Lee_P

Star trails around the North Celestial Pole. Taken from Bristol city centre, with no light pollution filter. The brightest line is Polaris -- close to the North Celestial Pole, but as this telescope view shows, not directly over it.

* 21 April 2021
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Mount: Orion Sirius EQ-G (turned off after initial slewing)
* Software: PixInsight, Photoshop, Lightroom
* ASIAIR PRO
* 180 x 120 seconds
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Total integration time: 6 hours
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By Lee Pullen

7 hours ago, Nikolas74 said:

I am really amazed from the results..... That looks even better than with my Redcat51 and same like yours equipment and bortle scale. 

Thanks, I guess the FRA400's larger aperture helps. 

Just updating this thread with some more example photos...

* January 2021
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Filter: Optolong L-eXtreme
* Mount: Orion Sirius EQ-G
* Software: AutoStakkert!3, RegiStax 6, Lightroom, Photoshop
* ASIAIR PRO
* 500 frames

---

The Soul Nebula
* January 2021
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Filter: Optolong L-eXtreme
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Software: PixInsight and Lightroom
* ASIAIR PRO
* 72 x 300 seconds
Total integration time: 6 hours

---

The Pacman Nebula
* Jan - Feb 2021
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Filter: Optolong L-eXtreme
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Software: PixInsight and Lightroom
* ASIAIR PRO
* 90 x 300 seconds
Total integration time: 7 hours 30 minutes

---

The Orion Nebula
* February 2021
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Filter: Optolong L-eXtreme
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Software: PixInsight and Lightroom
* ASIAIR PRO
* 89 x 300 seconds
Total integration time: 7 hours 25 minutes

---

The Pinwheel Galaxy and Friends
* March 2021
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Filter: IDAS D1 Light Pollution Suppression
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Software: PixInsight, Photoshop, Lightroom
* ASIAIR PRO
* 600 x 120 seconds
Total integration time: 20 hours

---

Nova Cas 2021
* 20 March 2021
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Software: PixInsight, Photoshop, Lightroom
* ASIAIR PRO
* 15 x 120 seconds
Total integration time: 30 minutes

---

M3
* March and April 2021
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Software: PixInsight, Photoshop, Lightroom
* ASIAIR PRO
* 300 x 120 seconds
Total integration time: 10 hours

---

Vesta
* 29 March - 2 April 2021
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Software: PixInsight, Photoshop, Lightroom, ezgif.com
* ASIAIR PRO

---

Markarian's Chain
* April 2021
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Software: PixInsight, Photoshop, Lightroom
* ASIAIR PRO
* 300 x 120 seconds
Total integration time: 10 hours

---

The Iris Nebula
* April 2021
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Software: PixInsight, Photoshop, Lightroom
* ASIAIR PRO
* 615 x 120 seconds
Total integration time: 20.5 hours

58 minutes ago, b36lbx said:

Great review, thanks for sharing the info and the sample file. Can I please ask what settings did you go for in the Asiair Pro autofocus, I really struggle to find the best combo.

Many thanks

Sure!

AF EXP: 2s for no filter / light pollution filter. 5s if I'm using the L-eXtreme.
Step Size: 30
Autorun settings: every 1H, before Autorun start, after Auto Meridian flipped.

For the more general settings...
Fine (Slow) Step: 10
Coarse (Fine) Step: 30
Max Step Limit: 60000
Backlash: 0

Is that all the info you're after?

On 27/03/2021 at 12:03, wimvb said:

Btw, if you drizzle an image, you don't need integer drizzle values. You could drizzle 1.5 x or even slightly less.

Sorry for what's probably a dumb question, but I tried setting DrizzlerIntegration to 1.5 today, but couldn't. The scale option only allows for integers. What am I doing wrong?

3 hours ago, simmo39 said:

Well my scope has come! hopefully will give it a quick first loght tonight. I agree this is a nice scope, seems well made and looks good. Just hope that it performs ( Im sure it will ).

Congrats, can't wait to see what you do with it 😃

1 hour ago, wimvb said:

There is a real difference in star profile in your image. The 2x drizzle image is in principle oversampled, and the non-drizzled is undersampled imo. Applying drizzle doesn't necessarily mean that you gain detail, it means that the detail is distributed over more pixels. But there is a difference in post processing. The oversampled image allows you to do a more aggressive deconvolution, reclaiming some of the detail that is lost to seeing.

So there is an advantage to process the drizzled image. But that advantage comes at a cost; your image file is 1.2 GB, four times larger than the non-drizzled image. This not only eats hard drive space, but also slows down the processing. What I would do with this image is first crop the drizzled version to maybe 1/4 size, and then start processing it. In terms of image geometry, this is equivalent to taking an image with a smaller sensor camera which also has smaller pixels.

