Filroden

I'm liking the less bright full image more than the brighter cropped image. It's not so much the brightness but the high contrast across the cropped area that makes it difficult for me to see on a screen. I did have a quick play with the jpg to test this and I definitely found a lower contrast (and less bright) image easier to look at. That said, the contrast/brightness does clearly show the quality of the data and brings detail into focus that you just would not find in a lesser image!

Just to add the answer regarding darks for your flat frames. You will only need to redo these if you use a different exposure length for your new flats. If your new flats are the same exposure as the original flats then the existing darks should calibrate them. However, in practice, I find my flats always have different exposures. I do a test exposure to a fixed ADU value and use a light source that is variable - sunlight - so they vary quite a lot between sessions. However, because my light source is so bright my flats only take a second or two to expose so it's very quick to run off 30 new darks per filter (each filter also changes my exposure time).

Such sad news. I’ll always remember sitting with Heather and Nigel on Alderney watching the eclipse. When it ended I remember she looked down and spotted a pair of very amorous snails sparking a really interesting conversation on the effects the eclipse had on nature.

I would recommend giving PI a go for the image calibration, registration and integration as I think it gives much better results than DSS. PI has a batch process that simplifies this process at the expense at removing many of the options. It works in a similar way to DSS in that you load your bias, darks, flats and lights into different areas then select some calibration/integration parameters then leave it to work its magic. Alternatively, there is a really good step-by-step guide here for doing it the longer way. Again, I think this way gives better results. https://www.lightvortexastronomy.com/tutorial-pre-processing-calibrating-and-stacking-images-in-pixinsight.html PI has a new process called PhotometricColorCalibration that effectively replaces the above two steps into a single step. It uses plate solving to identify the stars within the image and uses that information to properly balance colours based on their spectral types. You have to get the initial scope/camera parameters right to enable the plate solving but once these are set, this is module can be used with default settings almost all the time. I also like TGVDenoise once you've stretched the image to help further reduce noise. There's a good noise reduction tutorial here. https://www.lightvortexastronomy.com/tutorial-noise-reduction.html Finally, I'd recommend Warren Keller's book, Inside PixInsight which received a second edition in 2018 to cover some of the new features in PixInsight. It remains my goto book to help me through my workflow.

I guess my only feedback is that I find the strong colours in the stars are distracting me from the galaxy. I'd be tempted to create a starless layer and only tweak the blue saturation in the galaxy disc. I'd also be tempted, in the star layer, to desaturate all stars a little (5-10% only) so that when recombined, the galaxy stands out a little more. Of course, this is totally unnatural, but the focus of the image should be on the galaxy and not the background! Had it been a photo, I'd have even put in an artificially vignette to further draw the eye into the centre of the image but it feels so wrong to do that having spent so long on flats to eliminate them in the first place Or do nothing more to the last image and call it a good one!

I feel this is too much a #firstworldproblem. We all enjoy nice internet and telephone connections so happily object to others, in less accessible places, not being able to access those same services because it might spoil our hobbies, without even quantifying how it might spoil our hobby. As Wim so clearly demonstrates, removing satellite trails is an integration 101 step. With sensor noise levels continuing to drop we can afford to take shorter and shorter subs, further reducing any possible impact on imaging. Global communication provides far more benefits to society than amateur astronomy, so I support the use of space to improve the lives of everyone even if it slightly inconveniences me. I can easily adjust my imaging strategy...large parts of the world cannot easily adjust their ability to integrate into the global communications network.

What are you using to stack the lights? A good pixel rejection algorithm will remove the track and might also remove some of the hot/cold pixels that are causing the "walking noise".

I think that will add some great highlights to an RGB image and help lift the galaxy.

Is there an edge glow on the left side of the second image in the montage? It looks noticeably brighter. Might be worth checking the ADU values across a row.

In the three bias frames on camera 1 that show the higher average ADU, can you detect any significant variance within parts of the image or is the higher value fairly constant across the image?

Neither look right to be honest. I can see the same elliptical graduation in the master. My solution - don't calibrate with bias (master or super). You will be better just using matching darks and flat-darks to calibrate your images as these contain and will correct for bias without the need for an additional step. The only time I can see a need to use bias is if you were using incorrectly matching darks and were using PixInsight to scale the dark. However, it's much better to always match your darks and flat-darks. As to why your bias looks wrong - what exposure length were you using? I can't remember if there was an issue with some exposure lengths conflicting with the rolling shutter and distorting the results.

It varies considerably by location and over time and is unlikely to be 5 degrees anywhere in the UK this year. Here's a link to the US/UK model for 2019: https://www.ngdc.noaa.gov/geomag/WMM/data/WMM2015/WMM2015v2_D_MERC.pdf As you can see, in the UK, the difference between true and magnetic north in 2019 is more likely to be in the range of 0 to 2 degrees for England and Wales and in the range 1 to 4 degrees for Scotland and 3 to 4 degrees for Northern Ireland.

