Before you decide on the "best setup" it is necessary to clarify what you want from the equipment. If you want whirly/starry colors without much trouble and have little regards for the actual celestial objects then the "best setup" is VERY different from one that extracts the deepest and most faithful representation of actual objects. In other words are you most interested in colorful "artistic" diversions or are you interested in the actual astronomical content?
In the domain of "serious" astro-imaging, Bayer (including DSLR) is not regards as a real astro-cam because DSLR/Bayer cameras are markedly inferior to dedicated astro-cams. There are numerous technical reasons for this, starting with the highly destructive Bayer matrix combined with the spectral characteristics of astro-objects. So if you are interested in going deep then get away from DSLR. And don't be suckered into getting a bastardized "color astro-cam". Of course, "real astro" also requires a "real scope" and that can get complicated and expensive.
But in the domain of "pretty pictures" where content is secondary to prettiness then Bayer may be the way to go. If that's your path then the optimal scope is small, short and not all that expensive.
As you can probably tell, I'm not much of an afectionado of pretty pics for prettiness sake and am much more oriented towards revealing actual DS objects. I have considerable experience in that domain and will further advise if you like.
Stan
AstroStan wrote:
the Bayer matrix does not lug much behind a LRGB setup (talking similar exposure).
I have to take issue with that claim, at least in regards to dim objects. The Lum is the workhorse of LRGB and a Lum exp captures approximately 4x photon flux (information) than a Bayer exp of the same time. That may not be a big deal for a relatively short exp of a bright object but it is fatal for a long exp of a dim object. Some galaxies require 2+ hours with a 14+" unfiltered aperture. It is unreasonable to try to achieve that with Bayer 8+ hour exp!
Noted DS galaxy masters such as Adam Block always use LRGB.
Stan
AstroStan wrote:
What constraint imposes a limit of 2-5sec?
primarily:
1) f-ratio and sky brightness. A dark sky and/or slow f-ratio is problematic.
Hi-res demands long FL and hence slow f-ratio. Reducers always degrade the PSF and are deleterious to real resolution. But the tiny pixels of CMOS are problematic for long FL because the greatly oversampled read noise is significant and low-flux unstable banding can be a very nasty issue (even with the ZWO cooled mono 1600).
Of course, you can use a shortened FL and high frame rate. But then there is not much need for a high frame rate because that configuration is not really hi-res. For example, the M57 you referenced is not a hi-res image, nor is it very deep (checkout my version on my web site). And 1/2 second is a bit too long for most seeing corrections, i.e. the resolution difference between 0.5 and 2 sec subs for that scope and cam are probably negligible (unless the mount is crap).
2) brightness of the object. M57 is very bright as are several PN that can withstand a high frame-rate on fast or moderate f-ratio. But with a large "slow" scope on a dim galaxy the results are not good.
Stan
The snobbishness and arrogance you have displayed in this thread is really a disservice to the amateur astrophotography community. You come in here with the attitude that unless people do it your way, they are just making, as you say "pretty pictures where content is secondary to prettiness." I would argue that your H-alpha images are similarly just pretty pictures unless you are writing scientific papers coming up with new insights about astrophysics. Are you? If not then you are just making pretty pictures, just like everyone else here. And you presume that unless one has a big telescope and cooled mono CCD, that one can't make great pictures. You are welcome to your opinion, but many others here probably have a different idea of what they want and what is a great picture. Thank goodness those heading the NASA APOD site have a more open mind as to what constitutes great astronomy pictures!
And even if you are writing scientific papers about your results, that does not mean others want to do the same.
You seem to think that the only real serious astrophotography is your method of high resolution with big telescopes, adaptive optics and tiny fields of view. Don't get me wrong, your images are gorgeous. More power to you. But I have no desire to produce such images, and I'll bet many others here also do not. Tiny faint things are not the only interesting things to image. There are many large scale objects and structures that can only be imaged with wide field optics. Jerry and my examples of the IFN go very faint, for example. My IFN gets to about magnitude 27/sq arc-second, and Jerry's to mag 28 or 29. That is quite impressive for ordinary CMOS DSLRs.
You seem to think that narrow band is the only thing that shows "real" content. Simple visible RGB shows many processes not recorded by a single or even 3-wavelength narrow band imaging. For example, H-alpha + H-beta + H-gamma shows red to magenta color with the gradation due to how much interstellar dust is present. Interstellar dust is brownish if no emission is present, except in unusual grain sizes and scattering conditions where bluing occurs (MIE or Rayleigh scattering, as in the Pleiades). Colors of stars indicate their spectral class. So a simple visible RGB image I'll argue shows far more composition and astrophysical processes and even dust grain sizes than any narrow band image or 3-band combination of images. So dissing simple RGB color only exposes your ignorance and arrogance.
FYI, I am a professional astronomer. The vast majority of my work is narrow band imaging, from vacuum UV to far infrared, now mostly from spacecraft, previously from terrestrial observatories (e.g. on Mauna Kea--I've observed many many dozens of nights on the IRTF, UKIRT, and UH 88-inch).
But I am intrigued at the revolution in imaging over the last 10 years, that with such simple equipment, so much can be done so easily today with a stock digital camera and ordinary camera lenses. It is this simplicity that allows so many people to get into astrophotography, and that is what I advocate. If someone wants to move beyond this simplicity, more power to them. But there are few people with such dedication or income to make that leap to your equipment.
And there is so much one can image with such simple equipment--literally thousands of objects, that one can spend a lifetime with a simple DSLR and camera lenses to image all the possibilities. In fact, for many, portability is key, and a 14-inch is too big to transport. For example, I like to travel to remote places, so need to travel light. I can carry my equipment in a backpack to get to very dark places. Or on an airplane. For example, this year I took my setup to the Serengeti. That would not have been possible without a lot more time and expense if I was lugging around a 14-inch telescope, big equatorial mount, cooled CCDs and laptops to run it all. That is not my idea of fun, and probably not for many others either. Some people also have medical issues so could not handle big equipment. Big I'll argue they can still make great images, even your so-called serious ones, with simple equipment, and even publish results in the Astrophysical Journal if they desired,
And to be clear, with the coming sub 1 electron read noise digital cameras, people will be able to do high time resolution astrophotography with simple equipment. Your diatribe against CMOS has many ignored issues and I'll not spend the time trying to correct them all. The simple fact is that one can make great images with a vast variety of equipment, and as each year passes, more can be done with simple consumer digital cameras and lenses.
I would hope you stop dissing simple RGB color astrophotography. You will drive most people away.
Roger
