I am looking to get into some really hard core Solar Imaging and looking for the least expensive option.
If you really want hard core solar imaging, then you really need future options to re-configure things as you get deeper into this and as the maximum rolls in, in a few years. That means you should desire the ability to have as much aperture as you can get now. That means you should want the ability to double stack at some point, not necessarily right now (because double stacks for imaging are far less crucial than aperture is for imaging when starting out). And that means you will want the ability to have a robust focuser to handle complex imaging trains. It also means you will want to pay very close attention to focal-ratios of instruments for imaging purposes because you should want to nearly critically sample the wavelength you're imaging at to make it as hard core as you can (or in other words to actually record the potential resolution your system is capable of making it more worth while if you care about seeing as much as you can out of it). So that means you really need to know what size pixels and which cameras are going to be ideal for your goal with the instrument you pick as well, as there's no sense getting something that will be as difficult as possible to image with due to limitations from an imaging perspective. Lastly, almost everyone wants to do it all for the least cost possible. This is very understandable. But, the initial buy in is the biggest step that will make or break your experience in this, and if you really are into this for the long run and want to hard core image, getting something that has limited aperture and cannot be expanded on will cost you more money in the long run, as you do this a while then develop a little aperture fever or other mild case of money-spending-itis. I cannot suggest enough that it's far more worth while to go for the largest aperture you can afford, with the ability to double stack, ability to have a good focuser, now, rather than get something very limited up front. Aperture is where the money goes, in solar. Every few millimetres costs you incrementally more money. And for good reason. And it's not just size it's also quality. Starting out imaging, none of us were thinking about the size of the sweet spot (Jacquinot spot) for the purpose of imaging.... we just thought the whole aperture was going to be use for imaging.... but its not. You will not be able to image outside of the sweet spot. The bigger the etalon and the kind of tuning and the quality put into the build of the etalon will matter a lot when it comes to determining that sweet spot.
So that said, based on what you're looking at and asked:
Lunt 50 Pressure Tuner - A step above a PST, but still as basic as it gets. It will have a small sweet spot. It needs the focuser to be replaced ($$). It requires fiddling to even get a camera to come to focus on it. It has minimal aperture for resolution purposes and again the sweet spot is limiting. This is far more of a visual toe in the water device, than it is a hard core imaging instrument. But at least it can be double stacked up front or later. And at least you can change out the focuser later (Moonlite comes to mind). But you'll never overcome the 50mm aperture's limits and its sweet spot size for imaging purposes. The blocking filter is small but its ok because it's a tiny focal length and will not produce a large image circle anyways and the blocking filter can be changed eventually ($$) but again is not terribly necessary with an instrument this short. It's an F7 instrument, so there's no current pixels that come close to sampling at the critical level with this, so you're always undersampling significantly (which is losing data, making the aperture even less useful in that sense) unless you use a barlow to get the focal-ratio up closer to F10~11 or F14 essentially, but then you also have the limit of the tiny blocking filter and will need the larger blocking filter when doing this, so again, all the hidden costs for hard core imaging keep flooding in on this one.
Pressure Tuning vs Tilt Tuning - There's no detail difference to discuss. This simply has to do with tuning, uniformity and sweet spot shape and size. Aperture is what changes the detail. There are tons of tilt tuned instruments posting around here with excellent uniform images. Pressure tuning is considered slightly superior to get better uniformity, but it's hardly a big enough difference in the sense to go smaller on aperture just to get a pressure tuner, where the larger aperture will be far more important in the long run for a hard core imager.
