chaitra, vaishakh adi hindi mahine jinhen chandra-mas bhi kaha jata hai, ek khas nakshatra vale din samapt hote hain jaise ki chaitra mah ki purnima ko chitra nakshatra hota hai, baishakh sudi purnima ko vishakha nakshatra hota hai. anya mahinon ki purnima ke nakshatra is prakar hain- jyeshth ki purnima ko jyeshtha, asharhi purnima, uttarasharha, shravan purnima shravan, bhadrapad purnima uttarabhadrapad, ashvin purnima ashvini, kartik purnima krittika, margashirsh purnima mrigshira, paush purnima pushya, magh purnima magha evan falgun sudi punr iama ko uttara falguni nakshatra rahta hai.
krishn paksh ko budi bhi kahte h jiski antim tithi amavasya hoti hai. shukla purnima ya pundu hoti hai. kabhi-kabhi ukt nakshatron men kuch ghantane ka fark a jata hai karan chandrama ki dainik gati hamesha ek si nahi rahti. hindi mahinon ka namakaran purnima ko rahne vale nakshatra ke nam par kiya gaya hai. ab hamen yah gyat karna hai ki aj kis mahine ke kaun se paksh ki kaun si tithi hai? iske lie hamare pas do suchnayen hona jaruri hai. pahli yah ki pichli purnima ko kaun sa nakshatra tha aur dusri ye ki aj ya abhisht din ko kaun sa nakshatra hai? mana ki gat purnima ko vishakha nakshatra tha aur aj purvasharha nakshatra hai. is suchna ke adhar par ham kah sakte hain ki aj jyeshth mas ke krishnapaksh ki chaturthi tithi hai. gat purnima ko vishakha nakshatra hone se hamen gyat hua ki vaishakh mas samapt hokar jyeshth mas ka krishnapaksh chal raha hai. purvasharha nakshatra vishakha nakshatra ke 4 din bad ata hai. ek din (24 ghante) men ausat rup se ek nakshatra aur ek tithi hoti hai. purnima ke 15 din bad tak krishn paksh rahta hai atah aj jyeshth krishn chaturthi hai. nakshatra ashvini se revti tak 27 hote hain
jinka kram hamesha ek hi rahta hai jaise ki ashvini ke bad bharni nakshatra hoga, uske bad krittika ayega, uske bad rohini ayega adi. isi kram men mana ki aj adrra nakshatra hai jo vishakha ke 17 din bad ata hai. ismen krishn paksh ke din ghatane par aj jyeshth shukla doyaj tithi hai, aisa uttar diya ja sakta hai. is tarike se kisi bhi mahine ki tithi batai ja sakti hai. lekin yah anumanit tithi mote taur par (rafli) hi manna chahiye kyonki tithi aur nakshatra ka praranbh aur samapti kal alg-alag hota hai tatha chandrama ki gati men bhi ghat-barh hoti rahti hai. iske bavjud panchang dekhe bina nikatatam tithi ki jankari dena jyotish shastra ki vishishtata hi mani jayegi. kai dafa is ganna se tithi shat-pratishat sahi baithti hai. yadi vartaman mahina malum ho aur keval paksh tatha tithi gyat karni ho to gat mahine ki purnima ka nakshatra upar di gai suchi se len tatha us nakshatra se aj ke nakshatra tak ginane. mano aj dhanishtha nakshatra hai aur margashirsh mahina chal raha hai to krittika se dhanishtha tak ginne par 20 sankhya ai. atah aj margashirsh sudi panchmi hai. isi udaharan men mano aj anuradha nakshatra hai. krittika se anuradha tak ginne par 14 sankhya ai. atah aj margashirsh krishn 14 tithi hai, yah uttar banta hai. apne uttar ko bad men panchang ya kailendar se milan karne par pata chalega ki uttar kitna sahi hai.
panchang dekhe bina tithi janne ka dusra tarika bhi saral hai. yah chandrama ki kalaon par adharit hai. chandrama ke prakashit bhag ko chandrama ki kala kahte hain. chandrama akash men jis jagah udit hota hai, usse agle din 12 ansh khisak kar ugta hai. shukla paksh men yah purva disha ki taraf pratidin khiskta hua purnima ko purvi kshitij par pahunch jata hai. krishn paksh men yah pratidin pashchim ki taraf khiskte huye amavasya ko pashchimi kshitij par pahunch jata hai. us din suryast ke samay ye donon ek hi nakshatra aur ek hi rashi par hote hain. iske viprit purnima ko suryast ke samay ye ek dusre ke amne-samne hote hain arthat surya pashchim men aur chandrama purva ke kshitij par. shukla paksh men chandrama pashchim men ugna shuru hota hai aur krishn paksh men purva men ugna shuru hota hai. lekin donon hi sthitiyon men chandrama ke ast hone ki disha pashchim hi hai. shukla paksh men chandrama ki kala 12 ansh pratidin ki ausat dar se barhti hai. 180/15 = 12 tatha krishn paksh men isi dar se ghatti hai. amavasya ko chandrama ki kala shunya par pahunchne ke karan vah dikhai nahin deta. shukla paksh ki pratipda ke din bhi chandrama ki sthiti kamo-besh yahi rahti hai. shukla paksh ki doyaj ka chandrama suryast ke bad pashchimi kshitij par 2/15 pratishat roshni liye huye dikhai deta hai. us samay chandrama ki kala ka anshatmak man 24 hota hai. shukla paksh ki ashtami ka chandrama adhi roti ke akar men suryast ke bad akash ke bichon bich (hamare sir ke upr) dikhai deta hai. saptami ka chandrama akar men isse thora kam aur navmi ka isse thora adhik hota hai. purnima ka chandrama suryast ke samay purn golakar purva kshitij par dikhai deta hai.
shukla paksh ki chaturdashi ka chand purn vritt se thora kam hota hai lekin yah suryast se karib ek ghanta pahle purab men dikhta hai. chandrama pratidin ausatan 52 minat deri se ugta hai chahe krishn paksh ho ya shukla paksh aur ugne ke karib 12 ghante bad ast hota hai. is prakar chandrama ek nishchit kram se din men bhi udit rahta hai lekin suraj ki roshni ke karan yah prakashhin rahta hai. krishn paksh men ashtami ka chandrama ratri 12 baje ke bad ugta hai aur uski ters-chaidas ka chandrama suryoday ke karib udit hota hai. krishn paksh ko ‘budi’ ya andhera pakhvara aur shukla paksh ko ‘sudi’ ya chandni rat vala pakhvara bhi kahte hain. tithi aur paksh gyat karne ke is tarike ko ham ‘chandra-vedh-pranali’ (mun objarvens sistama) kah sakte hain. lekin is vidhi se hindi mahine ka nam pata nahin chalta, atah mahine ka nam anya sutron se len.