windjammer

spectacular !

>>as the HA signal is the strongest what ratio do you use? I use PixInsight for the early stages of processing, which includes a function called linfit which basically brings the peaks of each of the Ha/Sii/Oiii histograms into alignment before channel combination. So they are evenly balanced, which I guess answers your question ! I find this avoids a load of issues down the road. You might this further info on carastro's selective colour useful if you haven't come across it: http://bf-astro.com/hubblep.htm You have done a great job already BTW! Simon

ps: star field mismatched with nebula: I took your xstars nebula but redid the star mask from your first image: but not the same image dimensions! Anyway, ideas to work with!

I had a play with the image and star mask - hope thats OK. A bit of Topaz Denoise on the xstars. Star layer is levels and brightness and contrast - the levels is a bit black clipping and gamma control: don't know what the pixel maths is to emulate the gamma control. The brightness and contrast should be easy to pixel math it. 2 versions here - more or les stars!

A follow up thought: the bit depth of your cam is also important. Your astro data is a thin layer of useful signal above a fixed lump of LP - which you subtract. The more bit depth you have in the surviving narrow data layer the better. Is your DSLR 12 or 14 bit ? A 16 bit astro cam will give you 4x or 8x more detail than 14/12bit DSLR. Simon

I am in central/north London Bortle 10 or worse. I don't think filters will do the trick. I think a mono astro cam with RGB and narrow band filters is the way to go. I shelter my scope in a hide during ops, so direct light is cut off - my terraced house neighbours are light pollution shockers. I tend to choose the objects for imaging at higher elevations and choose the time of year to go for them - above 60 degrees; so things like the classic nebs down south are not really feasible. Getting hold of good gradient removal tools is a must if you don't have them already - GradXpert is v good and free. Narrowband will punch through anything - my cam (atik 460) and astronomik n/b filters will manage 600s+ exposure times before you see the LP step in the histogram (that is with about 60 arcsec square fov with my scope) . RGBs, 300s. Simon

Hi Here is NGC 281, the Pacman Nebula in L(Ha)SHO narrow band. A light crop and annotated image. The image is rendered with the Foraxx Palette Utility script in PixInsight. Apart from a little cosmetic tweaking at the end, the product is all Foraxx. Rig and processing details at the end. Data taken in Astronomik narrowband filters: Ha (656nm), Sii (672nm) and Oiii (501nm). Total exposure time 16.3 hrs. Ha 1x1 bin - 33x 600s = 5.5hrs, 19-20 August, scope West side, prime focus Sii 1x1 bin - 32x 600s = 5.3hrs, 20-21 August, scope West side, prime focus Oiii 1x1 bin - 33x 600s = 5.5 hrs, 21-22 and 22-23 August, scope West side, prime focus ----- Plate solver: Resolution ............... 1.248 arcsec/px Focal distance ........... 750.63 mm Pixel size ............... 4.54 um Field of view ............ 56' 19.6" x 44' 34.7" Image center ............. RA: 0 52 49.480 Dec: +56 37 45.92 Image bounds: top-left .............. RA: 0 49 35.794 Dec: +57 02 01.01 top-right ............. RA: 0 56 28.155 Dec: +56 57 36.20 bottom-left ........... RA: 0 49 14.640 Dec: +56 17 32.09 bottom-right .......... RA: 0 55 59.035 Dec: +56 13 12.43 and annotated: Simon ----- Rig: Imaging scope: SW Startravel 150mm F5 Refractor, Baader Diamond Track, (2.5x Celestron Luminos 2inch imaging barlow), Atik 460EX mono Guide scope: SW Evostar 90mm F10, with guiding XY stage, ZWO 120MM camera Guiding: 2 stage PHD: high frequency guide scope (mount tracking) and low frequency OAG image train guiding (guidescope flex) Mount: Home made German Equatorial pillow block mount, permanently rooftop mounted. Spring loaded DEC axis gearing. Other gadgets: ST4 based anti vibration shutter, ST4 based PEC ----- Processing Lights: PixInsight: Lights, Darks, Flats, Biases: master dark/dark library-> masterbias-> superbias-> calibrated flats-> master flat-> calibrated lights-> cosmetic correction-> aligned lights-> master light-> BXT PixInsight: Master lights-> crop-> linfit-> final master lights PixInsight: final master lights->StarNet2 starless-> LRGB Channel Combination (Ha, SHO)-> export xisf starless master. GradXpert Gradient removal:->import xisf-> GXPT(20pc,3sg)-> export xisf, fits Affinity Photo 32 bit image processing:-> import LSHO gxpt starless fits-> reject default stretch-> curves-> highlight reductions-> high pass masking x3-> paint (cosmetic star halos)-> Topaz Denoise(SN,19,0)-> Tpzdn(ST,15,1)-> export tiff 16 bit PixInsight: import tiff16-> channel separation-> Foraxx Palette Utility Script-> export Foraxx tiff 16 Affinity Photo final tart ups:-> import Foraxx tiff 16-> levels-> Shadows/Highlights live filter-> paint (cosmetic star halos)-> sel colour-> Tpzdn(ST,7,1)-> import star mask, blend mode 'screen'. ----- Processing Star Mask: PixInsight: final master lights-> RGB Channel Combination (SHO)-> export xisf GradXpert Gradient removal:->import xisf-> GXPT(20pc,3sg)-> export xisf PixInsight: import SHO gxpt master-> StarNet2 star mask-> export fits starmask Affinity Photo 32 bit image processing:-> import SHO gxpt starmask fits-> accept default stretch-> levels(G,B)-> vibrance-> brightness+contrast-> export tiff16 star mask PixInsight: import tiff16 star mask -> channel separation-> Foraxx Palette Utility Script (star mask and background LSHO channels)-> StarNet2 star mask-> export Foraxx starmask tiff 16 Affinity Photo 32 bit image processing:-> import Foraxx starmask tiff16-> accept default stretch-> levels(B)-> vibrance-> Ha master light star mask overlay (blend mode 'luminosity')-> paste Star Mask layer on top of starless final (blend mode 'screen'). -----