Two tips that helped me: the metal in the tripod can affect the compass so make sure it’s far enough away adjust for difference between magnetic and true north which is about a degree for me

It’s nice and subtly processed. You’ve kept it looking natural. My only feedback is your smaller stars are square.

Are you creating a synthetic L from all that RGB data in the LRGB version? Given how much you collected, it may strengthen the L data. Is something going on at the edges of the image? I'm not sure if its real or an artefact but the border looks distinctly different to the main image.

Nice method to quickly enhance contrast. The PS method is certainly simple to understand and control. For PI users, there is something similar in the LocalHistogramEqualisation. It doesn't need the mask and has a live preview option. Don't ask me what parameters to use - as ever with PI, trial and error! From the manual: "This process implements local histogram equalization with configurable limitation of maximum contrast enhancement. It is based on the CLAHE method (Contrast-Limited Adaptive Histogram Equalization). The main purpose of the process is to enhance local contrast and visibility of structures in low-contrast regions of the image. The process is designed to run on non-linear (already stretched) images. Histogram equalization takes the histogram and computes a transfer curve, which grants more brightness range to higher histogram peaks and less brightness range to histogram valleys. In other words, large areas of similar brightness get more contrast. Local histogram equalization works on individual pixels and computes a transfer curve from the histogram of a pixel neighborhood. The classical histogram equalization algorithm has the drawback of giving most contrast range to high narrow peaks, like a uniform noisy background. This problem is solved with the contrast limit property of the CLAHE method. This parameter limits the maximum slope of the transfer curve and prevents narrow peaks from getting too much contrast, effectively reducing noise promotion."

As far as I know, you can't make it bigger. I've just ran into the same problem. Mine is docked in the side pane. You can change the size of the "container" but not the actual histogram within it It might be worth you floating the question in the Adobe forum and/or providing Adobe with feedback.

Hi Rodd This is a tough one. I like the presentation of the first - both the wider context and the bolder saturation of the colours. However, I think the second is the better of the two images. The main things that swing it for me are you have colourless stars in the first, whereas the second image has coloured stars. They just make the second image look more natural. The other thing that swung it is that the first image appears "blotchy" in the background - almost like one "frequency" of structure has been over processed. The very largest scale structure looks good, and the medium and smallest scale structures are exquisite - but the large structures look "wrong". I don't see that issue in the second (but to be fair, the issue is most pronounced in the wider background which you've cropped out).

I've a different take for Photoshop. I do a lot of non-Astro photograph and have always used Adobe Lightroom to develop and manage my photos. The photographers subscription includes both Lightroom and Photoshop, plus I've also got 1Tb of online storage for my photos. All for £15 per month. I used to pay £7 a month for 1Tb of storage anyway, so I'm getting Lightroom and Photoshop for £8 a month. That's a fraction of the cost of a decent filter or eyepiece or other accessary per year. Given how important the processing of the images are, why be reluctant to spend on the processing tools when you are willing to spend on the data collection tools?

I wish my first attempts as astro-photography were so easily recognisable as astro-images! Well done. It gets better and easier from here Your M9 is much sharper than your M4. Did you do anything different? I'd recommend not using low numbers of darks (if at all). Unless your camera is cooled, darks could add more noise than they remove. Even if your camera is cooled, using only a small number of darks could likewise introduce more noise. I'd recommend taking 25-30 darks if I was using them as you can use better statistical rejection algorithms to combine them. I'm also not sure that your flats are fully working. You seem to have light pollution gradients (not surprising in HK) but they show the classic vignette of an image that has not been fully corrected by flats. What processing software are you using? There may be ways to improve the flat correction and remove the light pollution.

Really good tracking there with nice round stars almost throughout. I think the target might have benefitted from the longer focal length though I know it's hard to pass over a lens then performs so well!

All I can add to the advice above is make sure you test whatever set up you decide to use before you go on your trip. Things that are easy to forget and not easily obtained under dark skies include: A focus mask to go over the front of the scope/lens to help you get sharp focus on stars (works really well for cameras that offer a "live" view that can be zoomed in x5) Adaptors and extenders to join camera to said scope/lens Enough removable storage for the camera so you have enough space to take lots of shorter exposures (if you go down an alt/az route) A decent finder scope if you need to align a goto mount (I found the red dot finders useless, finder scopes much easier and the "live" view through the camera the best once in the right area) Good binoculars so you can enjoy the dark skies while you image A dew shield if you're using the scope and you're going to areas where dew will be an issue Otherwise, keep us posted on the results!

+1 this I don't know about Skywatcher mounts, but the Celestron mounts can polar align using any three stars. It does not need a view of Polaris. It does some wizardry and works out how other stars would move and you adjust your alt/az bolts to centre your chosen star (e.g. something close to meridian).

The rear clearance looks worse than an SCT with image train for the evo mount. I think pushing the newt too far forward could cause issues in the wind.

My 1600 runs quite hot. Would that impact the brackets? They could raise camera temperature, or deform?