The Lazy Astronomer

I think mr Spielberg beat you to it 😁 Sorry, childish, but couldn't resist. On topic: l can't see why this wouldn't work in principle. The 3nm Ha seems to transmit around 30% NII, so I guess you'd be be looking at an effective transmission of around 65% NII once subtracted. Like everything in this hobby, I suspect in practice it might not be as simple as it first appears. Personally, I'd probably opt for a dedicated NII filter if NII imaging was my aim.

That's looking really nice 👍 As has been said, short exposures for the core are needed for M42 - blend them together with HDRComposition. L is where all of your detail is, so generally you'd look to shoot more L than RGB, I usually do 3:1:1:1 LRGB. Because L is a less restrictive filter, you might also want to consider a lower exposure time - with B5 skies (same as mine) it's likely that your optimum minimum exposure time for L will be <10s, so plenty of scope to reduce exposure time without a loss of recorded detail. The L channel also seems to still be affected by a light pollution gradient, which is limiting what autostretch can do in terms of pulling out detail, hence your L doesn't look as good as your RGB, so maybe revisit DBE here. For some of the more complicated things like deconvolution and noise reduction, I think the EZ processing suite is a good tool to start with; it takes some of the manual complication out of the processes while you're learning. And finally, maybe consider looking into the fairly recently released GHS script for stretching, it can help prevent blowing out highlights when trying to dig out faint detail.

Fully remote controlled from the comfort of the sofa with a nice glass of red 😁 (once polar aligned - not a permanent setup sadly). I might browse SGL, read something, or just watch something. Occasionally I've taken a nap.

Ok, let's see if l can get this in on budget! 1. EQ6-R Pro, £1400 2. 80 - 100mm triplet apo, ~£1500 - £2000 with appropriate flattener. My personal vote, purely because I have one (it was also my 30th birthday present 😁) is for the Esprit 100. 3. Autoguiding set-up. These can be had relatively cheaply (around £200, including a basic mono guide cam), however I might suggest going for something a bit fancier here: the Evoguide 50 plus flattener (£280) - the reason for this is it's an ED doublet which actually makes for a great little widefield imager in its own right, so can be dual purpose; a guider for the bigger triplet, or a super portable widefield travel scope. You'll probably want to allow an extra £100 - £200 here to get some more rigid mounting hardware for a solid base (finder shoes not recommended!), but this could be a future upgrade. Following on with the dual purpose theme, I may be tempted to suggest something like the ZWO462MC as guide camera (£250) - this is a colour camera, and whilst mono is generally regarded as a better choice for guiding, it should be plenty capable, and is also a great lunar and planetary imaging camera for your mak when Jupiter's nice and high in the sky later in the year. 4. Imaging camera: to keep within budget, I've sacrificed sensor size a bit here to 4/3 or smaller, something like the ZWO294MC Pro (£980) or 533MC Pro (£899) would fit the bill nicely. The 294 has a slightly larger sensor, but some calibration issues have been reported when using dual a narrowband filter. Speaking of which, the 533 option leaves just about enough money in the budget to throw in a 1.25" Optolong L-extreme filter (£170), which will allow much improved results on emission type nebulae, even under quite heavy light pollution. Mono and filters is (arguably) the superior imaging option, but would likely involve making too many sacrifices in other areas, as you'd probably be looking at least £2.5k for the camera, filter wheel, and a full set of half decent filters. 5. Dew heater and controller, £30 for the heater tape and around £60 - £70 for the controller if you buy a 'proper' astro one, <£10 if you buy a PWM controller from ebay or the like and make your own modifications to it. This lot should get you a very, very nice imaging set up for just under the £5k mark according to FLO's pricing, however I have cheated slightly as I've not included power or PC control (or post process software!!). Obviously from home you could just get yourself an outdoor extension lead and just run off the mains (add an extra £40 or so for a power supply or two if needed). Out in the field, you'd need to think about some kind of battery pack. For image capture, any old laptop from the last 10 years or so will suffice (I generally assume most people do have an unused old laptop lying around somewhere). Possibly upgrade with an SSD and new/spare battery if still available for purchase. Capture software: Sharpcap Pro for polar alignment (only if area around Polaris visible) - £10/year (can also be used for planetary/lunar imaging). NINA for planning and running imaging sequences - £0 (other software available, but this is my favourite). Stacking and post processing software is a whole other topic by itself, but this whole part can be done without spending a single penny, and all the paid for options have free trial periods, so easy to try out a few and see which you prefer. As a final note: a nice to have option which you may be able to fit within the budget if you go for a triplet apo cheaper than the Esprit 100 is an autofocuser - the ZWO one is £184.

That's looking pretty nice on my phone - this region seems a bit underwhelming in broadband tbh; it really shines in Ha, but this is better than what I managed, so good work 👍

Just to add to this: you should also consider your RA and DEC RMS separately as well, and not just focus on the total figure. You want both axes to have similar RMS values (ideally, the same) whilst also aiming for a total RMS of 0.5x image scale

Being lazy rather than looking for myself (it is my namesake after all): does anyone have a reference image from a professional ground-based observatory?

I probably shouldn't get involved in this discussion, as it's getting slightly towards the more heated end of the debate spectrum, but I like to follow things like this when they come along (theory vs experiment) - I am a scientist by day, so right up my street! Anyway, from following along with the thread thus far, I see no evidence that anyone is suggesting the SCT image does not contain more detail than the refracter one, because it plainly and obviously does (and both are fantastic images, by the way!!). From my understanding, @vlaiv is suggesting the reason for this additional resolved detail is a function of the significant increase in aperture with the SCT, not the sampling rate (and please vlad, correct me if that's not the right understanding) - the most compelling evidence I see that shows detail at 1"/px is not fully resolved is the comparison between the SCT image, and what I assume is a downsampled Hubble image, both displayed at that resolution. Again, taking nothing away from the quality of these images; I hope I can one day get up to this level (and the fact that you manage it under UK skies gives me hope! 😁)

Yes, it's a slight oddity of ST - it doesn't tell you what formats it can output, you sort of just have to know.

Startools can output as tiff, jpeg and png. I'd love it if ST would allow to output fits as well - I'd like the option to mix and match ST and other software where appropriate, and it's a request I've seen made a couple of times on the ST forums, but Ivo doesn't seem too keen on implementing it.

Try saving as png?

It is becoming generally accepted that the online ccd suitability calculators currently available not give you good information with regard to recommended sampling rates. You're fortunate in that you already have some images, so rather than go into too much theory, you can assess practically: look at some of the images you have already produced, measure FWHM, then divide that by 1.6 - this is your optimum sampling rate in arc secs per px I have seen @vlaiv advise this time and time again, and if you want the maths behind it, he can explain it in great detail (I hope I got it right!!)

I can't say I pay too much attention to it, but NINA seems to want to flip when a target crosses the meridian, regardless of North or South.

Much as I enjoy Rory's videos, I think that was poorly explained. Basically he's saying for widefield imaging, you'd generally be shooting at a lower resolution and mount tracking errors would be less noticeable as each pixel captures a larger portion of the sky. When using longer focal lengths, generally you'd be at a higher resolution and tracking errors become more apparent. There's a bit more to it than that, but someone like @vlaiv will explain it much better 😁 Generally, you'd want your total RMS to be less than or equal to 0.5x your imaging scale (in arc seconds), and ideally, a roughly equal error in RA and DEC - if one is significantly larger than the other, you may see star elongation even if the total RMS is good. Your image scale is ~1.2"/pixel (although it seems the general consensus now is that the sampling rate for colour cameras should be doubled from what the calculation suggests, so your actual scale is ~2.4"/pixel). Honestly, I am unsure whether this means you should be aiming for an RMS of 0.6" or 1.2" (someone more knowledgeable than me will confirm, I'm sure). If the latter, that should be relatively easily achievable with your setup; the former will likey be more difficult.

Thanks - I did toy with the idea of doing inverse SCNR to neutralise the star colours, but since my original aim was to see if I could recreate Hubble's image, I decided against it. That said, maybe they are a little too pink and would benefit a slight hue change. RGB stars might well be something l do for the wider field image, which also includes M52 so RGB stars would probably look nicer.

I captured some narrowband data on the bubble and surrounding region a few months back, and have been playing around with it on and off (quite unsuccessfully) for what has felt like my entire life in Pixinsight. This is a significant crop of a much larger image - I wanted to attempt something akin to Hubble's 26th birthday image so I had a good idea of the sort of colours l wanted, but try as I might, I couldn't get them how I wanted them. I suspect my data and/or my processing skills are not up to the job (yet!). Somewhat disheartened, I went all the way back to the raw linear stacks last night and did a relatively quick and dirty process to come up with this. It's not how I wanted it to look in terms of colour, so there may well be additional versions to follow. Needless to say, I don't think the Hubble team have much to worry about 😅. Details: Approx. 12hrs split roughly equally across Ha, Sii and Oiii. 5 minute subs with an Esprit 100 and a 294MM. Full on magenta stars deliberately left in for the traditional SHO look. Any comments, critisms or tips greatly appreciated!

Very nice - this region always looks very dramatic when the busy star field is removed.

Personally, I would class guiding as good if: 1. The total RMS in arc seconds is less than or equal to 0.5x the imaging scale of the main camera 2. RA and DEC have approximately equal error 3. There are no or minimal large spikes in either axis

Guilty as charged! 😁

Not quite the setup, but a graphical representation of how it's doing 😁 Some of the best guiding I've had, being absolutely wasted by shooting 30s subs...

Pixel size (um) / focal length (mm) * 206.265 So for you, that's 3.76/2000*206.265 = 0.39, although you should probably double that you account for the reduced resolution on a colour sensor, so yes, 0.78. Not exactly - F ratio is basically irrelevant in imaging; what matters is image scale, and this is dictated by pixel size and focal length.

With the information you've provided, your optimum minimal exposure time is likely to be in the range of 1 - 2 minutes; this is the point at which your sky background swamps your sensor read noise. Based on that, your plan to go with 3 minute subs should be fine, but if you find you're having tracking/guiding issues, you can safely lower the exposure time a bit without compromising the image.

My experience is that the guiding assistant is usually within a couple of minutes of the Sharpcap figure - I tend not to pay attention to it either as l trust Sharpcap (minimal DEC guiding corrections back that up), but I certainly wouldn't say the phd2 figure was a waste of time.

I also believe what has been said above about tripod levelling not mattering is true (and I don't bother to level mine). However, what perplexes me is the reported phd2 polar alignment error - 300 arcmins is 10x full moon widths(!); that's a significant distance from the pole, despite OP specifying that very accurate polar alignment was done. Anyone have any ideas about this?