I have a DSLR and when I take photos at night or in low light I have noticed bright spots will be seen a second time somewhere else in the picture. Almost like a reflection within the picture itself. I first noticed it when taking pictures of the moon. How do I stop this?
That's exactly what the problem is, internal reflections within the lens due to a high-contrast scene (the light value of the candles will be many, many times greater than the rest of the scene). This can be challenging even for some expensive lenses.
Reducing the scene contrast by increasing ambient light is one answer, either by increasing existing light or using an external flash with a movable/bounce head, so you can boost the ambient light by bouncing the flash off the ceiling (or a portable reflector etc.)
Stopping down the aperture may also help reduce the internal reflections, but reducing the scene contrast with increased ambient light will help more as you're already working in a low-light situation - stopping down will impact on the shutter speed, not helpful if any of your subjects are likely to move.
- Remove any filters screwed onto the front of your lens. The flat rear surface of the filter is perfect for creating reflections of light bouncing off elements in the lens, or even from the sensor stack itself.
- Use a lens with better anti-reflective coatings or a camera with a less reflective sensor/filter stack.
- Try to compose shots so that the brightest points in your scene have bright visual elements at the corresponding point in the cross quadrant to make the reflection less obvious.
- Make a mask for the front of your lens that blocks half the field of view. Then combine two exposures, one with the mask on the left, the other with the mask on the right (or you might do the same thing with a strong graduated Neutral Density filter). The reflections would still show on the "dark side", but you would mask them out in post processing when combining the two images.