Star cloud just below the Lagoon Nebula and to the right of M22

[Brian W]

Last night wasn't promising. Then about 18:30 a hole started to open in the overcast. Ever the optimist out I went. For give or take an hour the hole stabilized. I concentrated on two areas: M4 and the star cloud just below the Lagoon Nebula. M4 to follow.

This shot is a combination of sixty colors, twenty flats and 20 offset/bias frames. Stacked in DSS and processed in Capture 1 Sony Pro.

The tracking technique was simple. Line up on a brightish star, take seven or so shots, re-align. Not exactly hi tech but it works.
ISO 3200 ~ Shutter Speed 3.2s ~ F2.8
Sony Alpha a58 ~ Tamron 90mm 272E

[xelasnave]

You must be very happy with the result.
Were you dithering intentionally???
Alex

[Brian W]

I am indeed. Admitting ones ignorance is a great way to learn: What's 'dithering'?

[Brian W]

I just googled dithering. I imagine that my slightly off re-aligns always in a different slightly off direction would produce dithering.
B.

[xelasnave]

I think it may.
At least you now know about it.
Alex

[Brian W]

thanks

[rcheshire]

Good one Brian. Dithering will improve your images significantly.

[Brian W]

I'm going to look into dithering just a little bit more than I have.

[rcheshire]

A simple dither method with a fixed tripod is to let the stars drift across the sensor between shots - say 5 or 6 seconds. After several shots check the framing and re-frame if necessary. Repeat the process as required. The stacked image should appear 'smooth'.

[Brian W]

I have a 2 second delay to avoid tremors from pressing the shutter. With slow reactions and buffering there could be as much as 5 or 6 seconds between some shots and at least three between most.