Details Canon 5DH with 300mm F2.8L @ F2.8,LPR filter, in cam NR on,ISO 800 30X120 sec, Raw to 16b Tiff, stacked with Registar, levels etc in Photoshop, GradientXTerminator to remove vignetting. FOV 6.87X4.58 deg.
It was difficult to process because of the vignetting but I think I am nearly on top of it.
Might try again tonight at a lower ISO.
The quality of this lens never ceases to amaze me especially when in very good focus.
The original jpg is 11mb !
Here is another one with better framing. Done last night 28/02/06.
Details
Canon 5DH with 300mm F2.8L @ F2.8,LPR filter, in cam NR on,ISO 800, 30X120 sec, Raw to 16b Tiff, stacked with Registar, levels etc in Photoshop, GradientXTerminator to remove vignetting. FOV 6.87X4.58 deg.
This image is from the same data as the earlier image in this thread. The the data was processed with ImagesPlus and RegiStar. I also used a little Richardson Lucy 3x3 for 10 cycles Gaussian.
No Mike, it is a Canon 300mm F2.8L, and has a perfect (artificially grown) multi coated Fluorite element as well as two ED elements (lenses) plus many more. The front element is an optical flat, so when it gets scratched or damaged it is much cheaper to replace than an expensive objective lens.The Fluorite element is in a hermetically sealed (O rings) nitrogen atmosphere as Fluorite is slightly hygroscopic. If Fluorite absorbs moisture it goes cloudy. It costs a packet but it performs as well as it's exhorbitant price.. Just zoom in to any level there is no CA. Also the MTF on this lens is close to 100% to 15 or 20 mm off axis at F2.8!
You can see some secondary astigmatism and aberrations only on the brightest stars near the corners. Check out the the dimmer stars at the corners. No CA or astigmatism!
Yes great image, and youre right, these flourite lenses are amazing, they almost seem to defy the laws of physics regarding fast lenses and abberations. Im getting more used to focussing yours now too, I take a short 5 or 10 sec shot at large Jpeg setting (for quick loading), zoom in, check star sizes, move focus slightly, and repeat, if images larger I move the opposite way twice as far and within a few mins manage to home in to a fairly accurate focus.
Scott
No Mike, it is a Canon 300mm F2.8L, and has a perfect (artificially grown) multi coated Fluorite element as well as two ED elements (lenses) plus many more. The front element is an optical flat, so when it gets scratched or damaged it is much cheaper to replace than an expensive objective lens.The Fluorite element is in a hermetically sealed (O rings) nitrogen atmosphere as Fluorite is slightly hygroscopic. If Fluorite absorbs moisture it goes cloudy. It costs a packet but it performs as well as it's exhorbitant price.. Just zoom in to any level there is no CA. Also the MTF on this lens is close to 100% to 15 or 20 mm off axis at F2.8!
You can see some secondary astigmatism and aberrations only on the brightest stars near the corners. Check out the the dimmer stars at the corners. No CA or astigmatism!
Bert
Is the lens an auto focus type or could it be adapted to a CCD camera?
Yes it is autofocus and only works on a Canon EOS Camera. But we do have an earlier version which is fully manual which is almost as good.It was made twenty years plus ago and in still pristine condition optically. For full story do a search on my posts. Also see tornado33's latest post today. It is currently with Tornado33 and you would have to see him if you would like to try it as he has it on extended loan.
They are extremely rare but now and again the turn up on ebay. The one I bought cost $2K+ Aus. by the time customs had their %. It is the only early lens of a high enough quality. All other early telephotos dont use Fluorite elements and it shows as chromatic aberration. They are fine for low contrast but fail miserably with stars.
I originally bought it with the idea of putting an Astro cooled CCD camera on it. It should be a superb combination for deep wide fields. Especially H alpha.
Howdy Bert, gee I didnt know those facts about Flourite, no wonder these types of lenses are expensive.
Your shot is great especially as it covers so much area, my cameras 2/3 size chip cant get as much in. Youve even fitted in ngc3576 and ngc3603 at top right corner.
Whats focussing your newer 300mm lens like? With your manual one the trial and error method of shooting short exposures then zooming in to see the star sizes works well, moving the focus a few mm 1 then checking again, before too long I have pretty good focus. I have camera set to large jpeg when doing this for faster loading and better image on the lcd screen as shooting raw with my camera uses medium jpeg to display with not large, and takes longer to load anyway (just remember to set it back to raw for the actual imaging).
Scott
It is very difficult to get exact focus. I use a Canon Angle Finder C. It has mags of 1.2X and 2.4X and use 2.4X. Even then it is difficult as even a bright star still looks close to a point at focus and it is easy to be just slightly off. Trial and error seems to work by taking test shots as you do. I have tried a stepping motor and a toothed rubber belt and that was repeatable. Trouble is the night ends up chasing focus If there is too much temperature variation (summer). The only good thing is when you get perfect focus it is obvious.
very nice and sharp.
