rickwayne

Trust me, you're not paying by the photon and it doesn't hurt when you just spray them past the sensor. I thought that it would, but it doesn't. Now, if you really want to optimize everything, sure, a sensor as big as the light cone from your optical train will give you the biggest pixels (for a given X by Y) and thus likely the lowest read noise. And a bigger sensor does increase your FOV. But of course the converse is true, too: a smaller sensor with smaller pixels lets you image smaller objects without cropping. Eh, you tries it out in Stellarium and takes your choice, I say. I haven't yet used my reducer/flattener with the longer scopes and the 183, though I have with the Stellarvue. I had trouble figuring out how to make the backfocus work out with an OAG. A straight reducer would be good, but I only have the SFFR-70APO that came with the SV70t. Between the fairly flat field of an RC and the tiny sensor, I have not needed a flattener at all for the AT8RC or the AT12RC. When I went to the CEM70 I mounted my little 50mm guidescope right to the side of the saddle, so I could swap imaging scopes at will and still guide. But the guiding image scale is 4.77"/px and the imaging scale for the 8" is 0.3"/px, which is really asking a lot of the guiding system, so I want to get an OAG setup running again.

I would recommend that you start simple -- there's plenty to learn. A few hundred frames is plenty to start with, so I'd advocate (1) just going monochrome as you suggest, (2) limiting each "take" to less than 3 minutes, and (3) don't bother with derotation yet. 3 minutes is about the max for Jupiter without derotation, you can go longer on Mars (and maybe Saturn if you're not trying for too much detail). Having tried a couple of packages I'm pretty happy with FireCapture for recording and AS! for processing; I'm definitely not there yet with RS wavelets yet, so I just use Smart Sharpen in Photoshop. No bell-ringers yet, but at least the images are recognizably those of those particular planets! (See my Astrobin for my first wavering steps into planetary work.)

We are talking about deep-sky, yes? I would second Olly's advice to look for used gear, but you'll likely get better results more easily with more-recent cameras (meaning CMOS). Since the only moving part in these cameras is the fan, and that's pretty bulletproof, buying used is relatively safe. Expect about 75% of new pricing. I don't know what you're looking at that was $1500, but ZWO are selling the 533MC Pro for near half that right now. That is one of the most highly recommended cameras going if you can live with a square 1" sensor. After using APS-C I thought I'd hate that size but wow was I wrong. Totally enjoy my 183, and the 533 is worlds better tech than the 183. I imaged Andromeda with it and yes, a mosaic with a mono camera is a bit of a pain but OTOH I get nice sharp results on smaller objects.

Seeing fluctuations happen so fast, frames per second is almost as key a spec for planetary photographers as it is for gamers. Frequently we define and use a region of interest that's a fraction of the full sensor, all in service of the very shortest exposures possible, as close together as possible. I've no idea whether any astro-imaging drivers and software can do this for your Canon. Since planetary-capable cameras tend to have small sensors and don't need cooling, they'd the least expensive dedicated astro cams. The go-to app for planetary imaging is FireCapture, although there are certainly other great ones out there. Since it's free, you can try it out to see what ROIs and frame rates are possible with your rig.

You can upload a photo to nova.astrometry.net, and the site will analyze it to show exactly where in the sky you were pointing.

The goal is to have the range of exposures (if there weren't a range, you wouldn't need flats!) in the linear-response range of the sensor so the math can work out right. As Olly and Stefan say, an unclipped histogram is perfect, and a peak at 1/3 works out very well.

Even plate solving is going to be a challenge, I think. That's a 6" SCT with a 1500mm focal length, right? So the field of view is going to be 12 arcminutes wide. My system struggles sometimes with a 32' FOV. Too, the target is going to sweep clear across the sensor in 45 seconds if I'm doing the math right. Learning photography with a scope that long is going to be a real bear, my friend. It just exacerbates every little problem and they all add together. RA tracking is going to be a necessity, and the lack of goto will tend to frustrate you. Of course, you could get in the ballpark with a finder, center in a low-power, then a high-power eyepiece, then swap in the camera. That might work.

