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PixInsight => General => Topic started by: FlyingBeagles on 2018 July 23 03:07:46

Title: ***SOLVED*** Image (not star) alignment question.
Post by: FlyingBeagles on 2018 July 23 03:07:46
Hi All,

Have recently gone through the process of registering and stacking a series of LRGB and HSO images taken over a few nights.  No probs, the images stack well.  The process for registering was using one great LUM image as my reference in image registration for all the series (this worked much better than registering in batches based on filter).

My question (for which I am certain there will be a ridiculously easy answer) is when cropping, I use DynamicCrop to size based off my 'worst' image edges but the resultant images do not then align (if that makes sense).  So for example, if I crop the LUM and Ha using the new instance feature, the stars are out of whack from each other.  In products like After Effects (I do post production work among other things) aligning one over the other is pretty straight forward but I am having a seniors moment with this.

I suspect the answer is somewhere in moving the centre x, y / anchor x, y point but am not certain.  Unfortunately, the internet assumes that noobs like me would know how to crop an image so that the different images align and so I couldn't find much on this particular problem.

Of course, it's always a bit embarrassing posting a question to a group of highly skilled folks so please forgive in advance.

Title: Re: Image (not star) alignment question
Post by: Geoff on 2018 July 23 03:34:15
The procedure is:
1. Set your desired parameters in DynamicCrop
2. Save a new instance icon
3. Apply DynamicCrop to the first image
4. Close DynamicCrop
5. Drag the new instance icon to the other images you want to crop.

I am assuming all the images have the same dimensions initially.
Title: Re: Image (not star) alignment question
Post by: FlyingBeagles on 2018 July 23 04:47:24
Thanks Geoff,

Yep, initial images are the same size.  Will let you know how it goes.

Title: Re: Image (not star) alignment question
Post by: FlyingBeagles on 2018 July 23 17:54:02

In the end, it was my Oiii Subs that were the culprit.  I was using a version of Geoff's suggestion below (I was doing steps 1, 2 and 3 but instead of closing minimised and then did step 4). 

Using Geoff's steps, I carefully checked each crop against the "master cropped image" and they all aligned bar my Oiii.  So I went back to basics and did a dynamic star alignment on the Oili series against the master ref image (rather than relying on the automated process). 

It worked - when I applied the saved dynamic crop instance, it now aligns with the master cropped image so all good.

The Oiii subs were over two nights one at 300 and one at 600 seconds.

Thanks for your help Geoff, it confirmed I wasn't far off the mark and got me on the right track.