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BrendanC

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Everything posted by BrendanC

  1. Wow. Thank you so much everyone. First up, @ONIKKINEN, that's very interesting to note. I'm wondering whether this was a bad target for my first LRGB. It's very low in my sky, which could be introducing some light pollution, and if what you say is true about neighbouring bright objects, well that could also be contributing to my issues here. But to go on to @symmetal - thank you, thank you, thank you. This is amazing, to think you spent all that time to look into this for me and share your findings. Just to go through your points: I'm glad the flats look fine, but I'm still going to give them another go today. From what I've read, and as you say, it seems ZWO cameras might not like very short flats, so I'm going to add some paper on top of my LED pad to try and give them more time, and see what happens. I cropped very far in simply because I wanted to be sure of no artefacts. Also I was running a macro that helped me process more quickly, over and over again, and I just had that crop factor in the macro. I understand why you used FilmDev because of the noise, but I'd very much prefer to be using AutoDev because that's a sign of good data. When you say the Wipe result is good with RGB, it looks pretty bad to me! Those coloured patches are exactly what is causing me grief. I'm in a way not surprised that the image is noisy because I only shared ten subs of each channel, at 60s each, to avoid inundating you with a huge download, the total amount of which is around 20GB! In total I took 9 hours of 60s exposures, at gain 75, offset 21, figures I landed on after doing research into what other people are using, and also this page: https://www.cloudynights.com/topic/573886-sub-exposure-tables-for-asi-1600-and-maybe-qhy163/ When you say my L is fine but the ADU for R, G and B is too low, I had no idea L needed to be three times the duration. When I look on Astrobin, people seem to generally be using the same exposure times across all channels? Finally, while I've got you(!), would it be possible please to take a look at the fully stacked, calibrated LRGB subs in StarTools for me, and tell me what you think? I'm wondering whether you're getting the full picture (literally) by me just sharing ten subs. If so, they're here: https://1drv.ms/u/s!AqovBuVZMwj3kuU6Le1hAw_U3tQubA?e=8G6V4W. These were stacked and calibrated in APP. It would just be interesting to see what you make of them. The filenames have the total amount of exposures time in them eg L 12720s.fits is the Luminance and is 12,720s of exposure. The times are a bit different for each channel simply because a couple of things went wrong during the shoot. These can be compensated for in the StarTools Compose module by specifying the exposure times there. So in summary I need to: Retake my flats and dark flats at longer than 2 seconds Go back to unity gain and offset 50 (for now, bearing in mind you went up to 64 eventually) Think about shorter L subs and.or RGB subs (although I don't know how I'll do this without overexposing the RGB?) Learn much more about ADUs! Coming from DSLR land I'm all clued up with ISOs etc. One problem I have with APT is its histogram, which doesn't really tell me what I need to know, I think. I might give NINA a try and see what that says. One more final question: do the master dark, flat darks and flats look ok to you? The darks don't seem very, well, dark to me! They were taken with the camera wrapped in a scarf, in the fridge, all at -15C, just to make sure there was no light coming in. Does this make sense? Thanks (again) Brendan
  2. I probably won't be able to get it exactly right, but I know I had the camera at my 'neutral' position where it's aligned with the scope (which is why the diff spikes are nice and horizontal /vertical) so I should be able to get close. It seems ZWO cameras prefer longer flats, so I'm going to add some paper to my light pad when using the flats tool in APT. If that doesn't work I'm going to download NINA and try the flats wizard.
  3. Again, check: that's how I have the camera attached, with the EFW lettering on the camera side, the screw holes on the other removable side. Good thinking though. I just processed some of the individual subs in StarTools as an LRGB composition, and they look exactly as I'd imagine - a clear vignette, which the flats would calibrate out, but none of this extraneous colour. So I'm starting to think the problem is as I first suspected, something to do with the flats. Perhaps there was a leak when I took them. They were taken in twilight, with the LED screen pressed up against the tube, which has always been OK in the past with the DSLR. But perhaps with the additional sensitivity of this camera, I needed to be more rigorous. So tomorrow I'm going to put the whole OTA, camera, filters and all, into a very dark room, covered with a towel or two, retake the flats, and dark flats, and pray.