If you want basically a glorified intervalometer -- and I'm not dissing that choice -- sure. If you want to start using a more capable observatory-control suite that you can grow into, seems like everyone loves NINA. I am personally a big fan of KStars/Ekos in the same space, largely because I did not wish to limit my scopeside computer choices to Windows. I have used more and more of its capabilities as time goes on. If you want to move toward unattended imaging sessions at some point, Ekos or NINA seem to me to be the best choices. The time investment matters much more than the software license (Ekos and NINA are both free).

As the plural of "anecdote" is not "data", the singular even less so. Nevertheless. The USB ports on my 183MM Pro literally fell out of the back of the camera at some point. I have no idea where they wound up. ZWO never responded to my query about replacement parts, possibly because they peed themselves laughing at my haplessness. Can hardly blame them. So, yeah. Connectivity problems do not surprise me even a little.

What's even more hilarious is that the analogy turned rather too literal Tuesday night, when my chair and I rocked backwards off the deck into the weeds. Got the back feet just a little too close to the edge in the dark, I guess. At least it wasn't like the similar event when my camp chair capsized in soft beach sand -- that one threw me into the telescope, necessitating a polar-alignment do-over.

Cool! I just started my own first wobbly steps with planetary imaging, I got a moon shadow on Jupiter's disk but no moon. It's so different from deep-sky work, in particular the total neglect of some things that I obsess over for DSOs. Not easier, just different. Polar alignment? "Squint over top of scope, yeah, that looks about right". Autoguiding? "Punch DEC button on hand controller from time to time". Unattended automation? "Eh, I've been out here for an hour and have a few gig of video, think I'll hit the hay." It's kind of fun to be a total noob again. Sort of like when I was 40 and an expert skier (Senior Ski Patroller, yada yada) and decided to try snowboarding. "Well (WHAM) I guess that (WHAM! WHAM!) I am learning at least a little bit of (WHAM) humility here."

The new ZWO OAG has a larger prism than their previous one (12x12mm instead of 6x6) and also incorporates a helical focuser. If I don't succeed in DIY-ing myself a new stalk and prism for my old ZWO OAG, on of these will go into the queue.

That's enough integration time to start to see nebulosity and maybe dust lanes. You should try an imaging previewer like Stellarium or Telescopius.com to see what the framing will be like -- if you're able to make out M57, then M31 is likely to be a lot larger than your sensor. Here are a pair of screenshots with my AT8RC and Pentax APS-C standing in for your gear:

Many of us started with a camera and a lens and didn't get into telescopes till later. This approach has a lot to recommend it: You can get old prime lenses relatively inexpensively (relative to telescopes) It lets you start at shorter focal lengths, which forgive a multitude of sins Exposure, calibration frames, and processing are exactly the same, which gives you a big head start Strictly speaking it is not aperture per se but focal ratio which will yield shorter exposure times and thus make less demand on tracking. And shorter lenses will give you a better focal ratio for the buck than longer (or telescopes, for that matter). A 1970s-vintage 50mm f/2 will let you image the Milky Way, bits of the Orion Molecular Cloud, the North America Nebula, and more. The "rule of 500" is a guideline for star trailing WRT focal length, although many think it should be more like 300 -- let's use that. 300 divided by the focal length gives you the max exposure time in seconds. So for a 50mm lens, 6 seconds. For a 300mm lens, one second. For a 14mm lens, maybe as much as 20 seconds. If you add a basic sidereal tracker, you'll extend that time. Once you have the software and techniques to calibrate and stack images, the individual exposure times cease to matter as much. It's certainly not linear, but 30 1-second exposures are going to be somewhere in the ballpark as one 30-second exposure. So it's total integration time that matters. Highly recommend Charles Bracken's The Deep-Sky Imaging Primer or Steve Richards' Making Every Photon Count. That kind of knowledge base will serve you very well in evaluating what's feasible with your limited budget.

