Setting Circles? Q & A

Jack Kramer

On an Internet chat group, there was a question raised about setting circles, and two experienced respondents had differing views, both of which have merit.

Question: I have never used setting circles before and need to learn how.

Geoff Gaherty: "Actually you don't. The setting circles on most equatorial mounts are mainly there for cosmetic effect, to make the mount look "scientific". In most cases they are too small and too inaccurate to be of any use in finding anything. The main reason for having an equatorial mount is that it tracks by moving a single axis. I've been using equatorial mounts for forty years, and I probably have only used the setting circles a dozen times, mainly to find Venus in daylight. Forget about the setting circles, and learn how to star hop. The best book on this is Turn Left At Orion, by Guy Consolmagno and Dan Davis (Cambridge)."

Marv Johnson:"Star hopping works well when there is sufficient darkness to see the fainter stars, especially objects such as M44 and M67 which are low on the horizon and not in a star-rich field. However, setting circles, even on the cheaper mounts can be used very effectively for finding deep space objects too faint to see in the typical finder scope. One usually only needs to be within +/- 1.5 degrees to see the object at low power in the OTA. I've found both star hopping and the setting circles to be invaluable over my 30 years of viewing."