hi Han,

As promised files and log 

Fails when sub folder is present after DSS/AT and it reads the TIF files. I don't want it to read sub folders - no reason it should really. Anyway its an easy get round - just delete the temp folder created by DSS/AT

O.S. Files are just my std test files as used all along with ASTAP testing :-)

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[url] https://drive.google.com/open?id=1vzyhkM0NWEWz70FyJztQKLU9ysUVCzo3[/url]
link to files 

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13:09:09  █ █ █ █ █ █ Warning, could not find a suitable flat for ""! De-classify or add correct flat. █ █ █ █ █ █ 
13:09:09  Adding file: 6 "C:\Users\astro\Desktop\testatap\2017-08-12\M31\Lights\Plan_60_x_800_\60s\ATTemp\auto.tif"  to average. Using 2 darks, 0 flats, 0 flat-darks
13:09:09  █ █ █ █ █ █  Warning different size image!
13:09:09  Creating monochromatic x 4 binning image for solving/star alignment.
13:09:09  Will use mean value 18619 as background rather then most common value 580
13:09:10  Info: REDUCE OR REMOVE DOWNSAMPLING IS RECOMMENDED. Set this option in stack menu, tab alignment.
13:09:10  Not enough tetrahedron matches <3 or inconsistent solution, skipping this image.