Sorry if these instructions are spotty, doing it from memory.
This trip will require backpacking gear and at least 2-4 days depending on your ability.
The Vallecito Valley is packed with people but once you reach the Johnson Creek juncture you should be free of pesky day hikers.
30 Miles round trip.
From Durango or Bayfield, head to Vallecito Reservoir. Take the road all the way to the Vallecito campground/trailhead north of the reservoir.
Park in the parking lot for the trailhead. **Caution** my car was broken into during this excursion and I stupidly left my wallet in the car. Fortunately all ended well. That's a whole different story.
Take the Vallecito Creek Pack Trail north for 8 miles until you reach the Johnson Creek split in the trail. You will take the Johnson Creek trail to the west until you decide to camp... unless you decided to camp before this point. From the beginning of the Johnson Creek turn-off to the top of Jupiter is roughly 7 miles.
Once you get about 3 or 4 miles up the Johnson Creek trail, you can find some great camping on the right hand side of the trail. I was blessed to be camped next to a church group of about 30 people from Missouri or Texas or something. Needless to say I was not happy...
Anyways. From here, you can reach the top of Jupiter fairly easily by going up to Columbine Pass and following the trail to the North east towards Hazel Lake. Once you are at the ridge between the unnamed 13165 peak and Hope Mountain you can begin going north towards Jupiter. There are no trails.
Once you reach the base of Jupiter its a straight forward scree climb straight up. I almost killed my dad on this climb so beware of the loose rock.
The views from Jupiter are outstanding, and the best part of this hike is you get to avoid Chicago Basin and riding the train.
Backpacking gear. Food for 3+ days. Camera for great views :)