  4. OK, thanks, so it's not the screen, or the camera. The filters are 1.25 inch mounted, so I don't see how I could have put them on the wrong way around, as they screw in. I have no idea if there's a possibility of a leak around the filter wheel connections. I also have a cap around the end of my 130PDS to stop light entering the primary. If there's a problem with the old filters then I don't see how they're actually worth the money if this is what they produce! Surely I'm doing something wrong here. I haven't given NINA a go, but I might, and see if the flats wizard works any better with that. Thanks for the suggestion. This is rapidly turning into one of those threads where you read it and shiver and think 'I'm so glad that isn't me', except that this time, it's me.
  5. Ideally I wouldn't have to retake all nine hours' worth! They were shot with gain 75 which should be fine, from what I've read. The noise really isn't the issue, I can fix that (I haven't applied any denoise whatsoever to these images). I hope the filters cover the sensors because they're by the same manufacturer and came in a bundle. I have read that there may be some vignetting with the 1.25 inch mounted filters but this is far beyond what I would have expected. I can believe that the ASI1600 is difficult to create flats for, but I've been through the APT flats tool which should be creating the ideal exposure times for each flat. All I can think is that I need to redo the flats and take it from there. The other possibility is: would anyone be willing to take a look at some of my raw LRGB subs, master flat, master dark and master dark flat, and let me know what they think? If so, they're here: ten each of LRGB, plus masters: https://1drv.ms/u/s!AqovBuVZMwj3kuUA4E9LynWaVjMvQA?e=Wbv7Cu - masters produced in APP. Thanks, Brendan
  6. Thanks. I'm using StarTools so I expect that'll be looking after levels that aren't visible to me (I also use Photoshop, but the ASI1600 produces FITS files which I'd have to convert to TIFF to view them, or I can use FITS Liberator). I just thought I might have been using the wrong flats and flat darks, but I get something similar (and yes, there does seem to be some walking noise but this is with very few subs and I might just increase the dithering rate to handle this). I'm stumped, frankly. This is worrying.
  7. Two nights, but under virtually identical conditions, and no Moon. I don't know! How would I check this? I am, and this is a very good point, but I have definitely made sure I'm cropping out the artefacts. I'm doing another run with some different calibration frames so let's see what transpires. Thank you so much for the responses.
  8. Thanks for the questions! It's all very useful. I am calibrating the flats with flat darks, taken at the same time exposure time/gain/offset as the flats. I am also using darks matched to the same exposure time as the lights. The flats were taken separately for each filter, using the flats tool in APT, which I also used to create the dark flats. I use a 130PDS in a Bortle 4 zone, it wasn't a dewy night, there was no Moon, no dust. The object was quite low in the sky, which means it could have picked up some light pollution from streetlamps I guess. But I would have expected this to be a constant gradient, not separate colours in each corner. I take the flats using an LED screen like this, with a perspex cover on it: https://www.amazon.co.uk/Stone-TH-Drawing-Lighting-Animation/dp/B07N128B74/ref=sr_1_7?crid=34ZCCBXXBOH1G&keywords=led+tracing+pad+stone&qid=1648571555&sprefix=led+tracing+pad+stone%2Caps%2C64&sr=8-7 - which worked fine for two years with the DSLR. Perhaps this is the problem? It's not an especially sophisticated approach but it worked fine with narrowband with this camera, and worked fine with the DSLR. One thing: I am using the same darks across all channels. This is correct, right? The flats and flat darks are per channel, but the darks can be used across all? Perhaps I should try just calibrating the lights with the flat darks to see what happens, then calibrating just with the darks? Is there anything else I could be looking into?
  9. Good call - and this is what I get from just stacking 10 mins of each channel without any calibration files - still a decided RGB glow around the edges. So, probably not calibration then. Any ideas what could be causing this? I'm a total newb with mono imaging.
