ollypenrice

You could ask for an American member of SGL to buy the paint for you, perhaps, and send it on. Olly

The bloat is also quite magenta, so green is low - for whatever reason. Olly

I've had 8, 10 and 14 inch SCTs and still have the latter two. They do need dewsheilds but they need them a lot more than a refractor needs them! Whatever you use to combat dew, on a dewy night an SCT will get shut down before a refractor. Long before - and I live in the south of France, not Norway. Camping mat makes brilliant dewsheild material, by the way. Olly

I started to have a play with these data but ran into a problem with ABE creating contour lines. I don't have the time to try to sort this out because a robotic shed issue is all-consuming at the moment. However, I saw no reason for the background to become blotchy and I really saw no vast amount of noise to deal with. Is this because I may be stretching differently? I've seen lots of stretching videos where the imager keeps on stretching and then pulling in the black point, over and over. This seems crazy to me. Once the darkest part of your image has reached the brightness value that you want it to have, why stretch it any further? Why not pin it in Curves and stretch only above that? Why pull your dark signal up above the noise floor? In the case of this image, there is dark, sooty nebulosity well below the brightness of the more transparent background sky so, once this sooty stuff was up around a Value of 17 in Photoshop, I pinned it and stretched only above it. It all looked pretty good to me. I don't go for any of the bought-in, sliced cheese stretches with began with DDP, years ago. I'll use a standard log stretch till the darkest signal is where it needs to be then I'll only stretch above that. Olly

I've had that as well! Grrr. Olly

Where is the artificial intelligence in all this? It is just a regurgitation of numbers already out in the public domain, with one vitally important number replaced by the adjectives 'average' and 'good.' Since these are the numbers which define everything that the system will produce, what are they and where are they? I would rate this answer average to poor. lly

Lovely stuff, Maurice. I see that people are shaking off their sleep in Lagrand and putting the coffee on! Olly

I'd have to ask what criteria he uses to define 'reliably get 30-second exposures with his DSLR on his old driven equatorial mount.' My fear is that, in upgrading to a better camera, he would be wanting to upgrade his images and would, very quickly, find himself re-defining what he found to be acceptable tracking. 30 seconds, unguided, at well below an arcsecond per pixel? Science doesn't work by proving negatives but, no, I would need a lot of persuading. Olly

Yes, I understand this argument but the OP has wisely started out with binocular observing already. The problem with starter scopes, which is common to starter products in other arenas, is that the buyer risks finding, 'Yes, I like this,' and will almost immediately want to take the next step. When they do, the starter setup will be obsolete for them. On the other hand, many seasoned observers have a 4 inch (ish) refractor along with all sorts of other, more extravagent, instruments and they keep it because it remains a particularly useful tool. Personally, I have given up on 'starter products' because I invariably find that they have a very short role in my activities. This may just be me, of course. Olly

For me a small telescope with a very long focal length misses out on what a small telescope can do and a big one can't, which is deliver a very wide FOV. That's why I'd prefer to avoid Maks and SCTs. I also think that, in Norway, you will also want something which does not attract dew. SCTs and Maks are bad for this. I do like the look of this, mentioned above by Vlaiv. https://www.firstlightoptics.com/stellamira-telescopes/stellamira-110mm-ed-f6-refractor-telescope.html I didn't know about it. Olly

Aperture is important in visual astronomy but inevitably comes at a cost in terms of portability. Bigger is - well - bigger! Robustness is another aspect of real portability. For many, the 4 inch refractor hits their target. This one is an old established favourite. https://www.firstlightoptics.com/ed-pro/skywatcher-evostar-100ed-ds-pro-outfit.html It has a longish focal length for its aperture so isn't going to give as wide a field as a faster 4 inch, but it is very well colour corrected as a result. Being a refractor it is robust and won't require collimation. For visual observing, alt-az is nice and intuitive, does away with polar aligning and needs no counterweights. This would be one option. https://www.firstlightoptics.com/alt-azimuth-astronomy-mounts/astro-essentials-alt-azimuth-fork-mount.html On a suitable tripod it would make a kind of budget replica of the Televue 4 inch used by Steve O'Meara to write his classic observing guide to the Messier objects. You'd be on budget for a couple of reasonable eyepieces, too. ( Eyepieces stimulate a kind of mania among astronomers, many of whom have twenty or so. I use two, almost exclusively. Better two good ones than four poorer ones, in my view.) This is a setup you would pull out of the car, place on the ground and get started. A red dot finder would also be good and you'll need star charts but you could print selected regions from a digital planetarium. Olly

Yes, if you have a little backlash in RA, then running slightly east-heavy will leave the driven gear resting against the drive side of the driving gear rather than oscillating across the backlash. It does mean that you need to reverse the imbalance after a meridian flip. There is an equivalent procedure to reduce Dec backlash but which doesn't involve balance weights. You can deliberately polar mis-align the mount slightly then activate only the guide direction which corrects for that. You don't run the guider on the other direction. Trial and error decides which inputs to disable and, again, they need to be reversed after the flip. While I've had reasonable success with both methods, this was only as a stop-gap measure prior to fixing the problem properly. Olly

I like them all. BTW, cropping, of itself, has no effect on resolution. In daytime photography there is a careless tendency to confuse pixel count with resolution but they are not at all the same thing. Olly

