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davefrance

By davefrance
in Imaging - Deep Sky

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davefrance

davefrance

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Yep - same lens.

OK but I think that there will be a long wait as the forecast here is not good to say the least. Looks like the whole week will be a no no. I only just managed last night before the clouds rolled in.

Thanks again.

Peter

Here is an almost identical view to yours, taken the other night. Single frame, didn't bother stacking them as too much cloud drifting across. This was taken at the same settings f4.5 - 18mm - 30 secs - ISO 1600.

post-34685-0-24367000-1442150790_thumb.j

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PeterCPC

PeterCPC

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Early in the evening yesterday the skies were clear so I had another go. First I put the ISO up to 12800 and tried to get focus using the method discussed. I think that it was almost right but I can work on that more. I then did a run of eight 30sec exposures at ISO1600 in a similar area of the sky. I have attched a single 30 sec exposure (bear in mind that this is about 20:00 so the sky was not totally dark) and the result is not too bad. I also show the result of stacking the 8 exposures in DSS and there is obviously something going wrong here as there are trails again. I used the recommended DSS settings. When I have used DSS for DSO stacking it performs very well so I don't know what's happening with these short exposures from a tripod.

Any ideas?

Peter

post-35423-0-51603500-1442304234_thumb.j

post-35423-0-35449800-1442304447_thumb.j

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JamesF

JamesF

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The rotation in that image looks as though it is about a point within the image somewhere around 25% in from the top corner.  As Polaris doesn't appear to coincide with that point, I wonder if perhaps the tripod/camera mount isn't absolutely rock steady?

James

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davefrance

davefrance

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Maybe, but it did find plenty of stars once I turned off auto hot pixel detection - with it on it only found 1 star! It's a thought though. Thanks.

Peter

It's almost as if DSS is acting as "startrailing" software rather than "stacking" software.

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davefrance

davefrance

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Maybe, but it did find plenty of stars once I turned off auto hot pixel detection - with it on it only found 1 star! It's a thought though. Thanks.

Peter

Check DSS settings. If you go into Stacking Settings and click on the Comet Tab check that the "standard" mode is checked and not "comet" mode.

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Knight of Clear Skies

Knight of Clear Skies

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I suspect that DSS gets upset with fixed tripod stacking because of the offset between frames on a lens that produces significant distortion. It seems to match up part of the frame, I've seen this a lot in the 'getting started with imaging' forum.

Edited to add: to test this theory you could try stacking just the first few subs, to see if it is less distorted.

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davefrance

davefrance

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I suspect that DSS gets upset with fixed tripod stacking because of the offset between frames on a lens that produces significant distortion. It seems to match up part of the frame, I've seen this a lot in the 'getting started with imaging' forum.

Possibly, but as Peter is using the same lens as me and taking a similar view why should it get upset with his and not mine? 

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davefrance

davefrance

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Right, I have stacked the first 3 images and it is definitely better - ignore the colour. so what does this prove do you think?

Peter

I think it is still revolving around the star on the left top. Have you checked the comet settings?

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davefrance

davefrance

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Any other ideas?

Peter

Not really, I still think DSS is not performing as it should for some reason. The only  thing I can suggest is that you un-install and then re-install DSS to make sure no bugs or perculiar settings have crept in. Sorry.

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davefrance

davefrance

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I just tried using Nebulosity and voila...

So there is obviously an issue with DSS but I just have no idea what it might be.

Peter

Well done, at least you know it's not you or your equipment. Again I would try uninstalling and reinstalling DSS.

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PeterCPC

PeterCPC

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Had another go last night just before the clouds rolled in so it was a bit too early plus the Moon was up. This time I used a Samyang 14mm lens which is so much easier to focus - just set it to infinity. 10 frames @ 30secs iso 1600. I just need a dark sky now.

Peter

post-35423-0-03204700-1442918880_thumb.j

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