Confused lyra?

[GordonCopestake]

Took a few test shots tonight (a clear night!) of lyra/vega. This one is 9 subs of 30 seconds each at 18mm with the D70 registaxed together. I used vega because it was at zenith so LP was kept to a minimum. I dont understand though why i can see star trails that appear to rotate around vega not polaris? Am i just being stupid?

[GordonCopestake]

Hmm hang on thats a little large :shock:

edited, although now it looks parp. ffs

[Kaptain Klevtsov]

So? It looks like this after processing

Better? Took me 5 mins and I'm tired and emotional. Trailing is now obvious, as are many stars. Stupid? Nah. Grab some more and stack them, then get to grips with the software, CS2 doesn't bin the rotation, but other software does.

Nice shot, just needs more to stack and more processing.

Captain Chaos

[GordonCopestake]

Looks a lot better CC, this one was totally unprocessed other than stacking the 9 subs of 30 seconds each. The orange glow isn't so bad at zenith. The thing that confused me though was the star trails appear to be going around Vega, i thought they would all have gone around polaris..... I need to use 20 second subs to get rid of the trails but it was just a test shot.

[GordonCopestake]

Had a play and tried to get something a little better looking

[MartinB]

I am wondering whether it is edge of field distortion related to the lens rather than star trailing. Just a thought

[Kaptain Klevtsov]

The trailing comes because you selected Vega to align to with Registax. Vega therefore doesn't get trailed but the rotation shows up around it.

HTH

Captain Chaos

[GordonCopestake]

Ahhhhhhhhhhhhhhhhhhhh that makes much more sense CC, thanks!!

Martin you could be right, the lens i've used is the standard kit lens on the D70 and I doubt is of the highest quality. Although they cost £170 new so it shouldn't be dire

[MartinB]

The trailing comes because you selected Vega to align to with Registax. Vega therefore doesn't get trailed but the rotation shows up around it.

HTH

Captain Chaos

Yep, that would explain it!

[GordonCopestake]

If it's clear tonight i'll have another go and take 20 second subs with perhaps a higher ISO setting. Should get rid of the trails. How many subs is optimal with shots like this? The test above was 9 frames, there must be a cut off when more doesn't add much more to the image.

[Kaptain Klevtsov]

Its not trailing thats showing up, its field rotation after stacking. The individual frames should show very little trailing, if any, but over time the sky will rotate so you need to compensate for that. You can track the camera with a GEM or barn door tracker or you can align the subs either automatically or manually.

Captain Chaos

[GordonCopestake]

You are right CC but i am still getting star trails on single frames with a 30 second exposure. Going down to a 20 second exposure and perhaps a higher ISO to compensate should get rid of the trails. I'll have a play tonight. It's all a learning curve and im having fun actually with just me and the SLR rather than lugging all the 'scope and kit out. Spent all day playing with processing. Learning new stuff etc

[GordonCopestake]

I was trying to take some more shots but even though it was a fairly clear night a few high thin clouds insisted on drifting across my FOV and whilst usually this wouldn't bother me for visual the amount of LP they reflected back was staggering!

I'm begining to think this photography lark isn't for me hehe

[daz]

Nice colour!!! :shock: