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Newtonian · Dobsonian
305mm f/5 Dobsonian for serious deep-sky observing
Price in India
₹75,000
Price exclusive of GST. GST (18%) is added at checkout.
A 12" parabolic Newtonian on a Dobsonian base — the most aperture per rupee available, and the reason most experienced observers own one.
Not sure how big it will look? See it at real-world scale in your own space.
Ask an astronomer before you buyStand it on a sample balcony, or in a photo of your own space. Tube length is calculated from the 1520mm focal length and is approximate. We have not published a measured standing height for this telescope yet.
The Dobsonian is the cheapest way to put a large mirror under the sky. There is no tracking motor and no computer: you nudge it, and the simplicity is what lets the budget go into the mirror instead. This 12" model gathers enough light for galaxy structure that a smaller instrument only hints at, dozens of Virgo Cluster members in a single session, and planetary detail limited by the atmosphere rather than the optics. The Nightwatch is the value line: the same parabolic primary as the Professional, with a single-speed focuser and a smaller secondary. The optics are the same; the handling is less refined.
Every figure below is calculated from this telescope's own specifications using standard optical formulae. None of it is a marketing number.
Light-gathering power
1898× the human eye
Compared to a dark-adapted 7mm pupil. This is what determines how faint an object you can detect.
Resolving power
0.38 arcseconds
The Dawes limit for this aperture — the finest detail the optics can theoretically separate.
Limiting magnitude
~14.9
The faintest star reachable under a genuinely dark sky. Expect two to three magnitudes worse from a city.
Maximum useful magnification
610×
Twice the aperture in millimetres. Atmospheric conditions usually impose a lower practical limit.
Magnification with 25mm eyepiece
61×
Your low-power, wide-field view — used for finding objects and framing large clusters.
Magnification with 10mm eyepiece
152×
The workhorse range for planets, lunar detail and globular clusters.
The optical ceiling for a 305mm aperture is about 610x. On a typical Indian night, atmospheric seeing — not the telescope — limits you to roughly 150x–200x. Most of your observing will happen between 61x and 152x, and the view will be brighter and sharper for it.
Why telescope magnification claims are misleading →The Moon, two planets and a nebula through the GSO 12" Nightwatch Dobsonian, drawn from its own aperture and focal length rather than from a photograph taken through something bigger.
At 61×, the whole Moon fits in the eyepiece, spanning about 63% of the field.
At 305mm aperture
Magnification uses the same 25mm (Moon, nebula) and 10mm (planets) reference eyepieces as the specifications above. Which features appear is not a formula: each is shown from the aperture at which our own guides say it becomes visible. Star positions and crater positions are illustrative; how many appear follows the limiting magnitude and resolving power.
Illustration of a typical view under a dark sky. City skies and atmospheric conditions will show less.
No reviews for the GSO 12" Nightwatch Dobsonian yet. We publish reviews only from people who actually bought the telescope from us, so this section stays empty until there is something real to put in it.
Own this telescope? Send us your reviewSpecifications on this page are taken from GSO's official product documentation. Derived figures — magnification, resolving power, limiting magnitude — are calculated from those specifications using standard formulae, and observing expectations reflect what this aperture realistically delivers under Indian skies.
View the manufacturer's official listing
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Considering more aperture? The GSO 16" Professional Dobsonian is the next step up at 406mm, for ₹1,90,000.
The guides and comparisons most relevant to this telescope.
