diff --git a/beast/tools/convert_hdf5_to_fits.py b/beast/tools/convert_hdf5_to_fits.py
index b8654c73..c9cd0c6d 100644
--- a/beast/tools/convert_hdf5_to_fits.py
+++ b/beast/tools/convert_hdf5_to_fits.py
@@ -3,13 +3,17 @@
 import tables
 
 
-def st_file(file_name):
+def st_file(file_name, autotrim=False):
     """Converts HDF5 files (specifically from Ben Williams) into FITS format.
 
     Parameters
     ----------
     file_name : str (default=None)
-        Name of HDF5 file (will also be name of output file, with different extension)
+        Name of HDF5 file (will also be name of output file, with .phot.hdf5
+        replaced with .st.fits)
+    autotrim : bool, optional (default=False)
+        Whether to automatically trim column names that are too long for FITS files,
+        and will therefore make this function crash otherwise
 
     Returns
     -------
@@ -71,9 +75,7 @@ def st_file(file_name):
 
     # save everything to astropy table in a fits file
     print("making astropy table")
-
     new_table = Table()
-
     for tag in set0:
         new_table[tag.upper()] = np.array(data_dict[tag])
     for tag in set1:
@@ -81,13 +83,108 @@ def st_file(file_name):
     for tag in set2:
         new_table[tag.upper()] = np.array(data_dict[tag])
 
+    # Identify and replace too-long column names, if requested
+    if autotrim:
+        set0_trim, set1_trim, set2_trim = replace_largest_common_substring(
+            set0, set1, set2
+        )
+
+    # write to file
     print("saving to fits file")
     new_table.write(
-        file_name.replace("phot.hdf5", "st.fits"), format="fits", overwrite=True
+        file_name.replace(".phot.hdf5", ".st.fits"), format="fits", overwrite=True
     )
-
     f.close()
 
 
+def replace_largest_common_substring(set0, set1, set2):
+    """Finds the largest contiguous substring common to column names too long
+    for FITS key names
+
+    Parameters
+    ----------
+    set0 : list
+        set0, as produced by st_file
+    set1 : list
+        set1, as produced by st_file
+    set2 : list
+        set2, as produced by st_file
+
+    Returns
+    -------
+    set0 : list
+        set0, with any necessary tag trimming to allow FITS table to write
+    set1 : list
+        set1, with any necessary tag trimming to allow FITS table to write
+    set2 : list
+        set2, with any necessary tag trimming to allow FITS table to write
+    """
+
+    # Find all column names longer than 65 characters
+    sets = set0 + set1 + set2
+    indices = np.where(np.array([len(tag) for tag in sets]) > 65)[0]
+
+    # If no column names are too long, returns unchanged
+    if len(indices) == 0:
+        return set0, set1, set2
+
+    # Extract too-long column names
+    subset = [sets[i] for i in indices]
+
+    # Check the shortest possible shared string
+    shortest_str = min(subset, key=len)
+    max_len = len(shortest_str)
+
+    # Check substrings of decreasing length; break out when longest found
+    longest = False
+    for length in range(max_len, 0, -1):
+        for start in range(0, max_len - length + 1):
+            candidate = shortest_str[start : start + length]
+            if all(candidate in s for s in subset):
+                longest = True
+                longest_str = candidate
+                break
+        if longest:
+            break
+
+    # Raise exception if no fix possible
+    if not longest:
+        raise Exception(
+            "Some column names are too long to write to FITS table, "
+            + "but no shared string found to trim"
+        )
+
+    # Find maximum length of column names, and therefore how much trimming is necessary
+    longest_tag = np.array([len(tag) for tag in sets]).max()
+    n_char_trim = longest_tag - 65
+
+    # If longest shared string isn't enough, raise exception
+    if (longest_tag - n_char_trim) >= 68:
+        raise Exception(
+            "No shared string in column names is long enough to enable "
+            + "enough trimming to get column names short enough to allow "
+            + "FITS table to write without crashing"
+        )
+
+    # Use this to decide what replacement stirng should be, first checking if we can just replace - and _ characters
+    new_str_test = longest_str.replace("-", "").replace("_", "")
+    if (len(longest_str) - len(new_str_test)) >= n_char_trim:
+        new_str = new_str_test
+    else:
+        new_str = longest_str[n_char_trim:]
+
+    # Replace all colnames that contain our long shared string with the trimmed verison
+    set0_trim, set1_trim, set2_trim = set0.copy(), set1.copy(), set2.copy()
+    for i in range(len(set0)):
+        set0_trim[i] = set0[i].replace(longest_str, new_str)
+    for i in range(len(set1)):
+        set1_trim[i] = set1[i].replace(longest_str, new_str)
+    for i in range(len(set2)):
+        set2_trim[i] = set2[i].replace(longest_str, new_str)
+
+    # Return trimed column names
+    return set0_trim, set1_trim, set2_trim
+
+
 if __name__ == "__main__":
     st_file(file_name=None)