Astromart provides a level of service that is unparalleled in the used equipment market. 99% of my used gear came from here. If you buy "used" from any other source you are taking a much greater risk with your discretionary funds. Do your homework!
That stated, the other places I have occasionally purchased used gear from include eBay, astrobuysell, and craigslist.
There is only one constant in our infinite universe; it is change.
AP178 F/9, C11, C8, ED80, TV-85, TV-102, SW120ED, 6"Cave F/8, Solarmax 40, DM-6,
Losmandy Titan 50 GEQ, G11, AP800, Denk BVs, 7x50 Fujinons, 10x50 Nikons, 15x70 Astrophysics,
16x70 Fujinons, 22x100 Oberwerks, Sim Picheloup CPT, Canon 40D, 60Da, Vixen Polarie, SXV-H9,
DMK 41AU02, DBK 21AU618, Shelyak Lhires Lite Spectroscope
Vice President, City Lights Astronomical Society for Students (CLASS)
President, The Texas Astronomical Society of Dallas (TAS)
Select Member/Volunteer, 3RF Comanche Springs Astronomy Campus
Operations Team Lead, Texas Star Party 2013 (TSP)
NASA-JPL Solar System Ambassador (SSA)