I am now working on a new and exciting book for amateur astronomers everywhere. It’s entitled, Upgrading a Budget Newtonian Reflector, and, as its name implies, it will be aimed at empowering amateurs on restricted budgets to get the most out of their econo-Newtonian reflectors that are now available in a wide range of apertures from just 3 inches up to 20 inches and more.
The book has been a long time in coming. Though I’ve written a book surveying the Dobsonian telescope market some years ago now, it was written with little or no sustained interest in these particular instruments, and, as such, became more of a buyer’s guide than anything else. Some ten years ago, I was heavily committed to endorsing small refracting telescopes, having owned, used and written copious volumes on several dozen models personally tested in the field, and through many published reviews in magazines like Astronomy Now.
But as I learned more about the people who exclusively endorsed refractors (as I once did), I discovered a very nasty side to the hobby. More often than not, their owners were more interested in talking about their telescopes rather than looking through them! You don’t have to delve deep into the world of refractors before you discover this materialistic streak. Copious online threads designed to draw attention to large and very expensive refractor telescopes have led many unsuspecting individuals to believe that there is something altogether magical about them. And it took me quite some time to shatter this illusory perception.
You see, I’m a Newtonian convert. It wasn’t an overnight conversion though, but one reached after climbing a steep learning curve, as I slowly acquired the necessary skills to properly adjust, upgrade, acclimate and deploy various Newtonians in the field. That said, It’s neither a revolutionary or a heretical statement; I mean the ABCs of optics – or at least the optics I had learned at school – teach us that larger apertures collect more light to see fainter objects as well as delineating finer details. And the laws of economics show us that Newtonians provide the easiest route to getting the best of both worlds. Indeed, as I now firmly believe, having amounted considerable evidence in defence of this hypothesis from both the archives and first-hand experience, refractors are predominantly beginners’ telescopes, chosen because they are just that; small and charming – requiring little or no maintenance, and owing to their restrictive apertures, quite often perform near their theoretical limits. Indeed, these are the main reasons I continue to recommend small refractors to newbies. But to see more of the Universe you must scale up; and that’s something refractors just ain’t good at. That’s one of the main reasons hardly anyone would consider a refracting telescope larger than six inches(150mm) in aperture just for visual use, owing to their considerable cost, the unwieldiness of their long tubes, not to mention their heavy(read expensive) mounting requirements and sheer impracticality(apart from showing off) for visual use.
Newtonian telescopes are a breath of fresh air in comparison, with plenty of charm to boot, and I saved enormous amounts of money as a consequence! I discovered that one of the main reasons amateurs don’t stick with them is their temperamental nature. Bad collimation, inadequate acclimation and considerable ignorance concerning how to assess local atmospheric conditions, have given far too many amateurs pause to assessing Newtonian reflectors fairly. Indeed, this is not merely a modern phenomenon; the rich archives of historical astronomy proved to me once and for all that Newtonians were used to great effect by some of the best visual astronomers in history, who realised, then as now, that they offer by far the best bang for buck of all telescope types and deliver the readies! And not only that, Newtonian reflectors proved excellent in fields of amateur astronomy traditionally associated far more with refactors and catadioptrics; take double star observing as a prime example!
This book will therefore begin by explaining, in some considerable detail, my reasons for switching to Newtonian reflectors, having previously enjoyed all manner of other types of telescopes, including refractors and catadioptrics over the years and decades. Part of the reason for this is the marked improvement of mass-market mirror quality in recent years, where Synta/GSO are now routinely churning out primary mirrors with 1/5 or 1/6 wave PV figures, which are well above the run-of-the-mill ¼ wave (diffraction limited) or worse standard once offered. Sadly, it is often the secondary mirrors that leave a lot to be desired in these economically priced telescopes, so I will discuss what the amateur on a budget can do to upgrade these fairly cheaply to get more or less instant improvements in image quality.
