Few months ago I visited Mahakaleshvar temple in Ujjain. To me, it uncovered hidden secret about Shiv. Shivling, temple construction, and Dhvaja (flag) are typical part of Shiv temple. Plenty of literature available on temple construction which can be referred. Here, I am talking about Shivling and Dhvaja. There were questions in my mind such as why its name is Mahakal, why it is Dakshinabhimukh (southward opening) instead of Poorvabhimukh (Eastward opening), why Ujjain considered as center of India. To that, I had some astronomical informations such as tropic of Cancer-an extreme north point of Sun’s trajectory (considering geocentric motion), which divides India in two halves horizontally, passes through Ujjain.
Mahakaleshvar is the only Dakshinabhimukh Jyotirling among twelve. It means throughout year rays will enter Garbhgruh and Shivling will have constant eye over Sun’s entire trajectory (winter solstice to summer solstice) as Ujjain is on tropic of Cancer. According to Jyotish Shiv is Aadhipati of Sun and through this arrangement Shiv is continuously watching Sun from its southern extreme to northern extreme trajectory.
Understanding about Shiv would not have learned if I had not visited Jantar Mantar. I saw sundial to measure time. Those who are not familiar with it, construction wise it is simple pole on circular platform. Spatial position of Sun and time of day can be measured from length of shadow of pole and trajectory of shadow of tip of pole in day time. This was for estimation while precise instrument to calculate time was available besides it. Even many Britishers reported that in nineteenth century India time was measured from length of human shadow 
Pole and Flag
Money comes through only three means; agriculture, mining, petroleum. Everything human produces which is convertible to money is basically either of these three. Ancient India was agriculture country which entirely depends on seasons. Rain, proliferation of insects  etc seasonal phenomena depends on placement of Sun and Moon. Hence, exact spatial positions of Sun and Moon are necessary to precisely predict seasons.
Pole inserted on top of temple is a type of sundial where priest can predict seasons from the situation of shadow of pole. The flag inserted over pole helps in getting information of wind current. Wind coming from Nairuty (SW), will furl flag in Ishan (NE) direction, will bring moist air to begin monsoon while wind coming from Ishan (NE), will furl flag in Nairuty (SW) direction, will be dry air bringing autumnal season. I have already explained the significance of wind current in Vaastushastr in my previous communication .
Where is spirituality in this science?
Moksh is supreme goal of any Aatma and its gateway is through death: ultimate reality of every living creature on earth. Since Shiv rules death, every Aatma must pass through Shiv inbetween journey to Moksh. He only can subvert bad karm. Popularly Kaal is the single word used for bad time, bad karm, sin, and death. As shadow attached with pole signifies time, shadow attached with Shivling signifies Kaal of Aatma. On summer solstice (in current era it is falling on 21 June) disappearing of shadow of pole (or Shivling) resembles Aatma’s Kaal is devoured by Shiv. It means Mahakal Shiv is destroying Kaal at Ujjain. This is why he is ‘Kaalo Ke Kaal Mahakaal’, a supreme Kaal who has authority over all Kaals (karms).
Declared as intangible cultural heritage by UNESCO , it commences on specific combinations of planetary positions which I am yet to understand. The ritual similar to mass bathing of Rishis on river Drisdvati, conducted at every twelve years, is mentioned in Vaayu Puran  but its connection with Kumbh Mela is yet to be established. Astrolabes (Jantar Mantar) were needed to precisely calculate beginning of festivals.
Sun Jupiter Moon Other combination
Haridwar Aries Aquarius(Kumbh)
Prayagraj Capricorn Aries Capricorn J in Taurus S in Capricorn
Nasik(Sinhasth) Leo Leo J, S, M in Cancer
Ujjain(Sinhasth) Aries Leo J, S, M in Libra.
Currently Sun is in Capricorn, Jupiter in Scorpio, and Moon keeps changing zodiacs after 2.25 days. Interestingly, according to Jyotish, Kumbh (from which Mela derived its name) is the Mooltrikon sign of Saturn who signifies Karm (Saturn’s another ruling zodiac is Capricorn and he is exalted in Libra), Sun (ruling over Leo and exalted in Aries) signifies Aatma, Moon (ruling over Cancer and exalted in Taurus) signifies Mann, and Jupiter (ruling over Sagittarius and Pisces and exalted in Cancer) signifies Dharm. It means Atma, Mann, Dharm, and Karm are uniting at Kumbh Mela. This event occurs at the interval of twelve years because Jupiter takes twelves years to transit back in Kumbh. Considering Kalpurush Kundli, in fact this principle is foundation of Nadi Jyotish; Saturn identifies Karm (Karmesh in Kalpurush), Jupiter identifies feasibility/luck (Bhagyesh/Dharmesh in Kalpurush), Sun identifies month of occurrence (Panchmesh and Pitrukarak in Kalpurush) and Moon identifies day of event (Chaturthesh and Matrukarak in Kalpurush).
1. Chidambaram Iyer, “Aryan Miscellany Astronomical Series, The Brihatjatak of Varahmihir, Translation”, Foster Press, Madras, 1885.
2. Sankrant Sanu, “Whose new year? Return to better calendar”, India Facts, 2016.
3. Dharmesh Patadiya, “Dynamics of Machines, Fluid Mechanics and Science Behind Vastu Shastr”, WordPress, 2018.
4. UNESCO representative list of Intangible Cultural Heritage of Humanity.
5. Subhash Kak, “The Astronomical Code of The Rgveda”, Adity Prakashan, New Delhi, 2016.
ઝબકારો: I heard India is most auspicious land on earth, and it is true because Shiv, supreme Kaal, lives in every molecule of her. Shiv is everywhere (because everything on earth have shadow and Karm) and we can recognize him through satbuddhi given by him and with his wish. Jyotish is linked with Hinduism that is why most of communists hate Jyotish.