Lunt 60 or Solarmax3 60 - This is the first step to having an instrument that is good for visual and good for imaging with as much aperture as you can get in a better etalon without spending major money. It's more expensive up front, but you're getting a lot of what you needed that will not need to be replaced or upgrading later. You get a focuser up front that is good enough to image. You get a bigger aperture, with a better etalon, with a better potential sweet spot up front. You can still double stack this. While it seems not that much bigger than the 40 and 50mm options, it really is significantly bigger and better in every single way. And it costs more due to that, you truly get what you pay for here so for anyone wanting to venture into hard core imaging specifically, I would hazard to say that this is the beginning of that and nothing lesser is worth considering for the cost, because again as you get into imaging, the options you need in the future listed out above are almost all already in this instrument. The only two things you'd consider in the future for these instruments is the blocking filter size and double stacking it. Costs more up front, but ultimately is not needing the most upgrades and doesn't have the same limitations as something smaller and 60mm resolves all major structures of our star and its far easier to image with this instrument without any fuss to get a camera to come to focus and F8.9 is a far better focal-ratio for imaging options with today's pixel size and sensors as the 2.4um pixel options nearly critically sample natively with this focal-ratio (it's close enough to be good to go without adding anything and still get plenty of detail from your aperture's potential resolution).
Quark - The Quark is the biggest first step to high resolution imaging. Nothing else out there other than a rear mounted etalon can do apertures like 80mm, 102mm, 120mm, 150mm, etc, or more, with just this one purchase and an appropriate D-ERF (full aperture for some sizes and some telescope designs, but not all). The Quark's biggest compromises are that you will struggle to image full discs without detail loss due to the sampling and will require fiddling with adapters and focal-reducers and tiny aperture scopes to get a full disc (which sort of defeats using this). The other big compromise is the inability to easily double stack it. You'd have to get another etalon of some fashion that can be mounted in the rear and matches well with it to be able to double stack. This is possible. But none of the options to do this are inexpensive or simple and require some custom work to adapt it all together. The Quark has a 12mm blocking filter, so at least that's not a big limit, that's pretty good. To get the most out of a Quark, it's etalon needs to operate in the longest telecentric light cone that it can, F30 being where it starts, and longer is better (often wanting to be closer to F45 at the etalon, and then focal-reducing back down to a reasonable focal-ratio for imaging purposes to critically sample). It's common to need large pixels to critically sample with a Quark due to the long effective focal-ratio. That same large pixel sensor will not be good for full disc imaging because it will have a much shorter focal-ratio for critical sampling. So again, the Quark is far more ideal as an imaging device for high resolution partial disc imaging, not full disc imaging. The major benefit is that you can use any good refractor with a good focuser (and you need a really good focuser to handle the weight and moment arm) and it's the most cost effective way to get into high resolution imaging. But, at the cost of not easily double stacking, not easily imaging full discs, and the overall gamble of the quality of a Quark in general and relying on its electronics working in the long run to even heat it to be on band.
Also, quality really matters. You'll work less hard to image if you have a quality etalon (as in good uniformity, high finesse and a large sweet spot) and overall system. You'll have to do less crazy amounts of processing to produce an image that perhaps you have an expectation to produce with overall less work going into it. I would suggest you look around at images and consider which ones you like the most and want to eventually produce. Maybe ask how much processing went into it versus the RAW file(s) they started out with. A better system will have less issues and be a lot easier to image with than something that works but requires a lot of "fixing" in post.
In reality, getting into hard core imaging really means you'll be getting something else later on with this initial purchase. It's very hard not to end up with two things. Something for full discs. Something for higher resolution. Depends on your end game expectations and what you like the most. Also depends on what your seeing conditions can support. If you have good willpower, maybe you'll be able to stick to one thing. You can resist this by getting something far better at doing as much as possible up front. So the least expensive option is the last thing you want to get up front. You want to get the middle of the road option that is much better for imaging with more aperture up front. It only hurts once.
TL;DR: Get the 60mm dedicated options if you want full disc imaging in the long run and good potential for moderate resolution imaging of single structures. Get the Quark if you want the largest aperture possible for your seeing conditions to image high resolution single structures and partial disc regions. Avoid the PST, Lunt 50, etc, for hard core imaging in the long run.
And if you're really truly hard core life-long into solar imaging, I would skip all of this and go directly to a Lunt 80mm or Solarmax 3 90mm and call it a life time. You'll spend less on this overall once than crawling to it over time with multiple purchases along the way.
Edited by MalVeauX, 31 May 2020 - 08:55 AM.