Structure of the Book
The book is to be divided into two parts. Part I will consist of about 60 per cent of the text and part II will cover the remaining 40 per cent. Total length: ~200-300 pages(US English). The book will feature three Newtonian telescopes in detail:
A 130mm F/5 Newtonian (SkyWatcher primary) on an alt-azimuth mount
A 204mm f/6 Dobsonian (SkyWatcher primary)
A 305mm f/5 Dobsonian(GSO primary & secondary)
Part I: Projects to Improve the Performance of Budget Newtonian Telescopes
Chapter 1: A Tale of Three Inexpensive Telescopes: In this introductory chapter, I describe the acquisition of three inexpensive Newtonian telescopes, manufactured by Sky Watcher and GSO. I discuss the traditional advantages and disadvantages of Newtonians over other telescope types, followed by my initial assessment of their performance(star tests etc), describing both the telescopes, their mounting arrangements and supplied accessories, as well as my initial thoughts on their potential to be improved and a plan of action for making those upgrades.
Chapter 2: Improving the Optics: This chapter will outline in considerable detail how the optics on the three Newtonians were improved. Looking at the primary and secondary mirrors, I describe how I had the mirrors re-aluminized using state-of-the-art coatings that improve reflectivity, reduce scatter, increase contrast and durability. I show fellow amateurs how to accurately center spot their primaries and look at the importance of optimizing the central obstruction of the secondary mirror for visual use, and upgrading the secondaries with smaller, flatter mirrors delivering noticeable improvements in the quality of the images. I also consider other options available to me, discussing what the market offers amateurs on a tight budget, showcasing companies/services offered in Europe and North America. Is it more prudent to buy-in higher quality primary mirrors or to proceed with the existing primaries if their figure is found to be ‘satisfactory’ or’ good’ but nothing especially notable to write home about? I argue in the negative, as the effects of an up-graded secondary mirror are taken into account
Chapter 3: Aligning the Optical Train: Newtonian reflectors are capable of serving up very high-quality images of high-resolution targets only if the optics are properly aligned. Accordingly, this chapter will take a detailed look at how aligning the components of the optical train can be achieved using a variety of techniques including simple naked eye assessments with low-tech collimation caps etc, followed by a detailed look at the strengths and weaknesses of using a quality Cheshire collimation eyepiece. From there I proceed to looking at high-tech approaches to collimation using a variety of laser collimators, outlining their strengths and weaknesses(the inaccuracy of cheaper laser collimators, for example), as well as describing the operation of some of the best available gadgets( e.g. Howie Glatter, Barlowed laser methods and Hotech SCA laser collimators) to achieve highly accurate alignment of the optical train in a matter of seconds.
Chapter 4: Improving the Housing of the Telescopes: In this chapter, I describe how to improve the housing of the optical train using flocking material to minimize stray light, internal reflections and image contrast. I also describe how the thermal properties of the tubes can be improved using traditional materials like cork to reduce tube currents and other bugs normally encountered by Newtonian telescopes during their acclimation and during temperature fluctuations that occur in the field. I will also consider the advantages of upgrading the generic focusers on some of these telescopes in order to improve focusing smoothness and precision.I will also include a short discussion on telescope maintenance; including cleaning the optics and the best ways to store the instruments when not in use.
Chapter 5: Mounting Considerations: In this chapter, I consider ways to improve the mounts of three telescopes (5.1 inch, 8-inch and 12-inch), looking individually at each. The 5.1 inch was supplied with a simple, table-top lazy Suzan alt-azimuth but was re-mounted on a much more functional and stable Vixen Porta II mount. I describe low-tech upgrades to the existing plywood lazy Suzan Dob mounts using an inexpensive garden water butt, which both elevates the instrument (in this case the 8 inch Dob) off the ground and improves the smoothness of tracking the telescope both in azimuth and altitude, especially for high-power ‘push-to’ work. This is followed by a description of how one can improve the smoothness of motions in a budget Dob mount(using nylon strips, soaping surfaces etc) as well as balancing and pivoting considerations to improve balance in routine field use.
