LMC at 135mm with a DSLR

[alocky]

There was a slight break in the weather yesterday, long enough to drive out to York and get set up alongside Barry and his 28". Although it looked promising initially, clouds kept forming above and there were very few patches long enough to get a decent image.
Despite this, I was determined to see what the Zeiss Sonnar 135mm APO could do on the D810A. This is a stack of 39 of the least cloud affected 1 minute exposures at f2.0. And as far as I can tell this lens has no faults at all.
A higher res version is here:
http://www.astrobin.com/full/235968/0/
processing includes calibration, stacking and a quick levels stretch followed by a curves transformation in PI.
I can't remember the last time I got a cloud, haze or smoke-free night here, but of course my problems are trivial compared to the folks in the SW of the state who are really doing it tough right now.
cheers,
Andrew.

[batema]

Beautiful shot. I'm going to have a crack at this as soon as the clouds nick off.

Mark

[Placidus]

This is so far removed from what Trish and I normally try to do that I don't usually comment, but it caught my eye.

There seems to be a super-faint outer spiral arm passing anti-clockwise through the point exactly half way toward 9 o'clock, and still in vaguest evidence exactly half way toward the bottom left corner.

Like the subtle use of colour.

Best,
Mike

[alocky]

Thanks Mark!



Thanks Mike, I saw it too, and am trying to figure out if it's an artefact of pixinsight's DBE tool. It survived a few different iterations, so it may be a robust feature, and it doesn't seem to coincide with any of the control points. Many of the subs I used have some cloud in them, so I've been fairly harsh with the rejection criteria, but, I think I can see it in one of the subs that was good. If I ever get a night free of haze or cloud I'll know for sure, and at f2 that lens sucks a lot of light, so it is just possible it dredged something subtle up in 40 minutes!
Cheers,
Andrew.

[gregbradley]

That's a fantastic image Andrew.

Greg.

[IanP]

Great shot, Andrew .. :thumbsup: :thumbsup: :thumbsup:
Big stars are perfectly fine in the centre, but further outside they look “split-in-half”; I have the same effect with 60Da and a couple of low-F Canon lenses ..
:hi:

[alocky]

Thanks Greg!


Hi Ian- I notice the bands that split the stars are more or less concentric. I also saw the same effect with the Nikon 300 PF f4 lens I tried recently. both nights were hazy - although I don't know why there would be an interference effect.

[strongmanmike]

Great shot Andrew. Im out at the observatory and only viewing on my samsung galaxy but looks to be a fine lens!

I will have a better look on the puter moniter when i get home

Mike

[raymo]

Lovely image, can I ask what ISO you used?
raymo

[RB]

Beautiful image Andrew!

RB

[RickS]

Great result, Andrew!

Cheers,
Rick.

[alocky]

Thanks Mike - I certainly appreciate your constructive comments! I'm not entirely convinced the 'spiral arm' is real though, as there's a even fainter, concentric thing visible further out at extreme stretches and I've no idea if it's background cloud or not. I will definitely have another go at this image when there are properly clear skies to check.


Thanks! ISO was 1600. It was about 20 degreesC ambient.


Thanks Andrew

Cheers Rick! It's a very minimal PI workflow, but if I ever get a good night's imaging on this I think there's a lot more in that data.

[rustigsmed]

supurb shot Andrew, I also like the subdued colour (for a change!). :thumbsup:

with regards to faint parts of the photo - there is some discussion on the fainter parts of the LMC and beyond on this thread http://www.iceinspace.com.au/forum/showthread.php?t=118775&page=2

[alocky]

Thanks Russel! I resisted the temptation to hit that saturation slider this time, as I felt it was disrespectful to the colour ;)
Thanks for linking to that other post - the arm coincides nicely with the extended features in that magnificent shot.
Cheers,
Andrew.

[strongmanmike]

Ok, home now and looking at it on a good monitor...and it still looks good :thumbsup:

As for the extra arms and patches I think most of them are real but hard to find them all appearing consistently in other wide field shots

With the limited understanding I have of PI DBE I am concerned that it might sometimes manufacture as much as it reveals when it comes to the really faint stuff..?

But a great shot regardless :thumbsup:

Mike

edit: Ah, oops, ok you didn't mention DBE..? Where did I get that from then..? Going a bit senile...:screwy: :lol:

[alocky]

Not at all - I mentioned it in my reply to the other Mike! You can set the order of polynomial it fits the background gradient, and you can also see what it is subtracting, and in this case the only potential source is a random few bits of cloud lining up in the subs.
It certainly matches the features imaged by Troy in the link Russel posted, so I'm claiming a rediscovery :D
Cheers,
Andrew

[strongmanmike]

Ah yes :face:..I knew I had read it, senile, see?



Fair enough and good for you :lol:

Mike

[multiweb]

Very nice LMC Andrew. Sharp as. Well done. :thumbsup:

[cazza132]

Nicely done Andrew! I think you may have clipped some data though (I think anyway). The lens vignettes heavily at f2.0. At f2.5 with tracking (Astrotrac), this lens is awesome! Run some flats and you may pick up some extraordinary stuff around periphery of this field.

The Zeiss 135 on a D810A - what a weapon! You are going to have fun with that setup. I am running the same lens on my full spectrum 6D with some very satisfying results.

Yes, there is some spiral action going on with the LMC. It showed up with my all sky imaging project that I completed some time ago using the full spectrum 6D + siggy 35mm f1.4. I could hardly believe the extent, and that no one has recently picked it up. I have never posted the result of the all sky, but might just do so.

Although Orion has been quite a distraction, I am having a good go again with the Zeiss 135. I am hoping to reveal this section of sky in far greater detail. Cheering for clear skies in SE QLD - something that is quite rare this time of year.

[cazza132]

Prob some context revealed here

[alocky]

Thanks Troy, I used sky flats and didn't think the vignetting was that bad. But I went out last week and repeated the exercise at f2.5 so I will compare the two. I did notice that the strange split stars in the outer parts of the image changed to a more complicated type of split at f2.5 and the stars are a little tighter.
It was your image of Orion with this lens that convinced me to donate a kidney
and get this one. :)
Cheers,
Andrew.

[cazza132]

Split stars? A form of coma? I do get some internal reflections that can be seen around the brightest stars that becomes slightly offset towards those near the frame edge - can be seen in the Orion shot.
Otherwise, I do find the lens + DSLR runs quite well on the AstroTrac. Did you do any sort of tracking? A very good result for such short subs!
I have also had strange spikes in some stars in my shots before as a result of an unclean clip in filter (Astronomic XL-Clip 'L' filter).
I'm interested to see what these star splits look like. Can you show me an example?

[alocky]

Here you go - at f2.5 the pattern changes slightly.
These were taken on a G11 guiding at arc-second precision, the main thing that limits the sub length is the Tarantula nebula!
I've since returned to the scene of the crime and taken an hours worth of 2 minute subs. No doubt about those tidal streams at all.

[cazza132]

Yes - I get the same thing! Happens at the edge of frame with brighter stars. Not something that can be easily corrected either :( An aberration that I have tolerated as all my other lenses have worse aberrations and a problem that disappears when doing mosaics.

Looking forward to seeing the version with longer subs!