12-25-2014 04:59 PM
I just bought me a Canon T1i (body only) for Christmas to use for astrophotography. I'm having some problems getting started and am hoping to get some answers from here.
First off bc I'm using this for astrophotography I didn't buy a lens for the camera as I will be using my telescope as my lens. The problem I am having is once I switch the camera ON, all I see is the AF points in the viewfinder and can't figure out how to get it off. How can I see what I'm shooting through the viewfinder?
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12-25-2014 05:34 PM
12-25-2014 05:58 PM
Thanks for the info. I still haven't figured out how to get the Live View display to work either. All I see is a white screen. I can see this is going to be a little of a learning curve. I had been doing astrophotography the afocal way by just mounting my point and shoot up to the eyepiece and was getting some great images that way which is what led me to get this dslr. However I don't know if I have the proper kind of mount to do long exposure astrophotography. I just have an eq2 mount with an eq2 motor drive.
12-26-2014 01:52 AM - edited 12-26-2014 01:54 AM
Without a lens on the camera you wont get an image... it's just going to be a solid color and usually white. The telescope will become your lens. Once you get it mounted on the telescope, you'll be able to get it to come to focus and see something other than just a plain white image. Right now you just have random photons landing everywhere.
How you attach to a scope depends on the scope but you will definitely need a T-Ring (or "T-Adapter") for Canon EOS mount, and the rest depends on the scope.
A "T-Ring" has the bayonet mount type on the camera-facing side... and industry-standard "t-threads" on the scope-facing side.
E.g. one of these:
Here's the Celestron brand T-ring: http://www.bhphotovideo.com/c/search?N=10261256&InitialSearch=yes&sts=pi
But that's not a very good image of it... so here's an Orion brand (which happens to be more expensive but I'll link it because you can get a closer look): http://www.optcorp.com/orion-t-ring-canon-eos-5224.html
LOTS of companies make these and it doesn't matter which brand you buy or which scope you have... the T-ring concept is universal... it has the camera-specific mount on the camera facing side... and the universal t-threads on the opposite side.
Some scopes have t-threads on the end of the focus (where you'd drop in the eyepiece) and if yours does... you may be able to thread the T-ring directly onto the t-thread and attach your camera. Many scopes wont have t-threads right on the end of the focuser, so you'd get a camera nosepiece... this is a barrel that inserts just like an eyepiece would... except it has t-threads on the end so that you can thread it onto your t-ring. You then mount the nosepiece & t-ring onto the camera and insert the whole thing into your telescope... in the same way you'd insert an eyepiece onto the telescope.
They do make 2" nosepieces and 1.25" nosepieces (that's the diameter... not the length). Either will work with a camera that has an APS-C size sensor like your T1i. The 2" is, of course, intended for scopes that can accept 2" eyepieces. Cameras with large sensor can get vignetting in the corners but an APS-C size sensor should not get vignetting even with the 1.25" size.
Here's a link to a camera nosepiece (note that the nosepiece is "universal" in that it is not camera-brand/model specific.... it has industry-standard "t-threads" on the end. You then add the "t-adapter" or "t-ring" (they use this name interchangeably) and that's what gives it the camera specific mounting so that it attaches to your camera just like a lens would be attached... and the telescope becomes the lens: http://www.celestron.com/browse-shop/astronomy/astroimaging-accessories/t-rings-and-adapters/univers...
The next question is: What type of telescope do you have?
You wont have a problem with refractors or compound (catadioptric) telescopes (like a Maksutov Cassegrain or Schmidt Cassegrain type design). But Newtonian type reflectors can sometimes be a problem.
Many Newtonian type scopes have their focus travel designed for visual eyepieces. The problem with a DSLR camera is that the sensor has to be moved back a bit farther to make room for that reflex mirror to swing clear. That extra distance means the focus plane is farther back than the scope wants. As you focus "in" you'll notice th image is just starting to come to focus... but then you run out of focus travel before it is able to focus to a sharp image. Not all Newtonians have this problem. ...and some owners will "shim" the primary mirror up a few millimeters to fix the problem.
Long exposures need:
(a) an equatorial type mount (you can use an alt/az mount for exposures typically less than 30 seconds before the field rotation blurs the image too much to be useful).
(b) it needs to have a pretty decent alignment (imagers will often do a "drift alignement"). A typical alignment which is good enough for visual may result in the object just *slightly* drifting upward or downward in the field of view as the scope tracks the object (this indicates that the scope didn't have a very precise polar alignment.)