Perhaps a member near you might let you try your handset in their mount? Olly

Fabulous! Exceptionally deep and yet exceptionally clean with superb levels of local contrast in the Ha. Beautiful processing, too. The result has rewarded your effort. Olly

Très belle galaxie! Balanced colour and brightness giving a natural look. Olly

This target really comes to life in NB, with a distinct change in gasses, therefore colour, between body and pincers. Very deep and clean. A just reward for your patience. Olly

Your OIII is way better than mine, which had 11 hours at an exceptionally dark site. I was using a mono CCD (Atik 11000) and Baader OIII filter. This was a decade ago and I think we can say that the technology has improved! Great stuff. Olly

I certainly agree that the Samyang is mightily out-resolved by the RASA but here, we are comparing massively different apertures. As regards depth, I think it's 'aperture per pixel' which matters. I'll go back and compare our own RASA and Samyang data on the same targets. I've blended the two without paying particular attention to this. Olly

The theory will be overwhelmed by the practice in comparisons like this. An 8 inch scope has higher optical resolution than a 6 inch if both are diffraction limited. To give the same FL the larger scope has to be faster, making it more susceptible to optical imperfections in the grinding of the mirror, the collimation and the mechanical alignments. Which will be the real world winner? It depends on the specific instruments in use. In DS imaging, sharpening in post processing has an effect on final resolution and more signal can take more sharpening than less signal. This favours the faster scope. If you are over sampled the optical resolution comparison goes out of the window because you'll be seeing limited, but the larger, faster scope gets more light. See previous point. I firmly believe that these discussions are academic and that the success or failure of an image derives from a dozen other things before the niceties we are discussing here have any contribution to make. I also know from experience that not all reducers play nicely with all optics and, given the very questionable wording of Starizona's Hyperstar advertising, I would read anything they write with a high degree of critical distance. For example, The HyperStar 8 lens converts a standard Celestron 8" SCT from f/10 to f/1.9, making the system 25 times faster. That means 25-times shorter exposures! For this to be true, the Hyperstar lens would have to increase the area of the clear aperture by 25 times and then we could consider it to be the same 'system.' Olly

For some time I used a Takahashi EM200 mount which has no facility whatever for leveling the top of the tripod. EM200 users at latitudes outside the fairly limited adjustment range of the mount routinely tilt their tripods to reach alignment. I'm assuming a reasonable degree of intelligence in not overdoing this. Within reason it is a perfectly normal thing to do to make your mount's adjusters more comfortable. If they are OK when horizontal, then fine. You can also expect Polaris, if visible this close to the horizon, to be displaced visually by about half a degree by atmospheric refraction. I have observed on the equator and would not make Polaris my primary means of alignment if I lived there. Olly

Can't agree on NR. It already looks like 'vaseline on the lens' and that's the root of the problem. But I do agree that it's a good image. How about resampling it down to a lower resolution , accepting a smaller rendition, and getting a cleaner image? Olly

I disagree with most of the advice above. 7 degrees above the horizon is not going to work for any kind of Polaris-dependent PA routine. You'd need a fantastically low horizon and minimal light pollution to see it at all. No design of pier is going to get around this, so forget it. You can Polar align by other means, quite successfully. Use a compass, corrected for your magnetic deviation, to point the mount north. https://www.magnetic-declination.com/Sri Lanka/Colombo/1481546.html#:~:text=Answer%3A -2.09° (-2°5') For the purposes of this method, just remember that your compass will be pointing about 2 degrees west of north. That will do. Even just using the compass's magnetic north without correction will do. That gets you in the rough position for Azimuth. Don't use the compass close to anything magnetic, like electronic devices. The rough position for altitude is going to mean that your polar axis is only going to be about 7 degrees off horizontal. If this is a problem for your mount, don't hesitate to tilt your tripod to make it easier. The base of the mount does not need to be horizontal. Many will say it needs to be horizontal but they are mistaken. I would make a physical wedge with a 7 degree angle and place one side on the the mount and put a spirit level on the other for quick repeatability. Once the mount is in this position, just use the drift method. It has various versions. This is a very intelligent one for imagers. https://www.cloudynights.com/articles/cat/articles/darv-drift-alignment-by-robert-vice-r2760 Forget Polaris. It will not help you. Olly

I regard SCNR as a linear-stage tool. Sometimes I'll run it and not run it, making two versions which I can then blend easily and selectively in Ps Layers. Olly

Personally, I'm suspicious of this stage. The effects you describe look like excessive NR to me. Regarding NoiseXt, or any other NR, I don't know what the official recommendations are but I cannot imagine running NR before knowing where I wanted it and what its consequences were. Hence I run Noise Xt on the starless once it is sufficiently stretched to reveal noise. I apply it to a top copy layer in Ps so I can blink the NR version on and off to see where it's good, where it's bad and whether or not it's over-done. I can then erase it from where it's harmful, retain it where it's good and adjust its opacity. Using layers I can see what I'm doing as I do it. I don't think anyone could ever persuade me that making a guess at what to mask and hitting 'Apply' was a better way of doing it. Olly Edit: regarding green, try SCNR green. I run it on 9 images out of 10. DBE doesn't deal with it for me.