Fegato

Haven't got time to do anything right now, but might take a look tomorrow. First impression is that it's quite noisy, and you have a fair amount of "banding" type noise, which I think is common with DSLR / Canon cameras (although I'm no expert on that) - you can research that or someone will pipe up with a comment about how best to manage it. Obvious first questions are: 1. How much integration time went in to this? 2. What LP conditions were you shooting in, and were you using a filter of any sort? 2. Did you calibrate the subs (with darks, bias, flats...)?

I was pleased to grab three or four hours of clear sky between the cloud and wet on 1st and then 7th December. This allowed me to tick off another in my list of broadband targets that are more often imaged in narrowband. I went for a 2 panel mosaic to get a nice squarish field around the central targets of M52, the bubble nebula and companions, and to provide a reach from Sharpless 2-153 on the left to 2-156 (IC1470) on the right. There's so much going on in this field, plenty of which is uncatalogued. As well as M52 there is the smaller open cluster NGC7510 to the lower right, lots of emission nebulosity, dust and quite a few areas of reflection nebulosity. And then near the centre, that strange bubble-like planetary nebula NGC 7635. RASA 11 v2 on CEM120, ZWO ASI2400MC Pro, 250 x 30" (2h 5') across both panels

Yes, I think you certainly succeeded with that. Great advert for the Esprit 150 too... must admit I'd like that scope to complement my RASA. But with so little clear sky time here I just fear it wouldn't get enough use and targets would disappear before I'd finished them! I sometimes wonder about having one permanently down in Spain, but that's a lot of expense and complexity...

Sharpless 2-170 is at that location (and in Ian's list above). It's sometimes known as the "little rosette nebula".

I do see some funny coloured crabs that I really don't like. But that's lovely!

Nice one - this is on my list to do in broadband if I ever get a clear spell, as I saw another one fairly recently that revealed a lot of dust. Well done!

As the others say, best way is to capture two sets of subs for this target, and then apply some sort of HDR processing (I use Pixinsight, and the HDR processing works very well). With my last RASA attempt I used 20 second subs for the main shot, and a smallish number of 2 second subs for the core. To get to this I trialled shorter sub-lengths, looking at unstretched results until I had something that wasn't blown. Do your 8 second subs give you a non-blown out core and separation of Trapezium stars when un-stretched? If so, maybe HDR compression would still work. Not sure what post-processing tools you use and whether this is an option?

I've worked on the assumption of resampling to 300dpi - that's a sort of (high quality) benchmark for printing I think. I'm guessing somewhat less won't be too much of a problem.

I should add that I use Pixinsight and BlurXTerminator - the latter definitely helps a bit with star size reduction as part of the overall process

It's hard to manage a very bright star like that, and Alnitak is a favourite bugbear! Even starless processing generally leaves stuff behind which only grows with the stretches. I must admit with mine, I just decided it was part of the glory of the image and let it shine forth! I much prefer a big bright star than any obvious artifacts.

As vlaiv says, best result will always come from a single integration of all available subs. If the data is good, I keep all my light and calibration frames. Mind you, I have Welsh weather... so maybe there aren't so many of them! Must admit, the thought of having my own scope sitting in Extremedura is so tempting at the moment. Here I shoot F/2 to try and get the most out of poor skies. There - maybe F/7 max, so I don't get too overwhelmed with data!

Well, I was wrong in my previous post, a brief clear spell yesterday evening allowed me to complete this 2 panel mosaic. Panel 1 - 25th August, Panel 2- 6th November, just about sums up the recent weather. LBN 437 is a molecular cloud in Lacerta, and it sits on top of the faint emission nebula Sharpless 2-126. I wanted to capture the tail of dust up to the top right in this image, aiming to balance the emission and other detail to the left, and I think that composition works quite well. I find that StarXT is pretty good at leaving behind a range of small galaxies, and the main issue I had with processing this was avoiding these becoming large bright blobs! One or two aren't quite right, and I should probably try again. I guess PI's GAME script is probably the best way of dealing with these, so I'll probably have a go with that. With this I just used range masks... RASA 11 on CEM120, ZWO ASI2400MC Pro, about 2h 10' of 30" exposures across 2 panels. No filter.