(c) for long exposures the mount needs to have decent tracking performance. Worm gears can have "periodic error" where the scope seems to slightly speed up and slow down throughout the rotation of the gear -- and that will blur the object you're trying to image. I try to insert my camera so that "north is up" relative to my field of view (e.g. which direction would I need to go in the image to find Polaris)... because that way I can tell if my image is bluring on the right ascension axis (which usually means it's a tracking error) or if it's drifting along the declination axis (which usually means it's an alignment error -- alignment errors are easier to fix.)
Even with a decent mount ... if the exposure time is long enough you may need to use an auto-guider. The auto-guider can either be off-axis (through the same telescope as the imaging camera) *or* it can be in a separate telescope (piggy-backed on the first). The guider takes frequent images (e.g. once every couple of seconds... rather than a single image that takes several minutes to expose). As it does this, it notes if the selected guide star appears on the same pixel in the image in every frame. If it notices the star is drifting, it will send a corrective movement command to the mount to keep it on track. Commonly a mount intended for imaging will have an autoguider port. The standard is VERY simple... it's a 5-pin port. One pin is "ground" and the other four pins are "up", "down", "left", and "right"... and that's all it does is send little pulses to the mount.
I suspect that your EQ2 mount (I'm thinking you are referring to the Orion EQ2 and motor drive) is not going to provide ideal tracking for long exposures and you may have to shorten your exposures times to avoid blur. But this also depends on the focal length of your scope. The higher the focal length, the narrower the field of view and the more noticeable a tracking error will be. It's easier to work at low power and wider field of view because the error may not be enough to be noticeable. But do pay careful attention to how you align the camera... so that when you get non-round stars in your image you'll need to know if they are elongated along the declination axis or the RA axis (because it's a different fix depending on which way it's blurring.)
I went through two mounts (and much frustration) and ultimately caved and bought a MUCH better mount than the previous two. I now use a Losmandy G11 mount with the Gemini II system (that's their "go to" computer... but you can use their mounts without the Gemini and they are still motorized and can be auto-guided).
My first mount was a Celestron CG-5 mount (now discontinued and replaced by the Celestron Advanced VX mount (sometimes just abbreviated "AVX") which is a bit better than the CG-5. I then "upgraded" to a Meade LX-80 mount. I have to put "upgraded" in quotation marks because I was happier when I had the CG-5 mount (the LX-80 was not suitable for imaging... tracking performance was surprisingly poor.)
Wide field images are less fussy about precise tracking than narrow field images.
Bright objects take less time to expose than dim objects.
That means that narrow-field images of dim objects are VERY fussy about tracking AND require long exposure times -- making this the most difficult. But wide-field / low-power images of bright objects are not as fussy and don't require long exposures... making this the easiest type of image.
The moon is very easy and the exposure times is very fast. At f/11 the exposure for the moon is the inverse of the ISO setting... so at ISO 100, the moon is 1/100th sec exposure. At ISO 200 it's 1/200th, etc. (But remember that's at f/11... you have to know the focal ratio of your scope. If your scope is closer to f/8 then double the shutter speed (use 1/200th at ISO 100). If your scope is closer to f/5.6 then quadruple your shutter speed (1/400th at ISO 100).
Planets are slightly more difficult... but still on the relatively easy side. But these are so much tinier than the moon that any distortion is more obvious. To image these, you usually take many exposures (and usually it's a few hundred frames of video... which your T1i can do for you) and then you use "stacking" software. Registax is popular (and free) for processing planetary images.
Deep space "faint fuzzy" objects are hard because they require exposures that are usually many minutes long (4 mins.. 8 mins... 15 mins... etc.).
12-26-2014 05:47 AM
I already have the T-Ring and T-Adapter, however I haven't been able to achieve focus using both yet. I have a Newtonian telescope which I know is not made for AP. What I was able to do though is unscrew the lens tip from my 3X Barlow and screw it on to my T-Adapter and I was able to get the moon to come into focus. I am still in the process of trying to figure something out to achieve focus with just the camera and the T-Ring. The next thing I will try is attaching my camera with the T-Ring to the focuser and see if I can get focus that way.
12-26-2014 04:35 PM
This is a somewhat classic problem when using Newtonian reflectors. You should notice that it's only starting to get more focused as you rack the focus travel all the way inward.
A 2x barlow will help (because that pushes the focus distance back... but of course it's changing the effective focal length and focal ratio of your scope and you end up with a much narrower field of view.
I do know of some telescope owners who had to shim up the primary mirror at the bottom of the scope to fix the problem. You'd do this just *barely* enough to get the camera to achieve focus. If you go too far then the camera achieves focus but regular eyepieces wont achieve focus.