rickwayne

Well, you're certainly getting something out of your obsession! Good show.

I agree that the best strategy is to wait until you can afford one of the really good ones. In fact you might want to look into one of the dual- or tri-band narrowband filters, people have reported some very good results with those and you already have an Ha-compatible camera. I have shot narrowband literally under streetlights with reasonable results (e.g.). In the meantime, if light pollution troubles your images, you might want to look into upping your gradient-reduction chops in whatever software you use to process. I mean, no offense if you've already mastered that, but that's where I would go first. I've gone back to some of my old LP-sodden images with my newer skills and software this year and markedly improved them.

One more reason to use bias frames, if your camera takes them stably. Ekos calculates an exposure to give me 25K ADU +/- 1000, so every session it probably is a slightly different exposure. Of course, for my particular setup, dark current is pretty negligible for everything but my narrowband flats. Fractions of a second for LRGB ones.

Yeah, I rewatch that from time to time just to glean some more info and ensure that I haven't strayed. You see a lot of people pontificating on fora who seem very sure of themselves, but Dr. Glover just brings it, doesn't he? Harder to argue with the data right there in front of you. Of course, that certainly doesn't mean he's always right. But it's considerably more convincing than "I do it this way and my pictures are awesome so you should too". One of the reasons I treasure Vlaiv's comments on this forum -- he always sets out quantitative reasoning behind his assertions.

Couple of points to consider. Cooling, like other noise reduction techniques, is a game of diminishing returns. I wind up recommending Robin Glover's talk on CMOS exposure a lot, he shows some cooling/noise curves that should make you take notice: https://www.youtube.com/watch?v=3RH93UvP358 If you're in the field, the cooler is pulling watts out of your battery, and that curve isn't linear either. As you've probably already figured out, doing all your work with the minimum number of sets of parameters minimizes the number of calibration frames you need to shoot. And that's combinatoric too. I shoot at the same temp, winter and summer, the same offset, and one of two gain settings depending on whether I'm shooting narrowband or LRGB. That's it.

If you do decide to stick with camera lenses, you will probably get better results from fixed-focal-length (prime) lenses than zooms. Optical design is a game of compromises, and the more complex the design, the more likely it is to compromise something you wanted. Autofocus does you no good in astro, so a manual-focus lens is fine. Auto-exposure, same same. So you can actually look for quite old lenses in the used market, and they don't even have to be Canon brand. (They absolutely should be multicoated, though.) For example an M42 adapter that lets you reach infinity focus opens up a whole world of Pentax and other old, good glass. You should be able to pick up, say, a Pentax 300mm f/4 for under £120.

Astro Pixel Processor has a terrific gradient tool. It's quite easy to use and very effective. The app is of course also right up there for calibration and integration, I tune up the images I get out of it in Photoshop but I'm obsessive that way.

Gotta try it to be sure. That's one downside of those big sensors, you've got a lot of field to deal with! You can get shims -- basically just plastic washers -- in fractional-millimeter thicknesses, so if your testing indicates problems you could get a slightly shorter adapter tube (e.g. 16mm) and build up the required difference with those. Here's a useful little visual aid for deciding whether you have too much or too little backfocus. adjusting field flattener.pdf

Many DSLRs (mine for one) lock up the mirror at the start of the self-timer cycle.

Note too that DLSRs usually have two kinds of amplification, and different makes and models mix and match them differently. Vlaiv makes a cogent explanation of what's going on in the lower range, where analog circuitry is doing the driving. But at higher ISOs (and "higher" is what's different for different cameras), the camera starts multiplying the digital output. This gains you exactly nothing that you can't achieve with post-processing, at the expense of lowering the dynamic range and possibly blowing out highlight areas.

You may wish to attempt imaging without the filters first, and see what you can do with any gradients in post. It's one thing to image narrowband and work only with specific frequencies, but for broadband targets your filter is necessarily removing some of the desired signal along with that of the light pollution. Just a suggestion.

I'm big on the scope-side camera with WiFi or Ethernet, but YMMV. To me that flexibility is a big advantage of INDI-based software like Ekos, you can have the drivers running on an absurdly cheap, low-power computer at the scope, and then talk to it over its built-in hotspot in the field, or have it connected to your home WiFi, or plug in an Ethernet cable. Works exactly the same if you're sitting with a laptop next to the scope in the middle of nowhere, or controlling it from thousands of miles away over the Internet. Of course then your imaging software has to talk INDI. Once most folk get a software stack working, they're unlikely to give it the heave-ho!

