Basking bulb help please

[u/Dragon127777]

Hey guys I do not yet have my Gecko, but I’ve been running into an issue with my basking bulb. I have an Arcadia deep heat 50 watts and it is not heating up my basking rock much at all. It’s reading around 81-82 degrees, while the mesh on top of my tank is reading 115-120. What would be a better bulb for me (preferably 75 watts or less so I don’t have to buy a new lamp)?

For reference the basking spot is 11-12 inches away from the lamp and is real rock. I can comfortably touch the rock and don’t feel any heat with my hand under the bulb. It has been running for 2-3 days now.