ollypenrice

I'm quite certain your decision to go mono-narrowband is the right one given the nearby lighting and the EQ6 is a good mount for imaging at moderate resolution. While there are, of course, small narrowband targets like planetary nebulae, I'd suggest that most are extended and tend to get bigger the deeper you go! So I'd prefer a short focal length over a long with a chip as large as the optics will support. Another thing about NB filters is that they hold down the star sizes. This means that premium optics and larger apertures (which hold down star sizes in LRGB imaging) are less important for NB imagers. In other words, small widefield optics do better in NB than they do in LRGB. These would be my two arguments in favour of a widefield narrowband rig and lead nicely into a possibility you might not have considered - the Samyang 135 camera lens. It has its own thread on SGL and has become a modern legend. Olly

There is absolutely nothing to it and the whole point of premium instruments is that they are well made with very hard coatings. I clean all the refractors here about three or four times a year. I just put some Baader fluid on a lint free cloth and wipe them using curved strokes and not re-using the same bit of the cloth twice, since it might have picked up a gritty fragment. I've been doing this for over twenty years and host a number of refractors at any one time. If it were going to cause a problem it would have done so by now! The reality is that some particles landing on the lens, notably pollens, do have the ability to degrade coatings so not cleaning the lens is more risky than cleaning it. You are worrying about nothing. Olly

I think your latest one is black clipped, ie jet black sky with nebulosity jumping out because the faintest stuff has also been discarded. I very much liked your original and fairly light background sky. Olly

Surely a roll-off sentry box is your solution? I've made three of these and they all worked well, with one now converted into a motorcycle garage and one going strong over a 14 inch SCT. The great thing is that it only needs to be a box big enough to roll over your scope, which in the case of a 10 inch Dob is very small. (The sentry for this box could be a gnome!) I would want the Dob higher than the surrounding land to keep the base dry, so I'd go for a concrete block. Then what really matters is having the box both ventilated and insulated, this combination fighting off dew formation. It also needs to be soundly prevented from blowing away, but that's easy to contrive. This would house a 14 or even 16 inch Dob so yours could be about a quarter of that size, making it a dead easy build. Olly

Quite honestly I'd get rid of all the third party software and set up and run the mount via the handset to see it there's a problem inherent to the mount. Check your input data, so hemisphere, location, time (including DST where applicable) date in US format (month-day-year), tracking rate (sidereal.) See if it works properly like that. Olly

I dare say somebody did say it, but they were wrong. Integrity does pay the rent. Olly

12 years on, I still think about this nebula. Tom and I chopped the top off it with his 30-odd panel mosaic at 530mm focal length. The thing is that, despite its size, it has real structure and looks as if it's being swept by a particle wind from the west. Olly

Yes! When I left teaching in 2003, the internet was just becoming a mainstream mass medium and I don't think English teachers were geared up to examine it it in the way we examined the printed press or TV. We certainly looked long and hard at the latter, analyzing with students such things as loaded language, editorial bias, the role of supporting images, position on the page or in the sequence of news broadcasts, etc etc. We aimed to alert students to the ways in which the media would spin the news pretty much subliminally. (You want to discredit a politician? Interview them in a perfectly unbiased way but make the next item one about a talking poodle in Penzance, or whatever.) Media analysis has been part of English teaching for at least half a century and Internet Analysis needs to become a part of that - because internet gullibility is, quite literally, a threat to our civilization. Olly

I've seen this from the inside as an occasional reviewer for Astronomy Now and have nothing but respect for their editorial ethics. I wrote a luke-warm review of a product, once, and the supplier wasn't happy with it. The magazine was perfectly clear on this matter, accepting a change of tone in one sentence (not a change of content) and then said straight out, No more changes, the articles goes to press as it is. I felt I was entirely supported by the magazine. I would not write for them under any other circumstances. It's often stated that there are few unfavourable reviews, but consider this: how do I or other reviewers feel when asked to review a product I think will be junk? Do I want to disrupt the life of my observatory, go to inordinate lengths to set up a bit of equipment and inordinate lengths to test it, all in the near-certain knowledge that it will be a bad product? I do not! Life is too short. Similarly, I don't review books I don't want to read. Who would? So there's a selection pressure in favour of the good stuff. The internet is not the paper press. There are lots of U-tube and other 'reviewers' who, at the end of their review, say you'll get a discount if you order the product from such-and-such an outfit. You will, and they will get a sales commission as well. They are not reviewers at all, the are freelance sales people. Olly

I'm pretty sure it'll be great but I agree with Newby Alert regarding the threaded bars. It seems a shame to build a massive base and then top it off with rather spindly 'stilts.' Hark at me, though: I did exactly the same thing when adapting a pier for a new mount needing more height and it's been good. 🤣 Olly

To get a good idea of the problem you could try looking through your scope at some distant text. This won't give you an idea of your maximum useful magnification on the moon but it will demonstrate that, beyond a certain point, the enlarged image contains no new information and may, through loss of contrast, contain less. Try reading the letters backwards to prevent the brain from anticipating them. The only time 'excessive' magnification can be useful is in splitting doubles where the idea is not to get a good crisp view of the star but to try to see if it's a double or not. Personally, I think that staying at the eyepiece, concentrating and awaiting those precious moments of good seeing, will give you an experience of more lunar detail than you'll get by swapping eyepieces. Olly

