Xiga

I used 1s Flats when doing Broadband imaging. For Narrowband it was longer, I think they were in the region of 7s to 10s. Try not to use super fast exposures for your flats if you can avoid it. For mine, I just plonk my iPad onto the dew shield with a piece of opal plastic in between as a diffuser. I then lower the screen brightness until a roughly 1s exposure gives a histogram somewhere in the middle.

Seeing as i haven't imaged anything since October of last year (don't ask!) i've been forced to get creative and dig through some old data to see what i could come up with. As it turns out, i had some Ha data of the Crescent Nebula taken with my Ha-modified Nikon D5300 and SW 80ED from way back in Nov 2018 that never made it into a final image. Last October I did a mosaic of the entire Cygnus region in SHO for which i used an ancient 50mm Zuiko lens to shoot the Sii and Oiii (i did the Ha at 135mm) and so i had the crazy idea to try and use the 50mm Sii and Oiii data together with the SW 80ED Ha data to see if i could make something even remotely resembling a passable SHO version of NGC 6888. Try as i might, i simply couldn't get the Sii and Oiii data to register to the 80ED data. Hardly surprising i suppose! So in the end i just used PS to rotate and scale them to get them as close as i could. I was actually surprised at what came out colour-wise, even though the Sii and Oiii channels are obviously nowhere near nuanced enough to provide any small-scale structure to the colours they imparted. I was also expecting to just have to resort to using white stars in the final image, so I was even more surprised when i was able to generate useable SHO star colours for the majority of the stars as well. All in all, quite an enjoyable endeavour being able to turn old unfinished data into something half-decent (i hope!). Full details: 13 x 1200s (4.33 hrs) of Ha; Nikon D5300 at ISO 200; SW 80ED 21 x 1200s (7 hrs) of Oiii; Atik383l+ Zuiko 50mm lens @ F4 11 x 1200s (3.67 hrs) of Sii; Atik383l+ Zuiko 50mm lens @ F4 Stacked in APP, processed in PS. Downscaled in post to 65% of the Ha-80ED res. CS folks!

Good luck with your D5300 Michael, you will do very well to find a better AP camera for the money. I got mine back in 2016 and sent it off to JTW Astronomy (who luckily for you are based in Amsterdam) for Ha modification and it's been a pleasure to use ever since. I'm lucky to now have a cooled mono astro camera, but i still have my D5300 and nothing will ever make me part with it, it's that good. FWIW, i've never encountered the concentric rings problem in any of my images. I used ISO 200 exclusively, but then i never imaged at a fast F-ratio, i was always at F6.3 so maybe that was the reason. In any case, it's good that there is now a fix for those who were affected by it. Mark is a true genius it has to be said.

The picture above is just a low res version from the Irish Times' website. I've attached a full res one below for completeness:

Thanks Adam. Very kind if you to post this so cheers mate. It came as a bit of a shock I admit. I wasn't expecting it at all so it totally made my day when i found out ☺️ Alas, I don't get to take too many photos these days. This was my most recent one, and it was from last October! 😕 I really need to get my mount back so I can get back in the game. It's been over 6 months months now...☹

Reading this (and being Irish) i couldn't help myself 😅 ps - The overly-large moons do bother me a bit i must say.

That's sumptuous Tom. Striking, yet somehow subtle at the same time. And always nice to see something a bit different too.

Thanks Richard. Good to know, as I've no room for an obsy, but maybe something like your setup could be within my reach. Cheers!

Richard, I didn't know you used a pier. So do you leave your mount outside permanently? I see you don't have a Dome or RoR, so how do you protect the mount from the elements, in particular moisture? Also, do you need to use any other form of dew control other than the dew shield?

Well done Spongey and Happy-Kat! 🥳 It really was a cracking data set. It's so nice to actually get to play with data, rather than fight against it (as is usually the case with my own, lol).

That's an incredible image for what is essentially a Planetary camera. Your perseverance (1000 subs!) has certainly paid off. Touché! ps - If you want to see an absolutely insane Lucky imaging DSO image, then check out the one below. He took over 40k of Lights, ranging from 0.5s to 7s. I can only assume he has access to a SuperComputer 😂 https://www.cloudynights.com/topic/568316-m82-full-power-with-short-exposure-t300-qhy5iii-290-m-qhy5iii-178-c/

Thanks Vlaiv 🤙 I only picked Blue at random really, not because i would intentionally choose to shoot less of it, but it's good to know that Red is the channel one could potentially get away with less of. My query was really just one born out of curiosity, because i can definitely see me encountering this situation at some point (1 weak channel) and no opportunity to add to it for a long time (perhaps the following year) so i was just curious what would happen, and you've answered it perfectly so thanks! It makes total sense too. I just wasn't sure if i would need to multiply the weak channel myself or whether the colour calibration routine would effectively do that for me, and it sounds like it would.

