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Messages - Lightpath

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General / Re: Background noise- Not sure where to go from here
« on: 2019 November 27 16:48:27 »
DM sent, thanks.

General / Background noise- Not sure where to go from here
« on: 2019 November 26 18:25:32 »
Hey all-

I'm very new to processing, and I've been following the Light Vortex tutorials.  I've so far done up to DBE, but I think I have some weird large scale noise and I'm not quite sure how to deal with it.  If anyone could suggest some tools to try next to deal with the background I would really appreciate it.  Again, I'm very new, learning as I go.  I'm not new to the hobby, just to processing.

Also, any thoughts on how to improve my data at acquisition time would be very helpful.  I image in a very light polluted area, so I'm taking 14 second images (TONS of them) with a CLS ccd filter, and then my plan is to use 60s narrowband images for colour.

Thanks for any suggestions!

The only way I could get a decent image with my current skill level is by using imgur, so here is the image and it looks pretty representative:


General / asi1600mm Bright Star Reflections
« on: 2018 October 22 20:34:53 »
Hey all, I'm curious if anyone has any idea how to process out these reflections from Alnitak...  I'm using an ASI1600mm pro cool and an 80mm refractor with a 300s exposure.

Maybe a synthetic flat?

Thanks very much for any thoughts about how to correct this, I have a fair bit of data with this problem.

General / Re: Guide or Tutorial for how to evaluate subs?
« on: 2018 September 26 23:47:39 »
Thanks Adam, I very much appreciate your insight and information.

ATM I'm not in a financial position to subscribe to your videos, but I think it's great that they are available!


General / Re: Guide or Tutorial for how to evaluate subs?
« on: 2018 September 21 15:30:42 »
I might say there are different ways of thinking about evaluating subframes. For example, for some data S/N is more important than resolution. So throwing out frames based on a strict range of PSF/FWHM doesn't make sense. In fact, as many people know that have watched me deliver presentations, I tend to find every excuse in the book to *keep* data rather than cull it. Too often, I feel, image processors throw out data without taking into account the proper usage of weighting and rejection. In fact the weighting given to a subframe is probably (based on signal or noise) more important than any of the other "beauty" factors (PSF, eccentricity...).

Say you had a set of 15 subframes. You are now well positioned to combine them with good rejection choices. If you only have 6 subframes, your choices are more limited and the calculus of what makes a good subframe changes. But back to the 15 frames... if you have 15 frames but 4 of them show wind shake or bad guiding (loss of guide star). Most people throw those frames away based on the subframe selection formula. In my opinion that is too draconian. Instead choose the right rejection method and parameters and use the frames with the proper weighting and gain the benefit of the added S/N improvement.

Just something to think about. I think the reason you aren't seeing that many answers is that there are a few nuances and variations to consider.


THIS is exactly the type of information I'm looking for.

This demonstrates a deeper knowledge of how to adjust both evaluating frames and stacking parameters to make the best use of gathered photons as possible.  How did you learn/figure out that knowledge?  I find it difficult to move on to higher level issues (removing background noise, colour balance, etc) without actually closing the loop on my imaging system, and making sure I'm getting the best data I can. 

Then I'd like to be able to take the data that doesn't quite make the grade, and salvage what I can.

I think you're right-  This is a very nuanced topic, but I think perhaps it's a topic that we don't discuss enough?

I am typically dealing with hundreds of subframes.  I have a tiny, low patch of sky to image in, and tend to image the same thing for many nights in a row in order to get lots of data.  I'd like to be able to evaluate and save as much of that data as possible.

Do you have a link to one of your presentations?

Thanks very much for your thoughts!

edit:  I found this page extremely useful:

General / Re: Guide or Tutorial for how to evaluate subs?
« on: 2018 September 20 22:22:28 »
I have, actually, I generally understand what they're doing, since PI is so awesome about variable naming, but getting an idea of "why" the FWHM should be within a certain range, as an example, is what I'm kind of looking for.  I generally understand what's being done in the equations, but I'd like to be able to say to myself "Ok, I know I want the FWHM to be in [foo] range because [bar].  I was just wondering if someone had written something up sort of like "This is how to make sure you're getting a good subframe" guide.

One of the things I've been struggling with is using the image evaluation tools to get my exposure length dialed in for example.  Yes you can use subframes that aren't taken with the optimal exposure, but it'd be better to just make sure you have excellent subs from the start, and tweak your system as much as possible to get the best data you can get.

Maybe I just need to keep digging and reading, or perhaps I'm approaching this incorrectly.

Thanks for the reply!

General / Re: Guide or Tutorial for how to evaluate subs?
« on: 2018 September 20 19:30:23 »
Wow, no one has any ideas?  :D

It occurs to me that getting the subs right is probably one of the most important parts of this process!

General / Re: Inside PixInsight the Book
« on: 2018 September 08 21:02:08 »
A section on evaluating subframes with some general guidance on what makes a good one would be awesome!

General / Guide or Tutorial for how to evaluate subs?
« on: 2018 September 08 16:41:39 »
Hey all-

There's so much wonderful information on this site, it's like drinking from a fire hose!

I was wondering if anyone had a step-by-step tutorial/guide on how to evaluate subframes.  I would like to figure out what my optimal exposure is for my setup.  I have followed many of those tutorials and used the excellent tools in PI but the results were only semi-conclusive.  I would like to be able to measure my subs and actually understand what makes a good sub-  That would help me tune my exposure time, and help me understand what I should keep and what I should throw away.

I've used the excellent subframe selector script and the amazing new subframe selector process, but I still find I don't quite know what I'm actually looking for in a good sub.  I would like to be able to thoughtfully create my own formulae for rejecting/accepting frames, rather than blindly copying those that I see around this forum.

My approach to Astrophotography so far has been to take one problem at a time-  For example, getting my focus working well, getting tracking working well, getting flat frames properly exposed, and now I'm up to processing, since I think I have my mechanical bugs (mostly) worked out, and I'm trying to take it one step at a time.

Thanks very much!


General / Re: Quick start guide
« on: 2018 September 08 16:36:43 »
I have found this site to be exceptionally well written and informative:

No doubt the author is on this forum.


New Scripts and Modules / Re: Subframe Selector PCL Module
« on: 2018 August 29 20:17:40 »
I'm really enjoying tinkering with this tool!  It's really well done.

My problem at the moment is that I don't have a good solid understanding of what makes a "good" sub.  Does anyone have a resource I could read that would help me come up with my own expression?

Thanks very much-


General / Re: 206 frames with 16MP cam is too much for PI
« on: 2018 August 22 20:59:31 »
I'm not sure it's the software you're having an issue with.   8)  I just did 331 16mp darks.

Then again, my system is an i7/32gb/ssd.  It's a bit of a beast.

General / Re: Trouble with 3d Doughnut
« on: 2017 April 26 12:43:40 »
I'm actually quite proud of myself-  I managed to get the mask sorted out!  Now I'm trying to figure out TGVInpaint.  :)

Thanks again, I'm not sure I'll figure this all the way out, but I'm learning a lot about PI in the process.

General / Re: Trouble with 3d Doughnut
« on: 2017 April 21 14:17:55 »
Thanks Mike, there's certainly a lot to learn here.  I'll start tinkering!

General / Re: Trouble with 3d Doughnut
« on: 2017 April 21 10:28:47 »
Just to show that you can sort of repair this type of problem without taking the final image to another piece of software here is what I was able to do quickly in PI. I used PixelMath, TGVInpaint, Rangemask and Curves. A little more care on my part and the repair could be better.


Do you have a hint as to how you created the initial mask with pixel math?



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