Here are the star profiles for the drizzled and non-drizzled images

Btw, if you drizzle an image, you don't need integer drizzle values. You could drizzle 1.5 x or even slightly less.

Thanks, that's really interesting. For future images I'll try 1.5 drizzle -- maybe that's a sweet spot.

19 hours ago, wimvb said:

Time saving. Especially when mmt needs to calculate the wavelet layers, this can be time consuming for a large image. And as I wrote before, I’m not convinced the image needed drizzle to start with. In fact, I would like to see a non-drizzled version of this image. My guess is that the level of detail will be very much the same.

Sure, I've uploaded a non-drizzled version: https://drive.google.com/drive/folders/1wB3May69oEWniF8hikueUkSS-TJvjMKC

I'd be interested to hear your thoughts on the difference. My no doubt overly-simplistic reasoning was that a drizzled version would give me the option of a closer crop on the galaxy.

14 hours ago, wimvb said:

My take on your image. Also in PixInsight.

• Resample 50% to reduce the image size. Stars are still quite round after this, and I'm not convinced your image was undersampled to begin with. Undersampling depends very much on atmospheric conditions, and as long as stars don't appear too pixelated, you're probably good on the sampling scale. Just test with integrating this image without drizzle.
• Dynamic crop to get rid of stacking edges
• DBE approximately as per @Spongey's excellent write up. 
• Background neutralization and Photometric Color Calibration
• Stretch 1 using arcsinh stretch
• Stretch 2 using curves
• SCNR green cast removal
• Local colour saturation and dynamic range extension using MMT with a mask to isolate the galaxy
• Background desaturation
• Saved as jpeg

I didn't use any noise reduction except SCNR-green. Btw, you caught quite a few distant galaxies in this image.

Thanks, this is really useful. Arcsinh stretch is a new one to me, I'll research it further 😃

8 minutes ago, Spongey said:

Sure  

I find that two passes of DBE can be useful in heavily light polluted data like this, the first one with a higher tolerance, and a second with the default tolerance of 0.5.

As the aim of DBE is to remove large scale gradients, I use 7 samples per row. More than this is generally unnecessary and can create some strange artificial gradient subtraction depending on the placement.

Generally you want a sample size that is big enough to cover a decent amount of background (I wouldn't use below 10px samples), but you don't want to be struggling to find areas of background with no stars in. As the data is drizzled, and there aren't lots of stars in the frame, I used a sample size of 50px.

I also reduce the minimum sample weight to allow the algorithm to pick and choose among the samples a little more than with the default settings.

The first pass of DBE was run at a tolerance of 1.16 as shown below. This was the lowest I could get the tolerance while still accepting all of my samples.

Finally, the correction mode was set to subtraction.

For this image, the other default settings are appropriate and don't need changing.

As seen in the background map produced, the process did a pretty good job of modelling the gradient in the image.

This gives us a pretty good result, but there are still some traces of light pollution, particularly in the bottom right corner where it is strongest. For that reason, we run the same DBE process again on the new image. To ensure you have the same samples and settings as the first pass, you can drag the little triangle out from the DBE process window onto the workspace, close DBE, and then double click on the saved process icon with the new image open.

HOWEVER, for the second pass, we change the tolerance value back down to the default of 0.5. This gives us better rejection between the samples and provides a better estimation of the background. If there are other gradients present in the image, then you can now move some samples to better model these regions specifically (note that if we are only dealing with light pollution, there shouldn't be any other major gradients).

Running this second pass only removes the trace of light pollution left in the bottom right corner, where it was worst in the original image, as shown by the background map here:

The final image looks pretty flat, there is some large scale blotchyness to the image but that can be dealt with later in processing by darkening and desaturating the background.

From here I would proceed with colour correction, noise reduction, stretching etc.

Hope this helps!

That's absolute gold, thank you so much!

4 minutes ago, Spongey said:

I'd pretty much agree with Dave's sentiment, you've got decent data here.

However, it is worth bearing in mind that shooting broadband from Bortle 8 is never going to get you incredible results in a reasonable timescale (compared to a dark site). For reference, 20 hours in bortle 8 is approximately equivalent to only 1.25 hours in Bortle 1! This is typically why people tend to favour imaging in narrowband from light polluted areas; the gap between Bortle 8 and 1 is significantly closed when using narrow bandpass filters.

It makes sense that after performing DBE you'll be able to see the noise profile of your image much clearer, as you've subtracted all that unwanted signal from the light pollution. 

