ollypenrice

It depends on how deep your photographic knowledge is. If it ends with the idea that F ratio defines the speed of the system (which is usually enough knowledge for normal photography) it is certainly not adequate for understanding the speed of astrophotographic instruments. In the normal photo world, both focal length and pixel size are constants when different F ratios are compared. When these constants disappear without being acknowledged, you end up with nonsense like this, just copied from the Starizona website; The HyperStar 8 lens converts a standard Celestron 8" SCT from f/10 to f/1.9, making the system 25 times faster. It doesn't do any such thing. To make the system 25 times faster you would have to increase the area of the telescope objective by 25 times. I might just as well say, 'I can make your car twice as fast by reducing the distance you travel by 50%.' lly

Noise goes down only as the square root of the exposure time so that makes it a classic case of diminishing returns. The same is true though, of every step of the way between capture and final image. Processing, for instance, involves a host of tiny steps, none of which is particularly spectacular in itself. What I can say, though, is that using 'normal' telescopes I always budget for between 10 and 20 hours per target. Using super-fast systems like the RASA 8, which is about 4.5x faster than my previous fast refractor, we are usually happy with 3 hours. Like most people, I started off taking three images in a night whereas now it's more like three nights for one image. I certainly won't be the first to say this. I don't use a DSLR so can't help with the ISO. Exposure time is likely to be limited by light pollution in the UK. Experimentation is everything but don't make a habit of using different exposure times. Once you've found the optimum it will be far less target-specific than you might expect. Olly

Still going strong at 23! Olly

Agreed. The fix for this kind of 'out of shot beam' is to finish the shoot and then aim the scope more towards the source of the problem (let's say Schedar in this case) and try another shoot. Obviously the new shoot has to cover the problem area but I've always found it was possible to find a scope position which covered the problem area with a problem-free 'patch.' You don't need a full depth of integration to make a workable patch but you do need to be able to register it to the original. Lots of programs now allow this but in the past it was Registar or nothing. If AMcD doesn't have such software I'll be happy to do it on my copy of Registar. PM me. Olly PS If you want to blacken the stack, use stove paint. Being pigment-based it is non reflective outside the visible spectrum and this is vital for astro-blackening.

Thanks. Yes, I think too much technicality can a bit of a turn-off for the general viewer so I used popular names, mostly, and there is nowhere to put photographic details anyway. As you say, the numbery stuff is on Astrobin! I didn't feel the need for star reduction on a couple of the galaxy images but the majority have now been through StarX. I got to be quite quick at it after about 80 images. 🤣 Olly

After a rest from all the SmugMug stuff, yes! lly

Rather than keep on posting a succession of star-reduced renditions (Star Xterminator-modified) ) I thought I'd go through all my main images, re-process them where appropriate and put them all in one place. My SmugMug site has, therefore, had a long-overdue tidy-up and can be seen here: https://ollypenrice.smugmug.com/ One quirk of SmugMug is that some images suffer compression damage until seen as full screen, though most are unaffected. I'd welcome any feedback about how it feels to browse this site when you're not familiar with it. Olly

The problem with darks-for-flats with a DSLR is that you can't ensure they will be temperature-matched with the flats. If they're not, they are likely to do more harm than good. I would try uncalibrated flats first, to see if you have a problem. How important do I think darks-for-flats are? Well, with CCDs I used as bias as a dark-for-flats and that worked. Except when it didn't - which was for a long time with one particular scope-camera. In the case of this problem rig, nothing worked and, believe me, I tried everything. Flats over-corrected. So just see if uncalibrated flats work. If they do, you're good to go. If they don't, the bad news is that darks-for-flats may not solve the problem! Olly

To put that, rather brutally, another way: less junk versus more junk. In a limited time the DSLR will give a wide field of weak signal and high noise. In the same limited time the 460 will give a small field of workable signal and noise. I have an Atik 460. Would I swap it for a DSLR to get a wider field? The very idea is ridiculous, for me, because I'm trying to produce images that will be taken by magazines and attract customers to my business. I cannot do that with a budget, modded, DSLR in normal optics. (If I had a modded 5D MkIV in a Tak Epsilon I would aspire to images like those of Maurice Toet but that is not on the table, here.) Who's 'We?' Whoever you are, I don't concur with your advice, I'm afraid. Olly

Samyang 135 lens at F2? Tolerant of guiding errors, fast, portable and robust. Olly

Hosting six telescopes, all with their own dedicated astro-specific accessories, has taught me that the designers of these products must all be natives of Las Vegas. Before I went round with the black tape the site was ablaze with lights of many colors, flashing (at various rates) or permanently ablaze. They really don't get it! lly

Thanks Tony. It sounds as if we've followed the same path: Note the bit of black tape near the power lead on the camera. This blocks a small light which created a reflection heading down onto the chip from the cable! Olly

I remember seeing an image, I think in infra-red, years ago which confirmed that the cluster was moving through a dusty region rather than being surrounded by its progenitor gasses. What I particularly like in deep M45s is the clearly visible 'wake' created by the cluster's motion. Olly

