ollypenrice

Oh, I agree. A basic stretch will reveal defects, and the fewer the better. 

My enthusiasm for the RASA 8 and the Samyang 135 are predicated on the availablity of star-control software. Certainly in the case of the Samyang, I wouldn't consider it at all without StarX or Starnett. (I use StarX.) The RASA is much more attractive with this software but would be tempting without it.

We'd all like perfect optics, mount and camera. When we have to settle for less, it seems wise to reflect on which hardware shortcomings we can fix in processing and which hardware virtues we can best exploit. I find the RASA and Samyang data both fixable and exploitable thanks to post processing.

1 hour ago, andrew s said:

There are no laws in art only opinions.

Diffraction spikes rule ok. 😊

Regards Andrew 

In wafting, sing-song voice, 'I can't hear you, I can't hear you!'  However, you are welcome to add diff spikes to any of my images. May I suggest carving them into your screen with a pointed stick???

lly

18 minutes ago, vlaiv said:

Why?

- Big crude stars as produced by small amateur optics.

- Vast amounts of information contained in the data not rendered visible.  (Faint nebulosity from emission and reflection.)

Olly

Edit. I think this has more to say and is much nicer to look at.

OK, let's try it:

Of lesser importance, it is a horrible image.

Of greater importance, I gained no pleasure whatever from producing it!!  It offered all the intellectual interest of stretching an elastic band. If that was all that astrophotography had to offer I wouldn't do it.

Olly

TeleVue Genesis, bought very cheaply because it was out of collimation. I took a risk. Turned out that re-collimating the front lens cell is dead easy and took me about half an hour.

Olly

The outer rings on the flats are pretty much the light spectrum, so I wonder what might create that. A diffraction grating consists of elongated parallel lines which will open up white light into a spectrum. Is there, perhaps, such an object replicated in your light path? The rim of a filter or coupled adapters, for instance. If your light source for the flats is close to the objective, might it illuminate the inside of the dewshield or the lens cell in a way that light from the sky does not? Might it illuminate something circular which then works as a diffraction grating? This is just spectulation but how about extending the dewshield fully and moving the light source further away?

Olly

You can paint a self portrait by dipping your hand in mud and pressing it against the cave wall.

No need for all this, then:

lly

24 minutes ago, ONIKKINEN said:

Do i see doubled stars on the left side or am i imagining it?

Nice picture either way.

Yes, you do!  I hadn't noticed them and will look into them - or crop a bit smaller. 

Thanks,

Olly

Capture and pre-processing, Paul Kummer. My post processing. RASA 8, NEQ6, ASI2600MC.

The little planetary, just 1.8 x 1.5 arcmins, was dscovered by William Herschel and was created by a roughly 2.5 solar mass star.

The dark nebula is LDN674. This a crop from a wider field in Aquila. Wouldn't it be nice to see a time lapse of PNs popping into view and fading across this field...

Olly

Agreed. Our priority in this rendition was the dust rather than the gas.

Olly

2 hours ago, vlaiv said:

I'm not sure how keen are you on changing the workflow that you are comfortable with, but may I suggest something a bit different.

I'll use simple explanation for what is going on rather than exact technical terms, but hopefully that will be enough to understand. This workflow is for luminance only - it does not preserve star color in cores as it leads to clipping, so you'll need to restore those with some mask or something.

1. Do levels / linear stretch until you start seeing nebulosity showing up. This step is essentially just linear transform bringing white point down.

2. Do gamma adjustment (or middle slider in levels) - to a controlled value (say 2.2 - 2.4. Not sure about PS but Gimp has feature where you can just enter the number).

3. Adjust black point to your liking.

This is minimal stretch that will let star removal algorithms work - and it is actually reversible if there is need.

Make a copy of above image and run starless routine on it - this will produce starless image.

Now you need to do pixel math of sorts and simply take original copy and subtract starless image. This will give you stars only image. You will separately stretch that image just to a point where you are happy with stars. You might as well leave them at that level.

Process starless image as you would and then layer stars only on top of that with brighten mode (should be really add mode, but brighten will work as well).

I'm working with OSC data. I realize that I could extract a luminance layer and process that as you suggest, then process the OSC data as I would have processed an RGB layer, the objectives being rather different in processing L and RGB.

However, when StarX appeared, I (and many others) extracted the stars by subtracting the starless from the starry as you suggest. I never found that this worked as well as the routine I follow now.

I do like my present routine though it involves making some calls which vary from image to image and sometimes requires small stars to be processed differently from large ones.

3 hours ago, Elp said:

You can also use the minimise filter to reduce star size, but only by one or two pixels otherwise smaller stars tend to disappear. Your stars have to be selected first with a highlight selection with the edges feathered. Gaussian can be applied at the same stage whilst the stars are still selected, again only by a fraction as you'll likely know.

There is absolutely no need for this. The minimize filter, so far as I can see, belongs to the older processing techniques in which stars were not extracted. When they have been extracted, and the starless image has been given a very hard stretch without them, the extracted 'stars-only' can be replaced as a top layer. Using the grey point slider you can take them from entirely invisible, through tiny to small, medium and then large. What would I want to do with the minimize filter? The grey point slider gives me total control of star size.

Olly

5 hours ago, Elp said:

I assume you've already done the star minimisation technique? Whilst doing it you can also gaussian blur very slightly which softens the star edges.

