diff --git a/allsky_logger/cmdlnopts.c b/allsky_logger/cmdlnopts.c
index 89e785c..1577f92 100644
--- a/allsky_logger/cmdlnopts.c
+++ b/allsky_logger/cmdlnopts.c
@@ -40,6 +40,7 @@ glob_pars const Gdefault = {
     .port = "55555",        // port to listen boltwood data
     .server = NULL,         // server name
     .filename = NULL,       // input file name
+    .min_storage_time = 60.,// minimal storage period
 };
 
 /*
@@ -52,6 +53,7 @@ myoption cmdlnopts[] = {
     {"port",    NEED_ARG,   NULL,   'p',    arg_string, APTR(&G.port),      _("port to connect (default: 55555)")},
     {"address", NEED_ARG,   NULL,   'a',    arg_string, APTR(&G.server),    _("server name")},
     {"filename",NEED_ARG,   NULL,   'i',    arg_string, APTR(&G.filename),  _("input FITS file name")},
+    {"mindt",   NEED_ARG,   NULL,   't',    arg_double, APTR(&G.min_storage_time), _("minimal time interval (in seconds) for image storage (default: 60s)")},
     end_option
 };
 
diff --git a/allsky_logger/cmdlnopts.h b/allsky_logger/cmdlnopts.h
index ab802ce..a0874ba 100644
--- a/allsky_logger/cmdlnopts.h
+++ b/allsky_logger/cmdlnopts.h
@@ -34,6 +34,7 @@ typedef struct{
     char *cwd;              // change working directory to given
     char *server;           // server name
     char *filename;         // input file name
+    double min_storage_time;// minimal storage period
 } glob_pars;
 
 
diff --git a/allsky_logger/imfunctions.c b/allsky_logger/imfunctions.c
index 031c072..463e25c 100644
--- a/allsky_logger/imfunctions.c
+++ b/allsky_logger/imfunctions.c
@@ -154,7 +154,7 @@ do{ int status = 0;                                         \
  * file stored in current directory under YYYY/MM/DD/hh:mm:ss.fits.gz
  * @return file descriptor for new notifications
  */
-int store_fits(char *name, datarecord *data){
+void store_fits(char *name, datarecord *data){
     DBG("Try to store %s", name);
     double t0 = dtime();
     long modtm = 0; // modification time - to change later
@@ -168,9 +168,11 @@ int store_fits(char *name, datarecord *data){
     TRYFITS(fits_get_hdrspace, fptr, &nkeys, NULL);
     DBG("%d keys", nkeys);
     green("open & get hdr: %gs\n", dtime() - t0);
-    char dateobs[FLEN_KEYWORD], timeobs[FLEN_KEYWORD];
+    char dateobs[FLEN_KEYWORD], timeobs[FLEN_KEYWORD], imtype[FLEN_KEYWORD];
     TRYFITS(fits_read_key, fptr, TSTRING, "DATE-OBS", dateobs, NULL);
     DBG("DATE-OBS: %s", dateobs);
+    TRYFITS(fits_read_key, fptr, TSTRING, "IMAGETYP", imtype, NULL);
+    DBG("IMAGETYP: %s", dateobs);
     TRYFITS(fits_read_key, fptr, TSTRING, "START", timeobs, NULL);
     DBG("START: %s", timeobs);
     TRYFITS(fits_read_key, fptr, TLONG, "UNIXTIME", &modtm, NULL);
@@ -180,7 +182,10 @@ int store_fits(char *name, datarecord *data){
     green("+ got headers: %gs\n", dtime() - t0);
     gotodir(dateobs);
     char newname[PATH_MAX];
-    snprintf(newname, PATH_MAX, "%s.fits.gz", timeobs);
+    if(strncasecmp(imtype, "dark", 4) == 0)
+        snprintf(newname, PATH_MAX, "%s.dark.fits.gz", timeobs);
+    else
+        snprintf(newname, PATH_MAX, "%s.fits.gz", timeobs);
     // remove if exists
     unlink(newname);
     TRYFITS(fits_create_file, &ofptr, newname);
@@ -199,15 +204,17 @@ int store_fits(char *name, datarecord *data){
         else
             fits_report_error(stderr, status);
     }
-    DBG("Boltwood data");
-    // now the file copied -> add header from Boltwood's sensor
-    while(data->varname){
-        if(data->type == INTEGR){
-            WRITEIREC(data->keyname, data->data.i, data->comment);
-        }else{
-           WRITEDREC(data->keyname, data->data.d, data->comment);
+    if(data){
+        DBG("Boltwood data");
+        // now the file copied -> add header from Boltwood's sensor
+        while(data->varname){
+            if(data->type == INTEGR){
+                WRITEIREC(data->keyname, data->data.i, data->comment);
+            }else{
+               WRITEDREC(data->keyname, data->data.d, data->comment);
+            }
+            ++data;
         }
-        ++data;
     }
     long npix = naxes[0]*naxes[1];
     imdat = MALLOC(uint16_t, npix);
@@ -225,9 +232,7 @@ ret:
         modifytimestamp(newname, (time_t)modtm);
     }
     // as cfitsio removes old file instead of trunkate it, we need to refresh inotify every time!
-    int fd = watch_fits(name);
     if(chdir(oldwd)){ // return back to BD root directory
         ERR("Can't chdir");
     };
-   return fd;
 }
diff --git a/allsky_logger/imfunctions.h b/allsky_logger/imfunctions.h
index 6c96f20..83731c5 100644
--- a/allsky_logger/imfunctions.h
+++ b/allsky_logger/imfunctions.h
@@ -27,6 +27,6 @@
 #include "cmdlnopts.h"
 
