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Using an astronomy green laser when stargazing can help you identify different constellations. Before you choose a laser pointer, you might want to think about the conditions you will be using it in, since the weather, time of day, and air pollution can all affect visibility. If you are star gazing with a group, you will need a more powerful device than if you are doing so by yourself. Some models mount on a telescope, and one of these green lasers can be a good choice if you also plan to use this equipment.
An astronomy green laser is rated in milli-watts, noted as mW. There are laser pointers ranging from 5mW to 150mW, and there are many different intervals in between those. Generally speaking, the higher the number of mW, the more accurate this device will be, especially when there is inclement weather. A high-powered green laser may also be more expensive, so you may not want to purchase one of these models unless you plan to go stargazing on a regular basis.
Some laser pointers are intended for personal use; many may clip onto a belt or keychain as well. An astronomy green laser such as this may be rated only 5mW. This can be a good choice if you only plan to stargaze by yourself from time to time. Keep in mind that a laser pointer rated this low may only be useful if there is very little light pollution in your area. One that is rated 10 or 20mW might be better in that instance.
If you are planning to stargaze with a group of people, you may want to think about a higher-powered laser. A green laser that is around 50mW could be ideal for two or three individuals to use. If you are part of a larger group, you may want to consider one rated at least 100mW. In the event you are using a telescope, you may also want to consider a model that can be mounted onto this device.
An astronomy green laser is generally most effective when used in complete darkness. If you only plan to use a laser pointer at night, a lower-powered one ranging from 25 to 50 mW may be sufficient. In the event you are stargazing at dusk or dawn, you might need one that is at least 100mW. This is especially true if the area where you are viewing constellations has a great deal of air pollution, as this also tends to reduce visibility.