# Astrophotography - which camera?



## TrabimanUK (Apr 11, 2014)

Hi guys,

the ISS is flying over my house tonight and I really would like to get a shot or two of it. I have at my disposal a 5D2 and a 7D, a 70-200 2.8 IS2 and a tripod.

Which of the cameras should I use? Is it best to go for IQ/ISO over reach?

Many thanks,

Grant


----------



## Don Haines (Apr 11, 2014)

TrabimanUK said:


> Hi guys,
> 
> the ISS is flying over my house tonight and I really would like to get a shot or two of it. I have at my disposal a 5D2 and a 7D, a 70-200 2.8 IS2 and a tripod.
> 
> ...


Definitely reach.

Set up everything for manual.... Turn off auto focus and turn off IS for any lens you are using. Expose for the brightness of the moon.... The ISS will be about as bright... Manually adjust focus for the moon and use a couple of those rubber bands from a head of broccoli to "lock" the focus.


----------



## TrabimanUK (Apr 11, 2014)

Hi Don,

thanks - 7D it is then, and thank you for the additional advice - wouldn't have thought about using the moon for exposure.

chers,

Grant


----------



## weixing (Apr 11, 2014)

TrabimanUK said:


> Hi Don,
> 
> thanks - 7D it is then, and thank you for the additional advice - wouldn't have thought about using the moon for exposure.
> 
> ...


Hi,
I think Moon is still too bright... Last time I use Jupiter for pre-focus and exposure.

Good luck and have a nice day.


----------



## Don Haines (Apr 11, 2014)

weixing said:


> TrabimanUK said:
> 
> 
> > Hi Don,
> ...



True...

Jupiter and the ISS are similar in brightness, but hard to see without a really long lens.

I've exposed for the moon and then dropped my shutter speed by 4X for the ISS and it seems to have worked... The important thing is to not expose for the night sky...


----------



## bbasiaga (Apr 11, 2014)

ISS is tricky. It moves VERY fast sometimes and can be a bit difficult to pick up when it is first visible. I have used the 'ambush' technique, where I wait for it to pass in the camera's view and take shots in full FPS mode. 

I have also become fond of taking a star trail type shot of it. Where I set up a 10,20 or 30s exposure (depending on the transit time) and use a wider lens to capture it streaking across the frame. 

-Brian


----------



## weixing (Apr 11, 2014)

Hi,
I photograph it 2 years ago using my Canon 60D and Canon EF400mm F5.6L + Kenko 1.4x (560mm @ F/8). Pre-focus and meter using Jupiter. The ISS is very small in the image... I think SCT/MCT telescope are more suitable. 

Anyway, the attach image are from the best shots I got... all enlarge 2x... that's how small ISS is using 560mm lens. For those who interested to try, I use manual mode, shutter speed of 1/1000s and ISO 1000. The above settings is only for your reference as ISS brightness vary a lot.

Good luck and have a nice weekend ahead.


----------



## dcm (Apr 11, 2014)

TrabimanUK said:


> Hi guys,
> 
> the ISS is flying over my house tonight and I really would like to get a shot or two of it. I have at my disposal a 5D2 and a 7D, a 70-200 2.8 IS2 and a tripod.
> 
> ...



Depends on what you are trying to capture - a trail or an image of the 357'x167' ISS at 230 miles. Google "photograph ISS" for some pointers. Here's a few good articles.
http://www.universetoday.com/93588/a-beginners-guide-to-photographing-the-international-space-station-iss/
http://www.cameratechnica.com/2011/02/17/how-to-photograph-the-international-space-station/

Trails need a long exposure with a wide/normal focal length.

Images of the ISS itself is another matter. NASA has a page about it http://www.nasa.gov/mission_pages/station/expeditions/expedition30/photographing_iss.html. The ISS will be pretty small even with a long telephoto lens. Even a telescope will not give much detail - http://www.apstas.com/astrotas/Sayers/PhotographingtheISS.html 

Use the dimensional field of view calculator at http://www.tawbaware.com/maxlyons/calc.htm to determine the image dimensions. A 600mm lens on a FF camera has a 72864'x48576' field of view at 1214400', yielding an ISS image of 25px by 12px on the sensor. You would need a lens with a 120,000mm focal length to fill the frame of FF, or 75,000mm for APS-C.