As said, you create a copy layer before running the action on either the top or the bottom. However, the Astronomy Tools actions have actions 'As layer on top' or 'As layer underneath' and these will retrospectively generate a new layer for the post-action image. This is good because you can choose the opacity of a layer, maybe making it half as influential as it is on its own. Or you can keep it in some parts of the image and erase it from others. To select areas to erase, use Select-Colour Range. Maybe you've done a noise reduction which you only need on the darker parts of the image? Select the brighter parts, feather the selection and erase them, totally or partially. Maybe you've done a local contrast enhancement and you like the effect its had on the darker parts but feel it has brightened the stars too much. Make it a top layer and change the blend mode to darken. Then it will apply the darkening but not the brightening. Layers and selection tools give you stunning control and a real-time preview of what's happening. Olly

False click. Please delete. Sorry.

'APP's combine channel tool, option HaRGB 1.' I'm never keen on handing over a key stage of processing to a routine I don't understand. Does this APP routine give you any kind of preview? Is it adjustable? Or is it just some kind of generic guess? (Genuine question to which I don't know the answer.) When I add Ha to red in Photoshop's Blend Mode Lighten, I can see in real time what it is doing to the red. Is it lightening the background? If so, I can bring in its black point or lower its curve low down. Is it doing anything at all? If not I can stretch it further with any custom curve, in situ, in real time, with a real time preview. Tell me why I should ditch Photoshop! Olly

The aperture you can get away with is much affected by chip size, too. The deterioration in star shapes increases as you move off axis. Olly

My problem with all of this is that I only perform a global stretch up to the point at which the background has reached a desirable level. After that, I stretch manually but only above the background level. I can see no point in continuing to stretch the background (where signal is weak and the noise floor low) once it's reached its final level. Olly

I would experiment with a set of inter-connecting stop-down rings (filter rings), starting with wide open and looking at star shapes and vignetting. I'd then add a ring at a time to reduce the aperture and stop adding as soon as I found the corner stars acceptable. Alternatively you could use a compass-cutter to make a set of front aperture masks of diminishing aperture and experiment in the same way. Graphics outlets have compass cutters at low prices. Olly

It seems that Wega also stand accused of industrial plagiarism: https://www.facebook.com/deepskydad/posts/theft-alertwega-telescopes-from-germany-has-copied-our-design-for-wo-redcat-auto/842992756438285/ Olly

Thanks Paul. This mosaic is based on a target of 3 hours per panel in 3 min subs. Naturally you do get panels which have more scrappers than others. Note that I live at a seriously dark site, SQM 22 on the very best nights. Regarding the main cluster, which I've shot many times in other rigs, I've never had so much control over the brightest stars, despite the speed of the system. I also think that these captures found the best ERE (extended red emission) of any attempt I've made on M45. Shoot away: you have the technology! Olly

I honestly can't remember, but I probably saw this and discounted it because of the '30 to 40 working days' stock estimate - to which I have to add the best part of a fortnight while the delivery companies waste my time, energy and faith in human decency. Regarding the Christmas cracker Wega tat, I'll add that I put two heavy cable ties around the lens-camera system so that a failure of the tube rings will not send £2,500 pounds' worth of optics and cameras heading towards a well-made six tonne concrete floor. Olly

That one looks much better. Who sells these? Olly

Processing was interesting. I followed my usual routines in working on the starless image and got a result I liked very much. I then tried to extract the stars from the regular image and replace them, but they looked awful. I've used this method on at least 20 images without difficulty. A bit stuck, I tried placing the highly stretched starless image over the standard image which I'd stretched only till the stars were nice but the rest was still dark. I then changed to blend mode Screen and, with a little work in Curves for the bottom layer, I ended up with what you see. I really thought I was going to have to go back to stage one, but no. Olly

This product comprises a 3D printed set of tube rings with holder for the ZWO focus motor, a 3D printed dovetail and finder-guider bracket and a pulley system to drive the lens focus barrel. The concept is fine but the execution is lamentable. 1) The wing nuts for the finder guider are regular hex nuts onto which printed wings have been placed. They fall off and will always fall off. 2) The tube rings have clearly proved to be fragile so the manufacturer includes washers which prevent them from being over tightened. They also prevent the rings from holding the lens firmly. If you fit the washers and tighten the clamps, you can slide the lens up and down in the rings or rotate it easily. 3) The pulley for the lens is split to let it slip over the focus barrel. Its two ends are held together by a minute plastic press-in clip of such fragility and bad design that it broke of its own accord overnight. And, even before breaking, it allowed the focus pulley to turn on the lens barrel anyway. Useless. 4) There are no instructions. 5) This tat sells for £139.00. (One hundred and thirty nine pounds.) Having got this far with the wretched thing I'm going to continue. I'm not using the finder shoe anyway. I have put thin double sided tape around the focus barrel, slipped the pulley over that, threaded some copper wire through the holes for the silly clip and twisted the ends together before putting a drop of solder on them. With luck the pulley will now turn the focus barrel. I'll stick with the washers which prevent the tube rings from holding the lens but put the same double sided tape round the lens to see if it will hold still. I don't know who Wega are but they need to go back to school. Olly