  10. Hi all, I've recently moved from DSLR to mono imaging. I'm getting the hang of narrowband, but my first LRGB image is something of a disappointment. It's NGC 4236 which I've captured a bit of before, and love its blue disc, so I thought it would be a good first LRGB target to compare with. It came out like this: This is about 9 hours of 60s exposures, at gain 75, offset 21, ASI1600MM-Cool, ZWO LRGB 1.25 inch filters, with 25 flats, 25 dark flats and 50 darks. I think it's significant that I have red, green and blue glows, which implies something is wrong with my calibration, perhaps my flats? Any takers? Thanks, Brendan
  11. Thanks @vlaiv, all great advice, as always. 7nm is what I've got, unfortunately! It would also appear that, well, shooting in the poorest of conditions is giving me the poorest of images. The next few nights are very clear, with some windows of opportunity while the Moon is still below the horizon, so I'm going to try and get fresh, clean data during those times and see what happens. Cheers, Brendan
  12. Hi all, I've recently made the leap from DSLR (modded EOS1000D) to mono (ASI1600MM Cool with EFW). After the expected teething troubles, everything seems to be working OK. However, the first results are in and they're a bit disappointing! This is the very last shot I got with the Canon - SH2-155, the Cave Nebula, in HaRGB (10:40 of Ha and 3:45 of RGB): This is what I just got with the ZWO, which I have processed as HOO because HSO looks even worse: This is from 8:44 of Ha and 4:04 O3. It's a combination of 240s and 540s exposures, because I didn't really know what I was doing with the histogram (I think I do now). Also, this was shot during a full Moon - I wanted to do it under challenging conditions just to see what came out. There's more nebulosity I guess, but on the whole, I'm a little disappointed. The stars aren't great, and the image is generally kind of washed out. I completely get that I knew the DSLR inside out after two years, and could get results I was really pleased with, and that hopefully, ultimately, the same will happen with the ZWO camera. Also, the DSLR version was under better conditions. But I did expect quite a lot more from kit that costs quite a lot more! So can anyone please point in the right direction for what I might be doing wrong here, at any stage from capture to processing? Kit list is 130PDS, NEQ6, ASI1600MM with Baader 7nm narrowband filters, APT, PHD2, APP, StarTools, Topaz DeNoise AI, Bortle 4 sky, and I used 25 flats, 25 dark flats and 50 darks. I guess for now my questions are: * Am I right that HOO is more usually the better way to create natural colour images, rather than HSO? * Should I consider using a luminance channel too? If so, would that be the Ha? * Or... do I just need lots more data and/or should I accept that shooting during a full Moon is just too tough (which would be unfortunate because my understanding was that this was possible)? Thanks Brendan
  13. Hmmm, interesting, thanks. So, yours is all to the left too. So is the CCD histogram just not at all the same as the DSLR one then?
  14. Thanks! I've been using these tables as a starting point - narrowband for a full moon: https://www.cloudynights.com/topic/573886-sub-exposure-tables-for-asi-1600-and-maybe-qhy163/ So, I'm doing 240s exposures, at gain 200, offset 21, and I'm getting this, which doesn't look right to me:
  15. Hi all, Any APT users here who would care to share what a good histogram should look like for a CCD/CMOS camera? I was very familiar with the DSLR histogram, but have just started using an ASI1600MM Cooled. The histogram is very different and when I try to use exposure times that I see recommended online, I'm getting something very far to the left when I would expect to see it more towards the leftmost third/halfway, as per the DSLR version. Problem is, I have no idea whether or not I'm right. So, if someone could share an image of one, that would give me something to aim towards. If it helps, my scope is a 130PDS. Thanks, Brendan
  16. That's another conclusion I'm rapidly coming to, if I can't source a low-profile focuser. How much did you take off? Also, did you completely remove the focuser first? And what did you use to cut it?
  17. Yep, and I'm reading similar things. Darn it, Sky-Watcher, why couldn't you just sell products that work properly?
  18. Bum Looks like there aren't any for such a small Newt. However, it's given me another idea: buy a full-size spare, ideally second-hand, and cut that down instead, then replace it. That would still work, cost about the same, and would be reversible.
  19. This is a very good idea, the more I think about it. It's pretty much exactly the same as chopping the tube... without chopping the tube. And it's a lot less than buying a new coma corrector which might not even work. Thank you, this is actually a completely new idea I hadn't thought of, which might just do the trick! Nice one.
  20. Absolutely no idea! I guess I'm looking for a shorter tube, so if that's what that is, then yes! Thanks, this might be an option too.
  21. Thanks, yes, I have the correct backfocus, exactly as per that very diagram. My understanding is that, if I didn't have that, I wouldn't be able to focus at all, is that right? The tube focus point is very similar to the DSLR, but slightly further in (I think). Either way, I was hoping it would be further out!
  22. Just realised another option could be to get a new coma corrector, one that isn't also a reducer. Hmmmm........
  23. Thanks - I don't know about the 200PDS, but for the 130PDS it's definitely a noted problem that, especially with a DSLR and their own coma corrector (which is a 0.9x corrector, so also a reducer, which I didn't make clear in the original post and have just added), the focus tube intrudes on the primary mirror and causes little bitemarks out of stars, also known as 'pacman stars'. I mitigated this to an extent with a primary baffle, but I was very much hoping that a change to a dedicated astro cam would finally cure this. Instead, it's made it worse.
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