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oldannie

Is there a way of minimising aircraft trails?

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My last attempt at imaging was dominated by aircraft trails more than usual even though I was only using 300sec exposures. I know that they are a fact of life  have read somewhere that aircraft trails can be minimised by setting 'careful pixel rejection' .  I use DSS  for stacking - can this be done in DSS or is it time to look for a slightly more sophisiticated stacking software.  I know Pixinsight is not something I would cope with and wondered if APP would be a natural progression for me?

 

Annie

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Kappa Sigma stacking in DSS will reject pixels that are too far from the norm and works very well at removing aircraft and satellite trails.

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You could try ground to air missiles but they can leave a vapour trail.

Other than that as above.

Regards Andrew 

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Thanks bobro - I always use Kappa Sigma but it doesn't seem to have made much difference on this occasion - perhaps Andrew's suggestion is the only remaining option! 😏

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My 2p:

PI is not that hard to get to grips with , for me its just a different interface to say for example photoshop, also when I moved from PS to PI I actually found the processing process to me more logical and structured.

However to be on topic , I sometimes get one or maybe two subs with plane trails and as I am doing a lot of subs I normally just dump them. Not sure if APP can get rid of them , never used it.

 

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Thanks Paul - I am tempted to at least try PI.  Like you I try to do lots of subs and so am usually happy deleting just one or two.  Recently the weather has not been up to lots of subs.  I managed just 17x600sec LRGB on the Whirlpool Galaxy a short while ago and 12 had aircraft trails - ah well!

Annie

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4 minutes ago, oldannie said:

I managed just 17x600sec LRGB on the Whirlpool Galaxy a short while ago and 12 had aircraft trails - ah well!

The default Kappa Sigma setting for Lights (image attached) normally works pretty well. I understand a minimum of something like 6 subs is required, though I have never gone that low in number. Per Channel Background Calibration is used to adjust to differences in sub brightness so that Kappa Sigma works effectively. As long as the aircraft trails (lights) are not in the same place, Kappa Sigma stacking should remove the offending pixels.

If you wish to post the subs on a file sharing site and put a link here, I'm sure you will get help with using DSS.

Bob

Kappa.jpg

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Thanks Bob - I'll have another look at my subs and check my DSS settings.  I use Per Channel Background Calibration and Kappa Sigma but will double check tomorrow and then try and post my subs - I may have difficulty with that as we have a pathetic broadband speed which means Dropbox won't work.  I will try as I would appreciate the help.

 

Cheers

Annie

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Median stacking is a simpler method that just picks the central sub pixel value based on the number of subs sorted by pixel value. Doesn't quite give the same noise rejection as Kappa Sigma but is better than an average value which includes a fraction of each sub. Worth a quick try perhaps?

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Yes I will try that.  Until now I've been reluctant to try different methods in general with my imaging.   I usually find something that works (eventually!!) and stick to it but have a bit more confidence now to try different things.

 

Thanks

Annie

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Kappa sigma pixel rejection generally does a good job if you increase the rejected fraction. PixInsight has large scale pixel rejection that works extremely well.

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Only just seen your reply Wim - apologies.  Will try increasing the rejected fraction and maybe even Pixinsight one day!!

Thanks

Annie

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Most astro software programs have combine sigma reject algorithms that will do a good job. The secret is to have many sub exposures for the software to be effective. Generally, more than 10 subs will easily deal with aircraft trails. You shouldnt need to buy new software!

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If you are patient and have a steady hand  you could manually remove them in each sub using the PS Spot Healing Brush Tool 🙂

At least it lets you get some kind of image out of your hard won data.  It also keeps you occupied when it's raining.

Pixinsight has a Pixel Math process which makes removing trails a lot easier.  Though they still have to be removed on each affected sub prior to stacking to get the best results.

Edited by wornish

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2 hours ago, wornish said:

Pixinsight has a Pixel Math process which makes removing trails a lot easier.  Though they still have to be removed on each affected sub prior to stacking to get the best results.

As I wrote before, PixInsight has large scale pixel rejection, designed for just this. Set a sub without trails as a reference. No need to increase ordinary pixel rejection (sigma clipping), hence no loss in signal to noise ratio. And no need to correct each sub.

Have a look here (first an ninth post in this thread)

https://pixinsight.com/forum/index.php?topic=11067.0

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21 hours ago, wimvb said:

As I wrote before, PixInsight has large scale pixel rejection, designed for just this. Set a sub without trails as a reference. No need to increase ordinary pixel rejection (sigma clipping), hence no loss in signal to noise ratio. And no need to correct each sub.

Have a look here (first an ninth post in this thread)

https://pixinsight.com/forum/index.php?topic=11067.0

I completely missed that.  I  wasn't aware of the new feature in 1.85.  Thanks for pointing it out .👍

Edited by wornish

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I often have lots of aircraft trails and number of subs in the DSS stack effects success. Less then 10 I find not effective, personally I aim for more than 20 at least. As always the more subs the better.

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