nicely resolved Simon

Stars are too prominent in the final mix? The xstars and starless look good as you say (xstars a bit noisy?) I don't use PI except for the basics, so would combine xstars and starmask in Affinity Photo - the blend mode of the layers would be 'screen' or 'add', with live adjustment layers (levels, brightness/contrast etc) on the star layer to turn them down a bit - judgement by eye! Not sure what the pixel maths for that would be! Simon

I had a quick play on the noise - hope you don't mind : ) Simon

I agree, an in-betweener would be my choice. And IMHO some work on star colours, a bit too magenta-ish ? Looks like measles!

Thanks for this - good motivation to explore the far reaches of PI!

That tracking platform has really done its job! How long are the exposures ? Simon

spectacular as usual - but a bit pink ? Simon

Do you have any processing details ? Vg and vvg considering limited number of exposures

I'm pretty sure it is the Western Veil, Witch's Broom : ) Good stars, you kept 52 cygnii in its box.

Very nice nebula indeed - and good colours. Are the stars a bit eggy left to right ? BXT could probably fix that if you haven't tried it already. Simon

well. it is kind of Hellraiser red... : )

After I posted the Cave Nebula yesterday, I came across an automated script lurking in PI for rendering SHO images, the Foraxx Palette. You feed it stretched starless master lights, and rather than fiddle with Selective Colour, just click and it works. Astonishing how much of an improvement over the human's effort. Image and a side by side comparison attached. I think I will start going short on the monkeys... Simon and side by side comparison:

On my 150mm refractor I use the flat vignetting pattern to collimate. Obviously the scope is not a newt, so a bit different to you, but with a cheshire I could collimate the focusser but still get asymmetric star flares in the images. Aiming for a centred round vignetted flat pattern made a huge improvement, so that is now my goto collimation method. Something you might play with if necessary?