----------



## jrista (Apr 12, 2014)

It's often easier to do these things in arcseconds. The ISS is ~63" (arcseconds) long. We can compute the number of arcseconds/pixel ("/px or asp) using this formula: 


```
(206.265 / focalLength mm) * pixelPitch µm
```

For the 7D and a 200mm lens, our asp is _*(206.265/200mm)*4.3 = 4.43asp*_. For the 5D II and a 200mm lens it's _*(206.265/200)*6.4 = 6.6asp*_. If we take the 63" length of the ISS, and divide it by our sensors arceconds/pixel ratio, we get ~14px for the 7D and ~9.54px for the 5D II. 

Now you can slap on teleconverters to get longer focal length. The 7D will suffer from the effects of diffraction and less lignt sooner, meaning the 5D II will then be more capable of using a longer focal length with a teleconverter, or for that matter stacking teleconverters (you can stack in a number of ways...2x III + 1.4x Kenko, 2x III + 25mm ext tube + 2x TC III, etc.) Let's say you use a 2x TC on the 7D and two 2x TC's on the 5D III. The 7D and 5D II are going to be producing roughly the same noise, and diffraction softening will be roughly equal (slightly more on the 5D II):

7D: (202.265/400)*4.3 = ~2.2asp
5D II: (202.265/800)*6.4 = ~1.1asp

We have a roughly equivalent IQ case here (similar amount of noise), but a much longer focal length on the 5D II. The ISS is 28px large on the 7D, but 57px large on the 5D II. Since we are talking about highly collimated light, all you need to do really is manually focus in the stars or the moon...so you could, theoretically, stack as many teleconverters as you think your pixels will handle. The larger pixels of the 5D II will handle more than the 7D before you start achieving similar results on both (diffraction blurring will eventually reach a point where the ISS is blurred the same mount on both if you just keep stacking TCs, and the 7D will simply be oversampling that blurry image more than the 5D II, albeit with more noise.)


----------



## dryanparker (Apr 12, 2014)

jrista said:


> It's often easier to do these things in arcseconds. The ISS is ~63" (arcseconds) long. We can compute the number of arcseconds/pixel ("/px or asp) using this formula:
> 
> 
> ```
> ...



Yes, definitely arcseconds. Couldn't agree more.

Wizardry alert.


----------



## dcm (Apr 12, 2014)

dryanparker said:


> jrista said:
> 
> 
> > It's often easier to do these things in arcseconds.
> ...



I obviously haven't made the jump into Astrophotography yet ???


----------



## jrista (Apr 12, 2014)

dcm said:


> dryanparker said:
> 
> 
> > jrista said:
> ...



Angles are easier because the sky, for all intents and purposes, is the inner curved surface of a perfect sphere, and measured in degrees for the celestial coordinate system (Right Ascension and Declination) and, therefor, arcminutes and arcseconds naturally apply.


----------



## dcm (Apr 12, 2014)

jrista said:


> dcm said:
> 
> 
> > dryanparker said:
> ...



I agree. I just wasn't sure the OP was ready for that level of discussion so I thought I'd keep it simpler. Occupational hazard - I'm an engineer and often communicate with others that don't have the same level of technical knowledge so I tend to simplify things. ;D

BTW: I'm in northern Colorado. Maybe our paths will cross someday.


----------



## KeithBreazeal (Apr 12, 2014)

Here is one of my ISS attempts:


ISS photo editing process © Keith Breazeal by Keith Breazeal Photography, on Flickr


----------



## sulla (Apr 12, 2014)

Wonderfully explained!

Conclusion: a 200mm lens is wwwwwwwway too short for the ISS. It's hopeless, meaning, that even if you capture it perfecty, you will have a hard time spotting it in the final image. And for streak images, 70 is wwwwwway too long.

So, the question is not "which camera" but rather "which lens". The answer is: No lens at all, you will need a telescope for that. So if you plan to get into astrophotography, there just is no other option than getting a telescope. Fortunately, compared to EF glass, telescopes are rather cheap. They are basically mirrors, after all.


----------



## jrista (Apr 13, 2014)

sulla said:


> Wonderfully explained!
> 
> Conclusion: a 200mm lens is wwwwwwwway too short for the ISS. It's hopeless, meaning, that even if you capture it perfecty, you will have a hard time spotting it in the final image. And for streak images, 70 is wwwwwway too long.
> 
> So, the question is not "which camera" but rather "which lens". The answer is: No lens at all, you will need a telescope for that. So if you plan to get into astrophotography, there just is no other option than getting a telescope. Fortunately, compared to EF glass, telescopes are rather cheap. They are basically mirrors, after all.



It isn't quite that simple. Most telescopes are designed for visual observing. The ones in the range of a few hundred dollars to about a thousand are not really ideal for use as "astrographs". As it actually stands, a lot of people, including myself, price Canon's telephoto EF lenses like the EF 600mm f/4 L II as telescopes due to their superb optical quality as refracting telescopes. A good refracting telescope, such as an AOP Triplet, STARTS at around $1500, and the price can reach as high as $15,000 for a very good APO quadruplet or quintuplet.

Regarding reflector-type scopes. There are some newtonian astrographs, and they tend to be the cheapest, but you are still going to spend around $1000 for one. SCTs, or Schmidt-Cassegrain Telescopes, usually start around $1500 and can reach many thousands of dollars. You usually get a lot more aperture (physical aperture) with an SCT than with a Refractor, and they are usually optically superior to Newtonians. RCs, or Ritchy-Chretiens, are also "cassegrain" type reflecting telescopes, and are generally the preferred type of OTA design for "astrographs". It is actually pretty easy to get a good quality RC astrograph for a good price. 

Specifically, the best entry-level one is the Astro-Tech 6" AT6RC, which is a 6" diameter aperture (same diameter as the EF 600mm f/4 L II lens) with an f/9 focal length (1372mm, to be exact.) If you want to get an actual telescope for doing astrophotography, and don't want to spend a lot of money, the AT6RC is only four hundred bucks:

https://www.astronomics.com/astro-tech-6-inch-ritchey-chretien-astrograph_p19910.aspx

The AT6RC will make the ISS 100 pixels in size on the 7D, without any additional accessories. If you slap on a 2x barlow lens, then you have 2744mm of focal length, and the ISS will be 200 pixels in size. Keep in mind, if you push your focal length that much, you are going to need a VERY, VERY, VERY STABLE mount, because the smallest amount of shake will completely obliterate any detail you might otherwise resolve. You will, most likely, also want an equatorial tracking mount with the ability to use custom tracking rates other than sidereal or king, and the only mount I know of that can do that easily (for ~cheap) is the Orion Sirius (~$1000) or Orion Atlas (~$1400), because these mounts support EQMOD (which allows you to download and utilize custom tracking rates, and there are premade profiles for known satellites and the ISS that you can simply download). You would need a tracking mount for the AT6RC strait up, let alone with a barlow.

If you want to go larger/longer, you could look at the AT8RC, which sells for about $900. You would definitely want the Orion Atlas, so the total cost of the mount + OTA at that point is around $2400, however the larger aperture will allow you to resolve MUCH finer details on the ISS than a smaller OTA (resolving power and smallest resolvable magnitude of astronomical objects, including satellites and the ISS, is directly related to the physical aperture diameter).


----------



## Don Haines (Apr 13, 2014)

sulla said:


> Wonderfully explained!
> 
> Conclusion: a 200mm lens is wwwwwwwway too short for the ISS. It's hopeless, meaning, that even if you capture it perfecty, you will have a hard time spotting it in the final image. And for streak images, 70 is wwwwwway too long.
> 
> So, the question is not "which camera" but rather "which lens". The answer is: No lens at all, you will need a telescope for that. So if you plan to get into astrophotography, there just is no other option than getting a telescope. Fortunately, compared to EF glass, telescopes are rather cheap. They are basically mirrors, after all.



I think the real question is "which tripod"... Astrophotography can be of very small objects that require LARGE telescopes, it can be of wide images like the milky way, or it can be anything in-between... but for all of them you need a decent tracking mount. I have an 8 inch telescope that I use for planetary imaging and I also mount my DSLR onto the tripod for imaging nebulas and the night skies...

If you do not have a tracking mount, you will be limited to short exposures and you will have streaks of light on them.... The tracking mount comes before any camera/lens/or telescope in your wish list.


----------

