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7:16 8:02

Thank you! I'm looking forward to trying this once I have enough data on the Bubble Nebula (which happens to be my current target). What length of exposure did you do for the Bubble Nebula? (As I compare your images to mine.)

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Can I run auto linearfit instead of SPCC?

I guess that denoising and BXT take some info detail out of target out of image…and that even though it is not logical…stretching the noise also before removing it is not a factor at all in the end result. But I cannot help but wonder if this new alternative procedure that you have demonstrated is best suited for darker skies…where an over abundance of noise may not be a factor.

Yeah …agree residuals green can be left after SPCC.

Hola, excelente vídeo. ¿Podrías decirme si un reductor de focal es mejor con el mismo diámetro? ¿Puedo hacer zoom en la fotografía final sin perder calidad?

Interesting. The creator of BXT and NXT clearly states that BXT should be run before stretching, but does not provide any specific direction on NXT. Logically, I would expect NXT to do a better job after stretching as the noise would be more distinguishable. That's the way I do it. One comment I've read elsewhere states that the noise removal model was trained on stretched images so will do a better job there. The discussion below on the presence/absence of stars before running these is also interesting. I was taught that star removal is the last step in the "raw data" phase before artistic image processing . So that's the way I do it. Haven't seen anything similar to what you show here.

Still thinking about the information you presented in this and the last couple of videos. To me it makes more sense to think about the unobstructed light gathering area of a telescope. Because yes resolution is by physics depending on aperture but any obstruction (secondary mirror) leads to little light loss. It also doesn’t make sense to me that two telescopes with different aperture but same light collecting area should achieve different brightness (lets say a 5 inch apochromatic refractor and a 6 inch schmidt cassegrain that have different aperture but same unobstructed area).

hello, very good video. how do you make the tracing stars on the photo? thank you

Great video! This is something that I have realized also that focal ratio is not the main driver if you get a good image. With my 8" RC I can see that images build up as quickly as with my 70mm Apo even though the focal ratios are f/8 against f/6 meaning that the Apo should be 2/3 quicker from the focal ratio but in fact there is no difference. The small Apo was for long time my most used and most liked telescope but I am changing most of my imaging to larger aperture telescopes. I just realize that I have to use it again. Not that I don't like my small Apo anymore as it has its use-cases. So each of my telescopes is for a specific case except two which are very similar in focal length. I would not try to capture the Spaghetti Nebula with my 8" RC, my 6" Newtonian or 4" Apo. I would use the 70mm Apo as it is the use-case for such small telescope. Same with the Rosette or Seagull. Sure I could capture details with the others, do masaics but having the right scope for the target size is always more convenient. The limited number of nights with clear skies is the other downside why it does not make much sense to start a project like the Rosette in 9 or 12 panels. So have the right telescope for the use case if you are limited with clear nights. Don't look too much at the focal ratio, choose what fits your needs of the framing that you like to achieve. A larger aperture with a reducer is able to gather more photons because of is size than a smaller scope with just a flattner.

SNR and Image scale! Have a long - slow focal length big scope? Pair it with a large pixel camera or bin 2x2. Have a fast large telescope, Pair it with smaller pixels.. An F10 8" SCT and an 8" F4 Newt can image at the same speed and image scale if the pixels sizes are adjusted accordingly. They would also have the same SNR. It really comes down to camera choice-preference. I prefer my ASI533mm to other camera choices. Thus, my chosen scope would be an 8" F4 newt (or 10" F4) to image at 1 arc second (or a bit smaller)..

Another great instruction video! Thank you.

Zetas, you don't know what will happen to you. The decision has already been made, but you will be informed in the same way as you do. With you now only by your methods - we do but do not warn. Specify the date of the evacuation of all Zetas from the planet. It is close. The ships have already arrived, waiting. i creat for Zetas new word - uZeless - useless Zetas biorobots and Zetas too. Orion group by by too

this is best explanation about the f ratio i have ever seen .

