4.5 primary mirror boasts superior 1/12 wave surface error
New, stronger roller bearing design with thicker steel panels
Unique new roller side bearings with adjustable tension/braking by way of extra large, knurled side knobs!
Tube balance adjustment (fore and aft) of up to 25mm is possible
Strong 18-point primary mirror flotation cell - with a 4.7" cooling fan!
Easy assembly and disassembly of its heavy duty "TPL" truss tubes compared to complex 6-truss tube designs
Crayford style 2" 10:1 precision microfocuser with 1.25" adaptor
Oversized knurled collimation knobs allow easy mirror adjustment
Outstanding quality - overall! Black colour, not white!
No white reflective surfaces within the optical path in this design!
Features an achromatic 8 x 50 right-angle correct image finderscope
Limiting magnitude of 15.5 and resolving power of 0.29 arc seconds
You will see into deep space like you've never seen before...
Includes 2" 35mm eyepiece extension tube, 2" eyepiece accessory
tray
Please Download INSTRUCTION MANUAL in PDF from the link provided below.
Physical Copies of the manual will not be given.
Telescope Specification:
16" Parabolic primary mirror
Focal length: 1800mm, F/4.5
2 " Precision Micro 10:1 Crayford style focuser
2 " 35mm Eyepieces Extension tube
18 points mirror cell w/ 4.7" cooling fan.
Roller bearing wood base
All CNC made adjustment side bearing
Standard Accessories:
8x 50mm fully multi-coated achromatic Finder
Premium Plossl 9mm (1.25")
Premium SuperView 30mm (2")
Moon filter included
2 " Eyepieces tray
What's in the box?
16" (406mm) f/4.5 Newtonian optical tube assembly
9mm Plossl 1.25" eyepiece
30mm Premium SuperView 2" eyepiece
2" 10:1 Crayford focuser with adaptor for 1.25" eyepieces
8x50 fully multi-coated achromatic finder
Dobsonian base (assembly required)
Cooling Fan
Box Dimension:
GS 990 Tube UP............: 63 cm x 63 cm x 42 cm3. NW 8 kg/ GW 10 kg
GS 990 Tube Bottom.... : 64 cm x 64 cm x 76 cm3. NW 33 kg / GW 35 Kg
GS 990 BASE ................: 95 cm x 95 cm x 20 cm3. NW 30 kg / GW32 kg
8x50 Finderscope
Powerful 8x50 finderscope, multicoated objective lens. This little telescope will show many objects in direct vision for easy location.
Finderscope Bracket
The 8 x 50mm finderscope mounts in a quick release bracket that slips into a pre-installed metal mounting shoe nearer the focuser. The bracket is held in place in the mounting shoe by a single large hand-tighten knob that maintains the finder’s collimation, even if the finder is removed between observing sessions. The bracket has two hand-adjust collimation screws that work in conjunction with a third spring-loaded post in the bracket. This makes collimation faster than the traditional three- or six-screw collimation methods used with conventional finder brackets.
Optical Quality
The heart of any telescope is its optics. GSO produces parabolic primary mirrors of very high quality. It is our firm opinion that GSO offers better mirrors in this price range. We guarantee a diffraction-limited performance, which essentially means that the performance is limited by observing conditions and the laws of physics.
Primary Mirror
16” (400mm) diameter, 1800mm focal length, f/4.5 focal ratio with surface accuracy of 1/12 wave. The mirror is made of B270 “water white” optical crown glass that is free of internal stress and striae. B270 glass is equivalent to BK7 in performance and optical quality. The thermal stability of B270 glass is generally better than the soda lime float glass used for the mirrors of most reflectors in this reasonable price range. The mirror is ground and polished under computer control for guaranteed diffraction limited performance, coated with 91% reflectivity aluminum, and overcoated with a protective layer of silicon dioxide (quartz) for long life.
Primary Mirror Cell
Fully adjustable 3-point flotation system metal cell holds the primary mirror. The open frame of the cell allows the mirror to cool down to ambient temperatures quickly, so you can start observing sooner. Large hand-tighten color-coded push-pull collimation and collimation lock knobs make it easy to collimate the primary mirror with no tools required.
Diagonal Mirror
88mm m.a. B270 “water white” optical crown glass, coated with 91% reflectivity aluminum and overcoated with a protective layer of silicon dioxide (quartz) for long life.
Diagonal Mirror Support
Fully adjustable diagonal holder mounted on a low-diffraction four-vane thin spring steel spider.
Two Eyepieces
Fully multicoated 2” 30mm (40x) 68° field SuperView Erfil design eyepiece with a wide 1.7° actual field of view that’s almost three and a half times the diameter of the full Moon.
