This image isn't just first light for my new lens.
It's taken in memory of my beloved old Thoroughbred gelding "Bundy", who was put to sleep this afternoon. He now rests along side other well loved horses in my friends paddock.
Bundy never bit (unless he had to) never kicked (unless you got in the way) and could be trusted with the smallest of children on his back. He was cunning, vengeful and had a wicked sense of humour, locking me in the feed shed once, and another time rolling his feed bin to the far side of 40 acres just because I had the audacity to worm him. Such a character.
Anyways.....
Taken with my new Tamron 90mm F2.8, stopped down to 4.5
Canon 20d
1hr and 22 min worth of 2 min subs @ iso400 unguided
Processed using DeepSkyStacker
Photoshop CS3
Excellent images, both of them :-)
Yes, animals are family sometimes...
Re Orion image, could you post the 1:1 sized crops from corners? Just to see how this lens cope with CA and coma.
My tests with 200mm Tamron F2.8 revealed it is not worse than 200mm Canon FD (at F4 and external diaphragm .. and for 1/5 of the price.. for astro photography only, of course)
Excellent images, both of them :-)
Yes, animals are family sometimes...
Re Orion image, could you post the 1:1 sized crops from corners? Just to see how this lens cope with CA and coma.
My tests with 200mm Tamron F2.8 revealed it is not worse than 200mm Canon FD (at F4 and external diaphragm .. and for 1/5 of the price.. for astro photography only, of course)
As requested.
I've taken these straight off the DSS autosave file. No processing.
As requested.
I've taken these straight off the DSS autosave file. No processing.
JJJ, thank you
It looks very good, very very little coma and just a hint of CA, very good buy. If stopped down to 5.6 it will be perfect .
Also, try it with external F5.6 mask when you find some time (simply cut it out from black cardboard, opening diameter should be ~16mm).
I just obtained Canon 100mm F2.8 from ebay, and I would like to compare them (it is fitted with EOS adapter already, still need to adjust focus stops to reach infinity).
No...
I found out that both of my 200mm lenses (Canon 200mm and Tamron 200mm) show disastrous lateral chromatic aberration at corners, while a much simpler russian-made 133mm Tair -11A does not (but it shows more coma).
One of the differences between the designs was the position of iris:
Tair has iris immediately after the front element (it is almost 45mm in diameter when opened - large and most likely expensive, 24 blades) and both Canon and Tamron have much smaller iris (8 blades, 20mm dia or so), deep inside...
So I decided to keep the internal iris at max opening, and added the diaphragm or aperture (F5.6) in front of the lense(s) and try again.
The reduction of chromatic aberration was dramatic (it is almost non-existent with this arrangement).
See here: http://www.iceinspace.com.au/forum/s...ad.php?t=51866
and here:http://www.iceinspace.com.au/forum/s...ad.php?t=57870
This arrangement also removed pretty ugly spikes caused by 8-blades iris.. (the round opening of the external diaphragm must be as fine as possible of course.. unless you want special effects.. which I don't :-) ).
This morning I was reading Bert's post (Avandonk) and he mentioned that he is using the same trick to reduce CA (or, at least this is how I understood his remark.
In his images the spikes are non-existent, so perhaps this was his main reason for external aperture, his lens being 300mm L-series and known to be good wtr CA) http://www.iceinspace.com.au/forum/s...ad.php?t=58500
JJJ, thank you
It looks very good, very very little coma and just a hint of CA, very good buy. If stopped down to 5.6 it will be perfect .
Also, try it with external F5.6 mask when you find some time (simply cut it out from black cardboard, opening diameter should be ~16mm).
I'm yet to process Eta Carina from last night.
it was taken at f5.6, much better from what I could tell from the lcd on the back of the camera.
I'm very happy with the lens. It had been well looked after by it's previous owner.
Such a character. 
He was such a gorgeous horse too. Beautiful coat. All the best.
... hope you held up OK with the help of friends.
