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Scale in ArcSeconds?
Posted: Tue Mar 01, 2011 4:30 pm
by DavidBartlett
Is there any way that I can find the scale in ArcSeconds directly on the Picture for the APOD?
Re: Scale in ArcSeconds?
Posted: Tue Mar 01, 2011 4:55 pm
by Chris Peterson
DavidBartlett wrote:Is there any way that I can find the scale in ArcSeconds directly on the Picture for the APOD?
Generally not. If you know the sensor details and the focal length of the lens, you can calculate the pixel scale. Those things can be found in the EXIF header if the image was made with a digital camera, and if the header was preserved. For most astronomical images, you usually need to perform a plate solve to recover the pixel scale, although this information is occasionally provided in the caption or in linked data.
Re: Scale in ArcSeconds?
Posted: Wed Mar 02, 2011 5:08 pm
by DavidBartlett
Thank you Chris. Is there a standard pixel scale for the Hubble Advanced Camera for Surveys?
Re: Scale in ArcSeconds?
Posted: Wed Mar 02, 2011 5:26 pm
by Chris Peterson
DavidBartlett wrote:Thank you Chris. Is there a standard pixel scale for the Hubble Advanced Camera for Surveys?
For the WCS, the plate scale is 0.05 arcsec/pixel. You have to be careful with released images, and those published on APOD, since they are sometimes resampled to different resolutions. Don't automatically assume you are seeing an image at the native resolution of the camera.