My dark libraries are captured at -10. I would probably choose -5 if I ever get round to replacing them. The impact of dark current at these levels pales into insignificance as far as I can tell, so I'm sure I won't notice any difference. -10 is fine, except for occasional hot summer nights... I have once or twice had to compromise my subs at slightly less than -10... I noticed no difference calibrating with -10 darks.

Yes, looks like you have good data, it's just sorting the colour balance and contrast out I guess. I've been looking at my last attempt wondering about having another go... but you've reminded me how tricky it is, so I'm not sure now!!

Yes looks very promising! I also like my sleep.... so although I have no observatory, I've automated my set up - plate solving and auto-focus being the main aspects. Everything is controlled through NINAs advanced sequencer tool, and if I'm pretty much 100% certain it's not going to rain, I'll just leave it and go to bed. I did manage a 12 hour session last winter on that basis. I guess you have to image at home, and be confident on security to do it, mind. (I have to add... although I do sleep, they don't tend to be my best nights, you start hearing rain even when it's not there!)

Thanks! re: stars - I use PI I use BlurXTerminator after DBE and SPCC (just with Auto PSF, BX is a tool I should explore the detail of and experiment a bit more!). RASA stars can be hard to control and often tend to flare a bit. As well as tightening them up BX can help with this a bit. I remove stars with StarXTerminator after an initial stretch with Histogram Transformation. This stretch will be just enough to get the stars about where I want them (generally I like to see plenty of stars, but not overly prominent - but depends on image obviously). I only ever use HT (although Curves would be OK) when stretching stars. I find other tools aimed at retaining star colour (MaskedStretch, ArchSinh etc.) give my stars a profile I just don't like, and I'd rather have a nicer star profile than bright colours. As with everything - all a matter of taste. I give the stars only image a limited push on the colour saturation (using Curves). And then add them back in at the end of processing the non-star image.

I did obviously spend many many hours learning PI... the Covid lockdown really helped me with this! But tbh I'm sure I'm guilty now of having found a way that works for me and not exploring other options enough! The RCAstro tools obviously contribute to that, and as I've discovered how to GPU accelerate them, it can make the process very quick indeed!

Ha ha - yes, the weather has been so bad - nice to have a go at processing something! My effort below... Observations: 1. The integrated image was noisier than I'm used to dealing with, so I think as has already been said, the best improvement can be made with more data. I purely applied NoiseX with this, after initial stretches, and quite strongly. I think blotchiness is not really there, but I guess it's a bit "plastic" from the noise reduction 2. I got tiling artifacts with StarX, so had to apply the "Large Overlap" option to prevent this 3. I've probably not stretched as much as yours. This felt like a bit of a limit to me. I had to deal with some nice purple and green hues in the background dust, and used a range mask to push the saturation a little in the nebula and dampen it elsewhere Having said all that, processing this reminded me that I did find my own effort on the Cave a tricky one to process - I think maybe it's an area with quite a lot of obscuring dust that makes it difficult to pull out detail? Edit: looking at that, I've perhaps not got enough contrast - a bit too dusty?

OK yes, maybe just more data will have the most impact. With regard to the green cast, I thought it was BackgroundNeutralization that really got rid of that, rather than DBE? Mind you, I find I still have issues with background colour after further processing, although I'm often stretching hard to pull dust out, which puts everything a bit on the edge. NoiseX - I was sure it was recommended as best on non-linear, but I can't find any advice on this on the RCAstro site now, so can't really back that up. an endless road of discovery and re-discovery this hobby...!

