I need some help please. I’ve just processed a solar photo that seems to produce a high resolution that seems quite unlikely.
Here’s the photo that I’m having some trouble believing.
Please note the very small sunspot group at the bottom of the arrow, then the enlargement (the posted photo is not at full resolution).
The photo in question yields an apparent image resolution of ~0.15 arc-seconds. That seems most excessive. Dawes’ limit for my ‘scope is 0.57 arc-seconds. To make it even less believable the photo was (carefully) shot through an open window (my balcony didn’t face the sun at the time).
- ZWO ASI178mm camera (2.4 microns).
- 20 cm SCT ‘scope operating at F5.6 resulting in an effective focal length of 5.5 meters (including the camera).
The nearly whole solar image was the result of stacking 540 frames then drizzled at 3x and sharpened several times. The insert enlargement was shot separately using the same equipment but used 14-bit ROI and then selecting the best 10% of 3,400 frames.
The insert was heavily processed by…
- Drizzling at 3x, then re-sampling upwards by 3x more.
- 2-3 layers of sharpening tools separated by light blurring.
- Applying a variation of HDR to expand the dynamic range.
My questions are…
- I calculated my image resolution manually by taking the fraction of the image that is occupied by the smallest feature that I can resolve and then multiplying that fraction by the photo’s dimension in arc-seconds. I know this is not the same as resolving a double star used for calculating Dawes’ limit as it’s subjective. Is this sound?
- Is there a web page somewhere where I can upload a photo and have it measure the photo’s image resolution (not plate-scale)?
- I processed the insert photo for maximum resolution but it comes at the expense of a less natural rendition. Might there a way where I can do both?
I’d appreciate some enlightenment please.