I Need A Chainsaw! (M20 Trifid Nebula)

[JonCarleton]

I actually got two clear nights in a row!  The night before last I got a fair Eagle Nebula, so last night I went for the Trifid (M20).  The plan was for 100 shots at 60 seconds.  The execution, after review during stacking, yielded only 46 good subs.  This, due to 1 satellite pas, 1 airpane and a whole bunch of tree-limb-impaired images.  I have this really nice, silver maple that is in its full glory at the moment.  Alas, the upper branches were just a bit tall.

Still, I got 46 @ 60 seconds.  Radian Raptor, ZWO ASI178MC, PHD2, CCDciel, INDI drivers on a Pi4 Linux Ubuntu on the scope.  Processed on a Linux Ubuntu AMD64 desktop with Siril, StarTools and GIMP..

There seems to be a light area in the right upper corner that I should have addressed in processing.  Odd.  Can't think where it came from.  I am in a Bortel 4 area and the moon was not out yet.  No neighbors close buy.  A mystery!

 

Edited July 30, 2021 by JonCarleton

[ollypenrice]

Upper right and lower left corners show some strange, hard-edged artifacts.  I can only guess but they might be the result of vignetting aggressively over-processed. Did you take flats?

I don't think your focus is nailed and I would back off by a very long way on noise reduction. This has the 'vaseline on the lens look,' which NR produces. I'm not pulling any punches but giving you my honest 'quick assessment.'

Olly

[JonCarleton]

Oily,

Please do not pull any punches.  I am a rookie and make lots of errors.  Corrective suggestions are a help.  I am still getting used to the Raptor with the ASI187MC.  It doesn't act quite the same as the Skywatcher 250P setup and the autofocus seems to require more iterations for a reasonable result. 

I tried to get too much out of too few Lights with this image and perhaps got in a bit of a hurry to post.  I suspect there may be some "vaseline" effect resulting from the synthetic drizzle in Siril and the reversal via BIN in StarTools.  Or it could be all coming from StarTools...I am probably being a bit ham-fisted in my StarTools operations.  The individual subs look OK for focus, even when zoomed.  However, I am getting some guiding/tracking motion on longer exposures.  I am going to have to explore the mount PEC training, I think, as the GEM28EC is supposed to be better than that.

I did not use flats.  My limited understanding of flats is that they were primarily for removing dust motes...a problem I do not yet have.

Edited July 30, 2021 by JonCarleton

[alacant]

1 hour ago, JonCarleton said:

ham-fisted in my StarTools

Hi

To get anything like in just 46 minutes is an achievement in itself:)

StarTools works best with images which have been minimally pre-processed and simply stacked. Fed with such, it will look after you from start to finish. Do nothing in Siril apart from the basics. I'd lose gimp completely.

So keep taking frames until your patience leaves you and have a look at the StarTools guidelines.

Post your stack if you like...

Cheers and HTH.

 

 

Edited July 30, 2021 by alacant

[JonCarleton]

I mostly use GIMP for sizing and transferring to other formats and sometimes minor cropping.  

Here's another go at the data with less stomping around and gnashing of teeth.  I found that some of the problems were related to a couple of tree shots that somehow managed to get into the sequence.  Sometimes I can get ahead of Siril doing exclusions and it will skip some for which I know I clicked the exclusion box.  Still needs more data, but this looks a bit better.  And yes, StarTools bites back if you get heavy-handed.

I have attached my M20_stacked.fit for those interested and added a "tree image" because a picture is worth...um..something or other.

M20_stacked.fit

Edited July 30, 2021 by JonCarleton

[alacant]

11 hours ago, JonCarleton said:

a "tree image" because a picture is worth...

... €1.2 million when it's done its tour of Tate Modern London. Centre Pompidou, Paris and Reina Sofia, Madrid.

Think of a title. Something most people have to look up is good. How about, 'Rama Night Vingt'

[alacant]

17 hours ago, JonCarleton said:

mostly use GIMP for sizing and transferring to other formats and sometimes minor cropping.  

GIMP doesn't seem to handle cropping and resizing without losing information. Best to use StarTools throughout. Bin for resizing. Crop for cropping and simply change the .tif to.png, .jpg or whatever to choose your preferred file format for the final version, although I'd recommend at least a .tif in case you wish to change anything.

There is walking noise and the -FWOABW- 'refractor' stars are a bit overwhelming; I tried deconvolution both before and after colour with the latter giving something more reasonable.

Don't forget to dither between light frames and fit a uv-ir filter. StarTools is at it's cutting edge best with noise, but perhaps easier with a minimum to begin with.

Still, there's loadsa detail, so keep on adding frames, go with the dither and deconvolution, but above all, keep it simple, I think then you'll be onto something.

Cheers and HTH

 

Edited July 31, 2021 by alacant

[JonCarleton]

Thanks!

I see you got the larger stars under more control...something I struggle with a lot.  I have tried the Shrink Stars section, but haven't been exactly dumbstruck with the results.  Likely, I am not operating it properly.

It is clear I just need more practice with StarTools.  If ever we get another clear night, I may just get an opportunity to do just that.

And yes, I agree on naming convention.  I favor "Osmandian Protolapse," on the premise that understanding is counter to singularity.

Edited July 31, 2021 by JonCarleton

[ollypenrice]

On 30/07/2021 at 19:52, JonCarleton said:

 

I did not use flats.  My limited understanding of flats is that they were primarily for removing dust motes...a problem I do not yet have.

Flats do correct for dust motes but also for vignetting. I think that, if you take a set, you'll be very lucky indeed if they look like a featureless, entirely even surface when stretched. Even the cleanest and most evenly illuminated optics produce flats which are far from flat - which is why we need them. The image below shows a flat to which a flat has been applied.

If, when you take a flat, it does not look just like this (and it won't!) you need flats.

Olly

[alacant]

1 hour ago, JonCarleton said:

more practice with StarTools

Hi

I think those moving from IKEA effect apps have the worst experience; there is no longer a fixed order in which you are obliged to perform operations. If you don't like what you see currently, go back and redo it. Remove gradients, tree branches and apply deconvolution when and however many times you see fit.

A good rule to follow initially is to keep as close to the defaults as your artistic restraint will allow, knowing that whatever mess you make you will always be working with linear data which knows not only exactly what you did to get where you are now, but more importantly, when you did what you did to get to that same point. I call it a database (on Linux it's held under /tmp), Ivo, it's designer calls it tracking.

On a gaming machine under Ubuntu, most stacks can be brought under control in around 20 minutes.

2 hours ago, JonCarleton said:

Osmandian Protolapse

... guaranteed to fetch at least an extra million at auction.

Cheers and HTH

 

 

 

 

 

 

 

 

 

 

 

 

[JonCarleton]

@Olly:

Thanks.  That explanation makes sense.  I actually have a large LCD panel that I purchased several months ago but never used.  I'll try it.

 

@Alacant:

Artistic restraint?  I don't seem to have one of those.  I will, however, see if I can find one on eBay. 

Meanwhile, I'll take a look at the tracking/database thingy.  I used to be pretty good at extracting nuggets from log files and the like.

I have -tried- to rein in the urge to over-control and was warned against straying too far from the defaults in StarTools when I first started using it.  I am, at least, gratified that nobody (yet) has mistaken my attempt at astrophotograpy as a still life image of asparagus.

By the way...what is "HTH" in your closing?