California Nebula, 80 minutes with a full moon

[bomberbaz]

This is a quick process of data using new rig. Quattro 150p, HEM15 and Askar DB filter with 183MC pro, stacked in DSS, quick process in siril then a tinker in gimp ( 5 minutes messing total ).

Not bad I think for 80 minutes, loving the stars. Lights and darks only.

[TerryD]

I'm not familiar with Siril.  Does it have any type of background extraction tools?  Your data looks good but getting rid of the gradients would really improve things and make further processing easier.

[bomberbaz]

1 hour ago, TerryD said:

I'm not familiar with Siril.  Does it have any type of background extraction tools?  Your data looks good but getting rid of the gradients would really improve things and make further processing easier.

It dioes yes but the problem as I see it is most of the image is nebula so does make it a little difficult. The gradient is from hotel lighting adjacent to my garden, blooming nightmare it is.

I also have GMic & Py astro installed in gimp and I am sure there are tools in there for removing gradiant.

As mentioned though, this was a 5 minute bash, nothing more as there is insufficient data to get carried away.

[TerryD]

13 minutes ago, bomberbaz said:

It dioes yes but the problem as I see it is most of the image is nebula so does make it a little difficult. The gradient is from hotel lighting adjacent to my garden, blooming nightmare it is.

I also have GMic & Py astro installed in gimp and I am sure there are tools in there for removing gradiant.

As mentioned though, this was a 5 minute bash, nothing more as there is insufficient data to get carried away.

Give GraXpert a try.  It can work miracles and it's free.

[PeterC65]

NGC1499 is a great target, but I think it really needs a widefield setup so that you can see it in context. I had a go at it in mid-January using an Askar FMA135 which gives me almost 5 degrees. Here's what I managed with 58 x 15s frames and an L-eNhance filter, plus some (very basic) post processing.

 

[bomberbaz]

3 hours ago, TerryD said:

Give GraXpert a try.  It can work miracles and it's free.

I did, I am impressed.

Just used default settings, tweak on dark levels and saturation in gimp but wow, massive improvement

EDIT. I think this looks like a squids head, tentacles left to right. I claim as mine unless previously mentioned.

 

Edited February 27 by bomberbaz

[bomberbaz]

[bomberbaz]

5 hours ago, PeterC65 said:

NGC1499 is a great target, but I think it really needs a widefield setup so that you can see it in context. I had a go at it in mid-January using an Askar FMA135 which gives me almost 5 degrees. Here's what I managed with 58 x 15s frames and an L-eNhance filter, plus some (very basic) post processing.

owever some 

 

Don't tale this the wrong way peter but the stars are much tighter in my image. The L-enhance was the goto when first brought out but personally I think the latest range of filters, including my askar and the L-extreme have taken over in tersm of tight and tidy stars.

It's a personal think but when imaging nebula, I like more  colour, and less star. 

[TerryD]

7 hours ago, bomberbaz said:

I did, I am impressed.

Just used default settings, tweak on dark levels and saturation in gimp but wow, massive improvement

EDIT. I think this looks like a squids head, tentacles left to right. I claim as mine unless previously mentioned.

 

It's a great tool.  Glad it worked for you.

[PeterC65]

9 hours ago, bomberbaz said:

Don't tale this the wrong way peter but the stars are much tighter in my image. The L-enhance was the goto when first brought out but personally I think the latest range of filters, including my askar and the L-extreme have taken over in tersm of tight and tidy stars.

It's a personal think but when imaging nebula, I like more  colour, and less star. 

I agree that the stars are tighter in your image. Do you think that's because of the filter choice or because you were taking more and longer exposures?

I'm doing EAA so I'm much less particular, and I need to keep the exposures short which I'm not sure would be possible with a really narrow band filter. I have thought about getting an L-eXtreme but I think it would cut out too much light for EAA. The L-eNhance certainly reduced the star brightness. You should have seen it with no filter!

What I liked about the image I posted was that it showed the whole of the nebula in context.

[bomberbaz]

10 hours ago, PeterC65 said:

I agree that the stars are tighter in your image. Do you think that's because of the filter choice or because you were taking more and longer exposures?

I'm doing EAA so I'm much less particular, and I need to keep the exposures short which I'm not sure would be possible with a really narrow band filter. I have thought about getting an L-eXtreme but I think it would cut out too much light for EAA. The L-eNhance certainly reduced the star brightness. You should have seen it with no filter!

What I liked about the image I posted was that it showed the whole of the nebula in context.

Yes the whole image did look nice I agree, however mine is what it is with my scope I am afraid.

Someone on here tested the enhance, the extreme and my askar db filter on the same dso, same exposures etc. In the test the extreme had the tightest stars and best detail, followed by the askar  (there wasn't much difference between these first two, but the price tag and askar being available 1.25 made the decision for me) then the enhance. I also seem to remember the enhance gave to halo's around sone brighter stars

EDIT: apparently the extreme is available in 1.25 now but I am not planning changing, results speak for themself.

Edited February 28 by bomberbaz

[ollypenrice]

If you use a star removal software you can process the nebula and the stars separately. This would have been a holy grail five years ago. It is possible, using this method, to make stars as small and tight as you like, so much so, in fact, that I usually give mine a blur.

Stars can also be made to look tight if the image is black clipped, because the faint signal around the stars is discarded. Unfortunately so is the faint nebular detail as well - unless you are processing the stars separately. The histogram clearly indicates the clipping in both the images posted here.

