It takes HID lights about 5 minutes to reach full lumen output. Sometimes longer depending on the age of the bulb and the ballast used. You light sounds normal to me. Sodium bulbs emit a yellow/red light color.

If your attic is at body temp (98.6F) then it's too hot and you need vent fans to remove the hot air. Try to stay under 85 F and you should be alright.

Laterz