As the dome of twilight sinks below the horizon, a mechanical corps de ballet starts a slow-motion pirouette with each dancer keeping the unblinking eye of a telescope locked on a single spot in the heavens. Shutters open and ancient photons, ending a journey that may have started before the earth was born, collide with sensors that store an electron to mark that photon's arrival. With the dance in motion the directors sit back to watch the show; another imaging session has begun... Image by Marcus Stevens A Full and Proper Kit An introduction to the gear of astro-photography The young recruit is silly – 'e thinks o' suicide; 'E's lost his gutter-devil; 'e 'asn't got 'is pride; But day by day they kicks him, which 'elps 'im on a bit, Till 'e finds 'isself one mornin' with a full an' proper kit. Rudyard Kipling Like the young recruit in Kipling's poem 'The 'Eathen', a deep-sky imaging beginner starts with little in the way of equipment or skill. With 'older' imagers urging him onward, providing him with the benefit of the mistakes that they had made during their journey and allowing him access to the equipment they've built or collected, the newcomer gains the 'equipment' he needs, be it gear or skills, to excel at the art. At that time he has acquired a 'full and proper kit' and ceases to be a recruit. This paper is a discussion of hardware, software, methods and actions that a newcomer might find useful. It is not meant to be an in-depth discussion of all forms of astro-photography; that would take many books and more knowledge than I have available. But I hope that my descriptions and graphics will help a newcomer to the art understand a bit more what is involved in this wonderful pastime. Rick Saunders London Centre, RASC January 2011 My thanks to the Royal Astronomical Society of Canada London Centre for their input and support and especially Matt Neima and Chris Evans for taking on the task of sorting out my typos, grammar glitches and oddities of syntax. Copyright © 2011 Rick Saunders. All rights reserved. All credited images are used with the permission of the photographer Table of Contents Telescope Mounts.......................................................................................................................................5 Tripods and Piers......................................................................................................................................10 Gears and Periodic Error..........................................................................................................................12 Optics and Optical Tubes.........................................................................................................................17 Mounting Rings and Dovetail Bars..........................................................................................................28 Electrical Power ......................................................................................................................................31 Sensors.....................................................................................................................................................36 DSLR Cameras........................................................................................................................................39 CCD Cameras..........................................................................................................................................43 Astro-photography With Camera Lenses.................................................................................................45 Auto-Guiders............................................................................................................................................50 Focusers...................................................................................................................................................56 Focusing Masks........................................................................................................................................59 Automatic and Remote Focusing ............................................................................................................63 Field Flatteners, Focal Reducers and Coma Correctors...........................................................................65 Dew Control.............................................................................................................................................68 USB Hubs................................................................................................................................................70 Filters.......................................................................................................................................................73 Differential Flexure..................................................................................................................................78 Polar Scope Alignment.............................................................................................................................82 Telescope Balance....................................................................................................................................83 Drift Alignment........................................................................................................................................85 Exposure Control.....................................................................................................................................88 Collimation...............................................................................................................................................89 Flat Frames...............................................................................................................................................95 Dark Frames.............................................................................................................................................97 Light Frames............................................................................................................................................99 Stacking Images Using DeepSkyStacker...............................................................................................102 Stacking Images with IRIS....................................................................................................................107 Some IRIS Procedures...........................................................................................................................113 Processing Images Using the GIMP.......................................................................................................116 Removing Gradients with the GIMP.....................................................................................................126 Required Plugins for the GIMP.............................................................................................................128 DIY Circuit Boards................................................................................................................................131 An Efficient DIY Anti-dew Heat Controller .........................................................................................133 DIY Anti-dew Heat Strip........................................................................................................................136 DIY DSLR Power Supply......................................................................................................................138 DIY USB Hub Power Supply.................................................................................................................140 Adding a Motor to a Focuser.................................................................................................................142 DIY Focus Motor Controller..................................................................................................................143 Some Nomenclature...............................................................................................................................145 Links.......................................................................................................................................................148 Illustration and Image Credits................................................................................................................152 HARDWARE SECTION A cursory introduction to the hardware that imagers use. Downtown Milky Way by Jon Gunning Telescope Mounts The foundation of astro-photography is the mount. An amateur imaging mount has to be equatorial. In the world of amateur astro-photography the two statements above are axiomatic. A weak mounting can deliver good images under perfect conditions and for some types of imaging one can get away without an equatorial mount. For most applications though a strong, well-built equatorial mount is still optimal. What is an equatorial mount? An equatorial mounting allows a telescope to accurately track the sky as the earth rotates but not all tracking mounts are equatorial. For an example of a non- equatorial mount think of a camera tripod. Most camera tripods allow a camera to move so that it Fig. 1 tilts up and down, and swivels side-to-side. In astronomy this is known as an altitude-azimuth (alt-az) mounting system. To track the stars a mounting of this type needs to move both axes in concert which many do, but these are not optimal for astro-photography