Bharani Nakshatra Worship

Mantra for Moon in Bharaṇi Nakṣatra 
Dharmarāja worship according to Mantra Mahodadhiḥ Taraṅga 19
[translation source: Ram Kumar Rai, Prachya Prakashan, Varanasi, 1992]

This is a siddha mantra.
Its practice destroys all miseries,
prevents adharmic actions,

and removes enmity.

Viniyoga- With hands folded at the heart say:

asya śrī dharmarāja mantrasya
vāmadeva Ṛṣiḥ
gāyatrī chandaḥ
śamana devatā
mamābhīṣṭa-siddhaye jape viniyogaḥ

Nyāsa- Putting the mantra into the body:
hand placed on heart, say:
auM kroṁ hrīṁ hṛidayāya namaḥ
hand placed on top of head, say: 
āṁ vaiṁ śirase svāhā
hand placed on spiral of hair, say:
vaivasvatāya śikhāyai vaṣaṭ
hands crossed on cheast, say:
dharmarājāya kavacāya huṁ
touching eyes, say:
bhaktānugrahakṛte netra-trayāya vauṣaṭ
right index, middle and ring fingers (astraya mudra) slap left palm while saying:
Namaḥ astrāya phaṭ

Dyāna- Envisioning the form of dharmrāja to worship:
We meditate upon you yamarāja,
Adorned with ornaments,
Holding a big iron rod,
With a dark complexion like rain clouds ready to burst.
You are lord of the ancestors,
Ruler of the southern direction,
Son of the brilliant Sun-god,
Gracious to good people
Showing your terrible form to evil doers.
Rider of the Buffalo,
Husband of Saṁyaminī (self-restraint),
Your power is supreme.
Mantra:AUM kroṁ hrīṁ āṁ vaiṁ vaivasvatāya
dharmarājāya bhaktānugraha kṛte namaḥ

Another Mantra: For some worshipping the Yama directly may be too much and so he can also be worshiped in a very safe form. Yama, the lord of Dharma takes the form of a mouse to carry Gaṇeśa. So pūjā and worship of the mouse (Mūṣika) of the elephant headed god will appease Yama. The mantra for this is:

AUM maṁ mūṣikāyai gaṇādhipavāhanāya Dharmarājāya svāhā

Bharani is the three stars in the central red square within the constellations of Aries. Some have thought Bharani might be the constellation Triangulum above Aries, but that was not indicated in the 1924 Archaeological Survey of Indian Astronomy. The stars indicated above were exactly on the ecliptic in 3000BCE. Aswini is the head of the ram- which may have been seen as a horse by the earliest Vedic people.  Bharani is literally the tail end of this ram (or possible horse). 

Sharatan and the star next to it (Gamma Arietis) are the Ashvin twins. Hamal is the heart of the ram.
And the back-end star on the above line (to left) is the beginning corner of the yoni of Bharani.
To locate the stars of Bharani, first find the Pleiades and then the Sharatan and Hamal which are both more prominent in the sky. Then look for the triangle slightly above and between them.