I would guess 3 hours at F/7.5 (if that's right?) is a little bit on the low side, so more data would probably help In terms of workflow, there are obviously different options which work for different people, but a couple of comments: I always apply DBE as a first step, which is what is normally recommended. I've learnt to do this starless now (courtesy of a free Adam Block youtube video), which makes it so much easier on a busy frame like this. So run StarXTerminator with Unscreened option not ticked. Peform DBE on the starless image, making sure to tick the normalize option - much easier to place samples on the bits that have minimal dust or nebulosity. Then add the stars back with PixelMath - a simple $T + stars. Did you run NoiseXTerminator before stretching? I thought the recommendation was on a non-linear image (but not after too much processing). I tend to do it after an initial couple of stretches, but before any other processing.

I don't have any experience with fast refractors, just the Hyperstar and now RASA. But once you get down to F/3, your CFZ is obviously very tight, just handfuls of microns. So it might not be a problem with the reducer per se - could just be that your backfocus distance is a tiny bit out (plus any minor tilt). The shape of those stars might be some sort of optical issue, but they are all pointing in to the centre, so you might just need a tiny bit more distance to the sensor? My experience at F/2 has been that I need a precise tilt / backspace tool (in my case, Octopi) as part of the image train in order to do the various tiny adjustments necessary to get a nice flat field. The flat field is there to be had, but requires patience and the right tool to find it. If there's a tilter on the camera you could try tiny adjustments with that perhaps? (although those tend to be a bit rough and ready)

I suppose I've not been imaging seriously for that long - just over 4 years, but this is certainly the worst spell of weather here I can remember (with the focus on clear nights, although possibly anyway). Horrible since the end of June, and I've got used to July to September being pretty productive, so quite depressing really. I planned a 2 panel mosaic of LBN437 (the Gecko) and parts of Sh2-126, and wanted to capture a good wide field around it including the trail of dust away to the corner that you see in this image. I managed 56 minutes on this panel in reasonable conditions on 25 August. However, the second panel attempt in early September was plagued with hazy cloud and various issues, meaning that mosaic really doesn't work, and those subs need binning (meaning dustbin rather than the other sort of binning 🙂). No further moonless opportunities have arisen. My forecast here into November looks atrocious, so I fear this target is going to disappear for another year. So here it is - half a Gecko...

I think you're always likely to have some - I guess optimum will depend on your set up - optics, sensor size etc. Mine needs a little work at the moment - just checked a recent sub and it's 19%. Can definitely get a bit better than that. Key thing though is what the stars look like. If I get them round in each corner, I try to stop looking at the numbers!

Here's the curvature plot from CCDI and also the aberration inspector from ASTAP. Both look pretty good - numbers in top corners just slightly bigger than bottom. I think the mid points in the lines give you an idea on your backspacing, but can't remember which way round the numbers work for too close / too far. It'll be in the documentation somewhere I guess. But again, it's pretty close. I use the Hocus Focus Aberration inspector in NINA for my tilt management and so on. It uses a whole focus run to compare curves for all corners, so takes a little while, but you get a good clear picture. I think the ASTAP documentation recommends this method of using our of focus stars either side of focus to build up a picture. Looking at the stars, it does look like some slight adjustments might help, but you'd need a precision tilter probably?

I like that - not seen a Pacman with surrounding dust before. You encourage me to have a go at it in broadband, I'd sort of written it off as an interesting target for my RASA. I'm not so bothered about the colour - I like the way it blends in to the surrounding dust. In Pixinsight I might have tried a Range Mask to just highlight the bright parts of the image (i.e. just the Pacman area) and boost the saturation there a bit. But you don't want to spoil that blending with the dust. I guess it's not particularly sharp... you could try some sharpening, but I must admit I rarely try this as I'm never really happy with the results. And after all, it is "nebulosity"! Maybe it might benefit from some more data, depending on the speed of your system, but 3 hours is a fair bit for broadband?