The SkyPointer green laser pointer is a new variation of an old idea that amateur astronomers have practiced for many years : a narrow-beam high power flashlight has been used to point out celestial objects. Tiny particles of dust, pollen, and moisture scatter back enough light from the beam to produce a visible line in the air. If the beam extends far enough, a designated location on the sky can be unambiguously pointed out. Nowadays, with increasing interest in science and astronomy education, and the growth of astronomy clubs and star parties, the SkyPointer provides a convenient and practical way to show and teach celestial geography.
Red laser pointers have grown cheap and ubiquitous, but unfortunately, they are not very effective as sky pointers. In contrast, green laser pointers are very effective because of the eye's greater sensitivity to the 532 nanometer green light. Under dark sky conditions, the beam from a 5 milliwatt green laser pointer creates a dramatic impression, and the beam apparently extends for more than a kilometer. Any bright light source, ranging from light pollution induced sky glow to a crescent moon, will reduce the apparent brightness of the SkyPointer although the beam will usually remain visible. The light pollution acts in such a way that people closer to you will still see the beam, whereas those further away may have difficulty.
The reason for the high price of green pointers as compared with red lies in their additional internal complexity. They use a battery powered laser diode controlled by a miniaturized circuit, just like the red ones. However, the diode uses about five times the power of the red ones and emits it's laser light at an invisible, infrared wavelength of 808nm. The infrared laser output is focused into to a small crystal of Neodymium doped Yttrium ortho Vanadate (NdYVO4), which then lases at a longer wavelength of 1064nm. The 1064nm output beam is absorbed in an adjacent crystal of Potassium Titanyl Phosphate (KTP) which resonates at twice the pump light frequency to produce an output of 532nm green laser light. A multilayer interference filter removes residual infra-red light, and the output is focused and collimated into a thin parallel beam. Both of the crystals are artificially grown, and must be cut, polished, and multi-coated to very small tolerances. Only a handful of companies are producing these crystals now.
The SkyPointer is custom produced to my specification, and I check out, test and seal each one before shipment. I believe they are the highest quality green pointers on the market. They are constructed of strong metal tubing with a pocket clip. The laser power output is guaranteed to be between 3 and 5 milliwatts, and is typically very close to 5mw. The SkyPointer is powered by two AAA alkaline cells. They work very hard when the pointer is on, supplying about 280 milliamps. The theoretical pointer on time is two to four hours at average drain, but if used frequently, with long on times, the battery lifetime will be somewhat less.
They come with one set of batteries, in a hinged black metal presentation case. They should be treated carefully and not dropped or banged around. They are warranted against defects for six month. All green class IIIa pointers sold are designed for momentary use in pointer service. This means that they cannot be kept on continuously ; about one minute is the maximum.. After being on this long, it should be allowed to rest for a similar period. If the pointer is kept on longer or continuously it may dim out, however, it will not be damaged because the control circuit will prevent current from rising to a harmful level.
Safety precautions must be followed when using the SkyPointer. The beam should never be allowed to enter the eye. Although instant permanent blindness will not occur with a momentary, glancing exposure, visual damage could occur if the beam is allowed to enter the eye and fall upon the same area of the retina for more than about 1/4 second. This is an unlikely occurrence, given the aversion and blink reflex, however, all precautions should always be followed to avoid direct eye exposure
The SkyPointer should never be pointed at vehicles, boats, or aircraft, even distant ones.
Precautions for astronomy
When others are observing, the SkyPointer should only be used with permission,
The SkyPointer should not be pointed at nearby reflective objects because the brilliant reflections will temporarily destroy dark adapted vision. The beam in air does not noticeably effect dark adaptation.
The SkyPointer should not be used when others are imaging, as a sweep of the beam through the imaged field might register in the exposure.
To insure that the previous precautions are followed, the SkyPointer should not be used by unsupervised children.
The price of the SkyPointer is $US 80. Shipping within the U.S. by Priority mail with delivery confirmation and tracking is $5. International shipping by Express mail, which includes insurance and tracking, is about $19 to $26 depending on country of destination. Please contact me for exact shipping charge.
For more info and ordering please contact Howie Glatter.
Reviews of the SkyPointer on the Internet:
Howie Glatters SkyPointer Green Laser
Howie Glatter Laser Pointer