BrendanC

Again, thank you @vlaiv and @symmetal, you've been absolutely brilliant. I've learned a ton of stuff over the past few days, and I also have 'The Astrophotography Manual: A Practical and Scientific Approach to Deep Sky Imaging' on order so that I can get to grips more with the theory as well as the practice.

Outstanding. I love that you've kept the background from clipping and the stars look amazing. Thank you so much again. What a relief! I'm going to get more Bodes data to build on this, now that I think I'm doing things right. I'll probably go down from 60s subs to 45s luminance, and 180s to 120s for the RGB, just to see the effect it has. I'm still puzzled by the amount of vignetting, but I'll keep seeing what I can do about it. It could just be down to my shooting conditions and the camera being much more sensitive than the DSLR. Cheers, Brendan

I only quite recently learned the star sampling technique in ST for getting the colour right, and it really worked with this one. I know what you mean though, ST can be quite unpredictable.

That looks great - thank you. I'm starting to get the hang of the data in StarTools too, I think, but I agree that the background is what's causing me grief - I had to be aggressive with the gradient wipe, much more so than I anticipated. But you know what it's like when you have new kit? When you start, and it's not right, it could be ANYTHING, so I'm really grateful to you for going through the data. I really like your attempt and I may have overcooked mine a bit, but it does seem that I have a direction to follow now: stretching less, wiping more, and trying to identify where that gradient might be coming from. I only use APP for stacking but I'm increasingly interested in its gradient removal tool, assuming that it doesn't disrupt the linearity of the data too much for StarTools. If only it had a user guide! Again, thank you everyone for your help. If this is starting to sound like an Oscar acceptance speech then don't worry, I'm not going to slap anyone...

... and THAT'S why people wear aluminium foil hats, right? Thank you again @vlaiv, I will be doing this exact test over the next night or so. In the meantime, with slightly more aggressive wiping than I would like, and a possibly clipped background, here's where I'm up to.

I'm not sure what you mean by subtracting one from the other. If I were to open them in, say, Photoshop layers, does this mean I would use the Difference or Exclusion blending mode for example? Also, given that I'm sure the darks I took in the garden are good - I mean, the scope was swathed in towels, including the camera and focus tube, the cap was on, there was a hat over the cap, and over the primary end, under the towels, all in astro darkness - then I should be fine classing them as the 'house' versions, right? And then I can do the thing you suggest, of taking equivalent darks but with just the cap on, and use them to run this analysis? Or to be on the safe side, should I retake some 'house' darks under the controlled conditions you describe? One more: when you say to use the cover end cap, would it be better to completely cover the end i.e. put a hat/bag or something over it too, if the idea is to identify light leaks elsewhere in the chain?

Latest version from an APP stack (which takes about 100x longer than DSS). This is another improvement, but again, I'm wiping the gradient very aggressively. @vlaiv, I'm definitely going to give your diagnostic recommendation a go, but if you could just clarify for me what the next step is, to compare my darks with, that would be great.

Thank you so much for doing this. I really, really appreciate it. Definitely, and again, thank you for taking a look. I've just run the image through StarTools with default values, which usually works. Having said which, I've managed to get something... see below. @vlaiv I must admit, I'm struggling to get my head around the various analyses you've done, but to summarise, you're saying that there's an issue with the data capture, not calibration or processing? And that this issue is a light leak of some sort? I have been taking some shots in broad daylight, with the ends of the scope covered but the camera/EFW/adaptors/focus tube uncovered, and I cannot see any obvious light leakage. The primary end, while I'm shooting, always has a waterproof hat over it to avoid this. Regarding your other advice, given that I have what I would call 'proper' darks now - taken with the scope completely covered, in astro darkness, without the remote possibility of light getting in anywhere - is the idea now that I take a dark in astro darkness but without covering the whole scope, just with the cap on? Would that indicate leakage? I'm not quite sure exactly what I should do. Finally, I've been getting help on the StarTools forum too, and this is where I'm at - but with quite aggressive gradient wiping which I don't feel I should be doing: The slight problem now is that I took a quick set of subs the day I got the camera, completely uncalibrated, and just quickly stacked them and removed the vignetting in Affinity, and I got this which, to my eye, is better! So, I'm getting somewhere, I'm just not quite sure exactly where yet... Thanks again everyone, I'm really appreciative of your help. Thanks, Brendan

Hey, thank you! Yikes. There is the zipped version too, but when I tested the unzipped download it seemed to have zipped everything up anyway so that may not make a difference.

Interesting, thanks!

Superstar. Thank you.

I've tried! Posted about it on the APT forum and tagged Ivo in a post on the FB page, no response.

OK, it's happened again. I'm nearly at my wits' end here. This is what I get for the Bode's and Cigar galaxies - stacked in APP... ... and stacked in DSS. (Yes, I know there are sat trails in the DSS version, and possibly walking noise in both, these don't bother me because I know the fix - dither more frequently, use a different algo in DSS) Both processed in StarTools, using pretty much the default settings, no noise reduction applied. I haven't tried getting 'the best' result, because I can clearly see these images are not right. I can process pretty much any other set of data I took with my DSLR using the same default settings and they're OK. This is a high, easy target which I've shot before with my old DSLR, no problem. No bright lights nearby, Bortle 4 sky, no wind, no clouds, no Moon. I've checked that the right filters are in the right slots, the right way around (they're mounted, so it's impossible to get them the wrong way round because they screw in), and that the right filters are selected in APT, by literally watching the correct filter appear when I select it manually. I'm going to try and provide as much detail as I can here, in case anyone can help. I've tried to (re-do) everything by the numbers here. I really do not know what I'm doing wrong. All lights and calibration frames are shot unbinned, at gain 139, offset 50, temp -15C (some of the Luminance flats were between -11C and -15C) Taken over two nights, but with everything absolutely untouched between each shoot and virtually identical sky conditions Luminance is 60s per sub, RGB is 180s Total integration time is L 5880s, R 2520s, G 1980s, B 2340s Flats were taken on the first night, in astro darkness, using an LED screen, with a perspex sheet and some sheets of paper, after using the APT flats tool to calculate exposure times Dark flats were taken last night, again in astro darkness, using the exact same plan as for flats so that all details matched up, with the scope on the mount, cover on, a hat over that, another hat over the primary mirror end of the OTA, and two thick towels over everything Darks were then taken in the exact same conditions last night, for 60s and 180s exposures 25 flats per channel, 25 dark flats, 50 darks per sub length Kit list is 130PDS, NEQ6, ASI1600MM-Cool, ZWO EFW with 1.25 inch mounted ZWO LRGB and Baader HSO filters, Sky-Watcher 0.9x coma corrector, Sky-Watcher auto focuser with HitecAstro DC Focus V2, APT, PHD2, APP and DSS to compare stacks, StarTools Questions are: When I was checking my filters, I noticed that my ZWO L filter is actually called UV/IR cut. I think this is the same, but could someone confirm? I have the 8-wheel EFW and just 7 filters, so position 8 is empty. Could this be causing any problems? Am I definitely right about the filter wheel being such that the EFW lettering is on the camera side, and the screws on the coma corrector side? I've read that the older ZWO LRGB 1.25 inch filters may suffer vignetting, especially with faster scopes. With my 0.9x coma corrector, I'm at around F4.5. Could this be an issue? I did get a calibration warning in APP while stacking, but when I retried the exact same files - as in, literally just pressed the integrate button again with the same file list in place - it worked. I've posted about that here: https://www.astropixelprocessor.com/community/main-forum/critical-warning-flat-field-calibration-2/ Could this be a pointer to what's going wrong? DSS didn't spot any issues. I know that the LED screen approach to flats isn't the best, but I know other people have said they use it successfully. However, again, could the flats be at issue? They worked fine for narrowband, and with my DSLR. How would I check? Should I try something like sky flats or the t-shirt method and see if that yields better results? When I'm processing in StarTools it seems fairly obvious to me quite quickly that there's heavy vignetting going on. Could that be the flats? Or, could it be the filters? Given that some of my Luminance flats were between -11C and -15C, surely that wouldn't have such a dramatic effect, would it? Finally... deep breath... given that I'm losing what little hair I have left here, would any kind soul (@vlaiv? @Elp? @Varavall?) be willing to take a look at the entire set of data? If so, it's here - subs, flats, dark flats and darks, total 13.4GB unzipped: https://1drv.ms/u/s!AqovBuVZMwj3ku8zByEPVWYQIHSeLQ?e=NaPSm2 ... or 5.7GB zipped in separate folders (I couldn't get the whole thing to upload in one big zip file): https://1drv.ms/u/s!AqovBuVZMwj3kvMCfUjIHVMBAxfbvQ?e=5QLric Actually, finally finally, what do I do if the camera is borked? It's second hand so I don't have much recourse if so, and I certainly wouldn't be able to sell it on. And if I did get, say, an OSC instead, and there's something wrong with my technique, then I'm back to square one. My workflow was totally sorted with the DSLR, so I thought it would be a fairly smooth transition to LRGB. I got the hang of narrowband with this camera pretty quickly, so perhaps it's not the camera, it's me: If you've managed to read this far, then thanks! TL:DR I'm going insane trying to get my new camera to work and if you could help, I'd really appreciate it. Cheers, Brendan

