Adreneline

Hi. This is my version just using SCNR and then boosting the saturation. I'm no expert and I appreciate there are much more complete and thorough methods for doing this but this "cheating method" at least gives you a feel for what might be lurking in the data. Good luck. Adrian Mosaic_LHE-aa-sat.tiff

Very nice - really tight stars - and love the framing. My personal preference is to remove the green in an SHO image (SCNR on the inverted image followed by SCNR on the re-inverted image and then play around with ColourSaturation) but that said your image has a real vibrance to it with lots of structure coming through. Thanks for sharing. Adrian

That is off the scale impressive compared with mine! Would you like my .fit master to play with? 🤞 Adrian P.S. Apologies Des @desmcm for sidetracking you thread.

Hi Lee. I just left it in place. I've never noticed any sort of reflection issues with the filter so I figured it would do no harm to leave it. The weather has not been great since combining the 294 and Samyang but I did manage 60 x 180s of the M81/M82 region in the hope of getting some IFN. I'm not sure whether I've got it or not! My initial processing of the osc images has not revealed anything, despite following advice from @AbsolutelyN ; what I can see may be just wishful thinking. I think my processing is letting me down Adrian

Hi Des, Experience with the Samyang has shown me that the spacing, as noted by @geeklee is absolutely critical and even changes of a fraction of a millimetre can have a profound effect on the focus position relative to the 'L' on the lens and the shape and aberation of stars. I have just set my Samyang up with my new ASI294MC having previously used it with the ASI1600 + 8 position EFW (with a mix of Baader (LRGB) and Astronomik filters (L3+NB)). On paper both the 294 and 1600 have their sensor set 6.5mm back from the front face of the camera housing. As mentioned by @geeklee I had my EAF mounted on the Samyang (works a treat) but it is now mounted on my RedCat so I am focussing the Samyang by hand using a BM. This is the ultra light weight setup with the Samyang and the ASI294 - no filters anywhere. I have removed the EoS fitting and replaced it with the M42 fitting supplied by Astrojolo in Poland. The spacing between the end face of the lens and the front face of the camera is 38.37mm so the spacing from the end face of the lens is 38.37 + 6.5 = 44.87mm. With that spacing the focus position is right in the middle of the 'L'. I have found changes of as little as 0.2mm have a big effect on the final focus position, in fact you can see a ZWO 0.2mm spacer adjacent to the camera body. Adding filters of any sort between the lens and the sensor will increase the spacing by nominally 1/3 of the thickness of the filter, so in the case of my Astronomik that is about 0.3mm. My experience is that a change of 0.3mm will move the focus position outside the foot of the 'L'. I've seen it stated that this lens will "focus beyond infinity" - wherever that is!! I also read that the spacing should be adjusted so that the optinum focus is achieved with the marker in the foot of the 'L'. Finally I obtained much better result using the Samyang with my ASI1600 + NB filters when I used a Hoya Pro UV cut filter on the front of the lens. The OIII images were much improved and I was achieving consistent FWHM results for Ha, SII and OIII - and far less 'blue bloat' when using the Baader RGB filters. Hope this helps. Adrian

Very nice Tristan - love the colours and the detail. M51 is one of my most favourite things to image. I need to point my RC at it next time it's clear - and dark! Adrian

Tell me about it! I find it frustrating all the differences between PCs, Macs, iDevices that I have. I hope you don't mind but I took you image into Affinity and used the colour picker to sample around the background space and pretty well everywhere the G value was slightly in excess of R and B - not by much but enough to give the cast I could see on my screen - so I used SCNR in PI to remove it. With or without the cast it's a great image. I love GC's but I'm rubbish at imaging them - or processing them - or both! Thanks for sharing. Adrian

Big improvement I would say. On my screen there is a slight green cast which I just removed in PI and M13 pops out even more. I've never managed a GC that I was pleased with - I think they are the hardest objects to image - you've got an excellent result. Adrian

I'm not sure the method I used is the right way but in outline this is what I did: Star aligned, dynamic cropped and background extracted the NB and RGB masters Combined the SHO data and carried out a partial stretch before removing the stars using Starnet Completed the stretch of the NB starless image, colour saturation, noise reduction, colour balance, etc. Duplicate the RGB image and use Arcsinh stretch very conservatively on one copy and knee-bend curve stretch on the other in Affinity. I then experimented by blending the SHO starless and one or other of the RGB masters using either PixelMath or Affinity using Lighten or Screen blend. Finally a little bit of colour balance and noise reduction in Affinity and Dfine. As you say there are no doubt numerous permutations on the above plus other processes that could be applied. I quite like the colours Arcsinh stretch provides but it is too easy to push it too far and get what I feel is then a very pretty but unnatural look to the star colours. The knee-bend curve in Affinity lifts the star colours conservatively whilst at the same time pulling out an RGB image of the nebula which I have found can both add and detract from the image. My image of IC405 combined the SHO with the Arcsinh RGB image using a Lighten formula in PixelMath. Having said and done all the above I'm still not convinced it is beneficial overall to put RGB stars into an NB image but that's just me over-thinking the problem. Good luck! Adrian

Very interesting Craig and well implemented. I know just how difficult it is to combine RGB stars with a NB image and make it look natural and not look as if the stars have been stuck on as an after thought. I spent a lot of time recently doing exactly the same thing with my NB image of IC405 & IC410 and a lot of time debating with myself whether it was the right thing to do in the first place! I was completely undecided at the end whether it was the right thing to do and I can't decide whether to do it again on another NB image. I will be really interested to see what reaction you get to your efforts and resulting image. Thanks for sharing. Adrian

I know I am in the minority but I prefer the starless version - it really allows you to focus on the structure and form of the nebula. Very nice - I really like the colours. Adrian

Very nice - love the colours. Adrian

Very interesting. I'm hoping to have a go at IFN with my Samyang 135 and ASi294MC - got to be worth a shot. Thanks for sharing.

