ollypenrice

I think you'll find precious little to choose between them, the deal you get being, in all probability, the major factor. I currently have two Meades, 10 inch and 14 inch, but only because they happened to turn up. On a dead level playing field I'd probably go for Celestron but would beware of storms in teacups. Olly

We do have certain hard information on astro colour. We can look up the spectral classes of a selection of stars on a planetarium and see what their colour is by referring to something like this. https://socratic.org/questions/what-does-the-color-of-a-star-indicate Herschel's Garnet Star in your image is a very good indicator, for instance. We also know that 'empty' background sky (where we can find it) should be a neutral dark grey with all colour channels at parity. We know that ionized hydrogen is a deep red. (It's in this that I think your image needs attention in processing because the Ha reds seem reluctant to come out. I think Wim and Onikkinen have had the most success here.) A useful trick in Ps is to use Curves to lift faint signal out of the background. Pin the curve at the level of the background, put a fixing point below that and lift the curve delicately above these. Olly

I can't donload a file that size but I think the most important thing is that you have pinpointed the problem in the the phrase above. We live in a world in which people post u-tube 'tutorials' in which they actually say 'I just play with the sliders till I like what I see,' as if this were a sane way to proceed. In effect, you answer your own question in posing it: understand the sliders. Actually, I think there's a degree of back and forth between two approaches to learning how to process. 1) Know the tools at your disposal and understand what they do. 2) Learn to look ever more analytically at an image and say to yourself, 'What does it need?' Once you've decided on this, go to the tools you have. Just don't go to a tool till you know what you want to do with it. What I would like to have tried with this image is go to Photoshop's Selective Colour and move the top slider in Reds to the left to lower the cyan in red. This usually boosts Ha signal. Olly

Come on, Rodd, step up!!! lly

Appropriately enough, given the name, you might like Bart Delsaert's 16 inch F3.75 Dream Telescope. It's located not far from me. Indeed, when he bought this observatory I bought his Mesu, now in the capable hands of Goran. Small world. https://delsaert.com/observatory/remote-controlled-observatory/ Olly

One of our guests once flew with a setup in the seat next to him, paid for and negotiated in advance. Olly

I've run two dual rigs in the past, the idea being to halve the exposure time. This was in the days of CCD and not particularly fast optics (or, more precisely, not particularly fast systems - since we don't want to fall into F ratio myth territory.) These were systems on which I was typically looking for 15 to 20 hours per image, this reducing to 7.5 to 10 hours telescope time. The scopes were the same, a pair of TakFSQ106Ns and a pair of TEC140s. I'm not a millionaire and never owned both halves of either rig. These were collaborative efforts. Cameras were sometimes identical, sometimes slightly different. Differences in pixel scale are solved by Registar in one click, which pairs up the data perfectly. Other programs can now do the same. If pixel scales were very different, you'd have to think abut how to work the rig. The low res side could shoot colour, for instance, while the high res side shot luminance or Ha. On many targets, low res OIII would also be acceptable. Aligning the scopes is harder than you might think. I ended up buying the staggeringly expensive, and now out of production, Cassady T GAD - currently for sale in the classifieds. If one FOV is larger than the other, alignment is less critical because you can crop the larger to fit the smaller. Our dual rigs were very productive and much appreciated by our guests in the days when I ran manually-operated all-nighters here. Old age and decrepitude have required a change in technology so I now run screamingly fast F2 CMOS systems robotically. One is a RASA 8, the other a Samyang 135 working wide open - on separate mounts. With CMOS cameras the new rigs are more than twice as fast as the old dual rigs which were twice as fast as they would have been as singles. Quite honestly, if you want super speed, the Samyang and RASA are fabulous with CMOS cameras. I loved the dual rigs but love the new rigs even more! Olly

The Samyang goes deep very quickly but not all the sky is as packed as Orion. There are still dark regions but, as you say, a very deep 'whole sky' image would be interesting. We have it in narrowband but not in broadband (to my knowledge.) Olly

Orion - with Paul Kummer and Peter Woods. One shot colour, no narrowband filters. Olly

When I process Samyang images I de-star them in Star Xterminator and when I put them back I pin them down to a size which seems commensurate with the very wide field in the image. They are too small to be blocky! I can also give them a slight blur, and usually do. You can't expect the same resolution of nebular detail as you'd get from a larger optic, just as you can't expect as wide a field of view from a larger optic as you'll get from the Samyang. If you choose targets which need the wide FOV, and don't invite cropping or pixel peeping, you'll get a super result. My personal favourite from all the images I've ever done was from the Samyang. Olly

About three hours per panel in 3 min subs at F2, Lee. Olly

I have something to say about your theory, Mr Smith: there is nothing to be said for it. lly

It's paradoxical, but I usually have two or three focal lengths on the go and find the following to be true of what I actually do with each: Super-wide field (short FL) - usually make mosaics. Medium field (medium FL) - sometimes make mosaics. Narrow FOV (long FL) - never make mosaics and usually crop out the object of interest before posting. This is not based on what the gear can do, it is not a recommendation, it is simply an observation of what I end up doing. With a wide field I want wider, with a medium field I sometimes want wider and with a narrower field I want narrower. I only post this observation because you might, quite possibly, find the same - in which case you might prefer binning over a reducer. I wouldn't buy any reducer which has not been shown to work with your scope. Olly

Measuring the length of the sidereal day? Olly

Regarding Samyang star shapes, my team of three finds them reasonable, but not perfect, on the 2600 chip at F2. But here's the thing: how good do they need to be? This is a very widefield optic, obviously, and, being small, will produce large stellar images. However, we now have StarXterminator or Starnet++ and we have the option of reducing the stars to a scale commensurate with the wide field - meaning very tiny. How good do tiny stars need to be? Any significantly-sized stars can be fixed by a one-click action and most will be too small to matter. I have no intention of beating myself (or the lens) up for shortcomings which will, in the finished image, be trivial. My motto is, 'Look at the big picture.' Olly

Indeed. I dare say that anything cyclical has a variant of 0/24 or start/finish etc. A spiral is just a circle repeated in an addtional dimension... is it? (I'm useless at this kind of thing.) Olly

I highly recommend The Book of Nothing by the late John D Barrow. It is as erudite as one would expect of the man occupying Newton's chair at Cambridge and yet is as approachable and entertaining as can be. He points out, for example, that nothing really matters... Olly Edit: A practical example of the original conundrum would be a start and finish line... Which is it???

IFN near M64, the Blackeye galaxy. This was christened the Double Flare Nebula by Rogelio Bernal Andreo who was, I think the first to feature it in an image. In our rendition, the RASA 8 was driven by Paul Kummer to make a 3-panel mosaic, so this is a wide FOV. My post processing. Olly

Of course, if you were only to kick the PI habit and post process in Ps, it would be so much easier... 👹 With the subdued inner nebula this is remarkably deep and informative. In the past, the outer nebulosity was strictly narrowband. I think this is a nice image and remarkable for the FL. Olly

As Alacant says, don't use darks with a DSLR, just subtract a bias value. Don't over-complicate your flats. There is no need for any fancy software, just set up your flat light source (what are you using?) and experiment with exposure time till you get a histogram peak between 1/3 to half way over to the right. If you can, it's good to put in a delay of a couple of seconds between flats to let the sensor cool. Rapid shooting of subs increases temperature and, therefore, noise. Oly

This will be the time to experiment... Olly

I've had ten IOTDs with small refractors. I've also used a 14 inch reflector extensively in the past and, quite honestly, modern cameras are making big instruments less and less necessary. Nor do I think that getting an IOTD has anything at all to say about a person's motivation. I don't think anybody stopped posting on SGL when Picture of the Week was discontinued. My best image on AB was with a Samyang 135 and it didn't get IOTD. I still feel it's my best image (with Paul Kummer and Peter Woods) but I think Id feel happier to see it down here on a mount than tossed into space on a Muskmobile. lly

The key thing is to understand what you're doing and why you're doing it. Darks record the noise that is there in your camera during an exposure even when no light at all gets in. It shouldn't be there so it will simply be subtracted when darks are incorporated into a stacking software program. However, this noise must be nearly identical to the noise in your exposures. With a cooled camera, it will be. With an uncooled camera, it probably won't. With an uncooled camera, not running at the same temperature during successive exposures and not necessarily at the same temperature as the darks, darks are likely to do more harm than good. So... what's your camera? Flats photograph the light path of your system. It should be perfectly even (flat) but won't be. All optics are brighter in the middle than in the corners and bits of dust create shadows. In a sealed system, left unchanged between nights, there is unlikely to be any change so flats can be re-used. If there has been a change then, clearly, flats taken before the change must be applied to subs taken before the change and vice versa. For amateur purposes, very small changes in focus between filters and during a run of exposures can be ignored. Olly

Not in the comfort zone of the RASA 8 (400mm FL) but, with a heavy crop, we get this framing, with both objects and a star field. Paul Kummer drove the telescope, as usual. I added high res Ha and OIII to the Owl from the TEC 140 since I had them in stock but the RASA OSC did find evidence of the outer OIII shell. Olly

Lovely. I might look again at the globular, which is rather green, I think, but I like the images and the way you leave a high black point. Olly