I haven't heard about this. How does this work? I must say, without a user guide, APP is not the easiest package to get to grips with...

Hi all, I keep noticing that I get this error message, as per this thread: https://www.astropixelprocessor.com/community/main-forum/critical-warning-flat-field-calibration-can-not-be-performed-correctly-2/ My flats and dark flats are actually created by the same plan! One with the scope covered, one not. The gain, offset, duration etc are, by definition, identical. So, how is this possible? Furthermore, this happened today, and out of curiosity I just started the integration again - and now the message hasn't appeared. In the past I've worked around it by creating the masters in a separate integration, but I don't like 'workarounds' and I don't understand why this is happening. It sort of wouldn't matter I guess, if the final image popped out OK. However, I'm having a heck of a time trying to get decent results from my new ASI1600, and this is just one of several issues I'm trying to iron out. Can anyone shed some light on this please? Thanks, Brendan

Wow. No takers. I guess I just put it down to 'one of those things'...

Great, thank you vlaiv, I'll do as you suggest.

Hi all, Last night I had the most bizarre error. If I specified a plan to have a conditional stop any time after 23:59, I got an APT Unspecified Error message, the camera (ASI1600MM) was just busy, and I had to stop the plan, disconnect and reconnect the camera. Any ConditionalStop time before then, up to 23:59, was fine. From 00:00 onwards though, it bombed. Every time. This was replicable and consistent behaviour. I went from v3.98 to v3.90 and it still did it. Any other plan, timed to end before midnight, was fine. Any time after midnight, it crashed. Even a plan that had previously worked, crashed. In the end I re-did the plan by just counting sub numbers before the NextPlan, which is how I used to do things before ConditionalStop came along. Today, as a test, I attached the DSLR. It seemed to be fine. Then I edited the test plan - the camera just said 'Busy', had to be disconnected and reconnected. Then, out of curiosity, I edited just the exposure time, not the ConditionalStop time - and the DSLR hung again. After trying everything, I could only come to the conclusion that editing ANYTHING in a DSLR plan was also causing the camera to hang, whether or not it had a ConditionalStop. So I reconnected the ASI1600. And guess what? It seems to be working again. Plans that stop before or after midnight seem to be OK. So I'm not even going to go back to the DSLR to confirm whether that's also working again. Does anyone have any idea what might have happened here? I mean, fingers crossed it works tonight, and I do have a fallback plan, but the only thing I can even imagine might have caused this, is that I deleted a profile in APT. I used to have one for shooting RGB, and one for Ha, which required quite different settings and it was a very handy way to achieve that. But I no longer needed the separate Ha profile, so deleted it. So perhaps deleting the old profile might have caused APT to get confused about the execution of plans in some way? By going back to the DSLR and then back to the ASI, might I have straightened out whatever it is went wrong? Any/all thoughts welcome, especially in case this isn't fixed or happens again. Thanks, Brendan

