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Filroden

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Everything posted by Filroden

  1. Check out this article: https://astronomy.com/news/2005/07/the-life-and-times-of-sirius-b
  2. 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?
  3. 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
  4. I love it. And from Bromley! Have you been having blackouts?
  5. Take a photo of it once it's displayed!
  6. 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 gradu
  7. 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
  8. 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.
  9. 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 lookin
  10. 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
  11. 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!!!
  12. 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.
  13. 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 w
  14. 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
  15. 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 = R1
  16. Glad you got this resolved. Isn't SGl a wonderful place?
  17. 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.
  18. 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.
  19. 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
  20. 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:
  21. Hi Carl, I have a Nexstar Evolution 9.25 OTA I'm not using. However, I wouldn't want to post it as I no longer have all the original packing materials. If you don't find anything before restrictions are eased, I travel down to Stroud and Bristol quite often, so could deliver it.
  22. 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.
  23. 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!
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