IMPORTANT, please read the text below!
The telescopes are operated in the evenings year-round on Friday and Saturday from 7:30 to 10:30 pm. Generally, the observatories are open and volunteers are available to show the telescopes and explain their history and operation even when weather conditions prohibit viewing through the telescopes. The observatories are closed, however, if it is raining or the area outside the observatories is wet.
The telescopes cannot see through thick clouds. Also, to avoid condensation on the telescopes, they are not operated when the humidity is above our limits. Nellie is not operated when the humidity is above 84% and the two refractors do not operate when the humidity exceeds 89%. The current humidity at the observatories is highlighted in bold yellow, below. The normal pattern for humidity at Chabot is for it to reach a minimum in the afternoon and increase over the rest of the day. If you are looking at this in the early evening and the humidity is in the 70’s or low 80’s it is suggested that you wait twenty to thirty minutes and recheck the humidity before deciding whether or not to make the trip.
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The information here and in the table below is current as of Saturday, June 7, 2025 @ 7:05 pm.
It is unlikely that we will operate our telescopes tonight. The humidity is already at our limit and trending upwards. The current humidity is shown in bold yellow below the following table. Additionally, there is a thick layer of fog over San Francisco and heading our way.
| Telescope | Status | Viewing |
|---|---|---|
| Leah – 8″ Refractor | Probably not operating | |
| Rachel – 20″ Refractor | Probably not operating | |
| Nellie – 36″ Reflector | Probably not operating |