ollypenrice

I'm not sure that we do! It depends what the observer wants. The OP wants to track down faint galaxies from an imperfect site and, for this purpose, aperture does matter most, I think. But it's not all about faint galaxies, viz... I agree. The view ascribed to a 6 inch is precisely the opposite of the reality in a large refractor. The image shows a blurred polo-mint-like glow around the core and the essence of the refractor view is the resolution of stars. Where I prefer a 6 inch refractor (if it's a good one) over a 10 inch reflector is on stars or wider fields in which stars define the quality of the view. I love observing through our large refractor because of the quality of the view, the tightness of the stars, the darkness of the background. I do think the view is more beautiful in a fine refractor but that was not what the OP was asking about. Olly

Sorry for the sidetrack but this grabbed my attention. Friends in my UK astronomical society actually bought a complete but dismantled Zeiss coudé six inch about 20 years ago. It had been used at the University of St Andrews in Scotland. I dare say it will have been very similar to the one you used. I only ever saw the lens but they did get it up and running. I agree with you on the big reflector beating it, though, for DS observation of faint targets. And big Dobs are incredible value. Olly

I agree with the 8x40 (or 8x42) option for ease. Higher magnification means higher jitters, the magnification mattering more than the weight in this case. In fact I find my pocket binoculars too light to absorb the natural jitters of hand holding so a bit of mass can be an advantage, within reason. Roof prisms are easier to hold than porros but are a little costlier to make. Probably worth it if ease is a big factor. Steve at FLO, the site sponsor, is very knowledgeable about binoculars and will give straight advice about quality, price and the relationship between them. Availability is also an issue. Olly

So the real question might be, Why go for either as a deep sky imaging scope and especially a first one? Goran? Michael? I wonder what you think. Olly

I agree with the thrust of your post but would argue that you don't need a very long focal length any more for small galaxies. Pixels have also become smaller. This M51 was taken with a 140mm refractor with a focal length of just over a metre. https://www.astrobin.com/342334/?nc=user Olly

Good story and result. If it's of any interest I have thousands of hours of DS imaging under my belt, run a business based on it, write about AP in magazines and have never used plate solving in my life. I believe RBA doesn't use it either, which you might find more convincing... Olly

Another no. Every pixel on your DSLR chip has a colour filter in front of it which you cannot remove. These filters make up the Bayer Matrix mentioned above and, very roughly, each filter blocks two thirds of the light, so the red filter blocks blue and green, etc. When you convert to greyscale all you do is ignore the colour information but you cannot recover the blocked light. Olly

I don't do darks with the camera on the scope. Having compared on-scope and off-scope darks I found a significant difference between the two. Given that I'm not particularly persuaded by darks anyway, I certainly have no interest in using inaccurate ones. I take off the camera and use the screw-on metal chip cover provided by Atik when I do use darks. When I don't, I use a master bias as a dark, a bad pixel map and a hot pixel filter. If you do want to do on-scope darks, do them in the dark. Olly

I bought a new handset from Telescope Service in Germany. Their website incorrectly stated that the one in question would not work with my instrument but, after checking on the net, I concluded that it would and it did. Olly

The 'R' might be a little more accurate but I've read formal comparisons which suggest no consistent difference between HEQ5 and NEQ6 in accuracy. The biggest variable is the particular one which comes through the post. At the short FL which interests you there is no great need for an OAG. I use guidescopes on my large and small refractors, the TEC 140 working at high resolution (0.9"PP). I think they're easier. I've used an OAG on a large reflector but that's another story. If you have a guiding issue with what you have then, unless there is flexure at the guidescope, an OAG probably won't solve it. Most widefield scopes are quite small unless you go for something like a RASA 8. Image scale also tends to be fairly tolerant on the mount. Olly

I think the priority order is mount-camera-optics and I wouldn't want to change anything without knowing why I was changing it. Mount: what you have is as accurate as an EQ6 which just has a bigger payload. Whether or not you need a bigger payload depends on what you want to put on it. But might you go for a long focal length, high resolution setup? If so, will an EQ6 be accurate enough even if it will carry the payload? Optics. The key question is, at what focal length do you want to image? Widefield? Small galaxies? You have to choose. Once you know that, you can think about how much aperture you can afford, how you would balance ease against fine tuning (since very fast optics are usually tricky), what size of corrected circle you need, etc. Camera. But first, can you get decent tracking with your present scope and camera? If so, it's an absolute no-brainer that your biggest improvement will come from buying a dedicated astronomical camera. Olly

You're the one knocking small aperture imaging. I'm not. I'm perfectly well aware of the advantage of aperture but I'm a pragmatist and put practice first. When your Newt images are as good as Sara Wager's Baby Q images I'll be really interested, I really will... LAZ. * Olly *Apparently it's fashionable to end posts with three meaningless capital letters so there you go.

