Back yard imaging

Hi: I've asked this question before, but in a slightly different way. I would like to do narrowband imaging from my light-polluted back yard. I can place a pier in a corner of the yard approximately 50 feet from my two story home and most of my images would be taken to the west, directly over the top of the house, but minimally 10 degrees higher. Would the thermals coming off of the house interfere with the quality of my images. Thanks in advance for your answer. Bill Caspe

william caspe said:

Hi: I've asked this question before, but in a slightly different way. I would like to do narrowband imaging from my light-polluted back yard. I can place a pier in a corner of the yard approximately 50 feet from my two story home and most of my images would be taken to the west, directly over the top of the house, but minimally 10 degrees higher. Would the thermals coming off of the house interfere with the quality of my images. Thanks in advance for your answer. Bill Caspe

Hi Bill:

My personal guess is that the thermals off of your house would cause some image degradation, particularly in the evening after a nice sunny day when your roof is good and hot. No one can really know though, since the thermal behavior of each house might be different depending on roof type, orientation, season and so forth.

I think that you ought to be able to get a feel for the magnitude of any thermal effects visually. In other words, observe something over the roof and then observe something away from the roof. With a few back and forth iterations you ought to get a reasonable feeling for whether the roof affects your local seeing much.

Jim

I do a lot of imaging at our observatory in a light polluted industrial park. I routinely shoot to the west over our factory building and do not experience much degradation of the image. If you were doing planetary imaging, then indeed you want to avoid warm roofs. Long exposure deep sky cannot resolve those finer details and would not be affected the same way, at least in my experience.

Attached is an image I just took last night, most of the 20 frames were taken directly over our factory building. Even with our severe light pollution, stacking 20 x 10 minute exposures produced images of faint galaxies down to mag 19.6 with the 8300 chip. lens size is 167mm, focal length 1000mm. resolution of stars was approximately 1.8 arc seconds FWHM for each of the 10 minute exposures.

Attached Image: