I do have PHD and an autoguider. That only gets you so far. Especially with the Orion SSAG cam you shared. I have that, and it just isn't very sensitive. Better guidecams with enough sensitivity to really do better cost about $500-700.
What autoguider do you own?
See my previous reply.
Weight is also an important factor, especially when you add up the counterweights/all other stuff. But I think most new astro-photographers aren't going to get telescopes that large/heavy.
Not new astrophotographers, no. But if your serious about getting good images, the sweet spot seems to be between 16-20" apertures, to maximize quality and detail. Things just get expensive because getting a mount that can handle that kind of capacity is just expensive. If your going to spend $10k-$20k on a mount, you might as well get a high end scope as well.
So a telescope like this Astro-Tech 406mm f/8 OTA?
The AT16RC Truss is a good place to start. That sucker still costs $7000, but I'm thinking more of something like this PlaneWave 20" CDK (which is on an Astro-Physics 3600 GTO, which is designed to handle scopes up to 24" or so....I think an AP1600GTO or a 10Micron GM2000HPS are both sufficient to handle the 16/20" RCs and 17/20" PlaneWaves, though):
These 20" scopes (RCOS and PlaneWave ones) seem to hit the sweet spot for deep sky imaging quality, star spot size, field flatness, imaging circle size which are up to 70mm. (When you spend $20k on a mount and $35k on a scope, you then can't spend $2000 on a 22mm diagonal imager, now, can you!
) The nice 37x37mm 4096x4096 9µm pixel imagers have a 52mm diagonal, and need larger image circles. Astro-Tech scopes, when fitted with a proper field flattener and focal reducer (they do not have a flat field intrinsically like an RCOS or PlaneWave), you get about a 40mm image circle. That isn't even large enough for a FF DSLR sensor, let alone a nice larger format square imager. The new generation of astro imagers coming out to the market have 65mm diagonals, and apparently even larger ones with 70mm diagonals are on the horizon.
A 16" Astro-Tech Truss on a Losmandy Titan (the mount in your picture, which is still $7000 in and of itself) is kind of like the low end of the higher quality scopes. It would certainly suffice for a lot of people, but your still talking about at least $14,000 of investment for just the mount and the scope in your picture. The Losmandy mounts must still be guided as well, and to actually maximize the image quality potential of a longer, 16" scope like that, you need really good guiding that isn't prone to differential flexure problems. So, now were talking about OAG (off-axis guiding), which means adding a quality OAG device with adjustable pick-off mirror to your imager (that's about another $800-$1000), a high sensitivity guide camera (so that it can find dimmer stars in the very narrow circular band of the field of view that a pickoff mirror can pull stars out of), and there is really only one: The Lodestar X2, which is another $700. You don't just twiddle your thumbs with an OSC imager when you get up to even AT16RC level scopes...so you want a mono imager with a filter wheel and some appropriately high quality filters. The mono imager is another $2000 at least, the filter wheel is another $1500-$2000, a set of LRGB filters is about $800-$1000 and a set of narrow band filters is another $1000. You probably want to upgrade the Losmandy mount with the higher quality worm gear and do some hypertuning, so another $500.
So, assuming we go with the low end 16" scope setup with an Astro-Tech 16" RC Truss and a Losmandy Titan, your grand total cost is still over $20,000. :\ Losmandy mounts are nice, but they are a pretty old design that hasn't been updated in quite some time. They are pretty pricey for $7000 (or so, depends on what accessories and counterweights you end up choosing at the time of purchase). The Losmandy mounts don't use any kind of high resolution absolute encoding, either...but absolute encoding is becoming a core feature of most of the higher end mounts. That makes their $7000 price even more difficult to swallow.
You can pick up the Astro-Physics Mach 1 GTO with high resolution encoding and PPEC (not quite as good as absolute encoding, but a hell of a lot better than what the Losmandy Titan offers), which is capable of doing unguided imaging up to 15-20 minutes, for $6000. The 10Micron GM1000HPS is about $9000, and it not only uses high res absolute encouders mounted directly on the axis (extremely precise for both tracking and pointing accuracy), it also embeds full blown sky modeling functionality right in the mount. Combining high res encoding with built in sky modeling via plate solving, and you have a mount that quite literally CAN NOT lose it's place.
