Filroden

I'd weight up the benefits of a field flattener when doing alt/az photography. It helps sharpen stars at the image edge, but this is where you'll get the most distortion from field rotation and are likely to be cropping out of the image anyway. I'd say it would only be worth it if it was a field reducer as well as a flattener to give you a wider field of view or if you moved to equatorial imaging when you can use the full field of the image.

That's a good start but I would caution using darks for DSLRs. Unless the camera is cooled, your darks are unlikely to be consistent or matching to your lights and can create as many problems as they solve. Try using just bias and flats and compare to bias/dark/flat to see which gives a better starting point. I would also say crop crop crop! You need to make sure you've cropped out all rotation from the image. I can see you have some areas around your image border where not all images have overlapped. These create massive post-processing problems when you try to colour calibrate, remove gradients, etc. So, make sure to crop inside before processing. You can always really stretch the image first to get an idea of where you need to crop, then undo the stretch and then apply the crop.

Check out this article: https://astronomy.com/news/2005/07/the-life-and-times-of-sirius-b

Beautifully captured. Would love to know how you created the black speckled border effect in the frame. Is that just a second image behind it or do you create the black border using the original image itself?

The single biggest tip for post processing Alt Az images is to crop. Crop heavy! You need to remove all the stacking artefacts caused by field rotation before doing any other post processing otherwise it will be a nightmare. And those artefacts can reach far into an image so really stretch the image to see them, undo the stretch and make sure to crop inside. Of course, the single biggest top for pre-processing any image (alt-az or eq) is use flats and either darks/flat-darks (for cooled cameras) or bias/bias (for uncooled cameras). The goal is to get your starting stacked image to be as clean as possible to make the rest of the processing easier, especially gradient removal and colour correction.

I love it. And from Bromley! Have you been having blackouts?

Take a photo of it once it's displayed!

Zooming beyond the point where 1 pixel of image fills 1 pixel of screen will start to pixelate, i.e. go blocky. By rescaling the image you're effectively adding many many more smaller pixels by using fancy maths to try and estimate how they should be filled (you can't create more detail but you can fake it!). That allows you to zoom further. The better the maths, the more real it might appear. However, resizing does like images that are smoother in graduation (easier to calculate the missing bits of data). Astro images can be quite detailed and because its stretched, can lose that smooth graduated feel of a daylight image making it harder to rescale. I've never found a good way to test what something would look like printed by viewing the screen. Screen pixels aren't the same size as printer pixels so viewing 100% on screen isn't what you'd see in print. I end up creating the right sized image using the DPI and desired print size then I zoom the resulting image until it broadly looks to be the right scale across, i.e. 20" of intended print area takes up roughly 20" of screen size (which might mean zooms lower than 100%).

You'd need to ask the printers whether they are happy to do the resizing or whether you would need to do it. I don't know if I'd push it as high as 48" by 40". Below is a slice from the image I created at that scale (300dpi). I think it holds up well. And don't forget the viewer will not be as close to the image as you are to the screen. Stand back 4 or 5 feet and tell me it's not an impressive image! I've printed my own images (ZWO 1600ASI images) at close to a cropped 40"x40" and they look awesome. My printer will do fairly cheap "tester" prints where they print maybe 1 inch of the full width of the image to show you how it would look (I get to chose which slice they print). It's worth talking through the options with them. Also, there are many algorithms to rescale the image. I only tried the default so better results might be found from the others.

I've just thrown the image into Affinity Photo and used a simple bilinear resample to make the image 48" x 40" at 300 dpi and it still looks good (to my eye). The file size on a 95% JPG quality setting is ~55Mb, but there are a LOT of pixels in there Photoshop allows similar simple resizing. I probably wouldn't use PI as its not really print production software. As for preferring JPG, I'm not surprised. Even at 300dpi, the compression in JPG at very high quality settings should still be unnoticeable to the eye at a proper viewing distance.

The simple answer is exposure. The more lights you can take and integrate, the more you can lift the signal and then deal with any noise in post-processing. The other answer is random dithering but that requires that the mount can be finely controlled between images. Getting the ISO right can be a bit of trial and error. You're looking for an ISO that minimises read noise without blowing the exposure (which could be a risk in very light polluted or moon-lit skies) and that differs by make/model of camera. There are some good sites that show the read noise curves for cameras. You're looking for the point where there is minimal improvement in read noise when increasing ISO (near the bottom of the steep curve). Don't worry about using lower ISO's. You'll recover the signal through integration and stretching.

Can't say I understand it all, but the boxes with italics are qualifiers to the metric in upright text, so a troy ounce or troy pound. If I read it correctly, there are 12 troy ounces in a troy pound and 15 troy ounces in a london pound. The different qualifiers come from the different types of things they are measuring. Troy is usually a measure of weight for precious metals. So this is a relationship diagram for all English weights (some of which are no longer used). Wiki show a nice timeline for how weights and measures changed over the last 800 years: Glad I was brought up with metric measures!!

