windjammer

Solar furiosa !

Absolutely loads in this pic, but background not suppressed enough? Here is a quick hack, hope you don't mind!

nicely resolved stars right to the centre and v good star colours. V nice. The background galaxies come in at around at 400 Mlyrs - good shapes and some colour. Amazing for only 1hr. My only comment would be to sharpen up the star edges if possible - a bit soft imho, otherwise vg!

Nice detail on the counter-rotating dust cloud

very nice. I like the subdued colours.

You could also crop the frame and cut the offending glows. Just do a close up image. Seems a shame to waste such good material.

mmm, I see what you mean. I've had the same trouble - never a really clear night without a high haze (or dew on the optics) and therefore uneven patches of crud popping up, as here. I don't know what software you have in the toolbox, but I would have a go with PI's new gradient correction process with the small scale removal knob turned up to full. Also graxpert's new AI gradient removal model is worth a try (its a free tool if you don't have it). I would have the stars removed before letting rip. I would also have a go with a curves tool to suppress the background as far as possible - you never know, the real object might just be bright enough to get away with it. In any event the blobs at 1, 6 and 9 you could probably convincingly paint out. I DID NOT just say that.

Nicely done! Is this an HOS ? My own version of this in HSO was so lurid and orange I moved over to SHO for everything since... I might revisit my data Two comments if you like: There is quite a lot of noise lurking so I had a play with Topaz Denoise (hope you don't mind). Also I would go for stars a little crisper, but thats just me.

>>but not without bringing out the bright background halos So is this because stars have not been extracted beforehand or the haloes left behind after extraction ? Haloes after extraction can usually be (ahem) cosmetically edited out.

