DSLR Antares and M4

[Brian W]

I know it's not much but it's a start. Using my Sony Alpha a58 and a Tamron 90mm 272E I took 9 shots and processed them in Capture 1 Sony Pro and Fiji. There was high thin cloud. Comments and critiques more than welcome.
ISO 1600 ~ Shutter Speed 3.2s ~ F/3.5 ~ Natural Light
Sony Alpha a58 ~ Tamron90mm 272E

https://2.bp.blogspot.com/-Ae9Oh9dFt7k/WWOJ1F-n6VI/AAAAAAAAaUM/mOilmKMCASUrNyQPgkevSjVCwdtbpZC-ACLcBGAs/s1600/m4.jpgSave

[raymo]

Right, you've made a start. Perfect focus is absolutely critical, and yours
is not spot on. How are you focusing? Does your camera have "Live View"?
3.2 secs is not going to show much, you need at least 10, and preferably
15 or more. The colour in the area surrounding M4 is strange, but that
can be looked into later.
raymo

[sil]

its hard focusing and judging focus, one trick I use in live view is focus VERY slowly as there is a slight delay between turning focus ring and the live view updating, so do this and look for Tiny dots appearing/disappearing as the stars on the edge of the resolution of the live view go in and out of focus, ignore the bright stars that are always there. Stop your focus when you catch the transitional ones on the screen when you step back from the camera. Take a single test shot anywhere in the sky and zoom in on camera to the jpeg and you'll see the difference between focused and unfocused.

[Brian W]

Hi Raymo, Manually focusing on Antares with live view. According to what I was told a 90mm lens with no tracking will soon show trails going much longer than 3 to 4 seconds? Bad pp for the colours.
Brian

[Brian W]

I'll give that a try. The DSLR equivalent to averted vision:)

[luka]

Brian, with some cameras/lenses I had perfect results using auto-focus on a very bright star (or the moon). After focusing this way I would change to manual focus and not touch it any more during the imaging session.
But as I said, this may not work for all cameras and lenses.

[Brian W]

The Tamron 90 has a stiff push pull for moving between auto and manual focus.
Brian

[Brian W]

This is a little better: