rickwayne

With anything but the very brightest targets, you will definitely want a lot more total integration time. As you probably know, folks doing DSO with traditional techniques reckon on hours of it. Best ISO depends on the camera. Usually above a certain threshold, all higher ISOs do is multiply the digital output by some factor, which you can do yourself in software designed for the task. Concur with the recommendation for SiRil over Deep Sky Stacker, which is getting pretty long in the tooth these days (ha, as if I should talk!). In an astrophoto the background is usually the most numerous value, right? So that's what your thin peak is. Ideally you want to get enough exposure that the peak is clear of the left edge that is, no black clipping. Left of that peak is nothing interesting, but your detail is mixed into the right part of it (unless you're doing clusters).

I actually like the second one better! MUCH more natural look. I am partial to Lonely Speck's tutorials on photographing the Milky Way, that's how I got started and I've always had a fond place for him in my heart because of that.

I'd be interested to see one of the original sub-exposures. This image is very heavily processed, probably via sharpening and noise reduction, so it's kinda hard to tell what's going on. Whether that happened in-camera or in post, I have no idea. Your text seems to imply that you stacked multiple exposures, but also that you took only one, which is a bit confusing. You definitely captured some of the area near the Galactic Center, which is always very interesting. The green color should not have been present in the original, unless you had very high levels of airglow or indeed there was an aurora going on. For me the aurora and the Milky Way are always in opposite directions but I'm in the Northern Hemisphere -- had to wrap my mind around the transform!

That last image has some hella dust-bunny signatures. How are you taking and stacking flats? Do you have a bias or dark flats?

Eh, when you revisit the target, create a synthetic luminance channel and stack the unintended NB subs to refine that a tad.

But aren't they required for the math for flats? Or are you saying that bias is OK and darks/dark-flats don't work? Not an EOS guy, so I am asking for info, NOT arguing.

Fotodiox has a Pentax 6x7-to-Nikon adapter for US$65, and if you're willing to wait for shipping, Ebay has 6x7 Pentax 200mm f/4s from Japan for well under US$100. AFAIK the 6x7 lenses don't mount directly on any digital bodies, so they are going for a song. Certainly going to have a big enough image circle!

Sure looks like coma to me. Pretty common with zoom lenses. The good news is that you don't need anything modern or fancy. Autofocus, zooming, instant diaphragm stop-down -- eh, who needs 'em? So you can scour Ebay or other used markets and pick up some much-less expensive single-focal-length glass. They made perfectly good optics back in the 1970s, and since you don't need any of the automation contacts, you can even use other lens brands, so long as you have an adapter that lets you reach infinity focus. The old Pentax screw-mount 200mm f/4 has launched many an astro career!

You can check your alignment with nothing more than your camera and the ability to slew slowly back and forth in RA. Basically you start an exposure, deliberately make a star trail by slewing during the exposure, and then slew back. If your PA is perfect the "out" and "back" trails coincide and you see only a single line. If not, then some DEC drift occurs -- remember this happens at right angles to the RA axis -- so the lines form a V, with the point of the V where you reversed direction. Here's a detailed recipe, see Drift Alignment by Robert Vice (aka DARV).

Flat darks would also be an option, no? If you can figure out a way to do so unguided, dithering would be a plus. You might also get a sharper look if you focus using a Bahtinov mask. It's not very far off, but I think it could be closer. I'd show you what "awful" picture of a galaxy looks like but people might be eating while reading this and so I'd better not. Trust me, I've worse than this.

A tumbling satellite can give a similar signature. But I think that if the ISS were tumbling, we'd have heard about it.

White balance is an operation applied only to JPEGs. If you're shooting raw data (as you should), the only white balance applied is a notation in the metadata to provide a hint to processing software.

So INDI is a device-independent instrumentation library for all sorts of platforms. It's very like ASCOM on Windows, but has several significant advantages. By far the commonest INDI client is KStars/Ekos, but that does not mean you must have both of them. The INDI server is a piece of software that mediates between clients (Ekos, PHD, etc.) and device drivers (e.g. for your mount or camera). You can actually configure and run it completely from the command line, but most folks use some sort of graphical UI to do things like select what drivers will be loaded. I don't know what the current state of play is for those; Cloudmakers had some programs for that at one point but they may have gotten out of the game. In addition to all its other bazillion features, Ekos has a module just for creating driver profiles and starting/stopping the INDI server with them. You can run just an INDI server to talk to your mount and guide camera, and PHD2 as only client, if you want to run everything else some other way (e.g., a DSLR on an intervalometer). The best place to ask questions is the INDI forum: https://indilib.org/forum.html I have muddled around with INDI on my Mac, but decided very early on that I wanted a dedicated computer at the scope instead of running it with a laptop, so I built myself a StellarMate device and just use the Mac as a terminal into that 99% of the time. I have run imaging sessions all on the Mac that way, though: CloudMakers' INDI server, with KStars/Ekos running as a client, and the PHD2 guiding option selected in Ekos.

I don't know what clip filters cost, but NA was referring to one that clips into your Canon's body, not a 2" one that screws onto the lens. The trouble is that your camera already has an infrared-cut filter that also strips much of the hydrogen-alpha emission at 656nm, this is by far the largest component of the emission that surrounds the dark Horsehead and gives it contrast. So adding an Ha filter would just eliminate everything else, such as the star color and any other emission or reflection light. IC 434, the emission nebula, has tons of really interesting detail and tones, so a wider view should be quite nice to look at. This is hydrogen-alpha light only (hence the B&W), and I've always meant to go back and add more integration time to obviate some of the objectionable noise in the areas that I stretched too hard.

Are you sure the tilt is due to the focuser mounting and not drawtube sag? If you have lots of drawtube travel available, you could put a tilt ring into your imaging train. I use one specifically for the 100mm thread of my RC's extension tubes, but others are available. The Gerd Neuman ones are super-nice, and can be adjusted without disturbing the train.

Daylight focusing is an excellent idea, but do be sure to use quite a distant object. There is a big difference between "infinity" and "a few hundred meters away" for many scopes, and that might mask the problem you're having.

What was the OAG change, and what differences did you see?

Oh, and once you have an idea of what camera you might use, truck on over to Telescopius.com -- or download Stellarium -- and play around with previsualizing various targets. The canonical beginner galaxy is Andromeda, which is a real Zen challenge. Anyone can image it, but doing it well is a never-ending journey. Anyway that one is huge, about 3 degrees IIRC, so it'll be hard to capture with an 8SE. But the universe does have a couple more :-).

For the lowest cost, a terrestrial (unmodified) DSLR or mirrorless will do just fine. Astro modding removes the IR-cut filter, which along with infrared also takes out the very deep red in the visible spectrum; the trouble is that the single commonest visible-light emission wavelength lives down there, hydrogen alpha or "Ha" at 656 nanometers. Folks astro-mod cameras in order to collect Ha light, but that's primarily of interest from emission nebulae (Horsehead, North America, Seagull, Heart e.g.). For galaxies, an unmodded camera does just fine. So if you have a DSLR or interchangeable-lens compact camera, you've got what you need already. If not, an old Nikon, Canon, or Pentax body would do you well and needn't cost a mint. Dedicated astro cameras suitable for learning deep sky start at about US$1000. You can go cheaper, but there will be compromises that will irritate you, later if not right away. (Although there's always the used market there too. Astrophotographers tend to baby their kit so used gear is USUALLY safe.) Best way to save money in deep sky is to buy and read one of the primers. I fancy Bracken's The Deep Sky Imaging Primer, Richards' Making Every Photon Count is also highly thought of. The 8SE would also be a pretty nice planetary rig, and astro cameras for that go for a lot less. Tiny sensor? No problem. Cooling? Feh! Get yourself one of those -- even the humble US$150 ASI 120MC-S will do -- and you can start messing around with FireCapture and AutoStakkert. One advantage to terrestrial cameras is that you can use them without any external equipment -- their built-in intervalometer will do to start, or you can pick up a cheapo that will do even better. All the astro cameras require a computer at the telescope. Welcome, and enjoy the journey!

