I personally Ascended pre-200 and within a day was smashing through Ascension levels, so I don’t think it is that important to stick to waiting until 1000. This gives you enough Heavenly Chips to get a bunch of extremely useful upgrades that will come in handy for future Ascensions.
That being said, a very famous cookie clicker guide says to Ascend first at 400 levels. There are different tribes of Cookie Clicker players that say different numbers, with some even saying you should wait until you are into the several thousand, but if you’d like to Ascend early, 200 is one of the best times to do so. The general rule of thumb for Ascending in Cookie Clicker, especially the first time, is at least 200 prestige levels.