ollypenrice

How do you orientate your focuser? Do it like this. Pieter Vandevelde knows what he's doing. What a nice location, too! 🤣 Olly

This is a big ask. I'll speak for Photoshop. Briefly you should try to get the top left of each colour channel's histogram peak aligned. You can only do this by moving them to the left. Move the black point slider to the right to do so. There is a huge difference in brightness between the artificial lights low down and the Milky Way higher up. The only way to see the best of both is to do two stretches and layer mask them. This is a good tutorial: http://www.astropix.com/html/j_digit/laymask.html Olly

'Seconds into minutes' might be very misleading. In their advertizing, Starizona talk as if you are taking the same picture with and without the lens but, of course, you are not. Just as the F ratio goes from 10 to 2, so the focal length is divided by five. This means that a galaxy which fills the frame at F10 is reduced to a tiny feature in the middle of the chip at F2. These two pictures cannot be meaningfully compared. A more useful comparison would be between two instruments of the same focal length, one of them a Hyperstar. So an 8 inch Hyperstar has a focal length of 400mm. That's comparable with, say, an Esprit 80 with a 400mm FL as well. The Hyperstar remains much faster. Exactly how much faster will depend on the size of the central obstruction but it might be five or six times faster in theory. However, the complications introduced by the Hyperstar include the difficulty of eliminating tilt, finding and retaining focus at F2's shallow depth of field, finding filters which work at F2, collimation without an eyepiece, routing the cables to avoid diffraction artifacts and so on. These may eat into you clear sky time. When looking at Hyperstar images be sure to note the difference between narrowband and broadband results. Narrowband filters hold stars down to tiny points. Broadband filters don't - and Hyperstar stars in broadband are not always of the best. Sometimes they're good (eg Greg Parker's) but often they're not. Olly

There are different imaging boards on SGL. Why not take a look at what people are actually using for the different kinds of astrophotography? Manufacturers are dead keen to persuade you that they have the perfect solution (like the Fastar or the Starizona Hyperstar) with numbers which prove the absolute superiority of their marvels. But do the people doing the imaging use them? A few do. A lot don't. I don't. Olly

You're a well known and respected astrophotographer and contributer to SGL. I'd be inclined to contact the suppliers to let you try what they have on offer and let you make your pick on the basis of your findings and report back on that. As the CMOS cameras make more and more inroads into AP there is a need for hands on experience. Olly

In the original pier you had a lot of extended threaded bar exposed at the top. Personally I'd be inclined to have as little as possible proud of the pier. It's an annoying aspect of many mount designs that they require access from beneath to bolt to a pier. There is no need to level the base plate to polar align since perfect alignment can be had with a pier top far from horizontal. It's really good to see that the low life brigade have not damaged your observatory beyond repair. Olly

When I started imaging I felt that a 1000mm focal length fell into a bit of a no man's land between nebulae and galaxies but, as pixels have become smaller, it is now a good length for galaxies and smaller targets because you have the resolution if you you use the right pixels size. About an arcsecond per pixel will bring you close up detail. Olly

Refocus: bear in mind that with mono you can, if you like. With OSC you can't. (My point is that good quality filters of the same make are parfocal. Non parfocality really comes from the optics, so with OSC you make a compromise focus because that's all you can do. You can make the same compromise with mono and filters if you like, or you can focus per filter if you prefer.) Multiple flats: I use luminance flats for all filters. What's the problem? In a sealed wheel bunnies don't come from the filters - in my experience. Come back at the end of the night: you'll be very lucky to get away with no refocus during the night. Temperature change clobbers focus. If you focus robotically you can build that into your filter changes. Olly

You're worried that 2.15 arcsecs per pixel is undersampled? Here are some images at 3.5 arcseconds per pixel: https://www.astrobin.com/327970/?image_list_page=2&nc=&nce= https://www.astrobin.com/383965/?nc=user https://www.astrobin.com/301531/?image_list_page=2&nc=&nce= Don't get too hung up on the numbers! Olly

Why wouldn't you leave the camera out in an observatory? If the worry is security then fair enough. But living in an observatory your kit would be perfectly safe environmentally. In protracted damp spells you could put a drape over it with a pet warmer or dew heater under it to keep everything above the dew point. It takes me about 10 - 15 minutes to get going with an observatory-based dual rig. Olly

While I agree with Vlaiv's analysis there are some creative practical solutions to consider which nullify some of the problems. 1) You can shoot luminance at the higher resolution and RGB at the lower, at the same time, and the lower resolution in colour will be of no significance whatever. After all some people bin colour 2X2 and let the luminance restore the resolution. This is what we do with our dual TEC in which one camera has larger pixels than the other. 2) You could shoot Ha at higher resolution and OIII at lower since, on the vast majority of targets, there is less fine structure to be found in OIII. Some notable NB imagers like Sara use Ha as luminance anyway so you'd be restoring almost all the resolution as in the case above. 3) There might be some smaller targets (galaxies and PNs come to mind) in which you might care to image the object of interest at the higher resolution and yet not crop the RGB starfield around it. So, long story short, you certainly don't have to have identical rigs if you think through the business of what you intend to do with each side. If you use perfectly matched scopes and cameras you will need a very precise alignment between optical tubes or you'll lose the edges where they don't overlap. Having a smaller and a larger FOV makes alignment much more tolerant. The high end alignment devices are very expensive. With different fields of view you might get away without one just by shimming the slave scope into alignment. Registar, though certainly not free, is a stunning program which makes light work of all resizing/co-registering and cropping tasks so that they become a total non-issue. Olly

