Rustang

Thanks again guys for all your help,im seeing some great processing on the data. In regards to softness, il keep an eye on the focus but one thing I've noticed is that all of a sudden I'm getting a very low RA OSC reading when guiding, it's always been sitting around 0.45 but during all of the imaging sessions for this target it's been going down to 0.06 so into the Red and barely goes higher than 0.18. Everything else has been the same and because the subs appeared ok I have carried on with the intention of finding out the problem later. Even when I tweaked a couple of settings that were mentioned online it had no effect on improving it. I put this down to seeing because of the bright nights but could be totally wrong, could this be adding to the focus issue/stars ? 

35 minutes ago, wimvb said:

Dark corners in your image. I'd say your flats are undercorrecting

I see, I get vignetting on all filters so I'm guessing they would also be produced on the flats for each filter!? Does make processing that extra bit of a pain in the back side but I can live with it. 

21 minutes ago, wimvb said:

Regarding local contrast, here's the same target captured and processed by Sara Wager

https://www.swagastro.com/ngc7822.html

Btw, @Rustang to get the most out of your data, you should apply flats.

Yeah her work is amazing. You have me worried now as I do use flats, I stack with Darks, flats and dark flats. Do you think the flats aren't working then, if so how can you tell!? 

10 hours ago, ollypenrice said:

This is, with absolutely no doubt whatever, a processing issue.  It has nothing to do with capture.  Others have demonstrated the potential for higher contrast contained in the data.  However, we can point you towards the processing techniques which will enhance both global and local contrasts but the extent to which you apply them will remain your call. Many images strike me as over-processed in the way Craig T82 describes above. So I'll give you a couple of ways to enhance contrast but don't take that as my saying you should use them. Make your own picture. Wim has covered the black point so let's look at...

The stretch:

When we stretch an image we do so non-linearly, so we stretch the dark parts by far more than the light parts, so increasing contrast in the dark parts. That's how we extract the nebulosity from the background. However, different stretches will give different levels of contrast. If you stretch in Levels you'll get a logarithmic stretch which looks something like this when seen in Curves:

This is a gentle curve and the difference in stretch between the red and blue lines shows the difference in stretch between those points. This will give a natural looking image with moderate contrasts.

The alternative is an aggressive stretch.:

Here all the contrasts between dark and moderate signal have been massively increased. Note the difference in stretch between red and blue. That difference is contrast.

I've shown this stretch before on here and it has raised eyebrows and disapproval but it remains one of my go-to operations, above all in narrowband where its increase of star size is not such an issue. When I demo these curves on this data with guests, most prefer the hard stretch. It was the stretch used in the Ha and OIII of this final version: https://www.astrobin.com/327970/

If you use Photoshop consider Noel's Actions (now called Pro Digital Astronomy Tools) which has an excellent routine called Local Contrast Enhancement. In Pixinsight try Local Contrast Equalization (which you can also replicate in Photoshop.)

Olly

 

Thanks for the heads up on this, I actually forgot I already have those actions so Ive taken a look at the 'Local contrast enhancement' and it works wonders. The images below show with and with out the preset and the areas it enhances are perfect!

39 minutes ago, vlaiv said:

Stars are fine - it is image format used to store data that is causing trouble (or rather how different software interprets pixel values).

It is best to save as 32bit floating point fits. You saved in 32bit integer TIF and 32bit integer can be treated as signed or unsigned - ImageJ and windows image viewer as shown by @wimvb treat TIF 32bit integer as signed integer and that means that very high values are treated as negative (up to half are positive - larger than half are negative - that is some sort of binary format stuff how to represent negative numbers).

Just export data from DSS as 32bit floating point FITS (or even TIF - 32bit floating point has strict definition) and you won't have these issues.

I just had a look at DSS and these are the options I have to save the data, none say '32bit floating point'!? 

Thanks again everyone, just need some improvements processing wise by the looks of it then, I think this data isant as sharp as normal even though the focus didnt seem any different so will have to keep an eye on that too.

20 minutes ago, vlaiv said:

Stars are fine - it is image format used to store data that is causing trouble (or rather how different software interprets pixel values).

It is best to save as 32bit floating point fits. You saved in 32bit integer TIF and 32bit integer can be treated as signed or unsigned - ImageJ and windows image viewer as shown by @wimvb treat TIF 32bit integer as signed integer and that means that very high values are treated as negative (up to half are positive - larger than half are negative - that is some sort of binary format stuff how to represent negative numbers).