Well, you didn't have a ton of time to gather data but what you have is decent quality. You pulled a fair bit of the blue nebulosity out of that short integration.

That is some ROCKIN star color there, friend. Really makes the whole piece. I like the hints of dark nebula around the reflection neb too.

The choice of sensor size can really be driven by what you want to image, your optics, and the image scale. You can use a tool like Telescopius to previsualize what various targets will look like with different-sized sensors. It's not always a case of bigger is better. You can calculate the image scale for a combination of focal length and sensor with the astronomy.tools CCD Suitability page. Simply put, smaller sensors usually have finer-pitched pixels, so you might achieve the same (e.g.) 20 megapixels on a smaller target with a smaller sensor. Smaller pixels means more noise, though with today's gear, software, and techniques that's largely a solvable problem. Most vendors publish an image-circle size spec for their scopes.

Flats correct not just for vignetting in your OTA, but also flaws or dust on the filters themselves. I certainly couldn't get away with just doing one set of flats. Fortunately with an electronic wheel it's super-easy, I just have one sequence that steps through all the filters. The advice you've already gotten on refocusing is correct. Unless the temperature is changing rapidly, once your gear has cooled to ambient around once an hour should suffice. But it definitely does change, e.g. the critical focus zone on my f/5.5 scope is 74 microns deep, so a contraction of 1/20th of a millimeter (assuming I nailed the middle of the zone) will put me out. The added wrinkle for mono+filters is that unless your filters are perfectly parfocal -- mine sure aren't -- you have to refocus with every filter change. Frequently folk with motorized focusers get around this by recording and averaging how big an offset is required filter-to-filter, then focusing once with the base and blindly applying that office when the filter changes. As for dark flats, the idea is to get a base signal from the camera with no light and subtract that. This can be done either with bias frames (shortest possible exposure, no light) but for some cameras, short exposures aren't repeatable, so those people use dark flats -- same gain, offset, and exposure as for the flats, but with the tube covered as for darks.

That's a real challenge and no mistake. I often spend some time on the starless image stomping on the smaller halo-holes with the Spot Healing Brush in Photoshop, with the brush set to around the size of the hole. For larger ones I might use a smaller brush and run it around the circumference, so that while there's still an artifact around the star, it doesn't have that telltale sharp edge that our eyes are so good at detecting. For something like Alnitak I'll use masking to bring that particular bit of a copy of the pre-starnet layer through, but then I have to stretch that one too so there isn't a discontinuity...yeah, it's a big mess. Noise tends to be most visible in the darkest areas, so you might experiment with (yet more masking) applying it sparingly, perhaps to just the areas of the Mountains where they peter out into dark background, while leaving the brighter bits alone. I do really like your noisier-but-subtler reprocess of the image. Not that I'm the arbiter or anything, but if that's what you like, I'm here to tell you that I do too. 🙂

Here's one of mine, for example. Straight out of the camera, the actual values only vary from a little over 25000 to a little over 24000 over the whole range, and it looks perfectly even. Stretched, you can see where there's a whacking great splotch of random snot, and the vignetting is pretty obvious, especially on the right side. None of the vignetting shows up in the final.

Yes, 25000 is not a magic number or anything. The idea is to have both ends of the histogram (except for hot and cold pixels) in the linear range of the sensor. There are "ends" because the intensity does vary across the frame due to vignetting, dust, or whatever (otherwise you wouldn't need flats!). The precise values don't matter at all. And of course the acid test is whether they work. If you stretch the flats, you can see where the image-train problems are. If your images don't display those (or artifacts from their removal) after processing , then your flats are just fine.

Holy buckets, this is a single subexposure? Wowsers! Stars are pretty blue, do you think that's the filter?

At the risk of re-re-re-reigniting the Ancient Flamewar, if you're imaging deep-sky objects, for the same sensor, an f/2 scope will require fewer seconds to get the same number of electrons in the photosite well than will an f/5 scope, regardless of aperture. Honest. See Bracken, page 38.

