Palomar vs TRO

I wondered how today’s CCD cameras compare with the old film cameras. So just for the fun of it I found a picture of the Horsehead Nebula that was taken on film by the 200″ aperture Palomar Telescope (at the time the image was taken it was the largest scope in the world!) and compared it to the former scope at TRO with an 8″ aperture and digital camera. As you can see in the images below, the film image is much less grainy and more details can be seen than the 8″. The image from the smaller scope at TRO has trailed stars from guiding errors. However, the TRO image shows up well for an instrument that is 192″ smaller! What this really demonstrates is how much more efficient the digital cameras are at recording light. The ST-7E at TRO records around 82% of the light and film records around 5% (unless it is chemically enhanced to get 10%-15%). So an 8″ scope actually performs like a much larger one with a CCD camera versus the same setup with film. The top photo is from the 8″ short focal length reflector and the bottom image is from glass plates taken with the Palomar 200″

horsehead cropped 2
8″ Newtonian with a digital CCD camera
horsehead palomar transparency from museum small
200″ Palomar telescope using a glass photographic plate. There will be some detail loss due to compressing and digitizing the image to put it on the internet.