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Archive 2013 · Opinions on changes of my line of telephotos?

  
 
SunBlack
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p.1 #1 · p.1 #1 · Opinions on changes of my line of telephotos?


I have a Canon 5D mkIII. I have a Nikon 300/2.8 AFS II and a Nikon 180/2.8 . Use: astronomy. I use the 180mm medium star fields, and the 300m for tiny galaxies too (where it is very important to the resolving power of the lens to center field and in this case stop to f3.5 or f4).
I would sell both and buy one of:
Canon 200/1.8 used + 1.4x used (that would be multiplied f2.5 w.o., and I would use it to f3.5 or f4 as said above)
Nikon 200/2 VR used + 1.4x used (that would be multiplied f2.5 w.o., and I would use it to f3.5 or f4 as said above)

I give up (since the use of the TC I would lose too much, even if stop to f3.5 or f4) or would it be a viable solution? better Canon or Nikon?



May 08, 2013 at 11:32 AM
cameron12x
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p.1 #2 · p.1 #2 · Opinions on changes of my line of telephotos?


I'd personally LOVE to have the Canon 200mm f/1.8 lens with a 5D3 body!

For now I use a Canon 400mm f/5.6 and a 5D2 for astrophotography.

If you have a nice budget, also consider the Canon 400mm f/4 DO lens and the 400mm f/2.8 lens for serious astrophotography (among other subjects, too).



May 08, 2013 at 12:03 PM
SunBlack
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p.1 #3 · p.1 #3 · Opinions on changes of my line of telephotos?


Uhm...tried to find a canon 400mm II (non IS) but not found, at least a reasonable price.


May 08, 2013 at 12:05 PM
Scott Stoness
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p.1 #4 · p.1 #4 · Opinions on changes of my line of telephotos?


Very interesting post - I am trying to do astrophotography with a 700mm reflector but I have a 200 2.8 v1 and a 500 f4 v1 and a 600 f4 v2 and was planning to try these lens on my tracking legs.

The only thing I will contribute because I don't know this answer but would like to understand is:
1) The digital picture images http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=432&Camera=9&Sample=0&FLI=0&API=2&LensComp=648&CameraComp=614&SampleComp=0&FLIComp=0&APIComp=2 suggest that the nikon and canon are close but Nikon looks a bit better to me visually at f2.8
2) Photozone.de has a link to http://www.photozone.de/nikon_ff/499-nikkorafs200f2vrff?start=1 which shows very high resolution to the nikon at f2 increasing a bit at f2.8 which is favorable to this lens. It also shows a bit of gain at f4 but not much and surprising good resolution at f2. It does not have a similar test for the canon.
3) The d800 is likely to do better than the 5diii is money is no object since it achieves more resolution because of higher pixels.

So if money is not object why not d800e and Nikkor AF-S 200mm f/2 G ED VR (FX) since you already have the nikon stuff.



I am sure the canon is pretty good too but sometimes low fstop does not mean that its as sharp stopped down with something less fast.

On that note, photozone.de shows that the canon 70-200 at 200 f2.8 v2 is pretty good too - not as sharp at centre as the nikon stopped down but pretty close- http://www.photozone.de/canon_eos_ff/510-canon_70200_2is28?start=1 Visually on the digital picture, the 70-200 is about the same at f2.8 as the nikon. http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=432&Camera=9&Sample=0&FLI=0&API=2&LensComp=648&CameraComp=614&SampleComp=0&FLIComp=0&APIComp=2 The 70-200 is a pretty good lens for other uses as well. And 70-200 2.8 v1 at 200 f2.8 is not much ( but a bit worse) different which you can pick up pretty cheap.

