Eta Carina with EOS & 400mm Telephoto

PhotonCollector (Paul) · #1 08-10-2005, 03:54 PM

Here's an image I did with my 400mm f/6.3 telephoto lens on piggybacked on the telescope.

It's three 3 minute exposures stacked @ ISO1600, 9 minutes total exposure time. I put a higher resolution version here http://www.skylab.com.au/pmsa/ngc3372d.html

Clear Skies
Paul M
http://www.skylab.com.au/pmsa

Itchy · #2 08-10-2005, 05:23 PM

I love it Paul

Lots of nebulosity, although there is considerable chromatic aberation on the edges of the frame.

Well done.

davidpretorius · #3 08-10-2005, 05:47 PM

Beautiful Paul,

i had a lovely time viewing this one the other night.

Top stuff

atalas · #4 08-10-2005, 05:58 PM

Looks great Paul ! well done.

Louie

seeker372011 (Narayan) · #5 08-10-2005, 06:53 PM

Nice to see NGC 3324 in the same frame as Eta Carina

iceman (Mike) · #6 08-10-2005, 07:41 PM

The humunculus stands out really nicely, great shot!

PhotonCollector (Paul) · #7 08-10-2005, 08:37 PM

Quote:

Originally Posted by Itchy

I love it Paul

Lots of nebulosity, although there is considerable chromatic aberation on the edges of the frame.

Well done.

There's a story about the chromatic aberation. The 400mm f/6.3 telephoto lens that I used is an old 42mm Screw Mount lens from the 1970's (thereabouts) and you can actually buy EOS adapters for these screw-fit lenses.

Using this lens a decade or two ago I had a lot of success (images were good, field was flat, no aberrations) taking 35mm SLR Film images with it (piggyback style), so it seemed like it would be a good thing to try out with the EOS SLR.

But to my surprise the EOS shows a lot of aberrations and violet fringing that was not apparent in any of the film images I did with the same lens.

Here is an example of exactly what I am talking about.

35mm FILM SLR http://www.skylab.com.au/pmsa/ngc3372a.html
DIGITAL SLR http://www.skylab.com.au/pmsa/ngc3372d.html

I still haven't convinced myself I know why the Digital SLR shows all the aberations when the Film SLR does not.

Paul M.

PhotonCollector (Paul) · #8 08-10-2005, 08:42 PM

Quote:

Originally Posted by seeker372011

Nice to see NGC 3324 in the same frame as Eta Carina

Hi,

Yes! having NGC 3324 in the same frame gives the image same scale too. Hhave a look at this image which shows N3324 much better http://www.skylab.com.au/pmsa/ngc3372a.html

Clear Skies
Paul M

PhotonCollector (Paul) · #9 08-10-2005, 08:51 PM

Quote:

Originally Posted by iceman

The humunculus stands out really nicely, great shot!

Thanks Mike

PhotonCollector (Paul) · #10 08-10-2005, 08:53 PM

Quote:

Originally Posted by davidpretorius

Beautiful Paul,

i had a lovely time viewing this one the other night.

Top stuff

I have reprocessed it just today using some new techniques. Hopefully this one is somewhat better than the one you looked at.

Clear Skies!

Itchy · #11 08-10-2005, 09:46 PM

Quote:

Originally Posted by PhotonCollector

But to my surprise the EOS shows a lot of aberrations and violet fringing that was not apparent in any of the film images I did with the same lens. ...snip...

I still haven't convinced myself I know why the Digital SLR shows all the aberations when the Film SLR does not.

Paul M.

I know what you mean. There has been several deep discussions about this on digital_astro. It appears that all the Lens manufacturers are now facing this fact: DSLRs are showing up faults in their lenses that no one noticed before on film.

Strange but true.

cheers

avandonk · #12 08-10-2005, 10:29 PM

Quote:

Originally Posted by Itchy

I know what you mean. There has been several deep discussions about this on digital_astro. It appears that all the Lens manufacturers are now facing this fact: DSLRs are showing up faults in their lenses that no one noticed before on film.

Strange but true.

cheers

No it is not strange.The demands a modern sensor places on an optic is extreme to say the least.
In the past with film how many people could zoom in to 300% of image size for a cursory examination of the image quality.
So what did everybody do? They fudged! Present the image in its best (excuse the pun) light.
You cannot beat a quality lens, and even then, if you want to be a perfectionist test several versions of the same lens.Yes there are manufacturing differences which are random.
If you want to know more just ask.
Have you also considered that with film the three colour layers are at different positions so hiding the inherent chromatic aberration?
The other thing hiding these problems is that film was formulated to represent human vision (spectrally).They have not got this quite right with digital.It can't be hidden.

Bert