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Yet Another Site Comparison, David McClain

Yet Another Site Comparison

Yet Another Site Comparison, David McClain

Yet Another Site Comparison

Description

Raw H channel frames courtesy of Deep Sky West Remote Observatory in New Mexico, USA. (deepskywest.com) Data obtained with FSQ 106EDXiii / QSI683wsg / Lodestar / Paramount MyT.

This comparison should be more accessible to most people who do not have decades of experience interpreting FFT images.

We can tease apart images into wavelet layers where each layer emphasizes features of a particular scale length in pixel size. Most often, the second smallest scale layer, not the smallest, contains the lion's share of feature edge structures. And I will frequently boost that layer's contribution to finished images by just a hair to help bring out more detail. The smallest scale layer is dominated by pixel noise and so not as useful.

This image compares that layer #2 on the left for the integrated H channel image from Rowe, NM, and on the right for my integrated R channel image taken from my best attempt in my backyard. Clearly the signal to noise ratio of small scale features is higher in the left panel. I first downsampled both images by 2x2 to remove all the effect of my Bayer matrix in the comparison. Our respective exposures are about equal - aperture area times duration times number of subframes, so differences in the SNR are only attributable to site differences, not exposure differences.

If equipment were the sole determiner of what is possible, I should have the advantage. My aperture is twice as large, making my diffraction limit half of what the Rowe, NM Takehashi can do. And my pixels are 10% smaller on the sky than the imaging system in Rowe, NM. Yet I clearly cannot hold a candle to what the "inferior" equipment in Rowe, NM can do.

What remains is the site difference between my backyard and the site in Rowe, NM at DSW.

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Yet Another Site Comparison, David McClain
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