Xiga

To the best of my knowledge, down sampling helps to 'hide' noise simply by virtue of the fact the image now has less resolution. The end result is the image will look less noisy, but when the image is viewed at 100% it will just look less zoomed-in, due to the reduced resolution. Which for a mosaic is probably not a big deal, as the FOV is already massive. One word of caution though. Don't ever use PS to down-sample. It uses a pretty basic resizing algorithm which will result in smeared details. Use P.I or APP instead, as they will let you use far superior algorithms like Lanczos-3. I tested this myself on an image not that long ago, and i found the difference was actually really noticeable, which surprised me.

Looks good Richard. 👍 🙂 I presume you used PS. How much did you blur by? I think when i tried it i used a Gaussian Blur of just 1.5 pixels. I'm guessing you went a bit higher, as you nixed a bit more of the colour noise than i did. NGC 1333 has lost a smidge of colour in the process though, but we're basically splitting Balrog hairs at this point, to my eye at least this has definitely made a slight improvement. ps - One last point. Did you consider down-sampling at all? I know it seems a shame to have to do so when you have a large sensor and lots of pixels, but perhaps in this case it could be justified? Just a thought.

Very generous of you Richard to share these with the SGL community. 👏 For those who maybe don't know, Richard is one of the elite-level processors on here, so these should be a joy to process. I hope to get around to having a go myself at some point, time permitting. I'm especially interested in the Dusty Taurus one, being that i can't capture it that well with my current setup and skies.

No not yet. I thought I was going to have a chance a couple of nights ago, but the camera didn't like the USB cable I bought off Amazon. No idea why! The one I use for the finder-guider worked ok, but I needed that for guiding obviously lol. I have another arriving tomorrow, no chance of trying it out in Astro Dark now, but still hopeful of getting a couple of hrs in Nautical Twilight with no moon before the end of the month.

What a Field of View that makes for! I recall now you saying a while back that you were chipping away at this area. I thought you just meant NGC 1333, i didn't know you were working on something as big as this. I love big mosaics, they might just be my fav type of image. I've more or less given up on trying to capture dust, i just don't have the skies for it i think. I have some under-whelming Iris Nebula data sitting on my HD gathering (ahem) digital dust, which i might process at some point, so it's always a pleasure to see an image that does it justice. ps - One possible idea for dealing with some of the colour noise might be to do a slight blur on a Color Layer. Regular Chroma NR kills too much colour and robs the dust of the nice reddish warm tones, but sometimes just blurring the colour can retain some of this whilst still reducing some more noise.

Thanks AstroArgy. Yes each one had roughly 2.5 hrs of total exposure time. I can't remember exactly how much but they would be very close to that. Taken in Bortle 4 skies. If you look me up on Astrobin you can see the exact capture details. I only use ISO 200 on the D5300 and for broadband, the exposures are usually 6 mins long.

Being a spreadsheet nerd, whenever i hear the word 'Concatentate' i can't help but think of MS Excel. Sad but true 😅

Nice! This is a big improvement on your version from last year Adam. The colours are looking great. 😎 The reflection can be fixed in a few ways. I think the way I did it in your M94 image was to use the Burn tool at a very low amount (only a few %) and carefully paint over the streak in a single stroke, with a brush size close to the same width of the streak. This significantly reduced the effect, enough so that Noel's Horizontal Banding Reduction action was able to clean up the rest. HTH.

Imaging small galaxies at short FL is not something i've done a lot of myself, but it can certainly be done, so definitely have a go! All shot with a D5300 and an 80ED. None more than 2-3 hrs each: Leo Triplet: M81 & M82: And a 100% Crop: M101: NGC 4565:

Ah yes, you're out of back focus, i forgot about that. The OAG i have is around the 22mm mark, so would be too wide. Sorry! If you want to use the new cam for guiding on both scopes, then perhaps the smaller pixels of the 290 would be the safer bet. That way, at x1 bin you could get the benefit of a higher pixel scale on the finder-guider, and on the OAG with the big 1200 FL scope you could bin it x2 to get something close to the pixel size of your 8300 camera. The smaller pixels are more versatile this way. It's true that the Lodestars do have a good reputation, but i think a lot of that is close to being outdated now. From what i've read, most of the larger-sized SCT folk have moved on from their Lodestars to the 174 as their OAG guidecam these days, as they say it is way more sensitive. But i think a fair few of them are using the Celstron OAG, which has a large 12mm prism, so they actually get the benefit of the larger sensor. I have definitely read of people just buying the 174 without considering their OAG prism size, and then they are disappointed with the 'porthole-effect' they end up with due to the prism being too small (most seem to be in the 9mm range). No idea on the Solar side of things i'm afraid. Although i do know the 174 has a Global shutter, which is unusual in the ZWO range, and is apparently an important feature for Lunar imaging. Not sure if that extends to Solar imaging too, might be worth checking in the Solar forum on that one.

I agree, the 174MM-Mini is probably the best camera you can get for an OAG, but the 290MM-Mini would also work just as well and costs a fair bit less. And in fact, unless your OAG's prism is fairly large, then the larger sensor size of the 174 would just be wasted on it as it would have a serious amount of vignetting. How big is your prism Adam? If it's only in the region of say 9mm, then the 290 would be a great fit. Ps - I actually have an OAG with a 12mm prism I bought recently but is going unused. You're welcome to borrow it if you'd like.

