When to stack for sharpness with objects at infinity?

[irandar]

Hi folks,

I have taken 5 mountain shots on a tripod and wonder if stacking could improve the result. It seems it does not. A single frame is always sharpest. I have experienced this also with moon shots. Maybe with good lighting conditions this is always true. Could be different with very dim objects. Thanks for your help.

[John Rostron]

Why should you expect stacked multiple shots to give you a shaper final image?

Were your five images taken with identical settings? What stack setting did you use (mean or median)?

John

[irandar]

I did not expect anything but was just experimenting. It was set on median, same settings. What would you expect in this case? Thanks

Irving

[NotMyFault]

You can only achieve sharper images by stacking for certain frame conditions:

• unsharpness is a result of noise. You can remove noise by stacking. This mainly affects high iso captures.

you cannot increase resolution by stacking in Affinity Photo (alone). This can only be done by cameras who support pixel-shift by a fraction of a pixel 1/2 or 1/4, and combine multiple of those images. 

shots of nature, especially telephoto can capture lots of thermal noise and other atmospherical distortions. This often differ between the individual shots, leading to slight blurriness when stacking. You can somehow cheat the system by using focus stack instead of simple stack, as focus stack tries to identify the sharpest pixels from all frames and combine them. 
 

Always inspect the single images. Often one or more are sub-par. Remove them.

if using a tripod, deactivate image stabilization / vibration control. Otherwise it could amplify shakes. Some modern lenses / cameras do this automatically.

If using long telephoto, use remote trigger or timer based trigger, and put as much weight on tripod as possible.