I have been running Pis at the mount for several years now and you're getting excellent advice. I have run a Pi 3 with Stellarmate OS pre-1.5 (i.e., Ubuntu rather than Raspbian) and succeeded with that, although I had a lot of problems with it slowing almost to a halt, and plate solving on the main camera was very unreliable (the 1280x960 guide cam worked perfectly). So I upgraded to a Pi 4 with 4 GB, and have nothing but good things to say about it. It has both USB 3 and 2 ports. The WiFi is quite reliable in the field as a hotspot, doesn't do all that well outside the house where the signal isn't very strong. There are known issues with some versions of Raspbian and the 3.0 ports affecting the WiFi. I bought a 100' Ethernet cable for use outside the house which works flawlessly. I like the flexibility that INDI allows, and have occasionally used the Pi as a dumb device server, running KStars and Ekos on my laptop. But I agree that while that never overtaxes even a Pi 3, it's more fragile. I too customarily run the whole stack on the Pi 4 and VNC in with a laptop, tablet, or even a phone. StellarMate also has a dedicated app that gives a much more streamlined user experience, so if you spend $50 for StellarMate OS you have a turnkey solution with a mobile interface too. If it's already built into a keyboard, you could also have a scope-side setup by adding a little HDMI screen, or (if the keyboard doesn't have a touchpad) a touchscreen. Finally -- and this is a really clear case of "I do this so you should too" -- you can run a Pi off 12V pretty easily with a plug-in board. Not really an option for one built into a keyboard, I guess, but I got a Waveshare stepper-motor controller board with a barrel connector just like other astro equipment. Runs the Pi and also has motor control outputs from which I constructed an autofocuser.

This image has definitely got it going on, as the kids say over here. (Well, the kids around 40 years old, anyway.) I really like the detail you're getting in the Mountains. While the color is bold, I don't think it's too much, although more color in the stars would be nice. (Maybe starnet so you can put unstretched stars into the image?) I absolutely agree about the noise reduction, you've got the dreaded "plastic" look that's especially apparent in the Flame and I'll bet dollars to doughnuts that if you back that off, the gradients and tonality in the Mountains will further improve too. Embrace the grain, my friend! Alternatively, you could pile on even more integration time, though you'd probably be talking something like 2-4X to really make a big noise difference. I think you've done a pretty good job on Alnitak, that bane of Horsehead imagers. You could conceivably shoot some much shorter exposures and try blending those in, though it's a challenge to do that without leaving screaming artifacts. My main man Pete_XL says that one thing he looks for is a very subtle tell -- there's a star lurking around the top of the Horse's "mane". After I heard that, I went back and obsessed on that little area in Photoshop so Pete would be pleased with me :-). I won't post the image here because this is your thread, not mine, but feel free to have a look.

Right, the 10mm is the most magnification. You can get other eyepieces relatively inexpensively, but you're unlikely to get much more out of them. With my relatively giant 280mm reflector, I can utilize a 9mm eyepiece effectively and maybe a 6 when conditions are ideal. I haven't ever tried to mount a phone on a scope, so I'm just doing a search. Here's a page of adapters on Amazon: https://smile.amazon.com/smartphone-adapter-telescope/s?k=smartphone+adapter+for+a+telescope&_encoding=UTF8 The search also turned up this how-to article: https://nightskypix.com/smartphone-astrophotography/ And this video tutorial: https://www.youtube.com/watch?v=QrtnnMIpUGI I would also highly recommend that you hang out on this SL forum, since it's dedicated to precisely this topic: https://stargazerslounge.com/forum/279-imaging-smartphone-tablets/ Fair warning: this is really addictive stuff. I started out shooting some pictures of night landscapes with the Milky Way in them and kept wanting to go a little deeper, a little better...now I have five telescopes, a thousand-dollar equatorial mount with a $2500 one on the way, and a wife who is exceedingly patient with someone who will literally dream about how to fashion a bracket for an autofocus motor and then wake up and want to talk about it. At length.

You are correct that the Barlow magnifies the view. The Andromeda Galaxy is high in the sky and great for viewing, and there are some terrific bright nebulae near the belt of Orion that would be fun to look at. It's funny how often the recommended solution to an astronomy problem is "spend money", but you might want to see if you can find a holder for your phone to keep it still while you're taking pictures. The Moon is going to be a great target for smartphone work, and you might get some pretty exciting shots of Saturn when it's visible again. If you buy the right filter for your scope, you can even shoot pictures of the Sun, but that is super-dangerous if you don't know what you're doing so for the love of Bog please read up on it first! Orion might also be doable. Other deep-sky objects will be a lot more challenging. There's a reason seemingly sane people spend thousands of dollars on this stuff, after all. May you find joy in the journey!