Just export data from DSS as 32bit floating point FITS (or even TIF - 32bit floating point has strict definition) and you won't have these issues.

Apart from the ones around the edges! 🤣 Ok cool, I shall bear that in mind when I neck use DSS, thanks for your help with this.

22 minutes ago, wimvb said:

I agree with vlaiv. I just downloaded the image and opened it in windows image viewer (which doesn't stretch). Some star cores are just "rings". @Rustang, how did you stack the images?

It was stacked in deep sky stacker, in dumb dumb terms, what is the issue with the stars, I haven't noticed anything odd my end unless I don't kniw what the 'odd' thing is I'm looking for!? 

A 32bit tiff of some Ha data for your processing pleasure. Its from this month so not the darkest of nights at the moment.

HOOHAStack.TIF

18 minutes ago, tooth_dr said:

I don’t think my dedication can be called into question!  Running three cameras, three sets of calibration data, and trying get it all carefully coordinated through a 600mm dome slot without obscuring the field of view both pre and post-flip has proven tedious.  The adjustable dovetail saddle can’t handle the weight of two cameras without moving position after the flip, so I’ve decided just to stick with the two cameras and scopes!

 

 

I wasn't questioning your dedication, I meant as a hobby for everyone in general because of the level of frustration it can bring amongst other things Its a shame you couldn't get the 3 rigs up and running, it would have made shooting narrowband a quicker process.

9 hours ago, John Nodding said:

2 crackers!! 👍🏻 Noddy

Thanks Noddy 👍

Thanks for all your help guys, il start looking into my processing techniques to see if I can improve on them. 

55 minutes ago, ollypenrice said:

This is, with absolutely no doubt whatever, a processing issue.  It has nothing to do with capture.  Others have demonstrated the potential for higher contrast contained in the data.  However, we can point you towards the processing techniques which will enhance both global and local contrasts but the extent to which you apply them will remain your call. Many images strike me as over-processed in the way Craig T82 describes above. So I'll give you a couple of ways to enhance contrast but don't take that as my saying you should use them. Make your own picture. Wim has covered the black point so let's look at...

The stretch:

When we stretch an image we do so non-linearly, so we stretch the dark parts by far more than the light parts, so increasing contrast in the dark parts. That's how we extract the nebulosity from the background. However, different stretches will give different levels of contrast. If you stretch in Levels you'll get a logarithmic stretch which looks something like this when seen in Curves:

This is a gentle curve and the difference in stretch between the red and blue lines shows the difference in stretch between those points. This will give a natural looking image with moderate contrasts.

The alternative is an aggressive stretch.:

Here all the contrasts between dark and moderate signal have been massively increased. Note the difference in stretch between red and blue. That difference is contrast.

I've shown this stretch before on here and it has raised eyebrows and disapproval but it remains one of my go-to operations, above all in narrowband where its increase of star size is not such an issue. When I demo these curves on this data with guests, most prefer the hard stretch. It was the stretch used in the Ha and OIII of this final version: https://www.astrobin.com/327970/

If you use Photoshop consider Noel's Actions (now called Pro Digital Astronomy Tools) which has an excellent routine called Local Contrast Enhancement. In Pixinsight try Local Contrast Equalization (which you can also replicate in Photoshop.)

Olly

 

Thanks Olly, il take a look into that, just to clarify again my above Ha data was not fully processed it was just to show where I start getting to before then processing further but it can then sometimes start adding issues with noise etc. It certainly seems I have some improvements in processing to learn. I normally do levels adjustments first brining in the light and dark slider but that never really helps with contrast, it's the curves that helps the most but I'm not getting to far by then with the data. 

1 hour ago, tooth_dr said:

@Rustang I haven’t been posting on the forum just as frequently, only seeing this thread now. I do live at a good Bortle 4 site for sure which helps. But to be honest I’ve looked at all the images you’ve produced with the camera and I’m very very impressed. Your processing is very natural and your images don’t lack contrast.  

Thanks Adam, first and foremost I'm still really happy with my purchase 😊 I saw on your Camera sale thread that you have lost some interest in the hobby which is a shame but I fully understand that it's not for the faint hearted and needs a certain degree of dedication. When you get issues such as software it really does start to gripe so it's understandable, I hope you find a drive to keep going with it. I'm starting to understand the factors of my concerns and there are probably a few, some in my control and some not, I'm certainly a little lazy on my intergration time and I'm probably worrying to much about nothing but I'm always looking to improve 🙂

8 hours ago, wimvb said:

And the last image (DBE + black point) with an added S-curve, lowering the histogram peak to 0.075 and leaving the higher range unaltered. This isolates the main target a bit better, and gives a bit more drama. But again, it all depends on where you want to take the data.

