I've read 10 fold, not 20 but I'm not sure which is more accurate. He didn't use a telescope but that doesn't mean he didn't have new equiptment. He had equipment specially built, some of it, 10 feet high.
This article describes some of his equipment. Nobody before him used equiptment this good.
He more accurately measured the placement and precise angles in the sky of many stars and planets with 10-20 times better accuracy than anyone before him. He didn't use a telescope but that didn't matter. He didn't look deeper into the solar-system or universe, but he mapped it more accurately.
It was Brahe's accurate placement of Mars that helped Kepler work out his laws. There was even a rumor that Kepler killed Brahe to get full time use of his observatory and his notes on Mars, but exhumation provided no evidence of that. Brahe was known for his voracious appetite and partying and is thought to have died from excessive drinking.
The telescope didn't really help Kepler with his work either though he used one. Kepler's skill was primarily in mathematics, which helped him work out the laws of orbits.
Galileo, who came about the same time as Kepler, but in a different part of Europe, built a better telescope, that was also a 10 fold leap forward. The Telescope was instrumental in some of his key discoveries like Jupiter's moons and the phases of Venus. I don't know if Kepler had access to Galileo's telescope. It was considered a military secret.