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imakebeer

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Posts posted by imakebeer

  1. Same image as above but I had another play with the starless image using Siril's GHS tool to try and improve contrast. 

    All I've done in GIMP is recombine the starry & starless images, no further stretching. 

    Somehow I think I prefer this one, I think it's less pink and has a wider range of colour tones.

    The field does look more blotchy but as above I do wonder if this is genuinely signal rather then noise - more data needed to find out! 🤞🙏🔭

    NGC281_01b.jpg.989f182e529f253c5d270ca82dcb07c0.jpg

    • Like 3
  2. Like you I'm also SE of UK, also with work and dad duties 😉. Now I'm back up to speed I'm using a scope with tracking, but to get back into the hobby I did some wide field of Cygnus & Milky Way a couple of months ago.

    My D5500 Is a crop sensor whereas I think your D7500 is full frame. But I was using a fixed tripod, no tracking. With my 35mm prime lens I was fine with 15s exposures with no star trailing. With 18mm you could probably go longer (there's a formula somewhere to calculate max exposure length for a given focal length).

    For me I felt 35mm was a bit too zoomed in, while 18mm was maybe a bit too zoomed out, but you can experiment.

    Tracking will absolutely give you more, but you can still dip your toe in the water just with a DSLR on a fixed tripod (before deciding to remortgage your house and join the rest of us at the bottom of the slippery slope that is appropriate! 🤣)

  3. On 25/10/2024 at 14:26, TiffsAndAstro said:

    Im probably wrong but I think background neutralisation via top part of colour correction in siril should do this? Ie line up the channels. 

    No you're not wrong - I hadn't ever used this before but it did a good job of lining up the LHS of the histogram as well as the peaks.

    The result was a much more neutral background space colour rather than having a green or magenta cast. And much quicker & easier than doing it manually in GIMP - good tip, thanks 👍 

    It doesn't align the RHS of the histogram however, though I speculate this is because it's where the bigger/brighter colours we see in the image come from, e.g. Ha regions in the pacman nebula are reddish so we see more red in the RHS of the histogram than blue or green.

    • Like 2
  4. Very nice image 👍

    Orion is still a little low in the sky to clear the roof of my house but I'm hoping to revisit this one again soon.

    One comment/suggestion - I believe it's quite easy/common for the core to end up a little blown out. I've used layer masks in the past to improve this, example here in one of my early images. In that linked thread there is also advice to image the core using a much shorter exposure and blend the results together - never tried this but hoping to give it a shot soon 🤞

    • Like 1
    • Thanks 1
  5. Your first image is more pink/purple while the second one is heading more towards turquoise - not sure if you were using any kind of filter? Both are good but I think the second one has more detail.

    By the way, with regard to discarding bad frames - are you stacking in Siril? If so you can use the registration plot to include/discard good/bad frames based on various criteria 👍

    • Thanks 1
  6. Thanks for the feedback 👍

    JFYI, I posted the processed image here - I decided to align RGB in the histogram before I proceeded with further histogram stretching etc.

    2 hours ago, michael8554 said:

    This offset is not unusual, for example in Ha modified DSLRs, and is easily removed in image processing.

    Modified Canon 450D 😉 I know it can be removed, the question is more should I?

    2 hours ago, vlaiv said:

    Now, if you take your linear image and remove the background - you will get the same effect - without messing with histogram, or rather histogram will be aligned as a consequence of good background removal

    I stack and crop in Siril first, then I already did BE with GraXpert prior to further processing in Siril and then GIMP.

    Are you saying I should run BE again?

    2 hours ago, Elp said:

    Photometric Colour Calibration in Siril does a similar thing

    This is the first thing I do after BE in GraXpert.

    2 hours ago, Elp said:

    I'd guess that particular image is very red

    Yep, Pac Man Nebula which is (I think!) H-alpha emission, so yes, lots of red.

  7. About 2-2.5hrs data captured while I was waiting for M33 to clear the neighbour's house. I think it would benefit from more data of course, but I'm pretty happy for a first stab and I think there's a bit more to come from the histogram even as it stands.

    Canon 450D (modified) + Optolong L-Pro + SW150 PDS

    Edit: There's a bit of blotchiness in the background, but I'm wondering if it is genuinely signal rather than noise, maybe some faint H-alpha??? I didn't want to clip it out so I've kept it fairly neutral and low level for now but much more obvious if I stretch the histogram like crazy.

    NGC281_01a.jpg.e2298079e893553f3daf9e3683e4b0e2.jpg

    • Like 6
  8. Something I'm noticing lately when I bring my starless images from Siril to GIMP for final processing is that the RGB histograms are slightly out of register - in particular the green channel is shifted slightly left, e.g. Pac Man Nebula:

    fixed-not-histo.jpg.efbb2d190de41319ad4d1b23a331ca9f.jpg

    Now the cause might be my L-Pro/L-eNhance filters which @Elp was saying can cause a green cast (or it could be some aspect of my Siril processing!).

