diff --git a/py/desisim/io.py b/py/desisim/io.py
index 14ad8307d..710cbdeed 100644
--- a/py/desisim/io.py
+++ b/py/desisim/io.py
@@ -119,11 +119,11 @@ def write_simspec(meta, truth, expid, night, header=None):
     hdr['AIRORVAC']  = ('vac', 'Vacuum wavelengths')
     hdr['LOGLAM']    = (0, 'linear wavelength steps, not log10')
     hdr['EXTNAME']   = ('FLUX', 'Object flux [erg/s/cm2/A]')
-    fits.writeto(outfile, truth['FLUX'], header=hdr, clobber=True)
+    fits.writeto(outfile, truth['FLUX'].astype(np.float32), header=hdr, clobber=True)
     
     #- Sky flux
     hdr['EXTNAME'] = ('SKYFLUX', 'Sky flux [erg/s/cm2/A/arcsec2]')
-    hdu = fits.ImageHDU(truth['SKYFLUX'], header=hdr)
+    hdu = fits.ImageHDU(truth['SKYFLUX'].astype(np.float32), header=hdr)
     fits.append(outfile, hdu.data, header=hdu.header)
     
     #- Metadata table
@@ -155,12 +155,12 @@ def write_simspec(meta, truth, expid, night, header=None):
         
         extname = 'PHOT_'+channel
         hdr['EXTNAME']   = (extname, channel+' channel object photons per bin')
-        hdu = fits.ImageHDU(truth[extname], header=hdr)
+        hdu = fits.ImageHDU(truth[extname].astype(np.float32), header=hdr)
         fits.append(outfile, hdu.data, header=hdu.header)
 
         extname = 'SKYPHOT_'+channel
         hdr['EXTNAME']   = (extname, channel+' channel sky photons per bin')
-        hdu = fits.ImageHDU(truth[extname], header=hdr)
+        hdu = fits.ImageHDU(truth[extname].astype(np.float32), header=hdr)
         fits.append(outfile, hdu.data, header=hdu.header)
                             
     return outfile
diff --git a/py/desisim/obs.py b/py/desisim/obs.py
index e8c89326b..c3700d029 100644
--- a/py/desisim/obs.py
+++ b/py/desisim/obs.py
@@ -127,7 +127,7 @@ def new_exposure(nspec=5000, expid=None, tileid=None, airmass=1.0, exptime=None)
         #- 2D version
         ### truth['SKYPHOT_'+channel] = np.tile(skyphot, nspec).reshape((nspec, len(ii)))
         #- 1D version
-        truth['SKYPHOT_'+channel] = skyphot
+        truth['SKYPHOT_'+channel] = skyphot.astype(np.float32)
         
     #- NOTE: someday skyflux and skyphot may be 2D instead of 1D
     
diff --git a/py/desisim/targets.py b/py/desisim/targets.py
index 6f957cfe9..79653059c 100644
--- a/py/desisim/targets.py
+++ b/py/desisim/targets.py
@@ -10,6 +10,7 @@
 import random
 import desisim.cosmology
 import desisim.interpolation
+from desimodel.focalplane import FocalPlane
 import astropy.units 
 import math
 import string
@@ -186,7 +187,16 @@ def get_targets(nspec, tileid=None):
     #- Load fiber -> positioner mapping and tile information
     #- NOTE: multiple file I/O here; seems clumsy
     fiberpos = io.load_fiberpos()
-                        
+
+    #- Where are these targets?  Centered on positioners for now.
+    x = fiberpos['X'][0:nspec]
+    y = fiberpos['Y'][0:nspec]
+    fp = FocalPlane(tile_ra, tile_dec)
+    ra = np.zeros(nspec)
+    dec = np.zeros(nspec)
+    for i in range(nspec):
+        ra[i], dec[i] = fp.xy2radec(x[i], y[i])
+    
     #- Fill in the rest of the fibermap structure
     fibermap['FIBER'] = np.arange(nspec, dtype='i4')
     fibermap['POSITIONER'] = fiberpos['POSITIONER'][0:nspec]
@@ -195,10 +205,10 @@ def get_targets(nspec, tileid=None):
     fibermap['TARGETCAT'] = np.zeros(nspec, dtype='|S20')
     fibermap['LAMBDAREF'] = np.ones(nspec, dtype=np.float32)*5400
     fibermap['TARGET_MASK0'] = np.zeros(nspec, dtype='i8')
-    fibermap['RA_TARGET'] = np.ones(nspec, dtype='f8') * tile_ra   #- TODO
-    fibermap['DEC_TARGET'] = np.ones(nspec, dtype='f8') * tile_dec #- TODO
-    fibermap['X_TARGET'] = fiberpos['X'][0:nspec]
-    fibermap['Y_TARGET'] = fiberpos['Y'][0:nspec]
+    fibermap['RA_TARGET'] = ra
+    fibermap['DEC_TARGET'] = dec
+    fibermap['X_TARGET'] = x
+    fibermap['Y_TARGET'] = y
     fibermap['X_FVCOBS'] = fibermap['X_TARGET']
     fibermap['Y_FVCOBS'] = fibermap['Y_TARGET']
     fibermap['X_FVCERR'] = np.zeros(nspec, dtype=np.float32)