GSO Star Tracker Telescope, a ('minimalist') night-sky gazing set-up: An Overview

Author: Ravi Kailas

The rather imposing size of the set-up, belies the simplicity of the Dobsonian telescope design 

For observing the night sky, I primarily use a GSO Star Tracker, a 8" Dobsonian telescope (a type of telescope, which despite its bulk, is the best value for money for light gathering ability), manufactured by GSO (Guan Sheng Optical, a Taiwanese Manufacturer). I purchased this from Tejaraj & Sons, Mumbai, a reputed dealer, probably the only one of its kind in India, of astronomy related equipment, relying on their advice to buy this model (as against similar from well known brands like Orion), for its better value for money among identical optics in the alternatives.  

The telescope comes supplied with with 2 eyepieces - a 9mm 1.25" and a 30mm 2", among a handful of other accessories (see below). I also have a Pentax AMC XW 14mm, 1.25", which works for both wildlife watching with a spotting scope, as well as for astronomy with this telescope. I find both the Pentax and the 30mm 2" eyepieces provide very satisfactory views, with ample eye-relief, field of view and a wholesome image circle, but the Pentax is significantly more refined with excellent edge to edge sharpness. The 9mm is not as satisfactory to look through, with a poor eye-relief and a small, incomplete image circle, but centre sharpness and resolution is adequate and provides good views of difficult subjects like Epsilon Lyrae. The eye-pieces give me magnifications of 133x (9mm), 40x (30mm) and 85x (14mm) (magnifications are calculated by dividing the focal length of the telescope, in this case 1200mm, with the focal length of the eyepiece). Higher magnifications are better for planets, features on the moon, globular clusters and double stars and wider views for diffuse subjects like nebulae, star clusters, star fields and the like. 

Sadly, however, the light gathering ability of this telescope, with its 8" aperture (a size, on the cusp of what are called 'light buckets', for the amount of light that they allow inside), is wasted on Chennai's skies, where some of the more diffuse subjects are often hidden by light and atmospheric pollution. Also, the highly magnified perspective offered by a telescope, might not be ideal to observe large (apparent size) celestial objects, such as the Pleiades Star Cluster, and one might be better off using lower power optics typical in Binoculars (please see article for binocular basics as relevant to nature observation) to enjoy a more satisfactory view of these. 

Sometimes, all it takes is a good pair of binoculars

Other supplied accessories:

The telescope (tube, mirrors, front cover and focussing mechanism) is supplied with:

- guide scope, 

- AA Battery Holder to run the cooling fan, 

- Wooden base, which works surprisingly smoothly (at least until it was left out in overnight rain) to move the telescope around to point at the desired portion of the sky, 

- an adapter for 1.25" eyepieces, 

- a Neutral Density Filter (decreases brightness and increases contrast - essential for lunar features to 'pop' into view) that screws onto to the 1.25" eyepiece for observing the moon

- A 35mm extension tube 

- some collimation tools

- An Allen Key, size as appropriate for assembling the equipment

- A silica gel holder, which can be used in place of the eyepiece, while stored

There is a bit of DIY to get things up and running, much of the work to do with putting the base together. The instructions are fairly clear though, and if I remember correctly, I could get everything functional within 2 hrs (altogether another matter that I had to wait quite a while longer for clear skies - Murphy's Law governing new equipment, the law's effects, inevitably, directly proportional to the enthusiasm with which you want to try the equipment out!). 

Mobility & Ease of Use

This telescope is large, as all Dobsonians tend to be. As such it is best suited for situations where clear skies are close at hand (unlike in my case, where I live under extremely polluted city skies - but I was sorely tempted by the cost-to-brightness ration of the set-up, just in case I managed to move it to a dark sky location for any decent length of time). However, if you envisage moving your device around a lot, then a Newtonian or Refractor telescope could be a wiser investment. 

One reason Dobsonians tend to be cheaper are due to their simplistic design. Most (if not all) are manually operated, with no tracking or star location aids. For a relative newbie, when I invested in this telescope (my first one), I found the necessity to manually train the scope on the celestial object of choice, to be an educative experience, allowing me to 'learn the sky' in the process, but a tracking feature would have been nice all the same. Initially, the base was excellent for manipulating the scope, but later some play developed in the altitude adjustment, that has made it harder to hold highly magnified views in place.  

A slight nuisance of the Dobsonian design (or any reflector telescope) is the need to collimate its components, before first use, and at intervals determined by how much 'travelling' the telescope has done. This is essentially a technique to ensure that all the optical and mechanical parts of the device are proper are properly aligned. I collimated the mirrors just once, given the limited travel my telescope has done (between my home interiors and the terrace on a good day or night), and this was easy enough to perform on this telescope, with which I had only ever enjoyed the optics so far. 

