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Here's what I've chosen for my first telescope. How's it ?

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After almost 2 years of being fascinated by the night sky and observing from my backyard, here's a telescope I've settled upon. What do you think ?


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Optical Design
Newtonian reflecing Telescope
Primary Mirror	6 inch Parabolic 1/12 wave.
Precisely figured parabolic mirror - diffraction limited / BK7
94% enhanced coating
Focal Length	1200mm
Focal Ratio	F/ 8
Highest Practical Power	360
Faintest Steller Magnitude	13.7
Resolving Power
0.74 Arc - Seconds.
Focuser diameter	1.25" Precission Crayford style focuser". 
With 35mm Extensio Tube 1.25"
Eyepiece Standard 1.25"	Premium Plossl 25mm (1.25") 52° field.
Eyepiece Standard 1.25"	
Premium Plossl 9mm (1.25") 52° field.
Magnification with eyepiece	48x & 133.3x
Magnification with eyepiece	40x
6x30mm Fully multi-coated achromatic finder
Filter	MOON filter 1.25 inch
Mount type
DOBSONIAN- wooden base.
Mirror Cell	3 points mirror cell
Accessories Tray	Eyepieces tray
Total Height	52 inch
Tube length	45.25 inch
Stand height	27 inch
Base diameter	20 inch
Shipping Weight
Tube : Net weight - 9 Kg / Gross weight: 11 Kg
Stand: Net weight - 12Kg / Gross weight: 14 Kg
Shipping Carton Dimension	Tube : 32 x 40 x 128 cm3
Stand: 14 x 64 x 64 cm3

6x30 finderScope

powerful 6x30 finderscope, multicoated objective lens. This little telescope will show many objects in direct vision for easy location.

Finderscope bracket: The 6x30mm 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: 6” (150mm) diameter, 1200mm focal length, f/8 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 94% 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: 32mm 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 Premium plossl eyepiece1.25"
Plossl 25mm 1.25" OD (48x)52° field 
Plossl 9mm 1.25" OD(133x) 52° field

GSO 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 features: 

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.2.5kgs with a firm friction setting

Include 35mm extension tube 1.25" OD

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.

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 2.5 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.

Images :





It's an Indian made model with GSO parts and a very precise mirror for the price it is being sold at.

How would you rate it and what are the pros and cons ?


PS. A completely Unrelated question


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A 6" F8 Newtonian is an excellent all round telescope as a starter. The longer focal length makes it easier to achieve good magnifications for the Moon and planets without needing expensive eyepieces, a zoom eyepiece works well at F8. The only downside is that the alt-azimuth design limits astrophtograph to the Moon and planets. Welcome to SGL.  :icon_biggrin:

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Can you recommend a good equatorial mounted telescope in this range ?

I was previously bent upon the Celestron Astromaster 130eq but somebody told me that the mount is pretty unstable. So this is what I chose instead .

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It's a good choice for the reasons that Peter mentions above. The scope is pretty much the same as the Telescope Services 150 F/8 dobsonian here which also uses GSO componants:


The 1/12th wave primary mirror is an RMS figure rather than Peak to Valley (PV) by the way.

Personally I'd prefer a dobsonian over an equatorially mounted scope because I'm just interested in visual observing and the dobsonians are so much easier to set up and more conventient to use as well. I'd add a "red dot" type finder such as a Telrad or Rigel Quikfinder to the scope as an early modification.



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Good choice of 'scope :)

At a later date, you should be able to buy a set of mounting rings and dovetail to fit the 'scope to an EQ mount, would be a lot cheaper then buying a whole new 'scope/mount setup.

And welcome to SGL :) 

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As a matter of fact, the climate is indeed quite variable.

Previously I was myself thinking about the bresser refractors but changed my mind on realizing that I was hell bent on observing M42 from my light polluted city.

Also, I am joining a college this year and hopefully one which is quite near to the Indian ocean. I don't think climate will be a problem there.


PS. Which mount do you think is sufficient for the OTA of the dobsonian ?

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If you're not planning to go into astro-photography, a Dobsonian mount makes it easy to set-up and move about whenever you wish. The only thing you'll probably want to improve on quickly is the finder-scope. Trying to look through a straight-through on a Dob is ackward and likely to cause pain. I'd suggest you look into getting a RACI (Right-Angle Corrected Image) finder. An example of which is here:


And if you can possibly afford to do so, I'd suggest an 8" (200mm). But the 150mm is a fine telescope for the reasons others have cited. As a newtonian reflector, you'll be needing to learn to collimate it - optically align it - but there are many here who will be glad to assist you in this task your first-time.

Enjoy your scope!


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3 hours ago, AcisAce said:

As a matter of fact, the climate is indeed quite variable.

Previously I was myself thinking about the bresser refractors but changed my mind on realizing that I was hell bent on observing M42 from my light polluted city.

Also, I am joining a college this year and hopefully one which is quite near to the Indian ocean. I don't think climate will be a problem there.


PS. Which mount do you think is sufficient for the OTA of the dobsonian ?

A 6" f/8 Newtonian is a bit of a beast to mount onto an equatorial.  Back in the day, equatorially-mounted 6" f/8 Newtonians were rather popular, and the equatorials themselves were a bit large...


A minimum of an EQ5-class equatorial would be required, if not an EQ6, and for visual use...

EQ5... http://www.tejraj.com/skyview-pro-eq-mount.html

EQ6... http://www.tejraj.com/orion-atlas.html

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