Multiple (phone!) post. Mods please delete.

Multiple (phone!) post. Mods please delete.

Multiple (phone!) post. Mods please delete.

Thanks Olly. It would certainly make for an interesting comparison I think. I don't get much opportunity to image these days (I completed all of 5 images in 2020, and none so far this year) so I guess I'll find out myself what the precise downsides to this are soon enough!

@ollypenrice can i ask a technical question of you please? I'm about to get into LRGB imaging myself for the first time, and i was wondering, what happens if you have significantly less exposure in one of the colour channels? I know the answer is of course just to shoot more of it, lol, but for the sake of argument, let's say you wanted to make an image with what you had, but you only had 25% of Blue vs the other channels. When you do colour calibration (e.g PCC in P.I) will this account for things, to the extent that the image will have the 'correct' colour, but will just need the Blues saturated more, or will the colour balance be way out of whack? Or alternatively, would the Blue data need boosting at all? I know APP has the option to add a multiplication factor to any channel when combining the RGB together. ps - Like Adam, i too bought a 268M but i haven't had a chance to use it yet. I'm already starting to wonder if i should have gone for the Colour version instead (not for quality reasons, just mainly so i can get some sleep while imaging! I don't have a permanent setup, so have to resort to using a filter drawer).

Very nice Cosmic Question Mark Adrian with the Samyang 135! Looking forward to the Redcat version now. Should make for an even more awesome Cosmic Question Mark. Ok, ok, i'll get my coat....😁

Very nice Adrian. How does the 'Cosmic Question Mark' sound? 😋 There is a small circular patch of Ha below the main object, which doesn't usually make it into most images of NGC 7822, but when you see the whole thing, I think it looks like a question mark. https://images.app.goo.gl/GQiJ1oHrfVTQaYUJ7

Oh, what data! I tried shooting this myself a couple of years back, but i was so disappointed with the quality of the data, i didn't even bother to process it fully. This data set, however, was an absolute joy to process! For this, i used APP to create a Super Lum using both the Lum and RGB. APP also used to remove any gradients, combine the RGB, and do star colour calibration. Then into PS for the rest. The RGB was stretched manually in PS using Shadows/Highlights (to preserve the colour, although Arcsinh stretching also worked well). Some use of the Dehaze filter in PS, then Topaz Denoise AI used for NR and sharpening (core only). These days i always try and incorporate Sternet into my workflow, but on this occasion i had to admit defeat and resort to good old star reduction instead. I used a host of options, Noel's and Annie's actions, some use of the minimum filter, and also Images Plus too. Cheers!

Thanks for the spreadsheet, very kind of you to share that with us 🙏 Can i just check something please - should the 2nd line above actually read: Gain 100 for ZWO = Gain 56, mode 1 (High gain mode) on QHY ?

Wowsers, that's some Sunflower Tristan! So much detail on show, without being over-sharpened, and i love the colours too. Hats off!

That's great Adam, i'm really glad it's working out for you. That M108 looks amazing btw. I do remember an image of yours from last year with a similar streak now that i think about it. Not a huge deal like you say, and hopefully the summer DIY job fixes it. Being as handy as you are, have you thought of bolting some thicker metal around the outside of the tube near to where the focuser is to strengthen it? I've seen some DIY jobs like this done before on smaller reflectors, and sure there's no better man for a DIY job than yourself! 😉

Very nice Adam. I love the colour you've got in this, the blues and magenta in the galaxy are gorgeous! I wonder do you have some tilt issues? The stars seem to become elongated the more you move across the image from left to right. I'm no expert on tilt though! Also, what's with the streaks coming off the bright star at lower-left? Some sort of reflection maybe? Like you say, it just needs some Ha now, which will make an already great image even better.

Gorgeous stuff Richard! Nice and bright, to bring out all that lovely dust, yet still with good stars. No easy task! Ghost is looking great too at top-left. It appears that to bring out dust like this, one needs 3 things. Aperture, Fast Optics, and a Very skilled hand. 👏