For Astrophotography

Given the lack of mechanised tracking ability, this telescope has a fairly limited use for long exposure astrophotography. However, with the right adapters and filters, the set-up should be adequate, albeit with limitations, for images of our Moon and Sun. I have only ever tried photographing the Moon, by awkwardly manipulating my phone camera on the eye-piece, for modest results, not commensurate with the effort required to time the shutter release, in that fleeting, unpredictable moment that a decent image appears on the screen!

For some knowhow on astrophotography, and it's nuances, from yours truly, please follow links for basics and deep sky subjects, respectively. 

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Himalayan Serow and Brown Wood Owl at Pangot: Report

Author: Ravi Kailas

Dates: 7th to 9th June 2019

Himalayan Marten, among the highlight mammals of the trip

A brief summer visit to Pangot (2000m) a tiny village surrounded by temperate broad-leaved forest in the Kumaon Himalayas, was productive for a sighting of the uncommonly seen Himalayan Serow, as well Himalayan Goral and Himalayan Marten, among commoner mammals. Birdlife was a modest representation of Himalayan species, both summer visitors and residents, with Brown Wood Owl, Hill Partridge, Himalayan Prinia, Mountain Hawk Eagle and Wedge-tailed Green Pigeon among the highlights in the broader landscape, encompassing a elevational gradient and associated habitat. The trip coincided with the mad summer rush of tourists to the mountains, and Naini Tal, the gateway to Pangot, is among closest targets for the teeming millions residing in the bubbling cauldron that Delhi becomes at this time of the year - not ideal conditions if you are looking for rare wildlife in an idyllic Himalayan forest!

Detailed Report

Day 1: A large part of the day was spent exiting the typically hazy surroundings of Delhi, the inevitable traffic snarls, various highway bottlenecks, caused by a combination of repair works and fellow motorists, a (un?)healthy proportion heading to the hills, most trying to defy the laws of physics (it is a given that the laws of traffic are meaningless in this part of the world), by trying to squeeze through invisible gaps, invariably, through oncoming traffic, and finally arriving at the foothills around Kaladhungi at 1730, a good 3hrs after the ETA at the time of the departure (0930). Some casual birding, in the mixed forest on the cusp of the ascent, was good for Greater Yellownape, Grey-capped Pygmy Woodpecker and Large Hawk Cuckoo among others. While Great Slaty Woodpecker are known from Sal forest locations around the foothills, we did not attempt a sighting, given the delayed progress already. The rest of the snaking up the hills through a line of very slow moving traffic, along, mostly, disturbed habitat, was not especially productive, bar for commoner birds. Relative peace and quiet after the going past Naini Tal, onto the hour or so long drive on the forest road leading to Pangot. Despite the promising hour (1915 at the time of entering the forest road) for a safari, on a road known for a good population of Leopard, the rest of the evening proved unproductive for any wildlife on this windy evening. 

Day 2: Break of dawn on the 30km or so forest route from Pangot to Kunjakharak was satisfying for a variety of birdlife, including a various of Turdus and Zoothera thrushes, Chestnut-headed Laughingthrush, Rufous-bellied Woodpecker, Mountain Hawk Eagle, Rufous-bellied Niltava and Khalij Pheasant among others.While a sheer, grassy, hill slope, en-route is known for relatively regular sightings Cheer Pheasant, we did not find any, in the 30 minutes or so we stopped here, also enjoying a lovely view of the Corbett NP landscape below. While looking for C(c)heer though, we were granted our wishes, sort of, with sightings of several Himalayan Goral, popping into view from against background  of grassy hill slopes that they blend into rather too well. There were also Himalayan Langur and Indian Munjtac, among the modest selection of mammals that showed up in the 5 hr plus excursion. 