Chapter 6: Upgrading Accessories with Newtonians: In this chapter, I wish to explore how to upgrade the basic accessories supplied with these budget telescope packages, including eyepiece selection(how to choose eyepieces based on the different f ratios of the instruments under consideration(f/5 and f/6) ), Barlow lenses, finderscope upgrades and the use of dew shields etc.
Chapter 7: Acclimation Considerations: No matter how good the optics on a Newtonian telescope, it will not deliver its best possible views if it is not properly equilibrated to its environment. Accordingly, this chapter takes a close look at how best to acclimate these telescopes. I consider passive cooling, simple, air-blown fans to scrub the boundary layer from the primary mirrors, as well as considering natural ways to cool down Newtonian telescope optics, e.g. by using wind to act as a natural fan to cool down the primary mirror, tactics to minimize or even eliminate cool down time by housing the instruments in a dry-unheated outhouse, where it can be immediately employed for high power observing, as well as observing strategies that largely avoid acclimation issues altogether, e.g. by starting with low power, wide-field viewing, that is less critical to thermally-induced aberrations, before moving on to medium and finally high power applications later in an given observing session.
Part II: Assessing Performance
Chapter 8: Lunar, Solar & Planetary Performance: Properly collimated and acclimated Newtonian telescopes with good optics are capable of generating truly breathtaking views of the Moon and bright planets. I discuss the performance of the three telescopes discussed in part I, which will include details of magnification regimes employed, resolution tests(craterlet counting on the floor of the lunar crater, Plato), the importance of good seeing conditions to obtaining the best high power views, which instruments are better or less suited to work on a given subject, use of color, Tele Vue planetary filters, polarizing filters etc, and making sketches of the Moon and planets as well as other projects like accurately measuring the CM II longitude of Jupiter’s Great Red Spot to monitor changes in its size and position as a function of time. The chapter will also survey the kinds of solar viewing possible with a small Newtonian, including home-made full-aperture solar filters, and using inexpensive Wratten and interference-based filters to enhance views of sunspot morphology on the solar photosphere.
Chapter 9: Exploring the Deep Sky: The tremendous light-gathering power of medium-sized and large Newtonian telescopes makes them ideal instruments for exploring the deep sky, so this chapter will be describe what can be realistically expected form using upgraded optics( light gathering, resolution etc) on a suite of celestial objects, including star clusters, galaxies and other types of nebulae and the advantages and disadvantages of using nebular filters in the pursuit of certain types of objects(emission and planetary nebulae etc).
Chapter 10: Exploring Double Stars: In this chapter I will be detailing my results with these telescopes on a wide variety of double and multiple stars of varying degrees of difficulty in relation to well-established resolution parameters, and, in particular, the Dawes Limit. The chapter will also explore beautiful color-contrast pairs as they appear season-by-season, as well as ferreting out sub-arcsecond pairs when conditions allow.
Chapter 11: Using a Small Newtonian as a Terrestrial Spotting ‘Scope: Traditionally small refracting telescopes are used to view subjects during the day. In this chapter, I outline ways to use a small 130mm f/5 Newtonian on an alt-azimuth mount with slow motion controls to obtain correctly-orientated terrestrial views that are sharp, contrasty and free of chromatic aberration. I show the reader what optical accoutrements can now be purchased that flip the optics from up-side down and right-left-flipped to upright and correctly orientated left-right images. I also outline the considerable advantages of using a larger aperture instrument such as this in low light/ dusk, dawn viewing of wildlife, considering concepts such as the twilight factor etc.
Chapter 12: Travelling with a Newtonian Telescope: A detailed narrative of how I have used the small, 130mm instrument successfully all over the British Isles, choosing a travel case, equipment to bring on the road etc, where it has delivered excellent results on a wide variety of targets from the Moon and the planets to galaxies, double stars and a host of deep sky objects. The chapter will recount results from results all over Scotland, England, Wales and southern Ireland.
Index & Bibliography
To be continued…………………