For additional information, follow this link to a White River NF publication on this trail: https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5186764.pdf
Though the mileage to Cathedral Lake sounds minimal, with nearly 2,000 feet of elevation gain, plan on taking more time than you figure. The trail #1984 begins by going up through aspen forest (beautiful in the fall) and contours SW above the Ashcroft Ski Touring area and the Pine Creek Cookhouse to eventually reach the Pine Creek canyon drainage. The trail remains on the north side of the creek all the way up and enters the Maroon-Snowmass Wilderness increasing in steepness. As the terrain opens up, the trail goes through some sets of switchbacks. Then it enters an upper area with more willows than trees. There will be a section that crosses a larger talus field and after that, the trail gains steeply up a set of multiple switchbacks. When the trail tops out above the switchbacks, if you see any trail heading off on the right, it will be heading off for Electric Peak and Pass. Stay left to reach Cathedral Lake. The lake will be about 15 minutes more walking.
As the trail flattens out above the multiple switchbacks there is an area of designated? primitive campsites, but there are numerous camping opportunities elsewhere. Camping on the lake shore is neither allowed nor practical. There is a knoll on the east side of the lake that has some nice spots near these coordinates with a couple less used trails that lead to the area. See coordinates below. Bear cannisters are required for backcountry camping here. Also, White River NF requires a self-register overnight permit to camp here. You can register at the trailhead. No fee is required. Dogs must be kept on leash.