Look closely and you will see a Himalayan Goral blending into this grassy slope at Cheer Point

Scaly Thrush

Chestnut-headed Laughingthrush

Heading back on the road towards Naini Tal, we hopped off our vehicle at the superbly located Kilbury FRH and ambled back on the 5 KM road to Pangot. A walk along a  path, that soon, blended into a jungle stream, was a worthwhile sidebar, not just for the serene stillness, the interplay of tiny dots of light on the dark interiors of the temperate broad-leaved forest, but also for a Himalayan Marten disappearing up a rocky slope - but not before showing the requisite curiosity that their kind are known for. A pair of nesting Whiskered Yuhina and a noisy troop of Rhesus Macaque, with a faint apprehension of a potential black bear encounter accompanying the viewers, the guide having had an experience in this very location in the past, completed the picture in this idyllic setting. The walk back to Pangot, on the forest road, produced White-throated Laughingthrush, Black Eagle, Black-headed Jay, Black-faced Warbler and Maroon Oriole among the highlights

Temperate Broad-leaved forestscape

Black-faced Warbler

Whiskered Yuhina

The rules of plying the forest road at night are a little hazy, but since the road is not closed for traffic after dark, we used the opportunity the traverse the 30Km stretch from Pangot to Kunjakharak, known for frequent leopard sightings, but we were also interested in possibilities for Leopard Cat and Himalayan Palm Civet (perhaps not optimal habitat for the latter two though). In the 3 hr or so effort, culminating at midnight, none of these targets showed, however we did see the uncommon Himalayan Serow on the slopes of the aptly named Cheer Point (please see AM activity for context). Indian Munjtac and Sambar Deer were ubiquitous, and Wild Pig, foraging in a garbage dump near Pangot, completed the mammal list, while a large owl (Brown Wood?), that disappeared from a roadside tree into the thickets, was the only bird on show. 

Brown Wood Owl

Day  3: A pre-dawn start towards Tangdi, a settlement of horsemen and stables, on a vegetated slope close to Naini Tal, specifically hoping for good views of Hill Partridge, but also other skulkers that are known to pop outside the underbrush onto the paths, probably attracted by the insect rich ecosystem that thrive on dung and their donors. The hour or so drive, while at a promising hour for mammals, only produced Himalayan Goral, contemplating a slope downhill, as we arrived, but rather more decisive about its movements, just as I picked up my camera. It was meagre pickings at Tangdi, for birds, with only Rusty-cheeked Scimitar Babbler and Himalayan Shrike Babbler adding to the trip list, but we did hear Hill Partridge throughout the walk along the bridle path. However, we were luckier with sighting the bird, noisily feeding behind underbrush, near the Kilbury FRH, on the way back to Pangot. This little viewing was accompanied by persistent alarm calls of the munjtac - the closest we felt to sighting a Leopard on this trip. Later, a tip from a fellow birder, brought us to a roadside tree, where a duo of Brown Wood Owl were roosting, looking at us, sometimes one-eyed, but always disinterestedly sleepy-eyed, as we tried to find good angle for a picture, without unduly disturbing their reverie.

Indian Munjtac

White-throated Laughingthrush

Himalayan Goral

That (warm) evening, we descended, a few hundred metres, towards a mountain village (Buggar?), to look for birds that thrive in the forest edge-agriculture landscape of the region. A mix of colourful denizens, such as Blue-capped Rock Thrush, Slaty-headed Parakeet and Crimson Sunbird entertained, but the highlights were the range restricted Himalayan Prinia and Wedge-tailed Green Pigeon. Driving back towards Pangot at dusk, an Indian Hare and a family of Khalij Pheasant among the last observations on this brief visit to Pangot.  

Crimson Sunbird

Slaty-headed Parakeet

Himalayan Prinia

Wedge-tailed Green Pigeon

Logistics Etc

All arrangements, including taxi from Delhi, a bird guide at Pangot and stay at the Jungle Lore Birding Lodge were made by Asian Adventures.

Jungle Lore Birding Lodge, a very popular stopover for birders from around the world, is a mix  comfortably furnished, spacious cabins in a quaint corner of the Pangot village, its grounds, rustically unkempt as perfectly suited for nature enthusiasts. Unfortunately, the (considerably noisy, night revelling) spillover crowds from Nainital, had made their way over here (and have for some years now, considering the number of lodges and campsites that have popped up in Pangot over the last ten years), scuppering, I suspect, a more fruitful effort for mammals.  My naturalist guide, Deepak, was good company, and  knowledgable about the natural history intricacies of the region. 

List of Mammals Seen

Himalayan Langur Semnopithecus ajax
Rhesus Macaque Macaca mulatta
Himalayan Marten Martes flavigula
Himalayan Serow Capricornis thar
Himalayan Goral Naemorhedus goral
Indian Munjtac Muntiacus muntjak
Sambar Deer Cervus unicolor

Wild Pig Sus scrofa

Indian Hare Lepus nigricollis

Please see ebird links below for bird observations from the trip: 

List 1 (Day 2 AM)

List 2 (Day 2 PM)

List 3 (Day 3 AM)

List 4 (Day 3 PM)

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