That's already really nice! You're really getting some lovely tonal shading and detail. Nothing wrong with a nice bicolor, man. I too prefer mapping Ha to red -- I know that it's false color and so utterly artificial in the first place, but dang it, hydrogen is just supposed to be red! Just look at the ball-and-stick models! (If the ones you played with in school used some wrong color besides red for H, just shut up and sit in the back with your shame, please.) Seriously though, I was just going through some old links and found this really interesting passage in favor of the Hubble palette: https://support.itelescope.net/support/solutions/articles/232658-narrow-band-imaging-what-is-it-all-about-

My experience has all been with iOptron mounts. I hear a lot of great things about the EQ6R, to be sure. As for controlling with KStars, both my CEM 25P and my CEM 70 worked with INDI right out of the box, no problem. As Olly points out, iOptron is hardly immune to QA problems, though my mounts were great when I got them. Buy from a reputable vendor who will offer you refund or exchange is my advice, regardless of brand. WRT the mount itself, if you go with either the CEM 40 or the GEM 45 you will like that through mount cabling. I can't comment on the polar alignment adjustments for the 45; the 25P was usable but the altitude adjustment had a fair bit of backlash, I had to be pretty careful. The 70 is just a dream, the controls are large, smooth, and offer very little backlash. So maybe the 45 is in between the two? 🙂

Really nice job controlling the trapezium here, without losing a lot of the dim dust detail.

Just a data point for you: I did see a measurable increase in guide performance (and, IIRC, better stars) when I went from a 162mm FL guidescope to an OAG on my refractor, (a mere 336mm FL itself). My mount was rather overloaded by then so I was grasping at every possible improvement. I think the other folks have made excellent suggestions. I'll add that if you have the means to connect a "real" computer for testing, it would be worth your while to do so. You can run the full-up PHD interface and make use of the Guiding Assistant, examine the calibration graphs, etc.. And the GA can directly measure backlash. Finally, your mount may become a bit more responsive if you decrease the moment arm. In RA, adding counterweights means the motor has to move more mass, true, but at a much shorter arm, hence the moment of inertia goes down. More weight but closer in == starts and stops quicker. Likewise, if you can move any weight away from the ends of the scope to be more centered over the DEC axis, that's a win too. And finally, pay attention to cable routing, if anything's hanging off the end of the scope that also increases the moment.

Suggestion: Download ASTAP and run a couple starfields through its image inspector. That will quantitate the problem, though it won't distinguish coma from tilt. I'm an Richey-Chrétien guy so I don't know much about collimating Newts.

And by "rigidly", alacant means "you would not believe how rigidly". Flexure of only a few microns at the end of the guidescope translates into significant guiding errors. The "finder shoe" sort of mount that you have is notoriously bad for this -- the front of the mount holds the scope in a flexible ring so that it can move when the adjustment screws in back are, well, adjusted. I reiterate that we are talking about fractions of an arcsecond here. Please pardon the USA units of currency and measurement, but a US dime held up a mile away covers about an arcsecond. We are concerned with deflections of maybe two-tenths of that! One hack you might use, if you're mechanically handy, is to drill and tap three holes around the circumference of the front of the finder shoe tube, and put in your own jackscrews (any kind of bolt will be fine). Or if there's enough room for a flat nut between the inside of the tube and the scope, just a plain hole will do. Better would be to mount some sort of bar spanning the tops of your scope rings, and two suitably-sized scope rings for the guidescope on the bar. That is guaranteed rigid. You can also just try it out and see what you get. If your guiding graph looks great but the stars in your actual image are trailed or egg-shaped, that's a sign of differential flexure. So if you don't get that, meh, what me worry, eh?