    But is this OK, is it right or wrong - or neither! I can use the tools in Siril and/or GIMP to bring them back into alignment, but is this necessary? Or is it simply a question of applying my own artistic interpretation (such as it is!) to decide for myself?

    A couple of example starless images of the Pac Man Nebula:

    Histogram similar to above (i.e. not "fixed"), just a slight adjustment to the black point:

    fixed-not.jpg.cf2b1ec5cf989ef96ed17956b617fa97.jpg

     

    And now same image but RGB histograms more aligned, plus similar black point shift:

    fixed.jpg.4f61984613e65cf44aad5537996d030b.jpg

    For me both images have their pros & cons, too much green vs. magenta, the sweet spot is probably somewhere in the middle. Plus I also understand that the H-alpha we expect from this target is basically red so this must skew things a bit.

    Any thoughts and advice on this?

  9. 13 minutes ago, Paul M said:

    I'd be very happy with that image. It vibrant and natural. Not too forced,

    But if I was to ask a question, I'd ask; what's the source of the squarish stars/halos? Is it a GraXpert artifact ?

     

    A very good question! I have been wondering that. I wondered if it could be a collimation issue - I'll have to have a hunt through the images to see if I can track down where it first appears 🤔

    • Like 1
  10. 1 hour ago, TiffsAndAstro said:

    What sub length did you do for M33 btw?

    I'm going to try 2 minutes tonight up from 1

    Just posted my image here. At the moment I'm just doing 3mins on everything - I've tested 5mins with guiding which worked out fine but not dared commit to a full session, though I'm not really sure why! 😂

     

    • Like 1
  11. A big step on from when I last imaged M33 a couple of years ago, but still a way to go.

    Not sure why I didn't check the framing but I need to rotate the camera 90° 😖

    Otherwise I suspect simply more data will help, but it's a start.

    One thing I can't work out is why my galaxies are coming out turquoise, or if this is even "wrong". Could be filters or I wonder if it's related to some processing in Siril. Or both. Or neither.

    Canon 450D (modified) + Optolong L-Pro + SW150PDS, just under 5hrs, processed in Siril, GraXpert and GIMP.

    M33_01b.jpg.c4d7037187d58921cde29616a1119f52.jpg

    • Like 4
  12. 1 hour ago, TiffsAndAstro said:

    are you swapping in a filter for pac man? i was disapointed with my nb version of it i probably just need more time on it. 

    Well I tried a couple of years ago with an unmodified DSLR and the results were not great due to my inexperience at the time (as if I'm some sort of oracle now, hah!).

    Now I'm using a modified Canon 450D - to answer your question I'm just using the Optolong L-Pro which I suppose is really a broad(er) band /LP filter. I left this in from M31 the other day, plus I figured it would be more suitable for M33 which was the main target last night.

    I'll post pics once I've processed both so I guess we'll see! 🤞

    • Like 1
  13. I think you and I are just imaging the same targets at the moment! 😂

    I feel I'm happy enough (for now) with my latest M31 so I decided to move on to M33, both of which were among my very early efforts a couple of years ago.

    But since it takes a while for either of those to clear the neighbour's house I figured I wasn't going to waste the clear dark skies so.....

    • I did quick a bit of comet while I was setting up.....
    • Then a bit Pac Man Nebula.....
    • Moved on to M33 as soon as it was in sight.....

    But it turns out the camera had a hissy fit in the night which brought proceedings to an early end 😒, otherwise my plan was to grab some quick M45 before dawn.

    Certainly not a total loss though - I got almost 5hrs of my planned 6hrs on M33 which was the main objective for the night 👍 Almost all of that looks useable, plus the last couple of frames were disappearing into the trees so I don't think I'd have got any more useable data as it turns out anyway 🤞😃

  14. Update: 

    I had a go at combining the L-Pro data above with my previous L-eNhance data. I think this is bringing out a lot more detail but colours are tricky - I'm trying just to bring out what I see in my data and not be too swayed by the warmer images I see elsewhere.

    I'm also pleased with the way I've included more stars in amongst the actual galaxy. 

    M31_combine01_01c.thumb.jpg.f9318203383b082d942b63c7082fff72.jpg

    • Like 2
  15. (Edit: scroll down for v3!)

    New data compared with previous effort - this time using an Optolong L-Pro filter.

    2 panels, 3hrs on one, about 2.5hrs on the other (trees!)

    Canon 450D (modified) + SW150PDS

    I think more data will bring out more detail, but i also want to try combining with some NB data captured using an optolong L-eNhance. But I'd also like to do a bigger mosaic to get a wider view.

    Thoughts/questions:

    1. Have I gone too far with the turquoisey colours? Could this be coming from H-beta or OIII, I believe tthey are blue??? I think there's something real there, I was trying not to go too mad with the saturation!
    2. There are brown-red areas in the bottom left and top right corners - I thought initially this might be noise or edge artifacts but now I'm wondering if it's real regions of dust, H-alpha maybe???
    3. The black to the top left looks very black but I'm sure I'm not clipping the histogram.
    4. Very interesting to compare with @John Nodding 's image here - I think his is better, something to aim for, but interesting that we're doing something different with the stars, something for me to experiment with in GIMP.

