;+ ; NAME: ; MM_DIST ; ; PURPOSE: ; Converts between distance modulus m-M and distance in parsecs. ; ; CATEGORY: ; Astro ; ; CALLING SEQUENCE: ; Result = MM_DIST() ; ; KEYWORD PARAMETERS: ; MM: Input distance modulus m-M. ; ; DIST: Input distance in parsecs. ; ; OUTPUTS: ; If mM is specified, then Result is the distance in parsecs. If DIST ; is specified, then Result is the distance modulus m-M. ; ; EXAMPLE: ; Calculate distance of an object with distance modulus m-M=16.8: ; ; distance = mM_DIST(mM=16.8) ; ; Calculate the distance modulus of an object at 350pc: ; ; distmod = mM_DIST(DIST=350.) ; ; MODIFICATION HISTORY: ; Written by: Jeremy Bailin ; 10 June 2008 Public release in JBIU ;- function mM_dist, mM=mM, dist=dist nspec=0 if keyword_set(mM) then nspec++ if keyword_set(dist) then nspec++ if nspec gt 1 then message, 'Only one of mM and DIST may be specified.' if nspec eq 0 then message, 'Please give either mM or DIST.' if keyword_set(mM) then begin return, 10^(0.2*(mM+5)) endif else begin ; keyword_set(dist) must be true return, 5.*alog10(dist)-5. endelse end