Alnitak is the most easterly of the three belt stars. Here you can clearly see it's a double in your data and that's without taking short exposures for a full separation. Frankly that is quite extraordinary in a focal length of 135mm. The only telescope I've used which splits it easily in full length exposures is the TEC 140, which has over seven times the focal length. Reflectors also split it well if you can see past the diffraction spikes created by the main star! TEC 140 image: https://www.astrobin.com/full/394022/0/ Olly

What you have is a classic 'first world problem.' Unless you pixel peep you will see nothing wrong with those stars. The only purpose of pixel peeping is to spoil a good image so why do that? The reality is that your optics are performing superbly in this exposure. This widefield camera lens has split Alnitak as a double. Please read that twice. Then take a look at high resolution telescopic images which totally fail to contain Alnitak and are a million miles from splitting it as a double. Making truly great astrophotos has nothing whatever to do with fixing this non-existent problem. Get lots of data with this wonderful setup and learn all you can about processing. If you don't think your lens is wonderful, I'll buy it. I'm serious. Olly

80mm aperture is tiny? 85mm gave me the image below. It was many years ago that I used this 85mm scope and I'm fairly horrified by the processing of this image when I look at it with hindsight. However, that's not the scope's fault. The key point about an imaging rig is that, unlike a visual rig and the human eye, it can collect light over time. The eye cannot. With the eye it's light in, light out. My imaging rig priority order is, without any doubt whatever, mount-camera-optics. Olly

I do this as well but by a different means: I don't use a mask, I just select the background I want to de-colour-noise by using the colour select tool to find it. I'll expand the selection by one and feather by one and just reduce saturation on the selection. I think the result will be the same as yours. Which is easier? Neither is difficult. Olly

A man after my own heart. You could experiment with layer masking for the bright stellar cores. - Make a new and much milder stretch, stopping once the cores look about right. Don't worry about the nebulosity. - Paste this 'cores stretch' as a top layer over the full stretch. - Create a layer mask for the top layer and paste a copy of the cores stretch onto it. It will be greyscale. - Put a very big blur into the greyscale layer mask. (Try a Gaussian blur between 3 and 6.) - Use Curves to manipulate the Layer Mask. You want to increase its contrasts massively, so pull down the bottom of the curve and push up the top. The dark parts will get darker (more opaque) and the bright parts will get lighter (more transparent.) What will happen is that the layer mask will only be transparent where the bright signal lies - that is around the cores - so only the softer stellar cores will be applied to the lower image. Some jiggling with the mask and the top layer should let you get a seamless blend of the two different stretches. This technique is often used to blend different sub exposure lengths (eg for M42) but often all you need to do is blend two stretches, a hard and a mild. Olly

I've had huge success with filters at 4 inches and below - from dark sites. I can't comment on how they work under light pollution. Initially I used a UHC but its coatings failed so I tried a visual OIII the second time. They allowed me, finally, to see the full Rosette nebula clearly and the entire Cygnus Loop, both in a TeleVue Genesis. Basically they subdue the background sufficiently to bring faint, extended target into view. I wouldn't be without mine. Olly

What software do you use for post processing? We need to know that before we can offer too much advice. My own feeling is that, if I can see noise reduction in the image, there is too much of it - and I feel I can see it in the second. The most important thing in post processing is being able to process some parts of the image differently from other parts, so sharpen some areas and noise reduce others. Boost colour in some areas and reduce it in others Any program with layers makes this easy when used with selection tools like Colour Select. Olly

That's a very remarkable processing job. Top stuff. It would be nice to fill the saturated areas, too. Would you need new data for that? Olly

I stack and calibrate in AstroArt out of old habit, but when I see other calibration software in action I'm amazed by how slow it is compared with AA. You can try a free download which won't save. Olly

Very sorry about your mother, Peter. Regarding the reds, that's why I said elsewhere that the blue star was important in the image: it establishes or places the reds in the full colour spectrum. However, I would probably drop the red saturation myself. Olly

I was about to suggest the Samyang 135 as a possibility as well. It is fast and will open up your FOV while giving astonishingly sharp results. There's a whole thread on here about this lens. Olly

With CCD I always use a master bias as a flat dark to calibrate my flats. It produces a result which I cannot, by any means, distinguish from a result in which I've used dedicated flat darks. Taking dedicated flat darks would be needed every time I took flats and I'd need to shoot them for each filter - if I shot flats for each filter. Which I don't. I don't because I find that doing so is a waste of time, since my luminance flat gives the same result as my dedicated colour flats on the overwhelming majority of occasions. If, once every couple of years, they don't work on a particular filter, I shoot a dedicated flat. I don't do AP to scratch some kind of perfectionist itch, I do it because I like it! When I find a short cut which works, I take it. I'd rather the put the time into something which will make a difference to my final image, and there I take as long as it takes. Nobody has ever said to me, 'That's not a bad image but I see you didn't take a dedicated dark flat for the blue channel...' lly

No, I was thinking more of reflections shuttling back and forth between glass surfaces in the imaging train of a refractor. So that might be flattener/filter/chip window etc. Sometimes generic flatteners as devils for this. Olly

I'm sure that if we could find the right vocalist on SGL we could make our fortune with an adaptation of a this 1962 classic. We'd call it, 'She taught me how to Bortle.' That is, if Bortling is indeed considered vocal... Olly