Stacking wide angle shots in DSS with scenery. Help!

[StargeezerTim]

Hi folks,

I have taken some wide angle shots of the milky way on a fixed tripod with some buildings etc at the bottom of the frame to give an effect. The trouble is that when it stacks the subs, it is aligning on the buildings and the stars are either long lines or smudged. The scenery itself is sharp, whereas it should be smudged with the stars sharp.

I have used sigma clipping and average stacking modes but it is not working, it is aligning the background instead of the stars.

Any suggestions for settings or ideas please? I am trying to stack various runs from 30 subs upwards.

 

Thanks in advance, Tim. 

[wimvb]

Stacking buildings, that's a new one.

But as far as processing sky and foreground goes, the general approach is to isolate the two and process each individually using clever masking. I've seen a pixinsight tutorial about this. Without stacking though.

 

Wim

[happy-kat]

I would be inclined to use the dss tool of picking the star(S) to force an alignment on. I've not had this trouble with buildings.

On your final stacked image post process you then would reduce/remove the blurry buildings and replace the building bit from a single frame of a cut off the buildings with a little of the immediate sky to then create one image.

[dph1nm]

Be aware that DSS does not correct for lens distortions. This is potentially an issue for wide angle lenses on a fixed tripod, because the stars move relative to the lens field of view between shots and so it is not possible to stack them accurately over the whole field - depends on your lens of course. One way round this is to correct for the distortions using software (often provided by the lens or camera manufacturer) before you stack them.

NigelM

[StargeezerTim]

Thanks Kat,

Not sure I know how to force or select stars, I'll look into that, but if you know how to do that, please let me know!

I attach a couple of images to illustrate the problem. The first is of a stacked image of 60 X 15 sec subs. The second is of one of the subs.

 

[happy-kat]

Use the comet mode stacking function to mark your alignment star and then the stacking option of stars on the comet tab that then appears on the stack settings.

Also look at the edit stars mode (the red star) in the same menu where you have the comet option.

Try each one and see how it goes.

[StargeezerTim]

1 hour ago, happy-kat said:

Use the comet mode stacking function to mark your alignment star and then the stacking option of stars on the comet tab that then appears on the stack settings.

Also look at the edit stars mode (the red star) in the same menu where you have the comet option.

Try each one and see how it goes.

Thanks... I've tried removing the 'stars' from the foreground, but it still stacks the foreground, not the stars. Also tried selecting a star as a comet. Could not find a comet tab though. perhaps I am doing something wrong. In any case, it is not working.. so I am going to give it a rest and try again tomorrow!

[happy-kat]

Register images.

Then pick first light in list.

There is now a small toolbar with 4 icons. That is the menu where you could use the comet and pick you brightest star as reference, save then move on a select that star on the remaining lights. Now when stacking there is a comet tab chose comet.

Try that for try one.

Do another with fresh files and try the red star on same menu.

Have a read of deep sky stacker online manual/help.

[StargeezerTim]

11 hours ago, happy-kat said:

Register images.

Then pick first light in list.

There is now a small toolbar with 4 icons. That is the menu where you could use the comet and pick you brightest star as reference, save then move on a select that star on the remaining lights. Now when stacking there is a comet tab chose comet.

Try that for try one.

Do another with fresh files and try the red star on same menu.

Have a read of deep sky stacker online manual/help.

Thank you Kat,

It worked eventually using the align on comet function. I can get on now and produce a decentish image. M 15, 16 etc should be in there somewhere! This is one with 10 subs stacked, when I modify and save all 60 subs, it should process better. Also I have to superimpose the foreground, thanks to the problems I had, I now have a good stacked foreground to use!

I've learnt more about DSS through this. Trial and error plus Stargazers Lounges lovely membership does the trick again. Cheers... 

PS. the image was taken in Majorca last week... there are more to process where the Milky Way was so clear... I cant wait to see what is there when I get time to process them all...

[happy-kat]

That worked the images are so different.

[StargeezerTim]

13 hours ago, happy-kat said:

That worked the images are so different.

Just in case anyone has similar problems, I had more problems when I tried to stack all the images. It turned out that all the false stars that were contained in the foliage of the foreground, needed to be removed from each image to get a proper alignment, even using 'comet' mode.

Hurrumph....

[Stub Mandrel]

On 04/07/2016 at 00:07, StargeezerTim said:

Also tried selecting a star as a comet. Could not find a comet tab though.

I've managed to get the comet tab top appear by sacrificing a cockerel at Full Moon. I don't think there is another way.

[StargeezerTim]

21 hours ago, Stub Mandrel said:

I've managed to get the comet tab top appear by sacrificing a cockerel at Full Moon. I don't think there is another way.

I never thought of that...