ollypenrice

That's great, Goran. It's remarkable how different it is from mine and, quite honestly, how much more interesting! What our versions have in common is strong Ha around the dark B3 feature. (I always think it looks like a strawberry.) The vast majority of images don't have so much on show. You have interesting blue around the Ha which doesn't show in mine but I do get a hint of it if I ramp up the saturation. I should go back to the original data. The other thing is that you have much better separation between faint gas-dust and the background sky. I regard this as one of the biggest weaknesses in my processing. It brings more contrasty structures into view. Personally I would not take the colour saturation as far as you've done but that's always a personal thing. Yours is by far the better image and is a delight to behold. Nice one! Olly

It's not necessary, Dave. The laser will be more or less directed by the optics working in reverse. Not perfectly, of course, but plenty good enough for our purposes here. Olly

Actually I wasn't thinking of you, Ian, but others have been surprised in the same way. I think the trick we did with the laser was probably to shine it through the polarscope while looking up. This brilliant idea wasn't mine, it was dreamed up by a Belgian guest, Bernd Adams. It saves a lot of bending and grovelling but it does require you to be able to see and recognize Polaris. The idea is just to be sure that Polaris will be the bright star in the finder once you do get down on your knees. The usual caveats regarding appropriate use of lasers apply. Olly

Great! I'm glad you found it and of course you're welcome to the image. I just adore it as a feature. Olly

I'm not going anywhere near this one!!!! (Even if I am from Lancashire...) lly

I entirely agree about gadgets and faff, but I had a group of highly experienced imagers from the south of England who struggled to find Polaris at our dark site precisely because it wasn't 'all on its own!' But, seriously, I agree with you. There is a mania for gadgets. I have pretty much given up hope of trying to explain how to find our village. 'Follow the signs,' doesn't convince everyone. They MUST follow their Apps. Following the signs only applies to an alternative reality (the original one!!!) but following the signs takes you straight here. The wonderful Apps lead in all directions. Olly

In my formative imaging years I was much influenced by Dennis Isaacs who growled when images weren't North-up so I tremulously got into that habit! 🤣 I will deviate if I think the aesthetics really demand it but I do have the camera orthogonal with RA and Dec unless I really can't avoid rotating. Random angles, therefore, I naturally avoid. (They make it so hard to add data at a later stage if they're not orthogonal.) I did recently rotate an M45 image by 180° simply because I wanted it to look less familiar. Olly

Personally I'd put all the electronic gadgets in a big black bag in the house. All they'll do is ruin your night vision. We don't know where you are located so we don't know how far from magnetic north true north is for you. If you're in Iceland it could be a lot! 😄 However, I would just use a cheap magnetic compass and check your latitude, roughly. If you look north and up at the same angle as your latitude Polaris will be there if the sky's clear. Begin by getting it naked eye and fix it in your mind using local features on the ground. Don't get all distracted by gadgets and widgets. Olly

It's hugely effective for DSLR imagers. It really is. Olly

If you have Photoshop then Noel's Actions (now known as Pro Digital Astronomy Tools) has a very powerful 'remove Vertical Banding' routine. Large scale dither between subs would probably be a big help as well, 12 pixels or so. Olly

What about sending the FW back? Or asking the supplier for their opinion? In the scheme of things, getting a wheel to stop in about the right place should not be diificult. Olly

One test of the F/W positioning hypothesis would be to calibrate one flat with another from the same run. That would remove the possibility of wheel movement. (Or you could make one master flat from half your set and a second from your second set and see if they can correct each other. Your idea of dividing a flat by a flat is sound. I do this when teaching imaging to show what flats do. If a flat divided by a flat from the same run comes out genuinely flat then positioning will be the culprit. Sometimes flats problems can be utterly baffling. Olly

If you have a PC planetarium you can usually plug in your focal length and chip size to get an idea of how a target will fit your frame. I use SkyMap Pro but there are free ones like Carte du Ciel and Stellarium which, I think, also let you do this. If you use Photoshop for post-processing, a trick for extracting more Ha signal from emission nebulae is to go to Image-Adjustments-Selective Colour and lower the cyans in red by moving to top Reds slider to the left. This can be quite spectacular. Olly

Rather than put money into the wrong system I would suggest putting it into a system which is right from the outset. (I'll take some persuading that an F13 Maksutov on an alt-az mount isn't about as 'wrong' as it gets for DS imaging.) You already have a good DSLR and an excellent 50mm lens. Great. You can use these to take images from a fixed tripod provided you keep exposures short and stack a lot of them. Better, though, would be to mount the camera on an equatorial tracking mount. The Skywatcher Star Adventurer would be a good starting point, or you could invest more heavily in a mount that will, in the future, carry a telescope. Brace yourself for the discovery that mounts are of primary importance and expensive. One of the great things about astrophotography is that it has shown astronomers the truth about the deep sky: it is not only full of small objects to be seen in telescopes but also full of vast, extended structures only visible in widefield photographs. Enter your 50mm prime lens. Here's a great Orion by Stéphane Guisard and Rob Gendler from a Canon Nifty Fifty. Good, no? http://sguisard.astrosurf.com/Pagim/Orion_constellation-HRVB-50mm.html (Sure, this was done with a monochrome CCD camera and filters but you can see the power of the lens. Note that it wasn't used wide open. Stars are very hard for lenses to control and at F1.8 they won't do it.) Like many others I'll insist that your first purchase should be this: https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html So many aspects of astrophotography are counter-intuitive that a fundamental understanding of the underlying principles is essential in avoiding wasted purchases. And what's the least useful item in astrophotography? A smartphone. 👹 Olly

Really superb, and you've just answered a question I asked you on another thread regarding the combining of filtered and unfiltered OSC data. I like everything about this image, from the faint outer halo to the excellent core, all done without it looking forced. That's the natural field of the RASA and your camera? Pretty wide. I have to say it, though: you've cropped off that upturned extension on the galaxy's left side: you know you can't sleep till you pull it in with a second panel! The stars are also excellent. Your rig works. I can feel the sweet tug of temptation... Olly

Goran, have you tried comparing/combining pure OSC and dual band-filtered OSC? Essentially I wonder what, if any, is the 'cost' of the filter in terms of signal. Super image. Olly

Yeah, but it's uninhabited, right? 🤣lly

You lowlanders.!!! 🤣 Olly PS To ensure that it never snows again, just buy a 4WD. It worked for us!

I bet it's colder here than in Lincs by night. 3000 feet up, continental climate... We are in the Dept of the High Alps, after all. We'd see minus 12C routinely in the past with a coldest of minus 19C and we could get 80cm of snow overnight. In the last six or seven years it's warmed up considerably but we did see minus 10 last week along with some snow. This was a couple of weeks ago, looking down from the observatories. Olly

My wife says that in winter it's too cold and in summer it's too late! Olly

My argument over mono versus OSC versus time goes like this: Lum = R+G+B per pixel, simultaneously. You cannot shoot this with an OSC camera, you can only shoot R or G or B per pixel. Now the OSC filters don't have hard cutoffs so this is slightly overstating the case since the green OSC filter, in particular, overlaps into R and B. Still, the total photon count per unit time is very considerably higher in L than in RGB or OSC. Sticking to the simplified version where colour collects 1/3 luminance we can make this comparison in 'luminance units:' 1st hour: mono in R, 1/3. OSC 1/3 2nd hour: mono in G ,1/3. OSC 1/3 3rd hour: mono in B, 1/3. OSC 1/3 4th hour: mono in L, 3/3. OSC 1/3 Add this up and mono scores 6/3 while OSC only scores 4/3. While shooting equal amounts of LRGB makes processing easier, it would be perfectly possible to add another hour's lum in mono, taking us to 9/3 while OSC only advances in a further hour to 5/3. And so on... Some targets can be shot with a hugely extended luminance run, some cannot. Faint stuff like tidal tails, IFN etc can have way more luminance than RGB bot colourful targets do need a higher percentage rgb. On top of this you can, with CCD, gain further time by binning colour 2x2. Binning with CMOS is something I haven't tried and don't fully understand. And then, should you want to do pure NB, you will certainly want mono. But I don't argue in favour of mono CCD over OSC just on the basis of the arguments above but on experience of both and, the fainter the object, the more the real world advantage of mono became evident. On M42 there was nothing in it. On galaxies the OSC was rather lame. 2nd but: I've been really impressed by CMOS OSC data I've processed and also by dual band filtration of OSC. How does this work in the moon? Not a clue. Perhaps Goran could advise? So I would personally consider an OSC CMOS whereas I would not consider an OSC CCD. Complexity? On all our rigs I focus in L and let RGB look after itself. Non parfocality doesn't come, in our cases, from the filters but from the optics and it isn't worth worrying about. With OSC you cannot refocus between colours anyway. You can in mono but personally I usually don't. Nor do I shoot separate flats, except very exceptionally. Luminance flats work for all filters almost invariably. What you can usefully do in mono is shoot lum and blue with the object at its highest. Olly

Why not put the guide scope on the bracket mounted to the main tube? The main tube carries the mirror and it's ultimately the mirror you're guiding. You're not looking for the stiffest location for the guide scope, you're looking for the one which most accurately replicates the pointing of the mirror. Olly

Since this is a CMOS camera, bias will not work in the same way as they do with CCD cameras. In CCD you can use a master bias as a dark-for-flats, for instance and it will work fine. When making CMOS flats you must also make darks-for-flats (AKA flat darks) by shooting them with no light and at all the same settings as the flats. No bid deal, though, with OSC. Olly

I certainly never mentioned a 3D printer either! I scacely know what they are!! A few years ago Singlin wrote up a detailed and excellent article on fettling a Quattro. It would be worth finding, I'm sure. Olly