Worship performed during this festival is considered highly auspicious, and rewarding. Unmarried girls do this for decent marriage, married couples with compatibility problems, feel this improves their married lives; others worship for divine grace. Now the big question—when is Shivratri or Mahashivratri celebrated? What are the astronomical considerations for this festival?
Here Kumbha represents Shiva and Makara represents Mata Parvati. And there is a reason for this. As per Vedanta Jyotish (remember VJ has an important role in selection of dates for all Hindu festivals), Kumbha is a Rashi farthest away from the Rashi of Sun i.e. Leo (Singh in Sanskrit). Kumbha is represented by an EMPTY earthen pot. The immediate idea that we get is of abject poverty, and since Saturn owns this Rashi, you can add Karma with detachment. The other rashi, Capricorn, where moon is, is also owned by Saturn. Mars gets exalted status over here, and Mars, we all know gives exaltation results only through renouncement. Mata Parvati, a princess, belonging to a very rich royal family, renounced everything to marry Lord Shiva. She gets represented during Mahashivratri by Capricorn. She knew she was marrying Lord Shiva, and she knew that Lord Shiva had no worldly wealth and may never ever have a cottage of his own.
This is one more aspect of Dharm, which gets represented during Mahashivratri. Lord Shiva is usually shown in Samadhi. When his Samadhi is complete, creation of Brahma (i.e. the life on earth) collapses. Conscious to the world outside the body reduces destructive power of Lord Shiva. And symbolically, Moon represents consciousness. So that we do not miss this important aspect, every picture of Shiva contains a white silvery crescent of moon, on the top of the head, on the side of the right shoulder, indicating that Lord Shiva is conscious, but only slightly (only as much as the silvery crescent visible to the full moon, OR one can also say as per the ratio of moon visible on fourteenth dark tithi to the moon visible on full moon day), and this much CHETNA, or, consciousness is sufficient for the world to prosper.
The sun in Kumbha symbolizing Shiva indicates a person, who is not worldly, and one who performs all his Kama with detachment, and one who will be more comfortable in complete Samadhi, unconscious of what is happening to the outside world. This is what the world does not want, so the marriage of Lord Shiva with Goddess Parvati is celebrated by Hindus, on the 13th tithi of the dark fortnight. On that tithi, moon will be in Makara. And Makara symbolizes renouncement of all worldly wealth. This is what Goddess Parvati does for the sake of all Humanity. She marries Lord Shiva, renouncing all her wealth.
So that we may not miss out on this important aspect, all pictures of Lord Shiva show this moon as silvery crescent over Lord Shiva head. The rituals of Shivratri are only complete when the LAST moon is physically visible on the next day morning and attempt to view this moon over sun is made by the faithful.