AUM kaatyaanaaya viddhamahe
tanno durge prachodayaat
The three sandhyas (transition periods) of dawn, noon and dusk are appropriate times to chant the Durga Gayatri. According to tradition, 108 repetitions are recommended during each period of chanting. However, if one is constrained by time, this number may be reduced to any multiple of 9 (9, 18, etc.).
Meaning and Interpretation of Durga Gayatri:
AUM = the universal pranava mantra
kaatyaa-naaya = She who was born in the hermitage of Sage Kathyayana
vid-dhamahe = the omnipresent one
kanya-kumari = the one who is the "princess" among "girls"
dheemahi = give us the strength to meditate
tanno = we bow before you
durge = Goddess Durga, the inaccessible one
pracho-dayaat = give us blessings and inspiration.