Mods! Mods! This man is promoting light polluting smalls on SGL! Nobody's suggesting miserable ones. If 80mm scopes are miserable then the Samyang lenses must be positively suicidal... only they don't seem to be. Please explain! Olly

At night all socks are grey... lly

You could, and your way of working in Ps with OSC data is rightly popular. (Actually I think it's best not to blur the RGB but to add the L in small iterations, increasing the saturation of the RGB and blurring the partial L before applying it, but that's a detail. You don't even need to convert to greyscale to use one layer as luminance. If you choose that blend mode that's how it will be applied, I believe.) My experience with CCD OSC was simply that, in a given time (say three hours) I would not get a colour layer capable of supporting three hours of Luminance. I found that an hour each of pure colour in a mono camera found more colour signal. It would be asking a lot of the simple absorption filters on an OSC to match the interferometric colour filters used in mono, surely? But my CCD experience may have no bearing on CMOS data. You can only go so far in mutilating (I exaggerate!) your colour layer. I like to use RGB-only stars so I don't want them binned or hyper-saturated. I also want, on some projects, to use my RGB as I would use short subs for over-exposed parts. That means I do want it in high quality. Regarding Ps and PI, neither will give a better result than the other in my view. I posted a Christmas dataset of the Cave Nebula a few years ago for members to play with. Barry Wilson produced a rendition in PI which was insignificantly different from my version in Ps. The programs offer different working environments to suit different personalities and approaches. Olly

I certainly think it's better and you have the start of the much sought-after tidal tail from the Hamburger. That's an object which just takes time. Regarding saturation you can, of course, colour select the background in Ps and simply reduce its saturation. I often do that. To my eye you have a really good background now. Olly

I'm a cheapskate and put up with Leica. lly

Goran, is this LRGB? If so, I wonder why you went for L in the mono rather than Ha? I'd have thought you'd find more structure in the hydrogen with Ha. This is HaLRGB from a widefield cropped and rotated to match yours, roughly. Olly

What you're missing are the F ratio and the corrected circle. Fast optics are very expensive to make because they are very, very difficult to make well. And then you need a mechanical installation capable of letting them work by allowing and sustaining collimation and freedom from tilt. The Tak is a modified Newtonian astrograph, the Skywatcher a Newtonion telescope. So the Tak has a corrector which gives a 44mm corrected circle, letting it cover a large chip. I don't know the corrected circle of the Skywatcher but it won't be 44mm, I don't suppose. I was intrigued when you said you'd found a Takahashi Newt roughly equivalent to your 130PDS but you haven't. You've found a fast astrograph for large chip cameras. Olly

I have a WO as well! I never visit a Paris bordello without it.* I think that sometimes, though not often, plastic really is the right material. Olly * Or with it.🤣

Regarding the consequences of having short channel data I think Vlaiv and I are in agreement. You just end up with more noise in that channel. The problem with having less red is that many targets are dominated by Ha (though not all, of course) so these will have signal just above the background when the blue and green won't. In this highly stretched part of the image the noise will become an issue. So I'm not sure I agree with the 'less red is OK' notion on emission targets. If you are going to add Ha to red, though, it probably won't matter. In reality I sometimes find it advantageous to shoot more blue, though the 'reality' in question is aesthetic rather than scientific and may arise from the fact that I usually add Ha to red. Olly

No, I never give it a thought. I've left dead batteries in there on occasion but the holder is a plastic thing and has never minded. I'm quite surprised by this line in the thread. Twenty-odd years on and all is well. On three occasions I've bought smaller red dot finders all of which are now in the bin. Olly

Hang on, people are saying that they are using the same ones after over twenty years. What can be wrong with the build quality? They are quite big, yes, but they use proper batteries, not those festering little watch batteries which you can't just buy in a supermarket. Worst looking accessory? Who is to say. Some people like the look of William Optics telescopes. I think they look as if they belong in a Paris bordello but each to their own. lly

Until you have collimation nailed I don't think it's possible to comment on focus but I don't see any reason to doubt backfocus here. Olly

If you're thinking about taking up imaging, don't begin with a pre-conceived idea of a preferable mirror size. It really does not work like that. You can take good, bad or indifferent images with any size of mirror. Mirror size is about as important as the colour of the socks you wear during the capture. Olly