To dither or not to dither?

I have two similar sessions on the galaxy NGC3628, the ‘dimmer’ member of the Leo Triplet. One session was done without dithering, the second session with dithering. So maybe it’s educational to really compare the two results and verify what the effect is of dithering?

NGC3628 36x300S 800ISO Nikon D750 Esprit 120mm F7 NON DITHERED
NGC3628 54x300S 800ISO Nikon D750 Esprit 120mm F7 Dithered

The difference in background noise should be clear.

To be complete: the dithered image was 54x300s or 4hrs 30m exposure, while the non-dithered image was only 36x300s or 3 hours of exposure. Both nights were equal in quality.

Seeking the resolution limits of the Esprit

The Eskimo Nebula in Gemini is a very small object. It’s comparable to Jupiter in apparent size. It’s also a lot dimmer then Jupiter so longer exposures are required. The ASI184mmPro has small pixels (smaller then the ASI290) and could, when seeing allows, bring out the finest details. The diameter of the planetary nebula is 48″ !!! Here is my attempt from last Monday:

400x4s Luminance, 140x8s Green, Blue and Red by Gain =333 No Guiding

An intermediate NGC3628

This galaxy is the third member of the Leo triplet. During the last nights I could image this with the Esprit120mm and the ASI183MM Pro. This intermediate result is L-filter 6hr36m of data processed in APP and cropped. Best seen by clicking on the image!


NGC3628 ASI183mm Pro + Esprit 120mm + SW Flattener + No Reducer, No Filter

And below is the equivalent image taken with the Nikon D750 DSLR. I had a lot of noise in this 3hrs picture (36x300s), I suspect something went wrong with the dithering. The tidal stream is just visible.

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