The second is a fully multicoated high power 1.25” 9mm (133x) 52° field Premium Plössl eyepiece.
New Altitude Tension & Balancing System
This is another major improvement of this new altitude bearing system. The telescope can be balanced by moving it up or down a couple of centimetres. This may be necessary when adding or using very heavy eyepieces or a Camera. A scale on both sides allows you to easily achieve a symmetric bearing position.
Altitude Ball Bearings
Instead of the usual large circular trunnion bearings riding on a few Teflon pads in the semi-circular cutouts in the altazimuth base, the STAR TRACKER Dob uses innovative sealed metal ball-bearing systems to provide smooth vertical motion of the optical tube. The aluminum bearing housings fit snugly into cutouts in the sides of the altazimuth base. Because the bearings are sealed systems, the elements cannot affect the smoothness of the vertical motion, as it can when dust and grit invariably get trapped between the exposed trunnions and Teflon pads of conventional Dobsonians and scores the surfaces. The vertical motion of the STAR TRACKER tube is consistently ball-bearing smooth. And the sealed ball-bearings will not have to be replaced regularly, as is the case with the Teflon pads of many Dobsonians when wind-borne grit degrades the Teflon/trunnion interface.
Altitude Clutch
Large ribbed clutch knobs are built into the two altitude bearings. A gentle twist on either knob adjusts the amount of friction within the altitude ball-bearing systems. This allows you to keep the focuser from rising or sinking when changing between eyepieces of considerably different weights, as for instance when switching between 1.25” and 2” eyepieces.
Primary Mirror Cooling Fan
A lightweight 4.7” diameter low-vibration cooling fan is built into the mirror cell to assure faster cool-down times. The battery-operated fan is powered by a battery pack that uses eight user-supplied AA batteries and plugs into a jack on the mirror cell frame.
GSO 2" Dual Speed Crayford Focuser
The focuser is the most "visible" part of any telescope with the exception of the optics themselves. You touch the focuser all the time, the focuser is responsible for holding your eyepieces or camera in position and moving them precisely into focus in the first place. This way ultra-precise focus motion is possible for both visual and particularly photographical applications.
The finest focuser GSO manufacturer has to offer. It is far superior to most classic rack-and-pinion focusers:
No image shift when focusing
Large load capacity: Up to approx. 3kgs with a firm friction setting
1:10 dual speed microfocuser for far improved focusing precision
2" compression ring
2" to 1.25" adaptor with compression ring and 2" filter thread
1. Smooth Focusing Action
The Crayford style focusing control makes achieving precise focus for visual observations and astrophotography a breeze and you will experience very smooth and precisely controlled focuser motion with zero backlash and zero image shift.
2. High-Quality Construction and Features
CNC machined from aluminum and anodized black, this focuser comes with a base plate adapter to attach to reflector telescopes. The inner drawtube glides on 4 precision bearings and a roller shaft and provides. The inner barrel is baffled and painted a flat black to minimize reflections for maximum contrast.
The 2" focuser barrel features a brass compression ring so your eyepieces and other accessories will not be marred by the set-screw. Also included is a 1.25"-2" adapter with brass compression rings that is threaded to accept standard 2" filters.
The inner draw-tube barrel is anodized black and features a laser-etched scale.
3. Tension Adjustment and Focus-Lock
The focuser has two large thumbscrews on the underside. The thumbscrew on the telescope side can be used to lock the focuser, allowing the use of heavy accessories or cameras without fear or slippage or losing focus. The other thumbscrew on the eyepiece end can be used to adjust the tension of the focuser to achieve a focusing "feel" that you like. At the easiest (lightest) setting, the focuser moves extremely smoothly. At tighter settings, you can still use heavier accessories without sacrificing much of the smooth focuser action. GSO's rated load capacity for their Crayford focusers is about 3 kgs.
Eyepiece Tray
A standard equipment eyepiece tray attaches to the side of the scope’s altazimuth base. It has cutouts to hold one 2” eyepiece and three 1.25” eyepieces.
Azimuth Roller Bearing
A simple teflon friction bearing used by some other manufacturers (also by GSO in the past) offers a rather stiff motion that makes tracking at high magnifications difficult. This becomes particularly obvious when the telescope is pointed near the zenith so that the lever arm becomes very short. In this position tracking is almost impossible in some Dobsonians!
The new GSO Dobsonians have a modern industrial roller bearing for a very easy movement. Metal plates above and below the bearing prevent the rollers from sinking into the softer wood of the rocker box, so the movement will remain smooth even after years of use.