Couple of Close ups of the LMC - The Tarantula and Dragon's Face Nebulae regions.

[MarsG76]

Greetings Astronomers,

After imaging a wide field of the Large Magellanic cloud at 150mm FL...

... I imaged a couple of close ups of the more interesting regions of our Satellite galaxy... the Tarantula nebula and the Dragon's Face nebula.

Both of these photos are imaged with the C8 at f6.3 (Hirsch focal reducer/flattener) with a QHY268M. The first image was a SHO narrowband image of the Tarantula Nebula region, total integration time 12 hours and 35 minutes.

The second image was a result of not being anywhere happy to the "flat" field quality I am getting with the FR... the stars at the edges are ugly and I have to crop a lot of the frame to have a sort of acceptable result... but even than the field curvature is obvious.
When I try to research the reason, I find explanations like that the FR light path is too narrow for a true flat field with a APS-C sensor size, even when my back focus is set at around the (recommended) 105mm distance (testing the sensor further and closer didn't help)... using 1.25" filters probably isn't helping either... but I wanted to try and exhaust all possibilities before giving up... but also was not keen on losing any of the few and far between clear nights for this so I accepted that cropping it will remain for a while.
A long story/short is that I had a clear night but of particularly poor seeing, so imaging was not going to result in any quality images and so that night was spent on setting up the FR in a "out of the box" kind of thinking... and on that nights 180 second test subs, the (bloated) stars were round all of the way to the edges... but thats a story for another post in the "equipment" section.

I imaged the "Dragon's Face" region during the next clear night of decent seeing in HOO, total integration time of 5 hours and 10 minutes, and the stars were indeed closer to a flat field than previously, although there is still room for improvement... vignetting still has to be dealt with as flat frames don't completely remove it but the stars are still a lot better.

Sorry for the novel, thanks for looking and clear skies,

Mariusz

[tooth_dr]

Some fabulous objects that we never get to see up here!

The second one has some seriously nice detail in the middle, but the outer edges seem to be badly out of focus?  If that the FR or inherent in the telescope or from using too small filters? 

[symmetal]

Great images Mariusz. You're lucky having some spectacular dwarf galaxies visible in the Southern Hemisphere. 😃  You need to be quick to image it though as it'll merge with the Milky Way in a few billion years and lose its identity. 😛

Alan

[MarsG76]

10 minutes ago, tooth_dr said:

Some fabulous objects that we never get to see up here!

The second one has some seriously nice detail in the middle, but the outer edges seem to be badly out of focus?  If that the FR or inherent in the telescope or from using too small filters? 

The bottom image is the one (first imaged taken) before the back spacing tweek... both images are imaged with exactly the same equipment... and my small filters do not help the vignetting side, but if I can achieve a perfectly flat field.. ie nail the perfect back focus than cropping out the 5% around the edges is not much of a loss.
As you can see, the top image is better at the edges even though the bottom image was more severely cropped... I believe that a perfectly flat field is possible but requires a bit of trial and error... but I feel that I'm close. Theres also that tilt... although I'm suspecting the plastic shims with that problem....

Edited November 29, 2022 by MarsG76

[MarsG76]

2 minutes ago, symmetal said:

Great images Mariusz. You're lucky having some spectacular dwarf galaxies visible in the Southern Hemisphere. 😃  You need to be quick to image it though as it'll merge with the Milky Way in a few billion years and lose its identity. 😛

Alan

Yeah, I know.. sometimes it feels like the clouds are going to collide with the corrector plate and I'm imaging as fast as I can... currently I'm limited only by the speed of clouds but occasionally can accelerate to the photonic boost.