TEST - Tak Sky 90 +/- 1.4x Extender: Eta Carina

[dugnsuz]

Hello all...

With an eye on this thread...
http://www.iceinspace.com.au/forum/showthread.php?t=42721

Last night I caught up with fellow SA imager CraigL for an experiment.
We wanted to see how the Canon 1.4x Extender would perform when attached to a telescope - in this case Craig's very tasty Takahashi Sky 90!



In order for the extender to work we had to cover the extender to camera electronic contact points with a thin strip of adhesive tape in order to fool the DSLR into not giving us an error message as it can't find a lens!

We noted that even with a light polution/nebula filter attached to the camera T-Ring, there was still enough clearance for the protruding portion of the extender to be accommodated.

Subject - Eta Carina under an almost full moon (98%)

We took 5x180sec exps (ICNR on) iso1600 without the extender and 5x252sec iso1600 exps with the extender in place to assess performance.

Only downside was the slightly longer time we took to achieve a good focus with the extender in place. Either side of the focus sweet spot showed obvious colour aberrations, so critical focusing is a must.

Results below should give some idea of performance/image scale etc.
Coatings/Performance of the 1.4x Ext obviously has a major effect on the colour balance of the final image.

Processing - simple Levels stretch only.

1st pic - without extender
2nd pic - with extender

Full Size High Res Versions:
Without Extender...
http://s327.photobucket.com/albums/k461/doug-robertson/?action=view&current=TESTNoExt.jpg

With Extender...
http://s327.photobucket.com/albums/k461/doug-robertson/?action=view&current=TESTWithExt.jpg

Doug:thumbsup:


ps... got to say I love Craig's scope, the data was just so easy to process!!!

[Dennis]

Hi Doug

Both photos are amazing – superb quality all round.

It looks like the non extender version has very slight coma at the extreme corners, and did I see evidence of mirror slap in the full size x1.4 extender version? The full size version looks as if it has some (very) faint double stars reminiscent of what I used to get without mirror lock up?

Great side-by-side results though and I had to pixel peep the full sized versions to notice the above stuff.

Cheers

Dennis

[AlexN]

Nice results indeed! exactly what I was hoping to see!!

I am definitely keen to give this a go with the new scope should it ever clear up outside! I really like the processing on the 1.4x image, colours look fantastic! and the false colour seems to be non-existent when properly focused.. This is something that I've noticed with the TE 1.4x with terrestrial photography... Should the focus be ever so slightly out, it would show hints of chromatic aberration on things like white birds, light reflections on water etc..

Well done mate.. Thanks for doing this test, Now I'm very very keen to get out and give it a go..

Alex.

[Craig_L]

Hey Doug,

I had a go at processing these - just stacking the images in Nebulousity and then a simple levels only in Paint Shop Pro - no sharpening or curves or any other processing. Both images are cropped to the same size so you can compare the sharpness with and without the extender better. Only low res images I'm afraid.

Also, there are only 4 lights instead of 5 in the stack with the extender as one had some movement in the frame - could be what Dennis said was mirror slap or movement from my rickety wooden balcony.

It's tough going with a full moon and 3 min subs at 1600 ISO but its is only a quick test for sharpness with and without the canon extender.

1st image without the extender.

Craig

[dugnsuz]

Nice work Craig - there's not much between them!
Suggests the 1.4x Extender would be usable on quality scopes to get a little bit extra FL.
Now what about the 2x!? Mmmmmm?
Doug

[Craig_L]

Know anyone who has one Doug? Another test - certainly would be handy for those galaxies.

[dugnsuz]

Well this whole exercise was for AlexN's benefit - so he has my old 1.4x Extender and a variety of scopes, all the way up to the GSO RC 8" scope!

Come on Alex, show us some stuff!!:P

As for a 2x - not too sure!

Doug:thumbsup::thumbsup:

[Tandum]

Neither Alex nor I will be taking our scopes outside any time soon (http://www.bom.gov.au/products/IDE00902.loop.shtml). :(

I have a new camera that needs first light :(

I'm pretty sure 4 months worth of rain is enough for anyone. Someone tell heuy to knock it off :)

[Jen]

Beautiful pics :thumbsup:

[Lester]

Good ones Doug.

[AlexN]

Robin is correct... There is no chance of us getting gear out soon to play with new toys.. between his new CCD setup, my RC, my filterwheel and various other bits and pieces bought by other S.E. QLD residents, I dare say we have more rain to come :(

[leon]

Bugger, I wanted to do that at one time Doug, but then I sold my extender to you :P to get these awesome shots, well done mate, nice work. ;)

Leon :thumbsup:

[PeterEde]

Testing my 1.4 kenko extender tonight.
Definitely great for the Moon and sun. Almost fills the frame compared to camera alone