The pair is about 30 million light years and this distance estimate makes M51 as large as M31 in Andromeda.
Photo Information:
Date: 4-1-2000
Location: Fremont Peak, Ca
Time: 1:30 am
Telescope: Celestar Deluxe 8" at f/6.3 with Lumicon Easy Guider and Compressor.
Camera: Olympus OM-2
Film: Kodak PJM 400
Exposure: 45 minutes
Note: two cars drove by during the exposure of the picture. I was obliged to cover the Telescope and therefore losing the guidestar. When i opened the lens again the star was almost out of the eyepiece field of view. That, together with some alignement problem created the drifts visible in the stars.