You don't need a telescope

@gixxer Awesome shot

Mike6158 wrote in post #15544438
You did that with a 60Da and an Astrotrac? Astrotrac needs to pay you a sales commission. I've got a 60Da and I like it but I sure never tried anything like that

No kidding! I'm on my way to Google to check out the Astrotrac!

luigis wrote in post #15476828
Canon 60Da, 400mm F5.6 lens, Astrotrac Mount.
42 shots of 1 minute each at F6.3 ISO1600

No telescope involved!

Awesome shot!

Now, to quote you here "No telescope involved!"

What is a telescope?
IMO a light gathering device (optical tube) + a tracking device (Manual or powered, AltAz or Eq mount).

if you mounted your nice lens (optical tube) to a CGEM mount is that a telescope?

Wiki goes simpler, the optical tube itself is a telescope.......I'm sure this has been debated before, just typing away on a Wed evening after putting the kids to bed...
http://en.wikipedia.or​g/wiki/Telescope

btw, Astrotrac is on my short list to buy

mtbdudex wrote in post #15581151
Awesome shot!

Now, to quote you here "No telescope involved!"

What is a telescope?
IMO a light gathering device (optical tube) + a tracking device (Manual or powered, AltAz or Eq mount).

if you mounted your nice lens (optical tube) to a CGEM mount is that a telescope?

...

A telescope is whatever somebody calls a telescope. IMO, the primary differentiator between a telescope and a camera lens is that the telescope has provisions for putting in various eyepieces, enabling you to change the magnification, while a camera lens is intended to be attached to a camera body in order to be useful.

Also, a camera lens is highly corrected, being optimized for making the best possible image on a flat plane (the sensor). While a telescope is optimized for maximum light-gathering ability and often high magnifications, and typically gives up some field flatness and other aberrations to do it.

Obviously there is overlap when you throw adapters and converters into the mix, but I'm referring to its primary intended use. Focal length has little to do with it; a 600mm lens is a longer focal length than a friend of mine's telescope, and a 1200 Canon is longer than my brand new telescope. But nobody will call that camera lens a telescope, nor the telescope a camera lens even though you could use either one of them in the opposite way if you wanted to. They just wouldn't be optimal if you don't use them the way they're intended.

archer1960 wrote in post #15582355
A telescope is whatever somebody calls a telescope. IMO, the primary differentiator between a telescope and a camera lens is that the telescope has provisions for putting in various eyepieces, enabling you to change the magnification, while a camera lens is intended to be attached to a camera body in order to be useful.

Also, a camera lens is highly corrected, being optimized for making the best possible image on a flat plane (the sensor). While a telescope is optimized for maximum light-gathering ability and often high magnifications, and typically gives up some field flatness and other aberrations to do it.

Obviously there is overlap when you throw adapters and converters into the mix, but I'm referring to its primary intended use. Focal length has little to do with it; a 600mm lens is a longer focal length than a friend of mine's telescope, and a 1200 Canon is longer than my brand new telescope. But nobody will call that camera lens a telescope, nor the telescope a camera lens even though you could use either one of them in the opposite way if you wanted to. They just wouldn't be optimal if you don't use them the way they're intended.

To add to this statement, telescopes don't have autofocus built into the lens, they are designed to generate maximum quality images at prime apertures and long focal lengths, telephoto lenses suffer at the long end unless you have a very high end lens but even then stopping down your telephoto generally creates a better image while you do not need to stop down a telescope. Also most imaging telescopes are color corrected with many layers of lenses which is what makes them so expensive, you are paying for precision glass without all the motors stabilizers and moving parts of a camera lens.
Also dont forget they use an eyepiece.

While it's an interesting discussion, it would be nice to keep this thread full of pictures rather than text. Would you mind discussing it further in the talk section ?
Let's keep the definition simple for now - A telescope is anything that comes in a box with the word "telescope" on it.

calypsob wrote in post #15583383
To add to this statement, telescopes don't have autofocus built into the lens, they are designed to generate maximum quality images at prime apertures and long focal lengths, telephoto lenses suffer at the long end unless you have a very high end lens but even then stopping down your telephoto generally creates a better image while you do not need to stop down a telescope. Also most imaging telescopes are color corrected with many layers of lenses which is what makes them so expensive, you are paying for precision glass without all the motors stabilizers and moving parts of a camera lens.
Also dont forget they use an eyepiece.

I had mentioned the eyepiece, but neglected the aperture issue. You say that you don't need to stop down a telescope, but in fact I've never seen one where you *could* stop it down. Good point about telescopes being optimized for giving their best results at infinity focus...

To bring the pictures back to this thread, here's one I took last week and processed tonight of the Pleiades, using the 70-200/4L on a 7D at 200mm, f/4, ISO3200, and stacking 10 20-second subs, with darks and flats (my first go with flats). I processed a little in DSS, then finished in Photoshop (didn't do much), and reduced noise in Lightroom. Total exposure is 3m20s, and the limiting magnitude is 15.0. I'm really pleased with both the extent and the detail in the nebulae, my best so far.

Betelgeuse!
Canon 60D Single exposure on a tripod 5 seconds in Bulb Mode by hand with a remote Rokinon 85mm @ f1.4 iso 2500 just a bit of P.P. in Lightroom.

IMAGE LINK: http://www.flickr.com …/45984738@N03/8​459438671/

Orion Nebula
6 6 second lights 6 6 second darks canon 60D rokinon 85mm @ f1.4 iso 2600 stacked in DSS tweaked in LR

IMAGE LINK: http://www.flickr.com …/45984738@N03/8​456985081/

Madweasel wrote in post #15591838
To bring the pictures back to this thread, here's one I took last week and processed tonight of the Pleiades, using the 70-200/4L on a 7D at 200mm, f/4, ISO3200, and stacking 10 20-second subs, with darks and flats (my first go with flats). I processed a little in DSS, then finished in Photoshop (didn't do much), and reduced noise in Lightroom. Total exposure is 3m20s, and the limiting magnitude is 15.0. I'm really pleased with both the extent and the detail in the nebulae, my best so far.

Excellent work! Can't wait to use a tracking mount with my setup so the camera here is unmodded or?

Thanks Chris, yes unmodded. I like your Orion nebula picture - how many lights did you stack to get that?

EDIT: Sorry, I just reread it - I guess there were six.

Just awesome! Yes 6 6 second lights and 4 6 second darks which i think was too much i think it killed the color some yours is showing that awesome blue so good getting ready to get a good tracking mount can't wait your inspiring thanks!

This is a single light frame 30sec exp with 20D modified 200mm f/1.8 wide open, iso 800, on Astrotrac mount.