Another lens that is pretty good is the canon 300 f4. Relatively inexpensive (<$2000) and great Iq. The Canon 300 f4 is better than the Nikon 70-200 with 1.4x. But f4. Less than $2000 .http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=111&Camera=453&Sample=0&FLI=0&API=0&LensComp=648&CameraComp=614&SampleComp=0&FLIComp=1&APIComp=3

[In re-reading your post, if you are going to put a 1.4x on the lens to get it close to 300mm, why not just buy a Canon 300 2.8 v1 - it will do better than the 200 with 1.4x. And based on your description, I think you need a 500 or 600 ideally for small galaxies. A 400 2.8 v1 would be $6000 or so but a great tool ideal. The non IS version of this lens might be $4500]


Scott






May 08, 2013 at 06:29 PM
SunBlack
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p.1 #5 · p.1 #5 · Opinions on changes of my line of telephotos?


Well i think i give up to my idea, i saw results on digital picture for the my 300mm + 1.4x and the 200mm VR + 1.4x . Too loss of sharpeness even w.o.
Since it is not urgent, i'll be on the market for a 400mm f2.8.



May 09, 2013 at 01:48 AM
Scott Stoness
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p.1 #6 · p.1 #6 · Opinions on changes of my line of telephotos?


Sunblack: I have done some math prior and concluded that adromedra galaxy would be best at about 600mm with 5diii. My thinking is that you want the galaxy to fill about 2/3 or more of the sensor to keep the quality up and to permit a little bit of drift that can be corrected with alignment and stacking. This is the biggest galaxy availalbe.

Is my math wrong or are you just planning to do lots of cropping on 400 for any other galaxies which would be smaller.

In which case would you not want a 600 f4 and a idiv eg. 780 equivalent? Eg. is 400 mm the right lens? Can you share a galaxy picture you have currently taken and the amount of cropping you have done.

The v2's take to the 1.4x's much better than the v1's. So 400 v2 might be worth saving for.

Scott



May 09, 2013 at 07:44 AM
SunBlack
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p.1 #7 · p.1 #7 · Opinions on changes of my line of telephotos?


Scott Stoness wrote:
Can you share a galaxy picture you have currently taken and the amount of cropping you have done.
http://forum.astrofili.org/viewtopic.php?f=5&t=79902 use google translator.



May 09, 2013 at 07:57 AM
StarNut
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p.1 #8 · p.1 #8 · Opinions on changes of my line of telephotos?


The routine astrograph for serious and well-heeled astrophotographers for galaxy work is a 40cm f/8 telescope (3200mm focal length, more or less).

Anything you do with a few hundred millimeters of focal length isn't going to be "high resolution" by any standards. There are only three galaxies visible from earth that take well to short focal length imaging--the Large Magellanic Cloud, the Small Magellanic Cloud, and M31/Andromeda galaxy. There are a few others that will show up ok with fairly short focal lengths, like M81; but they won't be high resolution.

Short focal lengths can work well for large nebulae/star fields, though.

What focal length you would want to use would be a function of the size of your camera's chip, and the apparent size of the target you want to image. Only you can decide that.

Mark



May 09, 2013 at 08:34 AM
Scott Stoness
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p.1 #9 · p.1 #9 · Opinions on changes of my line of telephotos?


Thanks SunBlack. Says - Canon 5D mkIII mod + Nikon 300/2.8 @ f/4 26x2m15s 1600iso, crop. NGC 4517 is about 2m15s which is about 1% of adromeda if I understand it right.

At that size, the picture is not going to be great because you will be looking at a very tiny part of your sensor display. To get it to fill the screen it would be a 99% crop or so, if I understand it.

I am impressed that you could even find the galaxy because its so small. But until I get better, I am going to work on the bigger galaxies.

Thanks Scott



May 09, 2013 at 08:44 AM
SunBlack
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p.1 #10 · p.1 #10 · Opinions on changes of my line of telephotos?


@ StarNut: never said i want to do "hires" DSO!

@ Scott Stoness: 2m15s is exp. time.



May 09, 2013 at 09:55 AM
Scott Stoness
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p.1 #11 · p.1 #11 · Opinions on changes of my line of telephotos?


Also known as
UGC 8411
DSO Type
Galaxy
Sub-class
SBc - Barred Spiral
Right Ascension
13h 22m 54s13.38169956
Declination
28º 19' 00''28.31669998
Constellation
CVN - Canes Venatici
Apparent Magnitude
13.20
Apparent Size
2.2' x 1'132.0000
Surface Brightness
22.95

I was coincidently right about the size - very small about 1% of size of Adromedra.



