Steenamaroo

@vlaiv - Thanks for the information, although your descriptions explain why the background would become darker, or lighter, over time. If evening one's images started bright due to light pollution or transparency, and got darker because conditions improved, shouldn't the galaxy and stars have become brighter? Conversely if evening two's images started dark and became brighter due to conditions worsening, wouldn't the galaxy and stars have become faint over time too? As I say, folks, both nights were shooting the same target at the same time, and the target was more or directly overhead, far from the horizon. Position in the sky was the same for both sessions. @Swillis My understanding with dark frames is that I don't really need bias frames if I have dark frames, and I do need dark frames because without them hot pixels are a bit of an issue. How do you mean `Firstly, the temperature cannot be matched to the lights`? The temperature of the sensor? I take my darks on site with the same exposure length as the lights, so it should be the same?

Thanks for the thoughts, folks. I'll try to cover everything. @Stefan - I realise increasing ISO increases noise, but also that stacking reduces noise. I wasn't necessarily expecting a good result from the second set, but certainly the stack should always be better than the subs, no? Admittedly I didn't check the histogram, although clipping there would indicate overexposure? Agreed - Checking histogram in future is a good idea, but I'm pretty sure I've seen people's subs as bright as/brighter than, the ones I've shown here. @happy-kat - Agreed - 3200 is pushing it. Thank you though. I suppose I was kind of baffled as to why it seemed impossible to overexpose. Maybe that's just my lack of experience with fainter DSO's but gradually increasing exposure duration and ISO I expected to, at some point, look at a sub and think, "wow, that's way too far". That didn't happen. Comparing the first sub from night one and night two, I don't think it looks like I did an 8X on exposure and a 4X on ISO, even taking the Barlow into account. "5 darks would just add noise, flats are good to use" How's that? Darks are pretty much essential since I've quite a few dead pixels, and my understanding is, just as with lights, more = better? "Sky conditions can change throughout a night and be different between days even if it look clear" I suppose that's true. That said, these were two ridiculously clear nights. Pretty much no twinkling - definitely no visible cloud or haze/mist...nothing like that. "Did your secondary mirror get dew on it?" I have no idea - Maybe that's something to watch. Thanks for the thought! Local light pollution usually isn't great - There's usually someone with a security light on all night or whatever but for these two nights there was nothing. It really was as dark as it gets here. I think that's why I'm a bit bummed. I expected stack 2 to be more impressive but too noisy and then I'd do night three probably with 10 minute + 800 ISO, and a lot more stacks, but the results from these two nights kind of threw me a bit. @Elp - Targets were about as overhead as it gets. M81+M82 between 22:00 and 00:00 in UK. Moving closer to, or farther from, the horizon or any source of light pollution would make sense but, unfortunately, that wasn't the case here.

Hi all, I don’t really have a specific issue but was hoping someone might help with general advice for astrophotography. I’m using a 130pds with Canon 500D, shooting raw, on a belt driven guided Vixen-GP. Guiding is SVBony SV-106 50mm with qhy5l-ii-c. I did two test sessions - One on Monday night, one on Tuesday. Both nights were remarkably clear. (I know...hard to believe!) The first night I captured m81+m82 together, prime, with 1 minute 800 ISO images over about 90 minutes. I know that’s not a huge amount, but enough to gain some experience+confidence, I think. I learned that 1 minute at 800 probably isn’t enough but, regardless, the first subs looked usable. I noticed, after the session, that subs became darker as time went on. Shooting between around 22:00 and midnight that made some sense, as the sky was getting darker, but the subject (m81+m82) and stars got substantially darker too. I expected the backdrop would darken over time but the target+stars should remain around the same brightness. Am I wrong? The stack of these images really pleased me, though - Although the target galaxies weren’t particularly bright or well developed, the image was nice and clear and the backdrop smooth and dark. A success, from my perspective. For the second night I decided to improve by increasing the sub lengths and also decided to 2X Barlow and focus on just m82. I’m aware Barlow would make the subs much darker than at prime so I did some tests at 3 minute exposure. Not seeing a huge difference in target brightness I tried 4, 5, 6…and finally 8 minute. Surprised at how little difference there was I tested increasing ISO bit by bit too. I ended up taking 8 minute exposures at 3200 ISO, wondering why the target and stars still looked so faint. I only got around 10 subs but, this time, I noticed they became brighter as the night went on - The exact opposite of what happened the night before, shooting at the same time (22:00 to midnight) The stack this time was very disappointing - Very grainy/noisy, backdrop nowhere near as dark - Pretty much monochrome looking - It looked like something from the guide-cam but noisier! I’m stacking with DSS, took 5 or more dark frames for each session, and used the same flat frames for both sessions. I also tried stacking both sessions without flats, which didn’t account for the difference. Environment was the same both nights - Same setup position, same neighbourhoods lights (or unusual lack thereof!), no rising moon… I suppose my questions are Why would my lights get darker (background, stars, and target) as the night went on on night one? Why would my lights get lighter (background, stars, and target) as the night went on on night two? Why would night one stack perfectly but night two stack looks terrible? Safe to say 3200ISO was pushing it but the stack should still look better than any sub, no? Many thanks to anyone who read my wall o' text. First session first sub First session last sub First session stack Second session first sub Second session last sub First session stack

Hi folks, Just following up on this. I've had much more success over the last few nights. I think this issue was caused mainly by two things. One : Not giving the mount a rough idea of where it's pointing first - Thanks @BCN_Sean Two : I started using dark frames when solving. I noticed a few white specs - dead pixels maybe? - and it seems like these were really causing issues. I had a few failed solves which succeeded when I retried with darks in use. Thanks to everyone who commented and offered help! Much appreciated, folks.

@bottletopburly- I wasn't aware of that. Certainly something to try. Thank you. @alacant- As far as I know the values read and shown are correct. If I'm wrong of course I want to know, but everything seemed to match up with manufacturers specs.

I've tried to snatch some breaks in the cloud here and there but, honestly, it's been a real pain trying to get more than 10 or 15 minutes without cloud or rain. From the brief windows that I did get, I think I can confirm that it'll plate solve just fine if it knows what it's looking at already. If it doesn't, it wont. Kind of seems like that defeats the purpose a little, since the setup procedure for go-to use would involve slewing to some star then solving so it can realise it's not actually at that star then correct for it. @BCN_Sean- it was your comment that made me realise this, combined with noticing that every time I try to begin polar alignment, ekos decides my mount is somewhere else. I mean, I'll point the mount/scope at the polaris, tell ekos I'm at polaris...sync to polaris, set home polaris... If I click 'goto polaris' it goes 'beep beep' you're already there. Then I do polar alignment and the instant I click start it goes boom...your mount is somewhere else now, then fails. I've no idea what that somewhere else is or how to override it, other than manually slew to 'the pole', then going over and manually fixing the mount so it's actually at the pole again, in order to do polar alignment with successful solving. I guess now that I know that I can just do that but I sort of thought that's what 'sync' was for. Looking forward to the next clear night.

Hey, Thanks @BCN_Sean - That's really helpful! I'll give all of those things a go. Thank you.

I only have one camera of that make/model, and 190 is correct for the guide scope - Corrected to 188.something on successful solve, but thank you for that info.

Oh, I see it now. Looks like it's all auto-filled and not editable.

I can't see where I'd input that information, but I know I have never entered that manually so you might be on to something.

Not sure there's anything helpful in there but attached none the less. The current coordinates aren't meaningful, of course, as I just booted up to grab that screenshot.

Alright, that's good info. Thanks folks. To be honest I've never imaged over multiple sessions but I understand you'd want the greatest accuracy possible if you were doing that, so using the main scope in that case makes sense. For now, though, I'd just like to get solving working via guide scope as it did before, for goto convenience and/or single evening imaging. Last night was clouded out but I will be back after the next clear sky.

Hi, I'm not sure I understand? For imaging I'm using a DSLR so framing a shot would be manual rotation of the DSLR plus a few nudges of the mount control to get it just right. The guidescope and main scope are trained on the same point, so there shouldn't really be a difference whether I solve for mount position (and goto) with one or the other, right? I'm a beginner...Do people point their guide scopes at more star-rich areas than the imaging target when needed?

Ok, something else to try. Thank you. I'll try everything suggested here next time there's a clear sky. Not looking great for tonight but who knows...I'll keep an eye out.

Thanks again @AstroMuni I'm afraid I can rule out cloud - Last night was one of the rare clear nights while I was out. Here are some screenshots of my settings. The only thing I toggled throughout the evening was Solving Method Internal Solver / Online Astrometry.