Sorry i can't be of any help with the technical issues Adam. I have no doubt though the SGL community will get it sorted for you. But thanks to @wimvb i did go back and have another look at the core, and there was more signal in there that i had missed first time around. While there i also cleaned up the sky background noise a smidge too, using @ollypenrice 's excellent method of very slightly raising the level of only the darkest sky background pixels, rather than using traditional NR.

Thanks Adam. It appears to be a dead link though. It looks like the pdf no longer exists. I have found a good article by Craig Stark here: http://www.stark-labs.com/help/blog/files/GainAndOffset.php and also a good thread (comment #7) over on iceinspace here: http://www.iceinspace.com.au/forum/showthread.php?t=149431 so i'm going to give this a go and see how i get on. Couple of quick questions for you if you don't mind: 1. Being older tech, i presume i will need to warm up the camera before bringing it back inside? I've read that with modern cooled CMOS cameras it's apparently not needed to gradually cool or warm them, you can supposedly do either safely in just a few mins, but with the Qhy9 should i cool and warm over a longer period, like 10 mins? 2. You had mentioned that the back focus was 17.3mm. I've found two sources online that give 2 different figures, this one has a schematic that shows 17.3mm https://www.highpointscientific.com/qhy-qhy9-classic-8-3-mp-cooled-monochrome-ccd-imaging-camera-qhy9m but then i found a link to a manual that says it is 15mm here https://www.qhyccd.com/file/repository/PDF/QHY9 CCD camera user guide.pdf Are there 2 different models of this camera out there, and was it the previous owner that confirmed it is definitely 17.3mm?

This is stupendously good Olly, even by your own lofty standards. At this scale, it certainly needs no more blue. It looks pretty much perfect as it is. Touché!

Adam, i had a look at the data and i think i know where things went awry. When you calibrate the stars in APP, the default 'Red-Blue' setting doesn't work for this image. It produces way more Blue stars than Red. So you just need to move the slider over towards Red, then you will see the graph change such that the upper-right quadrant of the bottom graph becomes much more densely populated than the lower-left quadrant. I had a quick go at your data. I used a setting of 0.25 for the Red-Blue slider to calibrate the stars. Then into PS for the rest. I only had to use a small amount of NR on the Lum (about 40% of Noel's Space Noise Reduction). Really enjoyed processing this, so thanks for sharing. ps - I didn't focus on the stars too much. With this dual-rig setup, i think you are going to find that the stars will be the hardest part to get right, as they are completely different sizes due to the large difference in FL.

Very well done indeed, on a difficult target. The core is a thing of beauty.

Great image Dave. So many stars, tack sharp, but not over-done. Very nice indeed! One small point, it's very subtle, but do i see a hint of some faint horizontal banding running throughout the background?

Wonderful Richard. I just love that wee edge-on galaxy to the right of M106. Are those subtle wisps of IFN i detect?

Simply wonderful Richard. Love the way the galaxy shines out in that lovely inky black background. Slightly darker sky backgrounds work well in galaxy images i find, and this is a perfect example. When i tried this last year, i found the 80ED struggled with quite a lot of the stars. No such trouble with the Esprit i see, especially so in your hands. Glad to see the Esprit working well for you.

This is fantastic Rodd. So much detail on show, and not over-sharpened. Lovely processing. Those Astrodon filters really do make the Ha pop don't they!

This is great Adam. The Epsilon is really sucking down those photons now. So much signal in just 6 hrs! The inverted SCNR trick does indeed work in PS, but to do it properly you must do it all in a Color layer and then merge it back down. If you do it on the main layer itself, it will raise the sky background a lot and you will lose contrast. With such amazing data, i couldn't but help have a quick 5 min fiddle in PS with just some selective colors adjustments (hope you don't mind). I'll post the settings at the bottom, although you might not like as much bling in your NB images as i do 🤪 Here are the settings i changed:

Thought i'd give this one last go at processing, because, well, what else is there to do on these cloudy nights holed up at home?! Plus, i just can't get enough of crummy data it would seem, lol. Colours were all wrong, plus it was seriously lacking in contrast. Dialled the stretch back a bit, and have also downsampled it further, it's down to 25% now, which i believe brings the effective pixel scale up to about 1.36" now. Well, it is if you ignore the fact it was taken on a C8 that's never even been collimated once in 7 years 😂 Also added quite a bit more NR (okay, a LOT more NR), but with only 2 hrs of >F11 data there was simply no other solution. So yeah, not one for the purists, to put it mildly. This one was just for fun. A crazy image for these crazy times we are living in. CS.

Incredible amount of detail on show, well done! Just one small point: it looks quite green on my phone. Maybe hit it with SCNR / HLVG and see if it helps?

I understood perfectly James 😃 It's simply down to the extended optical train. My C8 has a Crayford focuser (which also increases the FL). After that it goes: Hotech SCA T-adapter - Baader Clicklock. Then the SW FF/FR followed by 55mm of spacers. This way, focusing and rotation are both easy, and the optical train is totally solid. No thumbscrews in use! When I finished I didn't touch the optical train, I just carried it up to the loft. Here's a pic: Pretty bonkers looking I admit though 😂

The standard F6.3 SCT FR will give a wider Fov, which would matter for larger targets. But it won't get you any more photons on a target that already fits, and it also produces terrible stars in all 4 corners. Tbh the C8 is not an imaging scope at all. This was simply a case of me having a go with what I currently have. I've never even considered picking up the SCT FR as I know it would be a disappointment from an imaging standpoint. I think it's more of a visual accessory rather than an imaging one.