The simplest way to figure this out is to just set the acquisition software to do live-capture video, and then hold the camera up behind the telescope, pointed at a daylit scene. Move the camera closer or farther away to focus. Note the approximate distance; duplicate that with whatever hardware you need. You only have to estimate it to within a couple cm since the focuser travel will let you zero in once you've got it set up somewhere in the neighborhood.

Wow, yeah. One hour, with a non-astromodded camera? I'd be chuffed!

As for diagnosing your image, 2500 seconds of integration time is...not a lot. First time I did M51 (huh -- my profile image, actually!) I got about an hour and a half at f/4.5. I fiddled with that image a LOT in Photoshop to show detail -- a ton of localized Curves to tweak contrast in specific places. My more recent version was four and a half, and hardly needed any manual work. That said, I'm a little surprised that your M51 was quite that dim. The Antares/Rho Ophiuchi region is up now, and IMO is a great target for 50mm. Orion is another good one, you can get the Great Nebula, Horsehead/Flame, and Barnard's Loop to fit pretty nicely. This is a pretty crude astrophotograph, but shows what a 50mm view would look like. As for filters...meh. All filters do is take light away, right? In specific cases, such as when you know you have light pollution from gas-emission lights (sodium or mercury), filters can increase the signal/noise ratio considerably. But more often they just introduce color-balance problems and decrease the light getting to the sensor. Unless you're talking narrowband imaging, which is its own specialized thing but does not work well with most terrestrial-type cameras.

The classic answer for DSO startup is "buy the biggest, best equatorial mount you can afford and carry". Everything else depends on the mount, it is (literally) foundational. People can and do it other ways, but the learning curve for deep sky is steep and the fewer hypotheses you have to generate for a given problem, the easier it will be to solve. It's not like visual observing. At all. Lots of sub-exposures adding up to long total integration times can address many problems for which you'd think you need aperture -- or even focal length! But if the mount wobbles, you won't like the results. This is why the other classic answer is "start with a small refractor that won't overload your mount". Just sayin'. The Skywatchers have their fervent fans, more power to 'em. The very best investment you can make is a good basic book like Brackens's The Deep Sky Imaging Primer or Richards's Making Every Photon Count. If you understand the basics underpinning the process, assertions like mine above will seem less like opaque proclamations and more like "Well of course, I could have told you that". When considering scopes and cameras, the thing to consider is the "image scale", the number of arcseconds spanned by each pixel. Without getting into the weeds (that's what the books are for!), you want that in the neighborhood of 1.5"-2". Ish. There is a great set of calculators on astronomy.tools where you can plug in scopes and cams to your heart's content. Filters: H-Alpha imaging is explained well above, it's a bit of specialist kit but not essentially more difficult, other than it requires longer exposure times -- I was using five minutes last night and it wouldn't have hurt to go longer. Guiding: If you get into this you'll want to, but I advise just noodling around a bit first. All guiding gives you is longer sub-exposure times with fewer subs thrown out. Neither of those is make-or-break. Welcome!

I'll add that ZWO did some performance testing awhile back and concluded that overall best results were with low gain for high dynamic-range targets where clipping would be a problem, and high gain where it wouldn't. If I sound as if I'm arguing with Alan, I'm not. Unity gain is an excellent starting place and you won't go wrong using it. IIRC he's also right about not using bias calibration frames with the 1600, it gets nonlinear at very short exposures. So darks, flats, and dark flats are the way to go. Which means it also helps to settle on a limited number of temperature, gain, and sub exposure-time settings to control the combinatoric explosion of needed calibration frames. Much better to get a "good enough" sub time and vary the number of frames. Many folk dance on the heads of the sub exposure-time and best-temperature pins and it's really beside the point. Noisy? More subs. No detail in the dark nebulosity? More subs. Tracking issues? Shorter subs and more of them. More integration time forgives any number of sins. 🙂

