Very long exposures requiring precise tracking needed for imaging deep-sky objects may now be achieved through an advanced imaging technique called autoguiding. This article provides a brief introduction and how one could construct a do-it-yourself guider that delivers equally satisfying results for a fraction of the cost of ultra expensive commercially available counterpart.
Guided imaging simply involves active monitoring of the telescope’s tracking accuracy by observing a reference object (any bright star) and making the necessary adjustments to nudge the telescope to the east or to the west so that the reference object remains stationary for the whole duration of an exposure. The simplest example is a setup involving an imaging telescope with (equipped with a finderscope) on a tracking mount. After the object to be imaged has been properly framed and focused, the imager adjusts the finderscope and centers its cross hair to the brightest star in its field. This bright star now serves as the reference object called the guide star and the finderscope now performs the task of a guidescope. The idea is that, for as long as the guidescope’s crosshair is centered on the guidestar, the imager knows that the telescope is tracking properly. To achieve better sensitivity to drift, more powerful dedicated guidescopes may be used.
Image 1. My first autoguider setup (2010): guidescope (left) mounted side by side with 6-inch imaging scope (right).
Anyone familiar with basic camera settings like shutter speed, ISO, and aperture (f/ratio) is more than capable of capturing decent astrophotos like constellations, meteors, planetary and lunar alignments, Iridium flares, ISS flybys, star trails, and even the Milky Way. In most cases, only a DSLR-on-a-tripod setup is required. In some instances, however, an additional accessory called a cable release becomes a necessity, and without it, it is simply impossible to take advantage of the most useful feature of a DSLR camera: the bulb setting. This article explains why such an accessory is important and how you can build one (for Canon DSLRs) that performs technically the same function, equally as reliable, but costs just a fraction of the commercially available counterpart (and the best part is, you actually built it yourself!).
It comes with an ID lace and a shirt!! :)
A little souvenir from the Venus Transit observation in UP Diliman (Philippines): an ID and an official ‘Rekindling Venus’ shirt (not shown)!
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© Anthony Urbano (Manila, Philippines)
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This site aims to provide useful information on astrophotography-related topics, visual observations, and equipment modification for fellow astronomy and science enthusiasts.
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The Venus Transit of 2012 is considered as the rarest predictable astronomical event. It is so rare that one person can only observe it for a maximum of 2 times in his or her lifetime. It occurs when the Sun, the planet Venus, and the Earth are in perfect alignment with each other. As viewed from the Earth, Venus appears as a black dot moving across the disc of the Sun.
Shown below is a brief summary of my observation as part of the Rekindling Venus public viewing and observation held in UP Diliman. The next Venus transit will occur on December 2117.
Organizers of the event pose for a group shot. Photo Credit: Angelie Alagao
Transit-in-progress approaching the final stages of the transit 11:28 am Photo Credit: Anthony Urbano