The inability to lose it's "place", or to lose what it's pointing at in the sky, is a feature that becomes increasingly important the more you move into LRGB and narrow band imaging with a mono imager...you usually have to expose for long enough that at the very least, you run into a meridian flip each night (you image on both the eastern and western sides of the meridian), but you also usually need to image over multiple nights to get all the various channels. Without absolute encoding and plate solving, recentering your subject exactly as it was centered previously can be a very difficult process. It's not impossible to image over multiple nights without absolute encoding/plate solving, but once you integrate everything, you end up having to crop a fairly significant amount of sky around the center of your image because the alignment of each set of frame is offset relative to prior sets.
So, back to my original estimate. If your going to spend tens of thousands of dollars on equipment, it's best to spend the tens of thousands of dollars properly. Instead of a Losmandy Titan, get a 10Micron or maybe an ASA mount. It's more expensive, but the expense is WELL worth it, as those mounts are so good they effectively eliminate all hassles related to mount performance. They can also easily be used right up to their capacity limits, where as a Titan or CGE or other lower end mounts usually need to be used at half capacity for imaging work.
You could still start with an Astro-Tech 16" RC Truss. Personally, that's my plan, but over the long term, I think I'd ultimately move up to a PlaneWave 17" or 20" and a larger format CCD imager. Even assuming you stuck with the Astro-Tech scope, your cost is still up around $25,000-$27,000. The mount is really the centerpiece, the most important thing. Once you have the mount, you can slap on any number of scopes with a variety of different focal lengths, apertures, and fields of view to do all sorts of imaging. But even the $7000 Losmandy Titan, or for that matter the $500-$6000 Celestron CGE Pro or Meade LX200 mounts, you are spending a TON of money on a mount that MIGHT get an arcsecond better tracking once you PEC and guide vs. a "low end" mount like the highly popular Orion Atlas. Personally, my guiding performance with the Atlas is already within the limits of seeing:
This is an image of my PHD guiding graph around the last time I did some imaging (we've had clouds here for nearly a month, haven't done any imaging since). My total RMS is 0.81", and my P2P performance is around 2" (my seeing, or atmospheric turbulence here in Colorado, tends to produce stars around 3" - 3.5".) My mount, unguided, has a 15" P2P periodic error...I've been able to guide that out almost entirely. The $5000 Celestron CGE Pro has a 5" P2P periodic error, however even THAT expensive mount can only do about 2" P2P with it's PPEC and guiding. If you happen to get an excellent copy, you might get 1.5" P2P. The Losmandy Titan doesn't get much below about 2" either. Guiding is a little easier with the $5000-7000 mounts, because of their lower periodic error, but they all still suffer from high frequency PE, which is why you can't really get any better than 2" regardless of whether you spend $1400 or $7000. All of them have to be guided...and once you throw guiding into the mix, it isn't worth it to spend thousands of dollars on a mount just for more capacity.
A 10Micron or ASA mount gets 0.1" P2P tracking or better with PEC, and they can usually track unguided for at least 20 minutes, and many higher end imagers get them to track up to 30 minutes without guiding (20-30 minute exposures are pretty common for narrow band imaging). Even guided, you couldn't get 20-30 minute exposures with a Titan, CGE Pro, or Atlas.
No, you don't have
to spend $20k or more. A lot of people get some pretty good results with only a couple thousand invested. But you can see a VERY clear difference in results between people who image with the lower end equipment, and people who, at the very least, invested in a true high end mount. You can take a Tak FSQ-106 (very popular APO refractor) and put it on an Orion Atlas and a 10Micron. Let the same guy do some imaging with both setups, and given his consistent skill, the images produced with the 10Micron will be superior. The effects of the poorer tracking (2" P2P or so vs. 0.1" P2P, a factor of 200x!) with the Atlas shows up quite readily in the quality of the stars and sharpness of detail. An arcsecond is only a fraction of the diameter of your average medium-sized star...but it's still enough to really kill off your star roundness, sharpness, and eat away at detail in nebula and galaxies. Swap out the $5000 Tak 106 with a $20,000 PlaneWave 17" CDK, and suddenly all the optical aberrations (for as good as the Tak is, it's still a refractor, and all refractors suffer from some abberations that show up in star fringes and flares and such...even my $13,000 600mm lens, which is as good as $10,000 to $20,000 APO refracting telescopes, still suffers from poor star shapes even when I stop down a bit) are gone and your star spots are simply sublime.
If quality is your goal, it's pretty tough to achieve it without spending at least $20,000.