mark_poseley

<p>Here is another option, I have not used it myself though.</p>

<p><a href="http://www.telescope.com/Astrophotography/Camera-Adapters-T-Rings/Orion-SteadyPix-Deluxe-Camera-Mount/pc/-1/c/4/sc/62/p/5338.uts">http://www.telescope.com/Astrophotography/Camera-Adapters-T-Rings/Orion-SteadyPix-Deluxe-Camera-Mount/pc/-1/c/4/sc/62/p/5338.uts</a></p>

<p>Here is text that covers optics; it gets technical so I don't know if it interests you, but it is interesting (at least I think so...).</p>

<p>http://www.scribd.com/doc/68015379/Optics-by-Benjamin-Crowell</p>

<p>Mike Dixon says:<br>

<em><br /></em><br>

<em>I also have an 8 megapixel camera that I always carry with me, but it weighs five ounces, has a 3.5-inch screen, autofocuses quickly (and lets me select focus and exposure points before shooting), and allows me to do post-processing and send images wherever I want. It also does a few other things, like record multiple tracks of music, listen to music, read books, use the internet, and make phone calls. ;-)</em></p>

<p>And all that for only 100 bucks a month... (-;</p>

<p>Sorry, I just had to do this.</p>

<p>If you shoot RAW your file size is what, about 21 MB or so with the embedded jpeg? If so, 21 Mb at 8 fps is 168 MB/s. So, the fastest card you can get will keep you shooting longer before the buffer fills and slows you down.</p>

<p>If you shoot jpg only, as noted above you can get by with a slower card since file size is greatly reduced.</p>

<p>As a comparison, I have a 5D MKII and a 30 MB/s card. I can get about 8 - 9 frames at full speed shooting RAW + jpg (roughly 30 MB of data per shot) before the buffer fills and frame rate slows to a crawl. My friend w/ 90 MB/s cards does much better.</p>

<p>Subject isolation contrast, subject can all contribute to what some consider a 3D effect.</p>

<p>I ran across a thread about this on another website (I hate to plug another outfit, but the content is relevant) several months ago and there is some good advice there; there are also a number of folks who take the issue far too seriously... ;)</p>

<p>Read at your own risk:</p>

<p>http://www.fredmiranda.com/forum/topic/1034865/0</p>

<p>Philip Wilson said:</p>

<p><em>I find that MF with an EOS body is quite challenging and the fact that the <strong>sensor (unlike film) has no depth</strong> means that focus is very critical.</em><br /> <em><br /></em>Philip - could you please explain what you mean by this? Sorry for the threadjack but in order to respond I need to understand what you mean. I agree about MF and EOS cameras being difficult but I put the EG-S screen in my 5DII and it does help.</p>

<p>I visited Yellowstone on the 19 - 21 of May in 2009. There was a lot of water moving from the snow melt. Crowds were very small (comparatively speaking...) and the weather ranged from warm and sunny to chilly and rainy.</p>

<p>The Firehole River Drive was still closed due to snow. The southern park entrance was subject to closure by flooding, and construction delays were in place at both the south and northeast entrances. Did I mention there was a lot of water moving around? ;) Check the website at www.nps.gov to see what may be happening.</p>

<p>The waterfalls were in full flow though, so that was pretty cool. There were a lot of animals moving around, a lot of long white lenses were set up at the prime sites so get there early if you want a spot. At one point, a convoy of Buffalo had taken over the road and there was a line of cars stopped to let them pass. They wove in and out of the line of cars w/o a care in the world it seems. They passed so close by my open window (2 - 3 feet away!) that I worried about getting bumped. Every one of them stared at me as they walked by; it was unnerving.</p>

<p>As we sat there, three wolves walked by in the wood 50 or 60 feet away. I had a 70 - 200 on the camera, but the woods were so dark I couldn't get a good shot. I saw one grizzly in a creek, but I didn't have enough glass for a decent shot. Lots of Buffalo, Elk, and Moose around though.</p>

<p>This Buffalo was along the road from the NE park entrance. I had a 24 - 70 on my 30D at 70 mm. I stopped to take a shot and he started stomping the ground, snorting, and using his horns to swipe at the grass. He was not happy with my presence so I packed up and drove away just as he turned to charge my car.</p>

<p>It was a memorable trip!</p><div></div>

<p>Sarah:</p>

<p>Here is a quick tutorial on gels and color balance over at the strobist site:</p>

<p>http://strobist.blogspot.com/2006/03/lighting-101-using-gels-to-correct.html</p>

<p>Flip some bits?</p>

<p>OK, I'll go away now...</p>

<p>There are several methods to clean a sensor; all of them carry risk of damage. If you are squeamish, then it might be best to let someone who is insured handle the task.</p>

<p>There are a few electrostatic brushes out there that will pull dust off. There are also some wet wipes available from various outfits.</p>

<p>I use the same solutions and cloths on my camera sensor that I use on my telescope optics, and it works well for me.</p>

<p>If I was going to switch methods, I would probably investigate these folks:</p>

<p>http://www.photosol.com/store/pc/viewCategories.asp?idCategory=9</p>

<p>What they have here is very similar to what I use, but these are custom fit to your sensor.</p>

<p>Why would you switch from something those nefarious _blanks_ thought worthy of stealing?</p>

<p>Sorry, my sense of humor can be a bit odd... ;)</p>

<p>When you view a 5D MKII image at 100% you are looking at an equivalent 52 x 78 inch print, on a screen w/ 72 - 96 dpi resolution. I am not surprised you see blurry photographs.</p>

<p>Print the shot at the sizes you might sell, and see what you get. I can print up to 13 x 19 at home and the 5DII is capable of amazing detail!</p>

<p>Also do what folks above have suggested to make sure hardware is OK. You do not mention what camera you used before; going from a crop to FF can be difficult in the DOF arena. It threw me for a few loops when I made the switch.</p>

<p>Understandable about CS and printing. I have done a lot of fooling around to get what I see on screen to look right on paper! It is a chore and can use up a lot of money in ink...</p>

<p>I hope some day to understand the whole printing process though; but I fear it is still far in the future before that day arrives. ;-(</p>

<p>I haven't acquired anything new worth posting yet so I am going back to 2009.</p>

<p>I was able to take some time off and drove out west to Joshua Tree National Park. I took one of the hikes out to an abandoned mine (Lost Horse I think), and passed through an area that had been burned out. This Yucca(?) had been severely scorched, but had not given up yet.</p>

<p><br /> The whole area smelled of burned wood. And as you can see the desert is more barren than usual. This was also my very first trip with my brand spanking new 5D MKII.</p><div></div>

<p>Hey Nathan - Ilford offers ICC profiles for my printer and their papers on their web site. Other paper mfrs. do as well. With Ilford, you have to create a free account to access profiles though.</p>

<p>I have been tempted to purchase some trial packs from Moab and Hannamuhle just to check them out. These two mfrs let you download profiles w/o an account.</p>

<p>Didn't you receive a copy of PS Elements with your printer? I purchased mine last year and a DVD w/ Elements 8 came with the printer. I believe you will have much more printing flexibility with that software. I use CS5 instead though.</p>

<p>Nathan, are you talking about the Canon Easy Photo Print EX software? I just fired it up and it does not offer any options but Canon paper, even though I have many other ICC profiles installed.</p>

<p>So, as far as I can see you must pick one of them.</p>

<p>The Ilford Galerie papers I tend to use all come with an insert saying what paper type to use for my printer. I have a Canon 9500 MKII. I generally print from Photoshop though, so I can pick an ICC profile for the particular paper I choose.</p>

<p>Ilford Galerie Pearl is one of my favorites; and they play nice with a lot of printers. ;)</p>

<p>I checked the Epson site (as I am sure you did as well) and they only reference their own printers to use w/ Epson papers, go figure... A quick Google search was not much help either.</p>

<p>That's pretty cool that they watch a wide field but only transmit 15 frames per second video of a section of the image the operator designates. But still, 400 gb / s? That's one heckuva WiFi link! ;)</p>

<p>And it can resolve people from 20,000 feet! that defensenews link was interesting.</p>

<p>There is a lot of info here on astrophotography:</p>

<p><a href="http://www.astropix.com/HTML/I_ASTROP/TOC_AP.HTM">http://www.astropix.com/HTML/I_ASTROP/TOC_AP.HTM</a></p>

<p>Here is an Adobe link on optimizing CS4 and CS5.</p>

<p><a href="http://kb2.adobe.com/cps/404/kb404439.html">http://kb2.adobe.com/cps/404/kb404439.html</a></p>

<p>If you are stuck in a 32 bit world with XP, adding more RAM does not make much sense. CS5 should run on your machine from what I read on the link above. I would start saving my money to upgrade my computer though.</p>

<p>Hope this helps.</p>

<p>I too would like to have Bob expand on his statement that a star is a diffraction limited point of light. I do not understand his statement (which is why I didn't directly address it.). ;)</p>

<p>I had hoped my ramblings would allow me to understand, but that was not the case.</p>

<p>A telescope can not really change its focal ratio. You can add a focal reducer, which is an intermediary lens and they sell two of them for my telescope. One can turn my F10 scope into an F6.3 and the other makes it F3.3. These optical enhancements will indeed make the scope 'faster' and result in a brighter image in the same time on the target. But these reducers, particularly the 3.3 are used for photography and not observations through an eyepiece. The 6.3 reducer can provide a brighter image for an eyepiece, but at the cost of some sharpness by adding more glass.</p>

<p>In a telescope the theoretical diffraction limit in radians is described by the formula 1.22 x wavelength (in Angstroms) / objective diameter (cm). There are 206,625 arc seconds in a radian. Theoretically speaking, my 20 cm scope could resolve about .07 arc second at a wavelength of 5000 A (conversion is 10 ^-8 cm / A). Well, that don't happen. :-) But diffraction limits are a function of objective diameter and wavelength, not distance. Telescopes wouldn't work very well if distance increased diffraction!</p>

<p>If you check the Cambridge link you will see they reference the wavelength of light as well in their discussion of diffraction in a camera lens. This diffraction formula is also valid in camera lens design btw. Trying to get all the colors of the rainbow focused on the same point is a big part of what drives expense in lens design.</p>

<p>A telescope is a lens in effect, but you have other items in the visual path and the sensor is your retina. A human pupil and the limitation it imposes adds complexity.</p>

<p>So no, a telescope does not violate the laws of physics and optics, so you can rest assured there. You do have to consider exposure time at a certain F stop though. As you make the F stop larger, you need to expose for a longer time to get the same brightness since you have reduced the size of the objective opening. In a sense you are correct in the F stop sets brightness thought, but without time it makes little sense in a practical application like photography.</p>

<p>A similar thing will happen when you introduce an eyepiece into the optical path of a telescope. A high power telescope eyepiece like a 9 mm will produce a magnification factor in my telescope of 2000 mm FL / 9 mm FL = 222X magnification, but the image will be very much darkened, and possibly of such low contrast it may appear very muddy. A 40 mm eyepiece (larger aperture) will magnify much less, approximately 50X, but will be brighter. You will get what is called kidney beaning though since the lens opening is so large; its a kind of vignetting in reverse. ;) 32 mm is the practical limit for my telescope in low mag eyepieces.</p>

<p>Here is a link on diffraction and camera lenses:</p>

<p><a href="http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm">http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm</a></p>

<p>Being diffraction limited in the camera and lens world means your lens / sensor combination has begun to soften the image due to the airy disk size in relation to your photo sites on the sensor. This happens when you stop down in an effort to increase DOF and it is dependent on photo site size, Bayer filter construction, etc.</p>

<p>In a telescope aperture is king; the bigger the hole to the sky on the end of your telescope the dimmer the objects you can see. I use the effects of diffraction in a point source of light (star) to collimate my telescope by purposely defocussing and tweaking the secondary mirror until the resultant airy disk is uniform in appearance. A GIS on collimating a Schmidt - Cassegrain 'scope can get you more info if you care.</p>

<p>A point source of light, like a star, will appear as an airy disk under high magnification in a telescope. Telescopes are considered diffraction limited when all the frequencies of light fall within that airy disk and no light is scattered outside of it by defects in the mirrors. Telescope optics (eyepieces and such) are considered diffraction limited when all light is focused within 1/4 wavelength at the same final focus point. In the world of telescopes this relates directly to resolving power. A good, diffraction limited scope will be capable of about 1 arc second of resolving power. It should be noted that seldom do you get better than 5 arc seconds or so of seeing due to atmospheric effects.</p>

<p>To get enough photons through a telescope to expose a piece of film or collect an image on a sensor is highly dependent on aperture. An 8" opening collects less light than a 12" and you can not get a sharp picture of a magnitude ten star w/ an 8" scope unless you can accurately guide the machine for a very long time. Another option is hundreds of images of the same part of the sky registered and stacked in software. The same goes for extended objects that are too dim to see through an eyepiece. Length of exposure is key there. If you lack aperture, you need time on target.</p>

<p>So, for your list:</p>

<p>1. True<br />2. Not really. It could be very bright, or very dim, and still show as a streak. This is simply because the earth rotates and the stars appear to move in the sky. Set you camera on a tripod and and take any lens and take a few minute exposure, the star trails will be all sorts of brightness and colors. Stars come in many colors, and this will show up in star trail shots.<br />3. Kinda true, the wider the field of view, the less apparent the motion and the longer it will take to become a visible streak. A rule of thumb many folks swear by is 1000 / aperture to yield seconds of exposure to avoid star trails.<br />4. True. However smaller apertures will require longer tracking time to get the same exposure brightness.<br />5. Wrong, see above.</p>

<p>If you have color aliasing, you most likely do not have a diffraction limited scope, you have set your camera / lens combo to a small aperture that caused a diffracted image, or your lens has chromatic aberrations. Telescopes, like lenses, may use exotic materials to try and ensure that all frequencies of light focus at the same point. The Cambridge in Colour link I opened with is quite good.</p>

<p>Tracking a point of light that is only a few arc seconds in size requires very expensive machinery... I was at Chaco Canyon several years ago w/ my telescope. They have an astronomy program there and they comped my camping if I let folks use my telescope. It was a blast. I have attached a picture of a guy I ran into there. He had just purchased this telescope, mount, and tripod. It cost several tens of thousands of dollars so he could move into astrophotography and track stars for long periods.</p>

<p>Whew! Longest post I have typed in many months. Hope it helps.</p><div></div>