September 20, 2014, 12:35:47 PM

Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - jrista

Pages: 1 ... 76 77 [78] 79 80 ... 304
1156
Lenses / Re: New Canon Tilt-Shift Lenses at Photokina [CR1]
« on: May 10, 2014, 10:44:56 PM »
Here is an actual example of tilt at macro distances and scales:



Your getting a whole lot more personal and insulting here.

Perhaps. Ignorance paired with loudness makes me aggressive at times.

Further, I am decidedly not an anonymous computer and prefer not to be treated as such. I took you by your words and they demanded retribution with regards to contents AND demeanor.

I agree we disagree. But only I am in the comfortable position to know what I know in the aristotelian manner of the craftsman (techne). You instead can only hope you might be right but wish to proof that in a lenghty scientific manner.

I never said you were an anonymous computer. You are, however, an anonymous person. I have no reason to believe you are as intelligent as your incredible arrogance might otherwise make you seem, therefor I have no reason to take you at your word that your supposed experience give you some insight that cannot be demonstrated in a "lengthy scientific manner."

Angry, arrogant, and insulting words have no meaning in the original context of this thread. Which means we have another derailed thread. Guess that isn't surprising, seems to be the M.O. around CR these days...

1157
Lenses / Re: Waiting for 35 1.4L II
« on: May 10, 2014, 10:04:00 PM »
If you need it this summer, consider the Sigma 35 f/1.4 ART

I second this option. Sigma Art lenses are pretty nice these days. Definitely viable options to Canon branded lenses, especially of the Mark II version you really want hasn't been created yet. :P

1158
Landscape / Re: jrista et al, Why Astrophotography?
« on: May 10, 2014, 10:02:06 PM »
You know, there is 1 main advantage I noticed with inexpensive telescopes/mounts, they're usually a lot lighter and smaller.

Very true. I guess that's one of the biggest pros of going inexpensive. If you need portability, then high end stuff just isn't viable. That's one of the reasons I got the Orion Atlas...I do take it out to dark sites about 40 miles away or so. The 10Micron GM2000HPS has an ultra portable version, where the head disassembles into two lighter weight parts, plus the control box. But it's still heavier than the Atlas...

I do love using my 600mm lens as a telescope. It's relatively short, so good for wider field work. Optically, it's as good as the $12,000 Officina Stellare HiPer API 152, and faster. Once I get a mono CCD camera, it will make for a superb wide field setup. I also like using my 100mm and 50mm lenses with my DSLR mounted to a Vixen dovetail for really wide field stuff. I haven't had many opportunities to do that...but the first clear night in almost four weeks is supposed to happen on the 13th...I plan to take the Atlas, my DSLR and those two lenses out to a dark site and see if I can get some wide field shots of the milky way core, scorpius, and a few of the Ha nebulas near the galactic core. :) I've been waiting for the 13th for so long, I'm kind of chomping at the bit. :P

1159
Landscape / Re: jrista et al, Why Astrophotography?
« on: May 10, 2014, 09:10:28 PM »
To he honest, post processing is my least favourite part, until I finished the image ,

I hear that! :) I haven't had many of those moments lately...I tried to do galaxy imaging with my wide field 600mm lens...wasn't nearly as successful as I originally thought it would be. It's pretty hard to do galaxy imaging in a wide field under polluted skies.

and good luck to getting that mount! c:

I'm actually really hoping the price on the absolute encoders these mounts use drops in the next couple of years, so that by the time I'm finally ready to invest in one, they'll be cheaper. Astro-Physics just started adding encoders to their mounts (they don't seem to be doing it as well as 10Micron). Their lower-end mounts (which are still all ultra high end in general) cost around $8000 or so without the encoders. Just adding the encoders pushes the price up to $15,000 or more. That's almost double the cost. If the cost of these high resolution, absolute encoders comes down in the future, these nice high end mounts should come down in cost as well, and I intend to be all ready to pounce the moment they do. :P

1160
I use my Microsoft Surface Pro out in the field. It's a full blown computer, weighs about a pound, and runs Lightroom 5 and Photoshop CS6/CC quite nicely. The battery life is the biggest problem, but that's largely been solved with the Surface Pro 2.

The screen is pretty good, I think my photos look quite nice on it, although just ever so slightly less saturated than on my desktop screen. I haven't tried to calibrate the Surface Pro yet...but I bet some calibration would probably fix the saturation problem.

You can even shoot tethered with the Surface Pro and Lightroom. You can plug in either a high capacity memory card or a USB drive, and write images to that. I've also set it up using an "offline files" folder that automatically syncs up to my NAS at home when the tablet connects back up to my home WiFi, but there is limited space on the SSD drive.

Anyway, if you want a nice way of showing your work to racers at the track, I really don't think you could go wrong with a Surface Pro 2 tablet. You could shoot tethered, immediately apply some basic processing in Lightroom, and it's a touch-based device, so sliding through a gallery of your shots for a race car driver would be not only easy, but full screen and beautiful. ;)

1161
Landscape / Re: jrista et al, Why Astrophotography?
« on: May 10, 2014, 08:43:13 PM »
While I do agree with everything you say, it's just that not everyone can spend 40,000$ to get optimum results. :(  Also, if you own a 13,000$ telescope (your 600mm lens) Why didn't you get a high precision EQ Mount? ???

Oh yeah, I'm not saying everyone can or even should spend that kind of money. Just saying that if you want to get great quality, it tends to cost a whole lot more to get it with astrophotography than it does with normal photography. With normal photography, if you have the skill, you can get very good results with fairly minimal gear. The gear matters, but not as much. With astrophotography, the quality of the gear has rather exceptional importance, which makes it a very (saddeningly, even) expensive hobby.

I do plan to get a 10Micron GM2000HPS UP mount. It's a $20,000 mount, one of the best (personally, I think it is the best...at the moment, 10Micron is the only manufacturer that has moved all the sky modeling right into the mount. The other high end manufacturers like Astro-Physics or Software Bisque still have all the modeling in software, that has to run on a computer plugged into the mount.) I haven't gotten it yet because, the obvious reason, it's ridiculously expensive. :P I just bought my 600mm lens less than a year ago (summer last year), and I still haven't really recovered from that expense.

The other reason is as much as I'd like to have it now, I can still learn with the ~$2500 worth of mount gear and my 600mm lens. Before I invest in a 10Micron mount and even an Astro-Tech AT16RC Truss (which would be $27,000), I want to have more skill. Acquiring images is only a small part of the process of producing great astrophotography images. Since you do astrophotography yourself, you surely know this: Processing is at least half, it not more like 2/3rds, of the art. I might spend six to eight hours acquiring images, which really involves about 2-3 hours of actual personal time invested (the rest is just the mount and imager and guider doing their things on their own.) I can easily spend a few hours sifting through my subs, picking the good ones and culling the bad ones and finally stacking, then another 10 hours at least of processing and tweaking and fine tuning my images in PixInsight and Photoshop. I've revisited some of my works two or three times, trying to get better results each time. In my Rosette image, I've probably got 20 hours of processing time in. I just started revisiting my Monkey Head image, which has at least 15 hours already, and I think I'll be spending at least another 5-10 hours on it to get noise levels down to an acceptable level and lift up some of the dimmer nebulosity.

Given that so much of the artform of astrophotography involves everything that comes AFTER image acquisition, I decided I should get good at that first, and make sure I am even capable of achieving the skill level I believe is necessary to produce Robert Gendler or Russel Croman level images...before I dropped $30k or more into more equipment.

1162
Lenses / Re: New Canon Tilt-Shift Lenses at Photokina [CR1]
« on: May 10, 2014, 08:33:43 PM »
I don't need to make the DOF deeper. I just need to change the relationship of DOF to my subject.

Initially you stated you were sure that you could get the whole head into focus by tilting. I felt free to assure you that was a wrong assumption, based on my experience. What was wrong with that?

Now you are practically stating DOF is not relevant for the purpose of getting the whole head into focus. But how can it not be with a threedimensional subject? So you were talking about a piece of confetti all along? Well, granted, TS-Macro helps with confetti.

I still do not think that a forum like this is about prooving each other right or wrong by going to the book-shelf. It can also be about listening to what other people have to say. Not everybody is raising their words only to be in the center of attention. Some want to keep others from going wrong when they see it coming.

You are only discouraging people with aquired knowledge to participate here. But your muzzles are inflated and full of air.

I will never understand why anyone has to get directly personal over these topics. I have not insulted you in any way, nor am I simply interested in "being right".

You demanded I simply trust your words at face value, and preemptively flat-out stated that you were not going to back up any of your claims (which for me, personally, comes off as one of two ways...either extremely arrogant and haughty, or as an indication that the other party doesn't necessarily trust their own position), claims which were supposedly steeped in a vastly superior base of experience (how you could know that, given that you don't know anything about me, given this is the first time we've ever encountered each other, is curious.) I explained, perhaps directly but otherwise without insult, why I could not simply take you at your word like that. Simply an honest but plain and direct explanation of my stance. Your getting a whole lot more personal and insulting here, and THAT is the only thing on these forums that TRULY does no one any good. We've had far too many threads destroyed by people like you getting personal like this. I don't really care what you think of me, but there are other people on these forums who don't like threads going way off the tracks by people flinging insults back and forth.

I'm not going to exchange insults with you.

Here is another image. Maybe this will replace a thousand words and all my "hot air":



Crappy, crude, but hopefully effective example of focal plane, DOF, and a "fly head". Maybe DOF increases, slightly, as there would be a very slight wedge. But that isn't really what I'm after. I lose DOF along the bottom of the fly eye and head, but I gain a small amount at the top of the head. It doesn't have to be a lot. It can be just a couple millimeters...that's all I'd need to push the focus falloff far enough to the back of the fly's head to matter. Add in some rotation (or swing), and I could reorient the focal plane and wedge to bring more of the fly eye in focus. Since the fly's head is round, I can afford to lose some DOF at the back right area where the head turns into the mandible (it's just empty air there).

How much actual lens tilt would be necessary to get this much focal plane tilt for a subject less than a foot from my sensor? I dunno. I haven't actually engineered such a lens myself. I've found a number of T/S Macro Bellows now that claim to have 15° of tilt. Some of these products are fairly pricey, $200-300 (just for a bellows, we aren't talking about any amount of optics here), so I am at least willing to suspect that 15° of tilt is enough to be useful for subjects very close to the lens, given these things are marketed explicitly as "macro tilt and shift bellows."

Anyway, I have no interest in proving right or wrong with you. Just being clear about what I'm trying to say. I haven't felt anyone has even understood what I'm trying to say, all I've gotten is direct counterarguments based on mistaken assumptions based on what you guys think I'm saying.

I disagree with you. You clearly disagree with me. We can exist happily in a state of disagreement without insulting each other, or demanding that either of us trust each other just on our word alone. For anonymous people on the internet, someone's word is worthless. However, at least I've tried to back up my claims with some evidence. At least I've tried to make my original point, what my ultimate goals would be if I had a specially designed TS Macro lens from Canon, clear. I believe T/S movements are beneficial for non-flat, non-product macro photography, such as insects. I don't expect to see some ridiculous improvement that would allow me to shoot at f/2.8, but maybe I can drop down to f/11 or f/16 from f/32 or f/45, and use tilt and maybe some shift to make better use of my focal plane, and envelop more of the interesting part of my subject within the DoF. I mean, that's what T/S is all about...changing your focal plane, which in turn changes what part of your subject falls within the depth of field, without moving the sensor.

I know that on my 7D, I can get pretty sharp results up to f/20 despite the fact that is a diffraction-limited aperture. Beyond f/20, the effects of diffraction (even in macro situations), really start to kick in and hurt my detail. By f/32, things are usually unacceptably soft. And, just to finish off the point. So what if I still have to shoot at f/22, even with tilt and shift? I've shot other macro subjects as narrow as f/22 before, and there is still usually a considerable amount of focus falloff. Even a small amount of tilt would be enough to MAXIMIZE the amount of my subject that is near the focal plane and within the DoF. Maximize doesn't necessarily mean entirely eliminating all focus falloff everywhere....it just means moving those points of falloff around such that more of your subject is sharp for the SAME or SIMILAR DOF. DOF doesn't have to get huge, or even larger...changing the angle of the focal plane is really all that I'd really need.

1163
Macro / Re: Flower macros
« on: May 10, 2014, 07:36:30 PM »
Wow, this is a fantastic thread! Such amazing work, from everyone!

I can't wait till the next round of flowers bloom in my yard. I haven't had any flower macro action for over eight months. :P

1164
Lenses / Re: New Canon Tilt-Shift Lenses at Photokina [CR1]
« on: May 10, 2014, 07:35:23 PM »
Here are some actual T/S products for specifically marketed for macro photographers:

http://www.novoflex.com/en/products/macro-accessories/bellows-systems/tilt-shift-bellows/
http://www.ebay.com/itm/CONTAX-C-Y-MICRO-MACRO-BELLOWS-EXTENSION-TILT-SHIFT-/380895790528?pt=LH_DefaultDomain_0&hash=item58af2885c0
http://www.bobatkins.com/photography/reviews/eos_macro_tilt_adapter.html

If T/S was so useless for macro, and is incapable of producing any kind of visible improvement in actual use, why would anyone invest money designing and developing T/S bellows or adapters?

LensBaby also offers a macro adapter for all their optics, and it works with all of their T/S optics:

http://store.lensbaby.com/products/macro-converters/

This is actually probably one of the most viable T/S macro products for Canon cameras on the market right now. I forgot all about LensBaby, but this stuff isn't even new. I was looking at their Composer Pro and macro converter years ago when I still had my 450D. If Canon doesn't make a T/S Macro, I'll probably put the LensBaby  stuff back on my list.

1165
Landscape / Re: jrista et al, Why Astrophotography?
« on: May 10, 2014, 07:18:25 PM »
Let me try it this way. Have you seen images produces with PlaneWaves on Paramounts, AP mounts, and 10Micron mounts? Have you ever compared them with the images your AT72ED produce?

I don't mean to offend, honestly...but no, I do not believe an AT72ED and a ZEQ25 are going to produce IQ that even remotely compares to a PlaneWave or RCOS scope on a high precision mount. I spend a lot of time looking at peoples images on AstroBin. A LOT of people use the Astro-Tech refractors (well, a LOT of people use Astro-Tech scopes period, including me shortly here as I'm about to order either the 8" or 10" RC) because they are an extremely good deal for the quality you ARE getting. Even those who are quite skilled and know how to get round stars still can't get the kind of CLEAN stars that a PlaneWave gets you.

If you look around and compare what $3000 worth of equipment can produce in the majority of cases, vs. what $20k-$40k can do in every case...you'll understand where I'm coming from.

My $13,000 lens could probably serve me a hell of a lot better if I put it on a higher quality mount. I'd also probably get at least twice as much sky time out of it if I had it on a mount I did not have to constantly fiddle with to keep tracking smoothly, or to get pointed at the right place in the sky, etc. There are just things you have to deal with when using lower-end equipment that consumes a very considerable amount of time. I have a four hour window to image from my backyard, given how the trees and houses around me affect my line of sight. On any given night, I usually get about 2 hours of actual time imaging. The rest is spent fiddling with getting my polar alignment down to 1' or less, getting my guiding set up and running (If you have ever used the Orion SSAG with PHD, you would know how you have to first find an acceptable guide scar (which, with the really low sensitivity of the SSAG, is often a real PITA), then let it calibrate which, assuming you use the recommended ~20 steps, can take at least five minutes, then let it "settle" once it actually starts guiding), then get your focus dialed in, frame and center your subject, get your imaging sequence set up and finally get it started. If the temperature is changing throughout the night, you gotta keep an eye on your focus, so you usually produce about five subs, then refocus, produce five more, then refocus, etc. If ANYTHING happens to your guide star...a light high altitude cloud of just the right density moves over it, you can lose it, then you lose your guiding, and your tracking goes to hell (from 2" to 15" or worse!) You can automate a lot of this, but all these little things take time. Using SGP, you can automate your pointing, centering, dithering, guide recalibration, focusing, filter selection, etc. All of those things consume about 40% of that 4-hour window.

Now, throw in a high end tracking mount that doesn't need guiding at all. Suddenly, the only things you have to do every few subs now are check focus, and maybe choose a new filter. All the other cruft to make sure your still pointed at the right thing, still properly centered on it, all the guiding crap, etc. is just no longer necessary. Focusing can still take away some time, but not nearly as much, so you have the ability to produce a lot more subs during your window of opportunity each night. Having enough subs to stack and average out all the noise is one of the most important things that I see high end imagers doing differently. You might see people using lower end equipment getting 30 4-8 minute subs with a DSLR, when they need at least 100 to reduce noise to manageable levels. The guys with RCOS and PlaneWave scopes are getting 15-20 10 minute Luminance subs, along with 9-15 10 minute subs each for R, G, and B. That's anywhere from 42 to 65 frames, each of which are higher quality with more signal and better SNR, than the 30 low SNR subs the guys using modded 350Ds on Orion or Astro-Tech refractors. It's a total integration time of at least 650 minutes, vs. a total integration time of maybe 240 minutes or so.

I understand why imagers with AT72EDs and ZEQ25's or AT6RCs and Atlases using modded DSLRs or $700 Atik OSC CCDs don't get more than 2-3 hours worth of subs. There are very good reasons for it, not saying there aren't. It's a far greater effort, requiring a far more active investment to keep your setup producing subs that don't need to be culled and will contribute nicely to the final integration, when using lower end equipment. I think that just speaks volumes about why someone would invest some serious money into high end equipment if they want to take their imaging to the next level, where their stars aren't just round, but perfect, where their color saturation isn't just good, it's sublime, and where their detail is just mind blowing. ;)

1166
Lenses / Re: New Canon Tilt-Shift Lenses at Photokina [CR1]
« on: May 10, 2014, 06:57:36 PM »
I think everyone is thinking I just want to create a giant wedge like you do with landscape photography, to make everything from the foreground to infinity "in focus". That's NOT what I am talking about. The DOF doesn't need to be "infinitely" thick.

That so isn't how tilt works, but, whatever.

First, there is a reason I put the term "infinitely" in quotes. When you tilt a TS lens down, you make the focal plane angle from below the lens outwards and away. The depth of field is narrower at the point where the focal plane meets the lens and image planes, and becomes increasingly wide the farther out you go. It isn't infinite (unless you follow the focal plane for infinity), but it DOES allow you to reduce your aperture and still keep your entire field in acceptably sharp focus. Indeed, you will generally be doing landscape photography like this at hyperfocal distance. But it is how tilt works.

From Wikipedia:

Quote
The DoF is zero at the apex, remains shallow at the edge of the lens’s field of view, and increases with distance from the camera.

As for all the rest, I know you love to ignore theory as if it has absolutely no bearing on anything in reality. That's your choice.

Still, I don't need to increase my DOF like tilt does for distant landscapes. All I need to do is tilt the focal plane around close up subjects so that the focal plane and DOF are better oriented relative to the subject. The change in focus doesn't need to be significant, a fraction of a millimeter change in the focal plane around a close up macro subject would produce a visible change in focus. Even if I can't get a full 20° of tilt at the focal plane out of a complex multi-element TS lens, it's still an improvement over not having tilt at all. Mere millimeters change in the focal plane are all that matter for macro.

Oh, and BTW, given that a specially built tilt/shift macro lens has not actually ever been built for 35mm format, NO ONE here actually has any first-hand experience with it. The theory is the only thing we have.

1167
Landscape / Re: jrista et al, Why Astrophotography?
« on: May 10, 2014, 06:31:03 PM »
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. :P

What autoguider do you own?  :D

See my previous reply. :P

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.  :o

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! :P) 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.

1168
Lenses / Re: New Canon Tilt-Shift Lenses at Photokina [CR1]
« on: May 10, 2014, 05:31:22 PM »
Your up-front refusal to provide any evidence to back up your claims only gives me immediate cause to doubt you. So sorry, but I cannot trust your evaluation. There is no reason to trust your evaluation. You can't simply say "I'm 'through' with backing up my assertions with evidence." and expect that to win you any awards.
...
 The back side of the head is immaterial, you can't see it anyway

First of all: Let me thank you for mentioning the back of the head is not in need of being in focus. ;)

I was referring to the visible part of the front and back respectively, speaking anatomically.

With my refusal I only meant to say I am not inclined to run yet another test series of tilted macros just so to be able to post the outcome and win anyone's "award". I did my testing, I am good. I never did feel any need to proove my point to you. But I thought you might be smart enough to tell between the lines, that there is a likelihood my experience to be better funded than your assumptions.

Let me be clearer then. What experience? What better funding? You've provided zero evidence to support your claims that you have more experience or have better funded your equipment. By refusing to supply any evidence of any kind, because you feel no need to prove your point, makes me question your points all the more. You have given no one here ANY reason to trust that you have more experience of have higher quality, more expensive equipment that would allow you to prove the point anyway.

Perhaps you do have more experience, perhaps your a TS lens collector and you've spent tens of thousands of dollars buying all of the ones available on the market. Why should I believe that? It's just your naked word, a word you've already stated you have no intention of backing up with any evidence. An up-front insistence that you aren't interested in proving your points, when proving your point with actual evidence would easily give me cause to reevaluate my own, eliminates any reason for me, or for that matter anyone else, to trust anything you say.

Just to be clear about WHY I don't trust your word. If you hadn't preemptively stated you refuse to provide any evidence of any kind to back up your claims (which still fundamentally miss the point I'm trying to make), I wouldn't be so insistent about my reasons for not trusting you...I wouldn't have a clearly and well defined reason NOT to trust you, and quite possibly the opposite. Only those who are afraid their own assertions may not be valid are willing to state ahead of time that evidence doesn't matter. :P

Your theorie is right, but the effect and possible benefit of tilting is so little at this distance (and with a three dimensional subject), that it approaches negligible.

Based on what theory? Your own personal anecdotal "experience"? Or can you lay down the math for me, and for everyone else, to prove the point? How negligible? Were talking about a few millimeters of DOF here...a few degrees of tilt could have a significant impact on how that few millimeters envelops your subject. It doesn't have to be significant, because were talking about insignificant distances and sizes in the first place.

Yes, you will be able to make the focal plain say more level with the right eye-portion of the fly (minimally, 4 degrees of tilt might be right for that). But the DOF will remain to be so shallow that you will find yourself stopping down to an f-stop where you will hardly see any difference to the untilted version.  And you will still have difraction. After all, this head isn't much less three-dimensional than a ball. Where do you want to slice it?

I don't need to make the DOF deeper. I just need to change the relationship of DOF to my subject. A few degrees of tilt WILL do that. I think everyone is thinking I just want to create a giant wedge like you do with landscape photography, to make everything from the foreground to infinity "in focus". That's NOT what I am talking about. The DOF doesn't need to be "infinitely" thick. It just needs to be reoriented to conform to the orientation of the subject, that's it. As for where to slice...well, perhaps a picture:



Details in the image. Everything is to scale. I calculated G based on f (Scheimpflug Principal), which is assumed to be 100mm. Tilt angle of the lens is 8°. All other terms were derived from G and f, and everything is to scale assuming 1 pixel represents two millimeters. Subject distance is 10" (254mm). For a 20mm ball (i.e. fly head), the effective gain in focus on the top of the ball is about 6mm farther back. You also lose about the same 6mm forward on the bottom of the ball. The loss of focus on the bottom of the ball/fly head doesn't matter, because it cannot be seen (it's underneath, given the position of the sensor/vantage point of the viewer.)

So, 6mm. That isn't much. It's quite trivial. Unless your subject is a freakin fly! :P Now, if I had a full 20° of tilt in the lens, instead of just a mere 8°, the actual change in the plane of focus on the subject would be even more significant, despite still being in terms of mere millimeters.

1169
Landscape / Re: jrista et al, Why Astrophotography?
« on: May 10, 2014, 02:31:21 PM »
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. :P

What autoguider do you own?  :D

See my previous reply. :P

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.  :o

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.

1170
Landscape / Re: jrista et al, Why Astrophotography?
« on: May 10, 2014, 01:32:34 PM »
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. :P

The point of a high end mount isn't really just about tracking performance, though. It's fundamentally about weight capacity. You can get up to around 8" scopes with lower end/midrange mounts that can handle 40-60lb. But to really be able to track properly, guided or otherwise, with larger scopes (12"+), you need a mount that can handle much larger capacities. Such as 90-110lb for 12-14" scopes, and around 130-200lb for 16-20" scopes. Larger scopes (larger physical apertures) are necessary to resolve more detail and resolve dimmer details.

Pages: 1 ... 76 77 [78] 79 80 ... 304