Its a while since I've posted, here is my effort at M81 - an RGHb mixed broad and narrow band image with excess Ha emission. Pics are a close in crop, the full FoV, and an annotated FoV. Holmberg IX, a satellite dwarf galaxy of M81 is just seen centre left as a vague blur, stars unresolved. Checking out the master lights, the G channel sort of shows some star points in the right position, but nothing made it into PI's Starnet star mask. More exposures might well have got Holmberg IX over the line, but the weather did not cooperate in March and April. Does it ever? The most distant galaxy catalogued is NGC28505, centre right of M81, coming in at 148Mpc (480 Mlyrs). It even has some colour. I've included info on the catalogued galaxies further down this post and links to the NED database where entries exist for those interested (OK, nerdy but fun). As usual, mixed feelings about the image. I have been thrashing it for weeks and conclude 12 hours of data with a 6inch achro is not really enough. The whirling dervish look of M81, fizzing across the cosmos with hair on fire works quite well. Some of the galaxy detail is a bit overcooked, but I like the excess Ha emission overlay, and the stars aren't bad, though a bit more colour in them would be nice. The double star pair TYC4383-1127 and -2044 just below and left of M81came out well without splurging (technical term) together. Exposure and processing details at the end. Simon ---- Close in crop: Full frame: Annotated image: ---- Galaxy object info: PGC HYPERLEDA I catalog of galaxies (Paturel+, 2003) (983,261 galaxies) Name RA(deg) Dec(deg) Mpc Mlrs PGC2728721 147.68 69.23 PGC2730379 148.07 69.44 PGC28505 148.29 69.00 148 482.48 PGC28529 148.45 68.97 3.685 12.01 PGC28630 148.89 69.07 3.675 11.98 PGC28757 149.38 69.05 4.408 14.37 Holmberg IX PGC2724146 149.48 68.82 PGC2726822 149.63 69.03 PGC28848 149.80 69.26 19.16 62.46 PGC28630 148.89 69.07 3.675 11.98 M81, NGC3031 https://ned.ipac.caltech.edu/byname?objname=PGC28505&hconst=67.8&omegam=0.308&omegav=0.692&wmap=4&corr_z=1 https://ned.ipac.caltech.edu/byname?objname=PGC28529&hconst=67.8&omegam=0.308&omegav=0.692&wmap=4&corr_z=1 https://ned.ipac.caltech.edu/byname?objname=PGC28630&hconst=67.8&omegam=0.308&omegav=0.692&wmap=4&corr_z=1 https://ned.ipac.caltech.edu/byname?objname=PGC28757&hconst=67.8&omegam=0.308&omegav=0.692&wmap=4&corr_z=1 https://ned.ipac.caltech.edu/byname?objname=PGC28848&hconst=67.8&omegam=0.308&omegav=0.692&wmap=4&corr_z=1 https://ned.ipac.caltech.edu/byname?objname=PGC28630&hconst=67.8&omegam=0.308&omegav=0.692&wmap=4&corr_z=1 --- Data taken in Astronomik broadband and narrowband filters: R, G, Hb (486nm) and Ha (656nm). Ha-RGHb total exposure time 12.3 hrs. R 1x1 bin - 24x 120s= 0.8hrs, 3-4 March 2024, seeing 1.3", scope West side, prime focus R 1x1 bin - 60x 120s= 2.0hrs, 3-4 March 2024, seeing 1.3", scope East side, prime focus G 1x1 bin - 30x 120s = 1.0hrs, 30-31 March 2024, seeing 1.4", scope West side, prime focus G 1x1 bin - 82x 120s = 2.7hrs, 30-31 March 2024, seeing 1.4", scope East side, prime focus Hb 1x1 bin - 12x 600s = 2.0hrs. 9-10 April 2024, seeing 2.0", scope East side, prime focus Ha 1x1 bin - 23x 600s = 3.8hrs, 14-15 April 2024, seeing 1.6", scope East side, prime focus ---- Master Lights: FWHM (pxl) pre BXT post BXT R 3.06 1.77 G 2.48 1.65 Hb 3.93 2.23 Ha 3.66 1.49 ----- Plate solver: Resolution ..............1.248 arcsec/px Focal distance ....... 750.39 mm Pixel size ............... 4.54 um Field of view .......... 55' 37.0" x 43' 39.4" Image center ......... RA: 9 55 32.466 Dec: +69 03 32.93 Image bounds: top-left .............. RA: 10 01 11.387 Dec: +69 22 03.61 top-right ............ RA: 9 50 42.343 Dec: +69 27 48.91 bottom-left ........ RA: 10 00 11.617 Dec: +68 38 46.40 bottom-right ...... RA: 9 50 02.906 Dec: +68 44 20.05 ----- 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 PixInsight: Master lights-> crop-> Gradient Correction-> BXT-> linfit-> final master lights PixInsight: final master lights-> RGB Channel Combination (RGHb)-> StarNet2 starless-> export starless fits32 RGHb master, export star mask tiff16. Affinity Photo 32 bit image processing: import starless fits32-> reject default stretch-> curves-> Topaz Denoise(ST0,81)-> curves-> Tpzdn(LL0,84)-> curves (B layer)->Tpzdn(LL3,0)-> curves-> levels (B layer)-> vibrance/saturation/selective colour-> export RGHb tiff16 PixInsight: import RGHb tiff16-> gradient correction-> export RGHb tiff16 Affinity Photo: import RGHb tiff16-> paste in star mask layer, blend mode 'screen' -> paste in Ha mask layer, blend mode 'screen' ----- Processing Star Mask: Affinity Photo: import star mask tiff16-> curves-> invert selection of brightest stars-> curves(invert selection)-> add to invert selection of brightest stars-> curves(invert selection)-> manual white balance-> vibrance/saturation-> brightness /contrast-> paste Star Mask layer on top of starless final (blend mode 'screen') ----- Processing Ha Mask - continuum subtraction: PixInsight: import R and Ha master lights-> pixel maths: create H2 = (k*Ha-R)/(k-1) for a range of k values, 2.0 a good starting point. Select a k which picks out excess emission without too much background-> k=1.5 in this case-> -> pixel maths: create H3 = H2 - K*med(H2) for a range of K values, 1.0 a good starting point. med(H2) function is the median value of the H2 pixel intensity distribution. Select a K which removes any surplus continuum emission in H2 as far as possible-> K = 1.02 in this case-> export H3 fits32 as Ha mask Affinity Photo: import fits32 Ha mask-> accept default stretch-> select target area-> curves (stretch)-> invert selection-> curves (suppress)-> curves (cosmetic suppress)-> convert to RGB16-> levels(suppress G,B channels) -> gausian blur (1.0 pixel)-> paste Ha Mask layer on top of image final (blend mode 'screen') -----

You could always try a barlow as an experiment: keep the bin2 but get to 0.5"/pxl. I went through that exercise on my 150/F5 refractor but reverted to prime focus. Just not enough photons/skies/optics. Vlad (shhh!) also made convincing arguments. I might revisit though..... Simon

I think the trick is to choose the right gb radius. The fov of this pic is so huge that nebulae of interest are tiny compared with the swathes of pollution! But overall, the method is indeed one of last resort!

I don't use the PI scripts, so for each filter I would do separately masterbias, superbias, master dark, calibrated flats, master flat, calibrated lights, cosmetic correction. At this point I would choose one of the calibrated/cosmetic corrected lights from whatever filter to be the alignment reference for everything else. Next step would be star alignment with that reference on each stack separately. Final step is image integration combining the 6.5 and 3nm stacks for each narrowband into the master light for each narrowband. Simples ? Simon

Hi I tried gradexpert, (my goto tool for this - it is free and vg normally), but was roundly defeated! Fiddled with DBE in PI but also butt kicked. So I tried old school: take an image layer and gaussian blur so all stars are blurred out and gone (gaussian radius about 20-30 pixels on your posted jpeg image). Subtract the gb image from the original. A bit of levels and repeat. This is what came out... hope this is useful ? Simon original - quick and dirty crop for square, suggest you add a black background to your mosaic to square it up first round of gaussian blur and subtract second round of gb sub and some curves:

Even with an ST80 it needs counterweight arms.