May 09, 2013 at 12:08 PM
SunBlack
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p.1 #12 · p.1 #12 · Opinions on changes of my line of telephotos?


Not exactly, i imagined NGC 4437 aka NGC 4517, u wrote about NGC 4517A.
Type of object: Galaxy
RA (J2000.0): 12h 32m 45.6s
Dec (J2000.0): +0° 06' 56"
B Magnitude: 11.2
V Magnitude: 10.5
Size: 10.5'x1.5'
Position angle: 83°
Classification: Sc



May 09, 2013 at 12:18 PM
Scott Stoness
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p.1 #13 · p.1 #13 · Opinions on changes of my line of telephotos?


StarNut wrote:
The routine astrograph for serious and well-heeled astrophotographers for galaxy work is a 40cm f/8 telescope (3200mm focal length, more or less).

Anything you do with a few hundred millimeters of focal length isn't going to be "high resolution" by any standards. There are only three galaxies visible from earth that take well to short focal length imaging--the Large Magellanic Cloud, the Small Magellanic Cloud, and M31/Andromeda galaxy. There are a few others that will show up ok with fairly short focal lengths, like M81; but they won't be high resolution.

Short focal lengths can work well for large nebulae/star fields, though.

What
...Show more

I did some calculating and googling:
For the moon to fill the sensor you would need about 2500mm lens. http://apod.nasa.gov/apod/ap061228.html
Assuming you want a compositin with 1/3 space empty around moon = 1700mm
Adromedra as an example is 6x bigger than moon in apparent size = 277mm (300mm)
Using a crop sensor = 173mm (200mm)

If you wanted to shoot NGC 4517 with good resolution, which is 1/10 the size of adromedra, you would need a 2000mm lens on a crop camera.

So:
1) There are only about 3 galaxies that you could do a good job with - with a 200mm on crop
2) And perhaps 10 more (guessing) if you have 600mm

Anyone see problems with my logic.

Scott



May 09, 2013 at 01:17 PM
StarNut
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p.1 #14 · p.1 #14 · Opinions on changes of my line of telephotos?


Scott Stoness wrote:
I did some calculating and googling:
For the moon to fill the sensor you would need about 2500mm lens. http://apod.nasa.gov/apod/ap061228.html
Assuming you want a compositin with 1/3 space empty around moon = 1700mm
Adromedra as an example is 6x bigger than moon in apparent size = 277mm (300mm)
Using a crop sensor = 173mm (200mm)

If you wanted to shoot NGC 4517 with good resolution, which is 1/10 the size of adromedra, you would need a 2000mm lens on a crop camera.

So:
1) There are only about 3 galaxies that you could do a good job with - with a 200mm on crop
2) And perhaps
...Show more

Your math seems fine, but keep in mind that "resolution" is arcseconds per pixel, not the amount of the sensor that's covered. For instance, using the same lens, you'll get much more resolution with a 7D than with a 10D (assuming your mount, guiding and stillness of the air conspire to allow you to maximize the resolution).

Like I said, you're going to be some combination of frustrated and disappointed if you limit your shooting to galaxies, since there are so few galaxies (especially in the northern sky) which have an apparent size sufficient for significant detail with short focal length. Broaden your scope (pun intended) to include nebulae, and you'll have a lot more fun.

Mark



May 09, 2013 at 02:00 PM
Pixel Perfect
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p.1 #15 · p.1 #15 · Opinions on changes of my line of telephotos?


Very simple rule that works well, 1mm on the sensor for 100mm of FL. Want to fill a 24mm sensor (vertically), then 2400mm FL required. On my 7D, 1400mm almost fills the frame vertically and you have to act fast and be set up with the moon not entirely in frame and then wait for it to come completely into the FOV to take the shot, as it's moving fast at that magnification.


May 09, 2013 at 05:51 PM





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