Mercury traversing the sun

[Alan Greene]

I got up early this morning to capture the sun rising with Mercury, but the fog thwarted my plans. The sky cleared up after a few hours, and I was able to capture this. Mercury is the dark spot in the upper-middle section of the sun.

Shot on RED Gemini with a 300mm RED Pro Prime. I used a solar filter for my binoculars that I got for the eclipse, and just cut it to fit in the filter tray inside the RPP. (The focus is as good as I could get it. I wouldn't mind having a 2:1 or 4:1 option on the display.) Click for the full frame.



It was pretty incredible to witness this. For anyone who hasn't seen it, Sunshine (Danny Boyle, 2007) features a scene of Mercury traversing the sun, and it is absolutely sublime.

[David Rasberry]

Sublime indeed. Be nice to see the uncompressed version. Nice shot.
What did you use for a solar filter?

[Karim D. Ghantous]

Very cool. I'm always up for astrophotography!

It shows that in many situations, it is the larger sensors which are limiting. Imaging trying to get this shot with Monstro. You'd need an ever longer lens. Or could extract a window from the frame but in that case why are you using a Monstro in the first place? Those who say that small sensors are limiting, while large sensors are the solution we have been waiting for, are very much armchair philosophers.

[Alan Greene]

Sublime indeed. Be nice to see the uncompressed version. Nice shot.
What did you use for a solar filter?

Thanks, David! Here's a TIFF for you: https://www.dropbox.com/s/ydxagbhfnt...cury.tiff?dl=0

As for the filter, I used one of the black polymer filters you see here: https://www.rainbowsymphony.com/solar-filters

I had bought it for the eclipse a couple of years ago, and just cut it to fit inside the filter tray in the lens. Worked like a charm! I'm wondering if the fact that it wasn't perfectly flat has something to do with me not being able to nail the focus, but I may have also just missed the mark.

[Alan Greene]

Imaging trying to get this shot with Monstro. You'd need an ever longer lens. Or could extract a window from the frame but in that case why are you using a Monstro in the first place?

I hadn't thought of that, but perhaps you're right. Still, there are reasons for using Monstro beyond its sheer size, right? If its dynamic range is beyond that of Gemini, I wouldn't have minded trying it out. Next time!

[Jeff Kilgroe]

The pixel size on Gemini is 6um (0.006mm) square. On Monstro the pixels are 5um square. In a nutshell, Gemini pixels are 20% larger in each direction, or what amounts to a 44% increase in pixel density going to Monstro from Gemini.

While it's true you would need a longer lens to get the same FOV on Monstro as you do on Gemini, if you shot with the same focal length (300mm in this case) and crop an area that is the same size as Gemini out of the Monstro frame, you get the same FOV with more detail. Given that the Gemini sensor is 30.72 x 16.2 mm in size and has 5120x2700 resolution, if you were to do a crop of the same size of the Monstro sensor, you get a 6K frame or 6144x3240 in the same 30.72 x 16.2 mm area. Sorry that became a bit redundant with restating it, but I put numbers to it.


Monstro is 40.96 x 21.6 mm 8K (8129x4320). And for what it's worth, the 300mm RPP almost covers except for slight corner vignette since it projects a 42.8mm image circle. Of course, you gain the larger FOV using the whole sensor.

Cool shot, BTW.

[Alan Greene]

Great explanation, Jeff. Thank you! I'm glad you know the image circle, as I couldn't find the info either on Phil's site or with Duclos.

[David Rasberry]

Thanks, David! Here's a TIFF for you: https://www.dropbox.com/s/ydxagbhfnt...cury.tiff?dl=0

As for the filter, I used one of the black polymer filters you see here: https://www.rainbowsymphony.com/solar-filters

I had bought it for the eclipse a couple of years ago, and just cut it to fit inside the filter tray in the lens. Worked like a charm! I'm wondering if the fact that it wasn't perfectly flat has something to do with me not being able to nail the focus, but I may have also just missed the mark.

Thanks!

I bought 8x10 sheets of solar filter film for the eclipse. Cut it and snapped it into a 4x4 plastic filter frame. Shot it with an Angenieux 12-240 on the Bolex. Miscalculated the time and ran out of SSD space about 5 minutes before the peak.

[Karim D. Ghantous]

The pixel size on Gemini is 6um (0.006mm) square. On Monstro the pixels are 5um square. In a nutshell, Gemini pixels are 20% larger in each direction, or what amounts to a 44% increase in pixel density going to Monstro from Gemini.

I didn't realize. :-) Maybe the Helium would be the best sensor for this kind of thing.

My theory about sensor size is that the narrower the AOV you want, the smaller the sensor should be. Look at the Olympus 300mm vs the Sony 600mm, for instance. Or look at the Micro 4/3 tele zooms vs the SLR equivalents. Sony E and FE cameras, however, are sometimes smaller than the Micro 4/3 cameras for the shorter focal lengths (I wrote a blog post about that), although those specs don't always tell the whole story.