How many hours did you expose with both telescopes? I have the C8HD with x0.7 a F7 and the william optics pleiades 68mm F3.8. Both got Asi294mcpro. I did both on the Crescent for 3h with a dualband HA-OII filter. And i have more detail with my F3.8 than the C8. I need more than 12h to get a good detail in the Crescent

I agree with what you are saying in this video, but i think why people like telescopes with fast focal ratio is because you improve SNR quicker. As you said, the light is less spread out, so each pixel on the sensor gathers more light in a given amount of time, resulting in less noisy images.

To see another comparison of the difference between wide aperture and narrow aperture at similar focal ratios, follow this link to the Sky Story Astrobin. The image is NGC 5194, shot on a 203 mm SCT and on an 81 mm refractor. The refractor image was shot in better conditions and had almost twice as much integration time. The wide aperture SCT still substantially outperformed the refractor. www.astrobin.com/bvs7mz/C/

Refreshing explanatoin. Some 40 years a go, had a lesson in school about this stuf. Strange how all is still in your head and that is comes to the surface when you watch a video that stirs in your brain ;) (I have a Altair Starwave 110ED-R F7)

Great debunking of misconceptions. Every astronomy fan from the times, when there were no digital cameras, knows that both the resolving power in seconds and the limiting magnitude of the telescope depend only on the entry diameter of the scope and nothing else. So it would worth mentioning not only the resolution formula, but also limiting magnitude formula which is 5*logD + const, where const depends on the receiver, whether it is basically an eye or photo sensor.

My "slow" Explore Scientific 127ED F/7.5 produces some of the best images for me.

I think the main reason people think and like to say a low f ratio is faster and therefore better than a higher f ratio is to make it simpler for beginners.

Very didactic! Thanks for sharing

this is why i love your channel, this info goes right in the face of all the youtube channels, peddling the redcat 51 and all its derivatives as if its alpha and omega of astro photography

I also just love spreading misinformation 👍

I would rather have an off axis f/20 than an f/2 hyperstar

more troll food?

Great explanation!

One thing I love about this hobby are the options for equipment, processing and presentation. I've made some deliberate choices on all and am very happy with those choices. Part of that decision making is around the effort I wish to expend collecting and processing images. Some love the task of getting every pixel "right", whereas I'm just looking for that pretty picture with a modest element of scientific reality.

Colour doesn't exist. Fascinating. I always wondered.

I think the big challenge for me in learning PixInsight was the lingo/labelling of the different tools, compared to what similar tools would be labelled in other software. Image Solver, Spectrophotometric Color Calibration, Deconvolution, Generalized Hyperbolic Stretch, etc. took some time to unravel. It did help to be familiar with image editing using other software, but it took a while to work through the complete workflow. And it was a bit of a challenge coming from a layer based workflow to one that is not. But luckily, humans are very adaptable. And the results are great.

Recently canceled my PS sub and and moved to using Affinity Photo. Also starting to feed it into my Astro photo processing so have been finding your videos very useful so thanks for that! Question: Have noticed that you use the erase tool instead of masking the layer. Curious about this choice? Is it just a method you are more comfortable with or are there other reasons behind the choice?

Hi, thanks for the video. I have the plugin for a long time. I use it in the startup part to connect everything. The problem that the camer is not aple to write to disk , is something I have too sometimes. But at that moment I have also that all other USB connetions fail. But I think that has something to do with the age of the laptop I use.

You seem to present subjective taste as a fact. Odd.

I prefered narrowband ones. Its subjective.

What was the background music in this video please

WTF…? At 12:50 there are two objectives in the right upper quadrant, moving away from the center of the picture. Is that live view through your Celestron scope?

Your info and insight are amazing! Thank you so much! Really helping me to understand astrophotography concepts. I am very grateful for your willingness to share. Thank you!

Hey Cliff, Interestingly, I was able to do the manual stack as on 70 FITS files thanks to your video instruction, however, it rejected 39 of them for some reason. Yet, when I do a SCRIPT-based stack, it registers and uses all 70 files. I must have some stringency setting in the manual mode that is causing this rejection. Any idea what might be the most likely cause?