My personal experience is that the ratio of acceptable-to-me subexposures increased dramatically when I started doing mono, and the flexibility is VERY appealing -- HaLRGB, RGB only, LRGB, etc. To say nothing of simply being able to collect good data quickly in my Bortle 7 back yard, or in full moonlight. It is more of a hassle -- all kinds of little things. The filter wheel makes it a bit more challenging to work with my OAG. I have to clean the things. Imaging sequence construction in Ekos is a little more complex. Processing, likewise. But overall, I am super glad that I made the jump. If nothing else, I got a couple years' worth of higher-quality imaging that would have been difficult to achieve with the cameras that I could have afforded when I started. The new sensors make OSC much more attractive to me. I wish I could do without per-filter flats, but my sadly-abused LRGB set (I got it used -- I did not do the abusing!) eliminates that option for me. There are ALWAYS artifacts that need removal, and I cannot remove them from the filters. Concur on the focusing, I haven't been bothering with per-filter focusing with my new scope, for which I haven't yet built an autofocuser. I do check with each filter change but so long as I nail the luminance or red focus, it's OK for me. But since thermal effects will mandate at least some refocusing during the night anyway, I'm going to refocus per-filter again when I get a rig going. Heh -- one advantage of an f/8 scope over an f/4.5 is that it's a little less psychotic about its critical focus zone. (The people with Hyperstars and RASAs must have WAY more patience than I do.) Assuming the autofocus works, I lose maybe 2 minutes per iteration. If I time filter switches to my temperature-dependent refocusing, that's two minutes per hour. Acceptable. Likewise flats, I'm running 20 frames per filter and each takes about 3-5 seconds to download, so 100" x # of filters used. Something like 7 minutes, plus the fiddle-faddle of getting the scope pointed at the sky and the LED tracing panel connected. Call it 10. I could modify my teardown workflow, take the scope off the mount first so that I can pack up the mount while I'm shooting flats, that would be a tad more efficient I guess. For me it's cheap insurance against having to Photoshop some weirdness out of my subs.

I started with just an Ha filter. I got some monochromatic images I really liked. As for the poor quality of ZWO filters, eh, check my Astrobin. I've got nothing but, and my LRGB set is one I got really cheap when I bought my first filter wheel used. They're in terrible shape, they look like they've been cleaned with cat spit and sand. There are flecks or pits or something which I cannot get off of them (I suppose I could ask the cats to help). I'm not saying "See, you can do APOD-quality work with ZWO filters". Just "Here's what one guy gets out of them". The West Veil image is probably the best performance I got out of the NB set. I used starnet++ on that so some of the haloing on 52 Cyg is doubtless from the software. (The M106 image was from the Dark Days of Collimation with my AT8RC. It's not the filters -- honest!) >;-}

Platesolving fanboi that I am, I admit that it can work flawlessly all night or be more...catlike. Sometimes I resort to dodges like bumping the RA half a FOV's worth (literally a dodge in that case). Sometimes sufficiently pungent language works. And at least for Ekos and its solver, the presence of, say, Arcturus in the FOV is guaranteed to overwhelm the poor thing unless I crank down the gain and exposure time that I get the insufficient-stars message.

As for transport, my 70mm Stellarvue came with a nice case; I also cut out some 10cm upholstery foam to cradle it in a storage bin, which can also carry camera, wheel, cables, etc. For the 8" RC, I bought a wheeled weather-resistant toolbox, and just laid a doubled-over 2cm sheet of foam in it for now. Plenty of room in there too for bits and bobs, of course.

So I've got an iOptron CEM70 mount, a ZWO astro camera with a cooler, and a Raspberry Pi to run the rig. I found a good 20 Ah LiFePO4 battery, which is enough to run the whole thing for a couple nights on a charge. A larger one, of course, would extend that time significantly. I also have a 5m or so cable with a cigarette-lighter plug which I can screw onto the terminals of the battery to supplement with the car's electricity.

I should note that by the time I tried ASIStudio, I'd already accumulated several years of traditional deep sky experience that probably smoothed the road a lot for me without my even realizing it. Just checking my privilege here.