first lager forgot to get og. when to do diacetyl rest?

[blitz77]

well we brewed up our first lager the other night, unfortunately we were also kegging 3 other beers and i spaced getting an OG reading. beer is a maibock pitched with a 1.2l starter (stirplate)
consisting of 3 packs of white labs 8336 and went with 1gm dme to 10ml water ratio.

because of the fact that i am new to lagering i didnt know i should make my starter a week prior and made it about 24 hours before the brew so starter fermented for 24 hours and then sat in the fridge for cold crash for another 24 before i pitched

cooled wort and starter to 48f pitched and raised to 55 in a a little over 24 hours
after that i ended up dropping temp to 52f (right in the middle of optimal for 8336)

since i spaced the OG i am wondering what would be a good way to tell that it is ready for a diacetyl rest.

i know it isnt anywhere near time just wanting to know what signs to look for to know that it is time.

this is a pic after about 22 hours, plenty of activity.

 

[waldoar15]

I brew mostly lagers and I don't get too wrapped up in timing the D-rest. Usually because I brew, then leave for a couple of weeks. I do it when I get back, then cold crash. Works for me.

The rule of thumb some go by is about 3/4 way to expected FG.