That's quite simply because I'm trying to get the hang of the camera. I didn't think the temperature of flats or flat darks mattered? The dates difference is because I wanted to get the flat darks done ahead of time while I could, before the shoot. As for the difference in focal length, I have no idea! That is quite bizarre. There are no light leaks that I'm aware. I live in a Bortle 4 zone, the back garden isn't really brightly lit, just a few houses around. The DSO I was shooting was however quite low in the sky, and I can well imagine there is more LP at that height, in that direction, than I previously thought with my DSLR, which the ASI1600 might pick up more readily. I also thought it was going to skim above some trees but I have a feeling it might have gone behind them for some of the subs. I'm stacking the top 50% of the subs as I type, so I'll see if that improves things. Also, I've been told my RGB subs were far too short. This is because I was under the impression all LRGB filters needed the same sub length but I was very wrong! I've had a couple of the good folk on the StarTools forum take a look and they've given me some great advice for next time around - basically, higher gain and offset, longer RGB subs, more L time overall too. I've taken some more shots of Bodes Galaxy and just need to get my flat darks (or dark flats, whatever we're supposed to call them) and darks sorted, then I'm hoping to see something a bit more presentable. Fingers crossed.

Brilliant, again, thank you Alan. I have just been reading up on this (again) and have noticed a lot of recommendations to use 50, so that's kind of nudged me towards actually using it. Unfortunately I just ran the APT flats tool at offset 21, and everything is set up outside ready to go! So, I think I'll either re-run at offset 50 (or 64 or maybe even 72 if that's what @vlaiv uses because he's helped me out plenty too in the past) with everything set up in the garden when it's dark enough; or I'll do the shoot at whatever offset I choose, then re-run the tool tomorrow in the closest possible conditions and do my flats then. Again, I'm so grateful for your help.

Thanks! You've been super helpful. I'm going for Bode's and the Cigar tonight, so hopefully that's going to be a bit easier. The DSS approach sort of works but FITS is a pain for viewing generally, I've found.

Right, well, this is brilliant. I am so grateful. I was freaking out initially, not really knowing where to start. I think you're both right in all respects. I should return to unity gain which also means offset 21 according to ZWO recommendations. My RGB exposures are too short. This is because I didn't notice that the table I was using was based on luminance. My L full integration time should be around the same as RGB combined. There's field rotation, and this is a known problem when I do a flip - I think I have cone error, which I've lived with for a while, and just need to fix, but it keeps getting pushed down my 'to do' list The object was shot low in the sky. There's another bright DSO just off the FOV. I need to learn about ADUs more thoroughly, and how to analyse images. The object was also captured as it should have skimmed a tree, but I'm now wondering whether I misjudged that, and the tree has in fact screwed up a decent proportion of the subs. The problem there is how to get a FITS file viewer that lets me skip through files quickly. I've tried a few and none of them are as fast/responsive as handling CR2 files. I might load them all into DSS and have a look there. Or, I might restack and just use the top 50%, see what difference that makes. So, all in all, I made a bit of a mess of this! Plus, I probably chose a tough first DSO. I'm going to try Bode's Galaxy, hopefully tonight, which is nice and high, circumpolar, and I've done it before so I get a decent comparison. I might even be able to have a stab at LHaRGB if I can get the LRGB bit to work out. Again, thank you, really. Cheers, Brendan

Very interesting, thank you. I've been advised that there is a bright DSO just off the FOV of my shot which could be affecting things and yes, the object is low in the sky above some streetlamps, which my DSLR probably would have handled but I think the increased sensitivity of the ASI1600 doesn't like it. At all. As for the blooming, well I'm working on a theory that it might have something to do with the filters vignetting and meridian flips, but I need to look into that more. Basically, everything that could have gone wrong, did go wrong!

I haven't checked, but they're the ZWO 1.25 inch mounted filters in the ZWO filter wheel, so I would hope there's no issue there. Sure, I've used darks, flats and dark flats tons of times with DSLRs and never really had an issue. But it seems there are multiple issues going on with my image, from the duration of my luminance vs RGB subs, to the flats and dark flats exposure time, and maybe even my filters. It could also be that I'm trying to shoot a tough target because it's very low in the sky and near another bright object, so I'm wondering whether I should go for something easier like Bodes. I've also been trying to run before I can walk with gain and offsets, so I'm going to stick with unity gain and offset 21 which is the standard setting. I've redone all my flats and dark flats - bearing in mind the flats might not be quite aligned any more, it's still worth a punt - and they're calibrating in APP as I type. I mean, I cannot be the first person to use an ASI1600MM-Cool with ZWO LRGB 1.25" mounted filters and a 130PDS, right? Surely this is possible.

So do I - but longer flats is all I have to go by currently as a possible fix for this.