Ganapati or Ganesa is the most revered Deity of Sanatana Dharma loosely called Hinduism.
Though many Gods are worshiped in India,each being revered more than the others in a specific pooja or Stotra.
One finds Shiva being called Supreme in Shiva Stuthis and in Vishnu Aradhana Vishnu stands taller than Shiva and others.
But in all the Poojas there is an exception to one God.
And that is Ganesa.
Ganesa steps in.
He ensures that obstacles are removed,you are blessed to give in your best to ensure best results.
This is the reason people perform Ganapati Pooja.
On a higher level Ganapati Homa is performed.
This Homa is performed when one is
Faced with obstacles he can not explain or control,
Results of his efforts are not in his favor,
Unexplained illness in the family,
About to enter into a new endeavor or entering a new house,whether rented or own home
Or praying for auspiciousness at home or business.
Being an important Homa this has to be performed with utmost care and devotion.
- The Ganapati Homa is conducted, ideally, in the Brahna muhurtha, between 3 45 and 4 30 AM.
Ganapati Homa in Tamil
Mnatra citation from the Links provided above.