I have total control of star size when re-applying them using blend mode screen and, yes, I gave them a Gaussian blur but maybe not enough. Now increased.

5 hours ago, vlaiv said:

If you don't mind me asking - how do you extract stars in the first place?

Do you create stars only image at all or do you work with integral data for stars?

Run Star XT then here's the workflow in Ps.

StarXterminator workflow in Photoshop.

1 Stretch standard image as usual to about 60 to 80% of final stretch. Simple stretch, nothing detailed. Save as Proc 1.

2 Run star Xterminator and save the starless image as Starless.

3 Continue to process Starless. Cosmetic repair of artifacts, harder stretch, contrast enhancement, noise reduction, sharpening, colour etc. Save. Select and copy.

4 Use Open Recent to re-open Proc 1 and paste Starless as a top layer.

5 Invert both layers.

6 Top layer active, change blend mode to divide.

7 Stamp down. (Alt Ctrl E)

8 Top layer active, Invert.

9 Flatten Image. (I seem to have to do this from the toolbar Layers dropdown because CtrlE doesn’t work.)

10 Save as Stars.

11 Select Copy

12 Paste onto Starless.

13 Blend mode to Screen.

Actions 5 to 9 inclusive can be recorded as a single action.

14 The stars can be reduced simply by lowering the mid point in Levels. Small stars can look too hard and can benefit from the simple contrast tool to reduce contrast. Large stars with halo or bloat benefit from an increase in contrast. Other possibilities include Gaussian blur or a reduction in top layer opacity by a tiny amount. Stars which look ‘stuck on’ over nebulosity can be made to settle into the image by means of a dab with the burn tool on the bottom layer, just underneath them.

Olly

OK, I've softened the stars a little - though I'll continue to experiment with ways of recombining them with a starless layer.

Thanks for the critiques.

Olly

Excellent images and the standard of judging has been transformed. To be honest, the Drechsler team just had to win this with their consistently ground-breaking work.

Olly

1 hour ago, vlaiv said:

I think that is actually down to blend mod.

Try "lighten" for example.

Here - look at this part:

Those larger stars look like they have dark halo around them. This is due to blending, but if you over sharpen things - you get the same effect.

They do, I know, and I've mitigated that effect to some extent by lifting the shadows around them. I used to use blend mode Lighten to re-apply stars but now greatly prefer Screen. There's a third way which I haven't yet tried.

I do think that the re-application of stars is an area to work on but, overall, star removal takes us way deeper into the nebulosity and I'm happy with what I'm doing as a 'method in progress.'

Olly

44 minutes ago, vlaiv said:

I'm getting distinct - "over sharpening on the stars" vibe from the image.

 

I actually gave them a Gaussian blur of 0.6 in Ps and applied the star layer at slightly less than full opacity to soften them. Perhaps I should gave given them more blur...

Olly

Paul Kummer and I have extended our 2 panel Bat to 3 panels to include the dusty Barnard 150. This was a good suggestion of Gorann's, and SGL member George Sinanis kindly supplied nice OIII data to bring in Outers 4, the Squid.   The spirit of this image involves featuring the dust so there is no Ha here, just OSC and George's OIII, without which the Squid is invisible.

It's always pleasing to mention the name of the great and honorable Edward Emmerson Barnard, who was both the last of the great visual observers and the first of the great astrophotographers.

Olly

I like the second one which has more colour range, the blues making themselves visible in the spiral arms.

I do some things in PI to start with: DBE/ABE, SCNR green, BlurXterminator. For the rest, I'm glad to get the hell out of there and into the touchy-feely environment of Photoshop.

Olly

I love this target and this is an enjoyable rendition. Regarding the stars, inevitably I'm going to say, 'somewhere between the two!' Sorry!!!

For me the stars don't add an illusory sharpness, they mask a kind of mottling introduced by star removal.

Olly

Both renditions are valid and attractive as well as being a testament to the portable equipment being used.

Personally, I don't do much in Pixinsight and prefer the Photoshop environment by a mile.

Olly

AstroArt has a feature called 'remove line' in the Cosmetic toolbox. You put a point at the end of each line and it disappears with a click. I wouldn't use it to remove all diff spikes but those which seem disembodied (from out of shot stars) or over-extended could probably be removed. Other software may have something similar.

4 hours ago, andrew s said:

I love them. They are made by real telescopes not toys. 😊 Regards Andrew 

Right, that's it! Feather dusters at 400 yards!!

lly

6 hours ago, GalaxyGael said:

 

I do like the hint of blue giant light reflecting off the lower ramparts of the dust though

It's nice that you should make this point because I felt the same. It was one of the little nuances that made it enjoyable to process.

Olly

My co-conspirator Paul Kummer described this as a 'B list image' or even a''C list.'  I don't see this rendition sending it to the top of the target hit parade either. 

But... it's there and it looks like this. Trust me, there isn't much to work with, but 85x3 minutes in the RASA 8 gives data which can be stretched to screaming point. This job had more to do with torture than with processing.

Capture and pre-processing by Paul, post-processing by me.

Olly

BTW, the 'Crescent' name makes sense if you observe this visually. Only the bright outer rim is visible and it does make a crescent shape.

Olly

Good!

Olly

This is very classy imaging indeed. Sharp, clean, balanced, free from exaggeration and with totally invisible processing.

Chapeau!

Olly