It is of critical importance to get the histogram right, with no black clipping. There must be a little flat line left of the peak.

If the image is black clipped it is impossible to know much about the stars because most of what you'll see will be stellar core and the faint object nebulosity is also gone for good. So is most of the star colour, which is contained around the outer edges. It can be tempting to use the black point to cut out gradient, but don't be tempted to do this. We use DBE in Pixinsight to remove gradients but other tools work as well. Clipping is never, ever, the way to do it. Check the histogram after every processing operation, and trust it.

Olly

 

 

 

Edited February 29 by ollypenrice
Clarification

[PeterC65]

That's very interesting @ollypenrice. When I do EAA I almost always black clip to darken down the background. It sounds like it would be better not doing this if my intention is to get the best possible image with post processing.

 

[ollypenrice]

36 minutes ago, PeterC65 said:

That's very interesting @ollypenrice. When I do EAA I almost always black clip to darken down the background. It sounds like it would be better not doing this if my intention is to get the best possible image with post processing.

 

Certainly yes. The thing about the faint data is that, when its gone, it's gone. Once you get your eye in, you can see when an image is badly clipped. The sky is jet black and even, because the noise-brightened pixels and any faint genuine signal have been clipped out. For a proper grasp of the black point, though, you need to keep looking at the histo in levels.

It is actually easier to remove LP gradients from an unclipped image because the software has a more genuine picture of where it is. Gradient removal should be the second operation on the stack, the first being the edge-cropping of any border artifacts. If you don't crop these out they will confuse the gradient tools and give a messy histogram which is hard to interpret.

Olly

[PeterC65]

50 minutes ago, ollypenrice said:

Certainly yes. The thing about the faint data is that, when its gone, it's gone. Once you get your eye in, you can see when an image is badly clipped. The sky is jet black and even, because the noise-brightened pixels and any faint genuine signal have been clipped out. For a proper grasp of the black point, though, you need to keep looking at the histo in levels.

It is actually easier to remove LP gradients from an unclipped image because the software has a more genuine picture of where it is. Gradient removal should be the second operation on the stack, the first being the edge-cropping of any border artifacts. If you don't crop these out they will confuse the gradient tools and give a messy histogram which is hard to interpret.

Olly

You might just have persuaded me to give this a try. So collecting some EAA snapshots for the express purpose of post processing. I think I could do that alongside my normal EAA practice by saving some snapshots without doing the histogram stretch in SharpCap.

 

[bomberbaz]

I have been guilty of black clipping myself in the past but not so now. I watched a nebula processing tutorial online which basically mirrored what your saying @ollypenrice

However having just checked the image above, it seems Gimp histogram shows it is black clipped but I am sure it wasn't when I processed it. I shall have another look at the master image and see if I can get something back out of it, strange.

steve

Edited February 29 by bomberbaz

[ollypenrice]

28 minutes ago, bomberbaz said:

I have been guilty of black clipping myself in the past but not so now. I watched a nebula processing tutorial online which basically mirrored what your saying @ollypenrice

However having just checked the image above, it seems Gimp histogram shows it is black clipped but I am sure it wasn't when I processed it. I shall have another look at the master image and see if I can get something back out of it, strange.

steve

Your image doesn't look obviously clipped, to my eye. Sometimes it can happen at the conversion to JPEG. Maybe have a look at your last 16 or 32 bit image prior to JPEG conversion for the web?

Olly

Edit: I have tested, several times, a screen grab against its original JPEG to be sure that the screen grab itself doesn't introduce any clipping and I have never found that it did. I think the screen grab does represent the original JPEG, therefore.

Edited February 29 by ollypenrice
Stated

[bomberbaz]

Yes I have just checked and can confirm I did indeed clip it. Having reviewed what I did I figured it out. I tweaked the black levels in exposure to darken the background and this is where the clipping took place.

I have quickly redone the image from the base stack but this time I ran graXpert before any gimp tweaking and it allowed me to retain all the data without clipping.

I do think some data from a dark site would help an awful lot though.  See below

5 minutes ago, ollypenrice said:

Your image doesn't look obviously clipped, to my eye. Sometimes it can happen at the conversion to JPEG. Maybe have a look at your last 16 or 32 bit image prior to JPEG conversion for the web?

Olly

Edit: I have tested, several times, a screen grab against its original JPEG to be sure that the screen grab itself doesn't introduce any clipping and I have never found that it did. I think the screen grab does represent the original JPEG, therefore.

[ollypenrice]

13 hours ago, bomberbaz said:

Yes I have just checked and can confirm I did indeed clip it. Having reviewed what I did I figured it out. I tweaked the black levels in exposure to darken the background and this is where the clipping took place.

I have quickly redone the image from the base stack but this time I ran graXpert before any gimp tweaking and it allowed me to retain all the data without clipping.

I do think some data from a dark site would help an awful lot though.  See below

I don't do background levels by eye, I always use the Ps Colour Sampler (in the Eyedropper tools) to measure it. I feel 23 per channel is ideal but sometimes have to settle for less. Imaging with the RASA complicates this because there is far less background sky than with slower systems. The RASA reveals faint nebulosity just above the background and also dust-darkened regions which lie just below the broader background. The deeper you go, the more you will encounter this.

Olly

Edited March 1 by ollypenrice
typo