 int test_fits(char *name);
-int store_fits(char *name, datarecord *data);
+void store_fits(char *name, datarecord *data);
 
 #endif // __IMFUNCTIONS_H__
diff --git a/allsky_logger/socket.c b/allsky_logger/socket.c
index 904c474..102628b 100644
--- a/allsky_logger/socket.c
+++ b/allsky_logger/socket.c
@@ -38,6 +38,8 @@
 // Max amount of connections
 #define BACKLOG   (30)
 
+static double minstoragetime;
+
 // keyname, comment, type, data
 static datarecord boltwood_data[] = {
     {"humidstatTempCode"         , "HSCODE"  , "hum. and ambient temp. sensor code (0 - OK)"    , INTEGR, {0}},
@@ -179,20 +181,19 @@ static int waittoread(int sock){
  * @return inotify file descriptor
  */
 int watch_fits(char *name){
-    static int oldfd = -1, oldwd = -1;
-    if(oldfd > 0 && oldwd > 0){
-        inotify_rm_watch(oldfd, oldwd);
-        oldfd = -1, oldwd = -1;
+    static int fd = -1, wd = -1;
+    if(fd > 0 && wd > 0){
+        inotify_rm_watch(fd, wd);
+        wd = -1;
     }
     if(!test_fits(name)) ERRX(_("File %s is not FITS file with 2D image!"), name);
-    int fd;
-    fd = inotify_init1(IN_NONBLOCK);
+    if(fd < 0)
+        fd = inotify_init1(IN_NONBLOCK);
     if(fd == -1) ERR("inotify_init1()");
-    oldfd = fd;
     FILE* f = fopen(name, "r");
     if(!f) ERR("fopen()"); // WTF???
     fclose(f);
-    if((oldwd = inotify_add_watch(fd, name, IN_CLOSE_WRITE)) < 0)
+    if((wd = inotify_add_watch(fd, name, IN_CLOSE_WRITE)) < 0)
         ERR("inotify_add_watch()");
     DBG("file %s added to inotify", name);
     return fd;
@@ -211,7 +212,7 @@ static void test_path(char *path){
 
 /**
  * Client daemon itself
- * @param G - global parameters
+ * @param FITSpath - path to file watched
  * @param infd - inotify file descriptor
  * @param sock - socket's file descriptor
  */
@@ -225,6 +226,7 @@ static void client_(char *FITSpath, int infd, int sock){
     fds.fd = infd;
     fds.events = POLLIN;
     char buf[256];
+    double lastTstorage = -1.; // last time of file saving
     void rlc(size_t newsz){
         if(newsz >= Bufsiz){
             Bufsiz += 1024;
@@ -255,7 +257,12 @@ static void client_(char *FITSpath, int infd, int sock){
                 }else{
                     DBG("file changed");
                     usleep(100000); // wait a little for file changes
-                    fds.fd = store_fits(FITSpath, last_good_msrment);
+                    fds.fd = watch_fits(FITSpath);
+                    if(dtime() - lastTstorage > minstoragetime){
+                        DBG("lastT: %.2g, now: %.2g", lastTstorage, dtime());
+                        lastTstorage = dtime();
+                        store_fits(FITSpath, last_good_msrment);
+                    }
                 }
             }
         }
@@ -293,6 +300,7 @@ void daemonize(glob_pars *G){
     int fd = watch_fits(G->filename);
     // CD to archive directory if user wants
     test_path(G->cwd);
+    minstoragetime = G->min_storage_time;
     // run fork before socket opening to prevent daemon's death if there's no network
     #ifndef EBUG
     green("Daemonize\n");