Hi Here is the Cave Nebula, SH2-155, L(Ha)SHO narrow band. A bad weather July delayed the final filter, but the final exposures eventually came in. I am pretty pleased with it - OK a bit of oversharpening and false edges in the bright bits, and stars still aren't quite right. But, for once, the processing was simple, A to B - so I have documented it below for my fellow grasshoppers out there.... Annotated image at the end. Simon Data taken in Astronomik narrowband filters: Ha (656nm), Sii (672nm) and Oiii (501nm). Total exposure time 12.1 hrs. Ha 1x1 bin - 16x 600s = 2.7hrs, 06-07 July, scope West side, prime focus Sii 1x1 bin - 22x 600s = 3.7hrs, 07-08 July, scope West side, prime focus Oiii 1x1 bin - 34x 600s = 5.7 hrs, 06-07 and 09-10 August, scope West side, prime focus Plate solver: Resolution ............... 1.247 arcsec/px Focal distance ........... 750.64 mm Pixel size ............... 4.54 um Field of view ............ 56' 31.3" x 43' 31.8" Image center ............. RA: 22 56 40.959 Dec: +62 38 08.18 Image bounds: top-left .............. RA: 22 52 48.395 Dec: +63 01 57.89 top-right ............. RA: 23 01 04.537 Dec: +62 57 13.95 bottom-left ........... RA: 22 52 23.052 Dec: +62 18 32.13 bottom-right .......... RA: 23 00 27.327 Dec: +62 13 55.02 Rig: Imaging scope: SW Startravel 150mm F5 Refractor, Baader Diamond Track, (2.5x Celestron Luminos 2inch imaging barlow), Atik 460EX mono Guide scope: SW Evostar 90mm F10, with guiding XY stage, ZWO 120MM camera Guiding: 2 stage PHD: high frequency guide scope (mount tracking) and low frequency OAG image train guiding (guidescope flex) Mount: Home made German Equatorial pillow block mount, permanently rooftop mounted. Spring loaded DEC axis gearing. Other gadgets: ST4 based anti vibration shutter, ST4 based PEC ----- Processing Lights: PixInsight: Lights, Darks, Flats, Biases: master dark/dark library-> masterbias-> superbias-> calibrated flats-> master flat-> calibrated lights-> cosmetic correction-> aligned lights-> master light-> BXT PixInsight: Master lights-> crop-> linfit-> final master lights PixInsight: final master lights->StarNet2 starless-> LRGB Channel Combination (Ha, SHO)-> export xisf starless master. GradXpert Gradient removal:->import xisf-> GXPT(20pc,3sg)-> export xisf, fits Affinity Photo 32 bit image processing:-> import LSHO gxpt starless fits-> reject default stretch-> curves-> paint (cosmetic star halos)-> Topaz Denoise(SN,9,62)-> Topaz Denoise(LL,23,12)-> Selective Colour to Hubble recipe (http://bf-astro.com/hubblep.htm) Affinity Photo final tart ups:-> Shadows/Highlights live filter-> Topaz Denoise(ST,6,7)-> curves-> brightness/contrast. ----- Processing Star Mask: PixInsight: final master lights-> RGB Channel Combination (SHO)-> export xisf GradXpert Gradient removal:->import xisf-> GXPT(20pc,3sg)-> export xisf PixInsight: import SHO gxpt master-> StarNet2 star mask-> export fits starmask Affinity Photo 32 bit image processing:-> import SHO gxpt starmask fits-> accept default stretch-> Recolour(hue, saturation) live adjustment layer-> Levels live adjustment layer-> Blur Diffuse Glow live filter -> paste Star Mask layer on top of starless final (blend mode 'screen'). ----- Annotated plate solved image:

Flats! They will get rid of a whole lot of crap in one fell swoop. Dust bunnies and vignetting - history. Don't waste any more time, get a light box for use as a flat lamp, like this https://www.amazon.co.uk/Tracing-Light-Box-LitEnergy-Ultra-Thin/dp/B073F97NS3/ref=sr_1_41?keywords=light+box&qid=1692037222&sr=8-41 They come in A5, A4 and A3 sizes, 12V or USB. Don't pay more than 20 quid. Simon

I think at least one galaxy crept in - centre, far left. And centre, top left... loads of the little blighters!

Well, suppose the focus moves 20mm forward. You have a 200 mm dia mirror and 1000mm FL. Consider the half diameter: the light falls 100mm in 1000mm, or 2mm in 20mm. Taking both sides, the minor axis of the flat is 4mm too small. Putting the ellipse to one side, what % of the light falls in a circle 4mm wider the the circumference of your flat ? Suppose for sake of argument flat is 50mm dia, then difference is % light lost = 100*pi*(27^2-25^2)/pi*25^2 = 16% Only a rough calculation, but you can see how it goes! Pretty soon you might end up in the same ball park as the 5 inch!!

Yes, Topaz denoise is very good - a real life saver and very effective. I had a go and experimented with the NXT free trial for a bit but ended up sticking with Topaz. Simon