As with any story, there are going to be some inaccuracies, a few errors. Some of these errors are going to be your fault and some will occur for reasons beyond your ability to control. In fact, if you're not mindful, you may not even know that errors are creeping into your observations. It's important to eliminate those errors that are your fault and take steps to identify those that are beyond your ability to control so that you can properly consider them. Don't be offended; everyone has errors, even professional astronomers. You just have to account for them.

The first step that you can take to reduce errors is to pay attention. Be alert and take yourself, and your work, seriously. Formalize your observation and analysis process so that you follow the same procedures every time; notes, a worksheet or a checklist will help. Also, wait until you're rested to conduct detailed analysis of your data. Accuracy is more important than speed!

Errors that you will not be able to totally control but that you might be able to influence in some small way include atmospheric extinction and environmental conditions. Atmospheric extinction is caused by making estimates through a thick atmosphere, such as when you observe a star positioned very low near the horizon. When a star is low, you're looking through a lot of air. This air, the atmosphere, is going to change the light that reaches your eyes or instruments. It's best to observe stars when they are high overhead. Think of the atmosphere as an ocean, an ocean of air and you are sitting on the bottom of this ocean looking up through it.

Of course, there will be exceptions, such as stars that never get very high relative to your location. Proper planning will help here. Plan to observe stars when they are highest in the sky. The meridian, an imaginary line running from south to north (or north to south, depending upon your perspective and hemisphere), will help you. When a star passes through the meridian it reaches it's highest point in the sky. This event, moving across the meridian, is called the transit. Observing stars when they are close to the transit will ensure that you are viewing them when they are highest in the sky. This is most important for those stars that never get very high in the sky.

Environmental conditions include the weather, site location and the Moon and Sun. For example, try not to make observations through light clouds or if possible, from heavily light-polluted city locations. Be careful when observing stars close to a bright Moon. Making observations just as the Sun sets or just before it rises can influence your estimates too. Again, there will be exceptions. Strive for the best observing location, best conditions and best orientation relative to the star that you are observing. When your observations are influenced in some way that may effect their accuracy, make sure that you indicate it on your records.

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