DASCH, the project to digitize the collection of glass plates at the Harvard Observatory, have now come to end. With data release 7 is the southern galactic hemisphere now available. I have spent the last months to update my database of Mira maxima with the new data from DASCH. About 3500 new maxima was added and the total is now 74800 maxima for 510 Mira stars.
The database is available as O-C diagrams at http://var.saaf.se/mirainfooc.php or as period diagrams at http://var.saaf.se/mirainfoper.php
Some extra interesting stars that received new data are LX Cyg and DO Her. LX Cyg is a Mira well known for its large period increase from 1970-2005. Before that, it was assumed to have had a stable period. With the new data it appears that the star also had a previous period increase and from what I can see the period has varied approximately like this:
1890-1910; Plateau at 425 days
1910-1925: Increase from 425 to 460 days.
1925-1970: Slow increase from 460 to 470 days.
1970-2005: Rapid increase from 470 to 585 days.
2005-2024: Slight decrease from 585 to 580 days.
DO Her appears more and more like another Mira with a continuously decreasing period. From 1897 to now, the period has decreased from 222 to 210 days. In its behavior, it is very similar to WX Her. Both are short-period Miras with the same rate of decrease, 0.045 days/cycle. However, for DO Her, the data series is 26 years longer.
Thomas Karlsson