asking for rec letter 6 weeks in

[serenade]

I'm a first year PhD student and have an external fellowship application due at the beginning of November. I need a letter from my advisor, which would mean asking him at least by early October. However, by that point he will only have known me for about 6 weeks since the start of the semester. Doesn't seem like enough time to know someone well enough to write a good letter. Don't want to put him in an uncomfortable position. 

Has anyone ever successfully gotten a good letter from someone they've only known for a short period of time? 

[dr. t]

Your adviser in theory knows you pretty well on paper - they had to read your application. Plus, you getting grants makes them look good. Ask away.

[TakeruK]

Yes, this is a normal thing to ask for  

[rising_star]

Totally normal. Definitely ask. When I applied for stuff during the first year of my PhD, I used letters from my PhD advisor (who barely knew me) and my MA advisor (who knew me much better, having worked with me for two years). Good luck!

[littlemoondragon]

Echoing what everyone else said, it is normal. I asked my advisor to write a letter of recommendation within the first month of starting. So no worries!