First try at widefield, any help/comments appreciated.

[pianorealm]

Hi.

I'm new to astronomy but really enjoy photography. I tried a few shots a couple of nights ago....well about 60 actually! I'm trying to work out what I've done wrong and what the 'semi halo' effect when I zoom in on the stars is caused by.

Any help or suggestions would really be appreciated.....and don't hold back......I've broad shoulders!

Nikon D200. On a standard tripod.

Image 1 f5.6 55mm 20 secs exposure

Image 2: F1.8 50 mm Prime lens 2sec exposure

Image 3 F1.8 50mm prime lens 2 secs exposure

Don't get me wrong...I'm glad I've captured the images at a first attempt but can't work out why there is a half light/halo/image on the stars.

Thanks, Howard

[Gonzo]

Some lenses are not at their best used in wide open, F stop down one click or two.

[davew]

My first guess would be because you're running at f1.8. I'm all for getting lenses wide open but most 50mm lenses won't have it.

As you seem to have a darkish sky try closing down in stages and test. I imagine the best results will be at f4 but f2.8 may just be workable.

There's only one lens I've seen that gives good results at f1.8 and that's the Canon 200mm.

Dave

[Leveye]

The lens is not coated well enough and you're getting some chromatic aberration wide open Either stop down a click or 2 or get what they call  a "purple fringe killer" filters if you want to try those. Personally i don't like starbursts on everything from stopping down so i try to edit them out in post. The only great camera lenses that this is a non-issue with are Mamiya, Canon and Nikkor ed all in f2.8 everything else you have to deal with this.

[pianorealm]

My first guess would be because you're running at f1.8. I'm all for getting lenses wide open but most 50mm lenses won't have it.

As you seem to have a darkish sky try closing down in stages and test. I imagine the best results will be at f4 but f2.8 may just be workable.

There's only one lens I've seen that gives good results at f1.8 and that's the Canon 200mm.

Dave

Thanks Dave. I'll give that a try.

To be honest,

I was under the mistaken belief that the wider the aperture the more light would be captured but didn't consider the lens might not be up for it.

I've a lot to learn!

Howard

[pianorealm]

Some lenses are not at their best used in wide open, F stop down one click or two.

Thanks.......this seems to be a common issue which

[pianorealm]

Thanks.......this seems to be a common issue which

Thanks for that. This seems to be a common issue which I wasn't aware of.......one more thing to learn......but that's why I really like this site. There is always someone willing to help and give advice...and do I need it!