 On undersampled data such as this, DrizzleIntegration can help tease out fine details, especially if you have a large number of subs that are well dithered, but it will invariably add noise to the image. Whether or not you are willing to make this tradeoff is up to you and dependent on the image. All things considered you've got a good base to make a nice image from here, despite the challenging conditions!

If you're interested in some further reading, this is a great article on SNR: https://jonrista.com/the-astrophotographers-guide/astrophotography-basics/snr/

Thanks, that's all very helpful! I think I'm falling down with the DBE step; I can't get it to look quite as good as you or Dave have. I'd be very grateful if you could maybe post a screenshot of how you did DBE?

35 minutes ago, Laurin Dave said:

No idea what the numbers mean but that looks fine to me, good I'd say from Bortle 8 and 400mm.    Here it is, all I've done is cropped all the edges back, re-sampled by 50%, (I expect that drizzling is just adding noise)  removed light pollution and given it a histogram stretch.   Plenty more to give with more processing..  Beware of Pixinsight Screen Transfer function stretch it is highly aggressive.  I'd suggest you re-integrate without drizzle and go from there .

Thanks, this is a great help! Can I ask exactly how you removed the light pollution? Did you use DBE, and if so, what were your settings?

Hi SGLers,

I’m hoping a PixInsight guru can help me. I’m a PI beginner, but am having fun learning. My question is about the level of noise in my images. After integrating and performing an STF stretch, the resulting image always looks quite smooth. But it doesn’t take long at all – just a DBE really, maybe then a gentle stretch – for the image to become really noisy. And then a lot of my editing is centred on battling that noise. My camera is an ASI2600MC-Pro, which I cool to -10. For a recent experiment, I gathered 20 hours of data from 120s subs. With that much integration time, and the low-noise camera, I was hoping for lower noise than I actually got. (I am shooting from Bortle 8, however).

So my question is: are my expectations wrong, and actually the amount of noise I have is what’s to be expected? Or, have I messed something up in pre-processing or integration?

In case it’s useful, I ran SCRIPT -> ImageAnalysis -> Noise Evaluation on the image straight out of integration and got the following:

Ch | noise | count(%) | layers |

---+-----------+-----------+--------+

0 | 2.626e-01 | 18.39 | 4 |

1 | 1.037e-01 | 12.01 | 4 |

2 | 1.636e-01 | 11.10 | 4 |

---+-----------+-----------+--------+

I’ve also uploaded the file (1.16Gb) for anyone kind enough to help investigate further:

https://drive.google.com/drive/folders/1wB3May69oEWniF8hikueUkSS-TJvjMKC?usp=sharing

Thanks!

-Lee

Thanks for the heads-up, there was a brief gap in the clouds last night and I think I got it!

I started processing your data, but early on ascertained what the issue is.

I took all your Light frames and ran them through PixInsight’s SubFrameSelector tool. This is a way of measuring the quality of Lights. Each Light was given a FWHM measurement: the lower the number, the better quality of the Light. That flagged up the problem. Your 18 Feb data is very good quality, but most of what you obtained on the other nights is much lower in quality, and would likely only serve to degrade your final stacked image. I think this screenshot shows what I’m talking about quite clearly:

Your 18 Feb Lights are excellent, so your kit and skills are capable of it. I think you had low-level cloud on the other nights, which would explain the readings.

So, the reason I didn’t continue editing your data is that my next step would have been to axe any Lights that didn’t make the grade, which would be almost everything taken after 18 Feb. Meaning I’d have been left editing the original data! I hope that makes sense and is helpful. Aim for four or more hours of data as good as your 18 Feb efforts and you’ll be able to produce a stunning image

As an additional note for the future, I recommend trying to organise your data in a simpler way. My preference would be to have one folder containing all the Lights (all with the same ISO and exposure length); one set of Bias frames; one set of Dark frames; one set of Flat frames. I appreciate that this works well for me because I’m using a cooled astrocam, which makes using matching calibration frames easier.

Let me know if I can help further or if you'd like me to elaborate on any of the points

-Lee

Great video, thanks for making it

19 minutes ago, astrobena said:

Brilliant, thanks! I've uploaded (EDIT: I'm still uploading) all of the files now and put them in a folder called 'Attempt 2' (still the same link)...

