I can verify that problem, Pierre.  The original Lynd’s Catalog from 1962 shows LDN 2 at coordinates RA 18 4 Dec -31 30 which, once converted to epoch 2000 coordinates, gives RA 18h 07m 14.6s, Dec -31° 29m 35s, almost exactly what you got when plate-solving your image. 

 

This is indeed where Guide shows LDN 4, which has the size of LDN 2 (1.24 sq. deg) listed for it as well.  Guide shows nothing at all in the spot where LDN 4 should be according to the epoch-corrected coordinates from the Lynd catalog (RA 17h 2m 30.1s Dec -22° 12m 15.2s)

 

I searched through the Guide folders and subfolders doing various text searches and cannot find where the LDN data is either.

There are lbn and ldn folders under nebulae. Guide uses these catalogs in FITS format which aren't human readable. If you have a copy of "fv" you can read them. http://heasarc.gsfc.nasa.gov/ftools/fv/
Andrew

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