Having just seen this thread I'm now tempted to do the same and invest in a new focuser. I've just seen FLO also offer the stepper motor for the Lakeside system so I can re-use the other bits from my existing set up and spend a little less to automate the focusing. Why oh why do I read threads like this that just invite me to spend more money!!!

Good first effort. PixInsight can take a while to get to grips with even the basics but once you become familiar with it, it becomes a lot easier to use. I'd recommend hitting your background with some noise reduction, particularly colour noise. TGVDenoise would be ideal on both RGB/K and chrominance. Extract a luminance copy of the image and apply it as an inverted mask to protect the brighter areas so noise reduction only works on the background. It should help reduce the speckle.

Deleted post - misread the original

Given you caveat then Lightroom should offer you most of what you need. However, it is not very good at taking linear astro-data and stretching it as it's really designed for normal photography and does not give fine controls over applying non-linear stretches to an image's "exposure". Personally, I would only use Lightroom once that initial stretch has been done. If you may want more control over the various functions (contrast, tones, etc) which would probably mean using a more dedicated photography package like Photoshop (not cheap), Affinity Photo (much cheaper) or GIMP (free) which will give you finer controls and they can all do non-linear stretching using iterations of either levels or curves. But you shouldn't consider image calibration and stacking as a time consuming process. It can be if you want to do a really good job and PixInsight as well as many other packages can do very good jobs. But you can do simple and quick calibrations and integrations in Deep Sky Stacker and then take the resulting TIFF into Lightroom for finishing touches. You can run a trial version of PixInsight for free for a limited period but it sounds like it wouldn't be right for you at this stage in your astro-imaging journey.

If you use a FL of 468 and a pixel size of 4.54 it will solve. And guess what it does? Makes the image more blue!! LOL

I fear we're mixing colour terminologies between RGB and HSL (or HSV). Saturation that does not change the colour balance (hue) only makes sense when considering HSL(V). To change saturation in RGB without affecting colour balance requires changing the rations of RGB and the luminance to which it applies. Of course, you can convert between the two at will, so you can apply "saturation" tools to RGB values but they will not appear to work the same. H53 S75 L50 = R128 G116 B032 with a luminance of 49% H53 S50 L50 = R128 G120 B064 with a luminance of 50% H53 S25 L50 = R128 G124 B096 with a luminance of 52% (rounding error as PS only shows integer values) So both scales describe the exact same colour balance but in different terms. I think this derives from RGB typically being used for print and HSL(V) for screen.

Glad you got this resolved. Isn't SGl a wonderful place?

GIMP should have all the same core processing abilities as Photoshop though they may have different terminologies. Where Photoshop will possible shine is in the available (paid for) extensions which can make astro-processing easier. Before investing, you may want to trial more dedicated astro-processing software such as Startools, PixInsight, Astroart, etc. These have more astro-oriented processes such as gradient removal and colour correction built in. Each has its strengths and weaknesses, and a lot of which package you eventually use will be subjective based on which workflow you prefer. Some of them also offer better calibration and integration tools than DSS. There are plenty of web and YouTube tutorials for each of them and I think they all offer trials. Edit: I should add, these packages have different ways to do colour calibration. E.g. PixInsight can plate solve your image and match the stars to their spectral type using an online database and then apply colour corrections to get your image as close to their "true" colour as possible.

I doubt you can avoid it. If you want coloured stars you may be better developing two versions of the same image - one with a very light stretch just to get whhat colour you can in the stars (the galaxy will probably be lost in the background) and one to process the galaxy then join the two images so the stars from one join the galaxy from the other.

I note you're only using DSS and Lightroom to process your images which could explain the blue colour cast. Whilst M101 does have blue arms, the giveaway to know the colours in the image are not balanced is that both the background, which should be a neutral grey, is much bluer and slightly more green suggesting red needs a boost and blue dialled back. Also, the centre of the galaxy should be a yellow hue. Your stars are fairly saturated so they aren't going to help you balance the colours unfortunately. Colour balance needs to be done early in processing. You'd need to separate the RGB channels and work them individually before they are stretched. And each will require it's own stretch. That way you can boost the red channel which looks to be weakest and tone back the blue. This is probably be beyond DSS and Lightroom so you may need to use a third package to do the bulk of the heavy lifting and use Lightroom to do the finishing touches (vibrance, sharpness, clarity, etc). Did you image under heavy light pollution or under moonlight? They may have introduced the colour cast so you may also want to remove any gradients in the image before stretching.

So any planet, whether an inferior or exterior, can be see at midnight at very high latitudes during winter because it's also possible to see the Sun at midnight at those latitudes! I think the BBC have over simplified something to the point that it's now actually more confusing. As Louis just posted:

I've only started to skim my digital copy but I can already see how useful the additional reference guide is going to be. I was expecting as fairly short second book but its 263 pages on its own! Nicely written too. More conversational than lecturing.

Where did you order it from?