Your colour is in broad agreement with Hubble. It just needs more saturation to bring it even closer. https://www.nasa.gov/feature/goddard/2017/messier-5 Could you mask out the background sky and increase the colour in the stars? I use two non-saturation-based colour intensifying methods in Ps but I don't know your software. Olly

It looks nicely resolved to the core to me. I haven't imaged M5 myself other than in widefield but other renditions show a bright inner core as yours does. If I had a doubt it would be that, for this location in the sky, it's quite colour cold. But the stars are small and tight. Impressive in my view. The mist probably gobbled up the faint warm golden colours we might expect. Olly

NB filters are staggeringly effective at beating LP. They work best with monochrome cameras because there is no colour matrix blocking the light on some pixels. They will only produce good standalone images on emission nebulae, though. Galaxies shot in HA only really show blobs of signal from HII regions. OIII and SII show little. Still, there are lots of emission nebulae out there. Balancing the colour in Ps: once you've stretched the image, open up the histogram in All Channels View so you have separate histograms for each channel. As a rule of thumb try to get the top left hand side of the histo peaks aligned - ie the same distance from the left hand edge. You can only move them one way, ie to the left, and you do this by moving the black point slider for that channel to the right. Since you can only move the peaks to the left it is vital during the stretch in Levels or Levels and Curves, to leave plenty of flat line to the left of the histo peaks. The background will look pretty light but don't worry about that. It can be darkened later. For now you must have plenty of flat line to the left to allow you to clip it and move the peaks into alignment. You can also put four colour sampler points on different parts of the background sky. The tool is in the Eyedropper menu. A good background sky, in my view, should be 23/23/23 per channel or a tad lower, but not lower than 20/20/20. While this will balance your colours it will not get rid of colour gradients, unfortunately. Since you have Ps you might consider Russ Croman's Gradient Xterminator plug-in. It's not free but it's effective. The best gradient tool is Pixinsight's Dynamic Background Extraction but GradX is also good. Do not fight gradients by clipping the black point. Olly

I'm surprised by this. At one time I used two Atik 4000s, one a mono with Baader filters and one an OSC. I didn't see much difference in Ha sensitivity. However, the point about Ha filters is not that they pass more Ha than a red filter. (I doubt that they do.) Rather, they block everything that isn't Ha signal, so emphasizing the contrast in the cloud structures. Let's not forget that we all shoot a lot of Ha, too. Usually far more than we shoot in any colour. Olly

I remember those! Very handsome frames. Olly

You'd need to be very confident in your focuser with the multiple setup. Like Louis D I think two scopes might be less fraught. Olly

There's no reason to believe that OSC would be quicker than RGB. The term one shot colour can be misleading because a more accurate term for these cameras would be quarter of a shot red, quarter of a shot blue and half a shot green - though I'll grant that this doesn't roll of the tongue! If you judge the exposure by counting photons per colour per unit time you'll find they are pretty much equivalent in both systems. On the other hand the RGB might benefit from an LP filter. I don't know much about LP since I'm lucky enough not to have it. I would make this the key factor in your consideration and ask for specific advice on the utility of LP filters when shooting colour. I'd also be careful about adding depth and detail with a colour image. Colour without luminance is slow going, and that's why L-RGB is faster than OSC. Going deep in colour is pretty difficult - or time consuming. Also going for detail involves sharpening and sharpening requires deep signal, so again LRGB will beat OSC. Be aware, also, that your Ha data will be considerably sharper on the hydrogen regions than anything you will capture in red or luminance. As the others have said, giving us a look at the problem RGB would be helpful. Olly (ex-Derbyshire myself.)

As you know, I'm really glad to see this made public at a size which distinguishes it from other Orion mosaics - even if it could go even bigger! 👹🤣. This does justice to a phenomenal capture in which I was privileged to play a part. After several years of psychotherapy I might even consider myself up for adding more, so as to bring in the WItch Head, for instance. Oh God, did I really say that? Olly

I was asked by a guest to help with collimating one of these scopes as well. We looked at Steve's videos, amongst others, and found them sincere - but they did not solve our problems because there was clearly another variable in play. What it was I do not know, but it defeated all our efforts. Olly

I agree with Vlaiv. Try it first. You certainly won't be wanting to make it any faster because a 6 inch refractor at F5 is already screamingly fast. (Keeping the F ratio low without colour fringing gets harder and harder as aperture increases.) Olly

I like the 'paint factory' gag! I'd stick with the Mk1 colour which has a great background. There are still waves of variable brightness affecting the mosaic, I think. I don't know how to address this in APP. Do you combine the linear then stretch? Olly

Very attractive and super processing. Olly

Ooooooh!!! Poor old Descartes. He thought that cause must be greater than effect. Little did he know that nearly 400 years after his death serious minds would be doubting the very substance of cause and effect. But let's not be complacent. What happened to him could happen to us... Olly

In theory. Can you link to images which confirm this? That's to say, images which blow old school CCD images out of the water? Olly