    Comments & suggestions welcome 👍🔭

    M31_02.thumb.jpg.0aa6775b5909697ac115e9cf23ba5392.jpg

    • Like 5
  16. Oh flippin' 'ell! Every time I get something I think I'm reasonably happy with, and that's an improvement for me, someone like you comes along and moves the goalposts! 🤣

    (but it's good because it gives me something to aim for as a next step while not feeling totally out of reach, and other ideas how to compose my own image)

    Very nice image 👍 I couldn't see the green cast on one screen but could on another better one. I like the framing and the level of zoomed-in-ness. Interesting to see how your image looks more starry than mine (will post it later) - not better or worse, just different.

    One other thing I thought is whether you could control the core a fraction more, but it could be my eyes playing tricks.

  17. Hey @simmo39 , just out of curiosity what scope & camera did you use?

    I'm just trying to figure out how you ended up with such a wide FOV in the first image (assuming it's not a mosaic???)... Ultimately I was happy with the image I got (SW150PDS + x0.9 coma corrector + Canon 450D) but the FOV is much closer to your first cropped image.

  18. Not amazing but definitely better then when I was starting out 2 years ago.

    2 panels, each with 72 x 3 min light frames captured over 2 nights.

    Canon 450D (modified) + SW150PDS

    Also used an Optolong L-eNhance NB filter which I know isn't ideal or doing me any favours for galaxies!

    Processed using Siril, GraXpert, MS ICE and GIMP.

    Bit still, pleased to have had a first crack at a mosaic, it's all experience under my belt! 👍🔭

    M31_02b_GraXpert_banding.thumb.jpg.63674f4275d91c1edd4685362e81b618.jpg

    • Like 1
  19. 7 hours ago, TiffsAndAstro said:

    you can possibly remove/reduce those by pre-cropping more before stitching.

    Actually that's more or less what I did - I cropped both stacked images before doing the background removal in GraXpert which seemed to improve things. Still room for improvement but at least I've got something in reasonably happy with now 👍

    • Like 1
  20. 15 minutes ago, alacant said:

    So that other air users don't suffer, perhaps you could summarise how to process DSLR images using the same?

    Cheers 

    The Canon 450D produces 14-bit RAW *.cr2 files and has a hardcoded offset of 1024. The ASIAIR Mini appears to convert these to 16-bit FIT files.

    If you're shooting with an ASIAIR Mini (I would assume other ASIAIR types behave the same) and want to process your images in Siril you have 2 choices:

    1. Work with the original *.cr2 files and let Siril convert them to FIT format for processing - in this case use a fixed bias settting of 1024 in Siril. (You also need to apply the setting in the ASIAIR to save the RAW *.cr2 files to the camera's SD card)
    2. Work with the FIT files from the ASIAIR - in this case use a fixed bias settting of 4096 in Siril (i.e. 4 x 1024 = 4096, because to convert from 14 to 16-bits you multiply by 2^2=4)

    One advantage of the ASIAIR FIT files is that they are sorted into separate directories. On the other hand purists may prefer to work with the original *.cr2 files but they will need to be sorted manually. My experience so far is that provided you use the right bias setting in Siril the result is nigh on identical.

    • Thanks 2
  21. 3 hours ago, alacant said:

    Siril retains the 14 bit (Max value ~16000)

    Really? The 2 screenshots below are from the preview in Siril's load dialogue - exact same flat file, one is the original CR2, the other was converted by Siril to FIT. But it could be wrong. In any case I think it's fine since I think I've figured out how to manage my data now 🤞

    Capture1.JPG.bd50bf02368504f1bbbbbb887abee17a.JPG

    Capture2.JPG.58448605a00f332f610c8380b6fef2a3.JPG

    2 hours ago, Elp said:

    Have you tried converting the cr2s to Tif using Canons Digital Photo Professional first? I always used to to this prior when using my Canon. But thats not resolving the air output.

    Thanks but not really necessary I think dude - now I understand (I think! ) what the ASIAIR is doing there's nothing to resolve as such. Even though I got there by 2 different routes, I was astounded how both methods yielded almost identical results, I mean the difference was really splitting hairs.

  22. 8 minutes ago, alacant said:

    Conclusion: the air is doing something to the cr2 after it arrives from the camera.

    Fundamentally yes, I have the same conclusion. I think I tested that before with bias frames at 1/4000s in darkness:

    • The RAW cr2 has an offset of 1024
    • The ASIAIR converts it from 14 to 16 bit and the offset is 4096 (x4 the 14-bit value)
    • But if we let Siril convert the cr2 to FIT file (which as far as I can tell is also 16-bit) it still has an offset of 1024 (this is the bit I can't figure out)
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