[astro744]

Originally Posted by Averton

Thanks to all for your kind comments.
Astro744 - you are absolutely correct, the size of Triton is incorrect. There are two reasons for this. One is the use of a small aperture scope means that the Airy disk exaggerates the size of small objects. In this case the apparent diameter of Triton at that time was 0.13 arc seconds & the Airy disk for a 6" scope at 560nm is 0.939 arc seconds. This considerably exaggerates it's size by a factor of approx 7 times. The second reason was we made a mistake in processing as when we created the mask for the increased exposure of Triton, we didn't allow for the bloat created. We were just rushing a bit as we had been happy to actually capture Neptune close to opposition (17/9). Considering the weather we didn't think it was going to happen and this is probably as close as it will get. We have attached a corrected version of the image with Triton closer to an appropriate size compared to Neptune. The actual ratio is approx 18:1.

Nice image!