Thanks for all the info, I should have explained that the above image I posted wasn't fully processed but was to show where I get to before taking it further but then adding issues such as noise so its probably my processing techniques that need some improvements. You have definitely managed to lose the washed out feel and brought out the darker sky in places I missed even in the final colour image I posted! . Il have some more goes at my recent data which hasn't been helped by the lighter nights. 

1 minute ago, vlaiv said:

Actually - being under sampled helps the quality of your image (or rather SNR) so don't worry about that. 

That's good to know then 🙂

8 minutes ago, geeklee said:

Fantastic again @Rustang  I had to look up this NGC number as I didn't recognise it was part of an area of sky I'm used to seeing with a wider FOV.  I really like this closer up shot too - both images look great.

Thanks mate, I hope to capture its entirety at some point down the line 🙂

6 minutes ago, vlaiv said:

I think that this can be easily "measured".

You can for example - post linear stack in 32bit fits format and people can then process that data. You can then compare your processing to see if it can be improved.

I agree with above - sky quality plays significant role for image quality - as does telescope used with camera (aperture at resolution). So does total integration time.

However, this is narrow band image and I don't know how much of light pollution gets thru. Maybe people whose images you look at - have good denoising skills? That lets them push data further without revealing too much of artifacts.

Thanks, il look at posting a stack tomorrow. I think I calculated that my setup could be under sampling which may not be helping also but that's going into territory that's starting to go way over my head! 😊

11 minutes ago, david_taurus83 said:

I think the previous owner lives in a nice dark spot!

Very true 😊

9 minutes ago, Nik271 said:

The sky brightness may play a role too. A lot of the light pollution these days is in all the spectrum because of the LED lights.  Perhaps you are comparing with images taken from darker skies or in better conditions?

You could be right, I'm just trying to narrow down the factors it could be and hopefully it's not me worrying about nothing. 

32 minutes ago, david_taurus83 said:

Are you comparing your images to others using the same camera/sensor? I'm not sure what exactly your asking?

Your right to ask this as I fully understand that equipment used will have a difference and its probably wrong to generally compare against others images like I'm doing so it's probably factor's such as equipment, quality of sky etc but I just wanted to make sure I'm not missing anything else. I have to say, Adam the previous owner of the camera has also produced the results I'm seeing often that I can't seem to achieve, you could straight away say then it's the processing so maybe I'm missing something there but it's a certain crispness to the contrast between the nebulosity and sky that looks alot smoother as to get anything close it adds more noise for me. I'm more than happy to except it could be lack of experience 😊

3 minutes ago, vlaiv said:

Will this convince you?

I've posted the final result with this data in the deep sky imaging section, I'm not sure if I'm explaining myself properly 😊  but to get a decent result for me starts to have an effect on the quality of some of my images, as said I have a feeling its down the to sensitivity of the sensor as most other images I see have a crisper, better contrast that doesn't seem have an effect on the quality of the image, the more curves and stretching I do to gain contrast starts to effect things. It could just be me/the equipment I have but I just wanted to make sure I could change a setting/do something different somewhere that's all. 

10 minutes ago, david_taurus83 said:

A gradient wipe would do wonders with that. Here's what a simple S curve will do on my phone.

 

Thanks, I normally get somewhere close to what I like but I really have to work things harder than I'm sure I should have too! 

3 minutes ago, CraigT82 said:

If you ask me that's a fabulous image! A lot of the work I see online is well overcooked (not so much on here but on other social media platforms) with contrast and saturation boosted to the max and a ton of sharpening and noise reduction thrown on top, which makes them look reasonably impressive at first glance in a preview, but not so nice when viewed at full size. 

Your posted image is the opposite of that in my opinion, conservatively processed, balanced and sympathetic to the data. A joy to look at. 

I think that a little more time on this particular image with the curves tool and you could get the look you're after without sacrificing the data? 

 

Thanks, i appreciate the comments. It's more so that I'm not sure if all the other data I see here there and everywhere always looks like it has more contrast between the sky and nebulosity given a sharper looking image, I don't think it's always necessarily how it's processed I just get the feeling it could be down to more sensitive sensors or something else. I understand totally what you mean about some over cooked images, I would just prefer some more contrast at the beginning to work the data so hard. 

23 minutes ago, GiorgioF said:

Really nice capture!

Thank you 😊