Now the imaging sequence of the 25.02 was with 50sec and ISO 100

The imaging sequence of the 26.02 was with 50sec but ISO 200 (I was planning on using this for all the following sequences) <-- here i accidently made an extra set of Darks with ISO 100 before i noticed it had the wrong ISO value and then made some more

And for the 27.02 its also 50 sec but for the ISO i wanted to use ISO 200 again (as mentioned) but for some reason forgot to do that and ended up with ISO 100, whereas the light, dark & bias frames are all ISO 200... (maybe here you could use the extra set of Darks with ISO 100 from the night before)

Oh and befor i forget: you will see there's a folder with all the images i've marked as not usable... I've done my best trying to sort them out, but im sure i have missed a few which actually could have been used / cant be used (in DSS I choose to stack only the best 95% for that exact reason)

I know this is by no means perfect in any way, but really just at the beginning of a steap learning curve with Astrophotography. Thanks again for helping me here.

Okey dokey, just let me know when they're all uploaded

10 hours ago, astrobena said:

Hey, so i've been capturing some more data... around 3.5h now, again ive tried editing it and still not great results... This may well have something to do with my way of editing (i dont have an incredible amount of experience) and I will definitly have a look at some more tutorials but before i waste my time trying to achieve something that isnt possible, but is there anything you or anyone can do with this data, better then the first? (its in the same link: https://drive.google.com/drive/folders/12NT4TmLCXvTfOXNPE_l8UWPRpgO2VjLe?usp=sharing, this time the Autosave015.tif)

I would really appreciate any attempts at this!

I'll have another crack at it. I'd like to do the stacking as well though, from the original light frames. Could you upload all of those, as you did with your first attempt?

That's tough... I think I prefer the original, sharper versions. The details just seem more defined. But the noise in your latest HOS is masked well. 🤔

Those are great! I always like seeing images taken from light polluted skies -- it's amazing how much data can still be pulled out. I've actually just finished the Rosette from my own Bortle 8 location, using Skipper Billy's old Orion Sirius EQ-G mount 😁 

* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Filter: Optolong L-eXtreme
* Mount: Orion Sirius EQ-G
* 450 x 120 seconds (total 15 hours)
 

9 hours ago, Adam J said:

I would disagree with that statement, on a technical level the gap between mono and OSC is exactly the same as it always has been, my observation is that sensor technology as advanced to the point that you can get results with a OSC that could only have been acheived with mono in past years / sensor generations. However, the gap between an OSC ASI2600MC-Pro and the ASI2600MM-Pro is exactly the same as the gap in performance between a older KAF8600 mono and OSC, its just that the OSC KAF8600 was below the sensitivity threshold required for it to take top draw images in a reasonable intergration time. But thats not quite the same thing as the gap narrowing and given three hours of data with the mono 2600 vs three hours of data with a OSC 2600 the mono will still win perticually in narrow band imaging and despite the advent of filters like the L-Extream. 

I think this will become clearer as we see images start coming with the ASI2600MM pro in the next year.

I agree with your choice not to go with the reducer, I think that its a big ask with a APS-C sized chip and that life will be easier all in all with the more tame F-ratio.

Adam

I could have been clearer in my comment, but I was referring to the development of dual and tri-band filters. I image from a city. Back when I was using mono that was really the only sensible choice. But now OSC (plus filter) is a valid option -- it's what I'm using and am getting what I consider to be very satisfactory results. Hence, the gap between mono and OSC has narrowed recently, thanks to filters like the L-eXtreme.

Here's another photo with the Askar FRA400, ASI2600MC-Pro, and Optolong L-eXtreme. This is proving to be a great combination even from my light-polluted city centre.

* February 2021
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Filter: Optolong L-eXtreme
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Software: PixInsight, Photoshop, Lightroom, Topaz DeNoise AI
* 450 x 12 seconds
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Total integration time: 15 hours

Dithering is a good shout, if you're able to. Ideally all your exposure lengths should be the same, so maybe you want to start again with longer lights. The exposure time for your darks should match your lights. If you take a good set of flat frames then they should be good to calibrate lights taken over imaging sessions spanning multiple nights, especially if you can keep your camera attached to the telescope (i.e. not shifting the dust around, or changing the camera's orientation).

Hi from a fellow Bortle 8 imager! I’m learning PixInsight, so used that to have a crack at your data. I teased out more detail in the spiral arms, but there’s a lot of noise. I could have smoothed that out a bit, but left it in as it might help you to see it.

Basically, you need to improve the signal to noise ratio by taking many more lights, and maybe using a light-pollution filter as well. Adding in flats would help with the editing too.

A more experienced imager would be able to do more with your current data, but I think the key message – more data needed – would still stand 😊

-Lee

Congrats, this is great! Really impressive for just an hour as well. Focussing is tough, especially using a filter like the L-eXtreme. If you've got the cash spare, I really recommend looking into an electronic autofocusser -- great for getting perfect initial focus, and also for automatic adjustments over a night when focus shifts due to temperature changes.