I suggest carefully selecting your tour company well in advance, and be prepared for the possibility of weather affecting your ability to see stars. We went on Hawaiian Eyes tours which had many positive reviews. However, I would NOT recommend them. The company advertised strict Covid protocols, but we were on a small bus of about 10 with approximately 2 to 3 feet of distance between passengers. There was no way to socially distance, and I saw no hand sanitizer. The air conditioning on the bus was minimal and we were very uncomfortable until we reached higher elevation. Mask wearing was not enforced and our tour guide never wore a mask which was concerning since we were on the bus for about 6 hours. The final trip up and down the mountain (about 30 minutes each way) was extremely bumpy so if you have back or neck problems you may not be comfortable. The visitor center was disappointing, small with overpriced shirts and trinkets, and some of the bathroom stops were porta potties only with no seat covers or toilet paper or lighting. (Bring tissue with you.). Our tour guide was not particularly informative and he drove too fast on our return trip. The highlight of the trip was the sunset but we could not remain at the top of the mountain for star gazing due to potential icy conditions. However, our tour guide had a telescope for us to look through from the visitor center parking lot. Other tour guides were doing the same, but they seemed to be more knowledgeable about astronomy. I recommend carefully researching tour companies before you go and do so months in advance of your trip. I scheduled the trip only days before so my options were limited. And be prepared that weather conditions may prevent you from seeing stars. As for Viator, the representative was very good and made scheduling the trip easy.