Thank you Martin. I've deliberated a lot about RGB stars in NB images but then I tend to think we use NB to reveal the nebula - we don't take NB images of star fields - does anyone take NB images of star fields? Having said that I'm not convinced myself about adding RGB stars to NB images. Having said that (and the previous "that"!) there also seems to me there is quite a lot of opposition to displaying NB images without stars even though the stars are far from being the right colour. Um? After all of those "that's" I tried not to over saturate the stars because I thought that would look completely false. Tricky! Whatever it's fun to experiment and see what comes out. Thanks again for the feedback. Adrian

Another attempt at blending RGB stars with an SHO image. This time the stars were taken with an ASI294MC osc (10 x 120s) and the SHO with an ASI1600MM (20 x 180s of S, H & O) both on the RedCat. The image is heavily cropped because the 294 sensor ended up at 90 degree to the 1600 when I mounted it on the EFW. OSC data taken through an L3 filter. Interestingly the focus point (checked with a BM) was identical for the 294 and the 1600 when using the L3 filter. As always C&C welcome. Adrian

I'm sure this is not easy. I'm sure you know magenta is an extra-spectral colour we see that does not appear on the EM spectrum because it is made up of blue and red - (255,0,255) - opposite ends of the spectrum. Magenta is the complementary colour to Green hence the "invert and remove green" but exactly how SCNR in PixInsight does it I have no idea. As to doing the same thing with Curves in Affinity (or GIMP) I have no idea. I was advised on this forum to aim to get background space to be around R,G,B : 23,23,23 - not too black in other words. Good luck and sorry again I can't be of more help. Adrian

Hi Jody. This really is a cracking image of M51 but I have to say there is still a magenta cast on my screen. If I do the PI trick again and remove green from the inverted image then M51 looks amazing. It really needs a GIMP expert to throw in their two-penny-worth because I have no idea how do this magenta removal. I took your image into Affinity and used the colour picker tool to scan/sample around the background. I many places the R and B values exceed the G value indicating a magenta cast which I presume prevails on the whole image. I hope you don't feel I am being picky or critical but there is a seriously nice M51 lurking in your data. I am sorry I cannot be of more help. Adrian

Very nice image Graham - really like the colours and the sense of depth you've achieved. Sorry I can't offer any insight into the filter questions you pose. Adrian

Hi Jody, I used PixInsight to remove the magenta. I 'inverted' the image and removed the green with the SCNR process and then re-inverted the image; it must be possible to do the equivalent in GIMP but I don't know how. Forgot to mention I then reduced the noise just a little across the whole image (I use a free, old copy of Nik Dfine2); I would normally create a mask and only reduce noise in the background. I then lifted the saturation on the whole image as well just a little in Affinity. If I had been processing my own image I might have played around with masks again to be more selective with the galaxy and the stars, which I now tend to remove, process the main target and then put back separately processed. Getting colour balance right is really difficult and I struggle loads to achieve. I also find that if I process on my PC laptop (rarely) and then look at the image on my MacBook Pro the colours are way different; if I plug an external monitor into the PC laptop they are different again! Adrian

Hi Jody. Hope you don't mind but I had a play with your image which is great and better than my first attempt at M51 by a country mile. On my monitor the image had a distinct magenta cast so I removed that and then increased the colour saturation a little. I've cropped the galaxy out and there is not shortage of colour. Bearing in mind I was only working with a low-res 8 bit version I am sure there is more to be had from your 16 bit original. The blue regions in the spiral arms is showing up really well. Hope you don't mnd. Adrian

Inspiring Göran. Another really thought provoking image. Adrian

The detail in the crop image is amazing - the RedCat does not disappoint. Adrian

Apart from the fact you have to take an image of M31 every year - well I do - this is taken with my new ASI294MC which I am in the process of learning to drive. What it lacks in colour it hopefully makes up for in structure. This is 10 x 180s, 120s and 30s all at -20 degrees, gain 120. I've been playing around with the processing and in more skillful hands I'm sure there is colour to be extracted - somewhere. As always C&C welcome. Thanks for looking. Adrian

To be honest it varies depending on the image. The halos on your image reduced because I reduced the green and pulled the black point a very small amount. I generally assess the stars in each master and if necessary use a star maks and MorphologicalTransformation in PI on the offending master - usually the OIII. In fact I nearly always end up reducing the star size a little in OIII to match Ha and SII; on the odd occasion SII needs a little reduction but if I've been really diligent with checking focus then I find Ha and SII are very similar. Adrian

No need to apologise for another Rosette - it's a joy to behold and an excellent first HOO image - certainly better than my first! I took the liberty of reducing the green in the image and pulling the black point back a tad - makes the blue core region more blue and less cyan. It also reduced the halos a little. Hope you don't mind. Adrian