Take a look at the EXIF data for the photo that was bright, but not sharp. Make sure the aperature was at the largest possible for your camera (smallest f/stop value).
Next, look at the shutter speed. Likely the "blurriness" is due to shake (any unintentiional camera motion while the shutter is open). If you brace yourself against a post, wall, ... you can manage much longer exposure time. Do some practicing near your computer so you can quickly download the picture and look at the details for sharpness. You will quickly figure out what the longest shutter speed you can use.
Keep in mind that the longest shutter speed depends on the focal length used. You will need a shorter time for longer lengths.