Hi Humayan.
Great first shot
Your first real astro shot is something that will stick with you for a long time. It's a real kick to get started on this journey.
ditto to what has been said above. Stacking multiple images is definately the go. As John H says you should be able to get around 20 sec for a crux shot. But why not get yourself a piggyback bracket for your LX90??? You will still get field rotation eventually but you will be able to get longer than 20 sec. Depending on the direction your are shooting (ie pole or celestial equator) You may be able to ge a minute or more of usable image at 50 mm. Strange as it seems but if you mount it on your LX90 and as long as you aren't pointing near the zenith/meridian, then shooting at 0 deg dec will probably give you the longest shot. Opposite to the still tripod shots.
As a comparison, I did a crux shot similar to yours a few months ago using the 50mm f/1.8 (Check here
http://www.iceinspace.com.au/forum/s...ead.php?t=2731) Makes a hell of a difference if you can lengthen your exposure times. All the images are 240 sec stack. On an equatorial mount though.