October 08, 2008
My first true astrophotos
After a nice cloudless day the cloud cover roller in as the sun was setting. But since the forecast had promised a cloudless night, I nevertheless set up my simple telescope. And boy was it worth it. Last spring the dark nights ended before I got to test the telescope with a digital SLR, but now the T-ring adapter saw its first use. Unfortunately I hadn't really prepared for searching more than two objects, and both of those were behind a tree on Harri's backyard after a rather short while.
Thus, it was time to improvise. We looked at the planisphere to see what would be visible, and the obvious choices were M31 (the Andromeda galaxy), Plejades, M81/M82 and M57. Not having a close-up chart makes it interesting to find a small bright smudge in an upside-down view of bright spots, where you basically can't tell brightnesses apart. And of course the close-up chart would have also indicated where exactly the feature is, instead of the generic smudge on a planisphere showing it somewhere between a few stars. Thus we couldn't find M81/M82, but the Andromera galaxy, Plejades cluster and the M57 Ring nebula were found to a big surprise. More over, the M57 was found with just generic understanding that it's somewhere between the lower Lyra stars.
Full frame of the M57 nebula (scaled down to 1600x1066):
2x scaled crop of the nebula:
Unfortunately the telescope motors drive a bit inaccurately and apparently uses full steps causing rather heavy vibration rendering anything beyond 30 second exposures useless. But still, it's a lot better than without the motor drive. More pics on this are on their way to the gallery.
February 14, 2008
First flight
No, wait, 'twas supposed to be first light!
These new entries seem to be coming up with an alarming speed this year, the first quartile isn't over yet and already a second blog post. Anyhow, last night the weather was pretty clear and dark although a bit windy, so it was time to go out and see the world thru a new and inexpensive 102/1000mm refractor.
O'boy, and see I did. A bit of gazing in the gale force winds revealed a shaking disk that didn't diminish into a point, most likely Mars if I did my math and pointing correctly. I also got to see the Great Orion nebula in all the grayness of low light stargazing. And took a few shots of the moon thru the scope with a hand held camera, as my T2-rings haven't arrived yet.
With the shortest (10mm) ocular plus 2x Barlow the Moon was shaking in the wind, but the few moments of good seeing were astonishing, like hovering a few hundred km above a rolling lunar surface. No wonder people get so carried away with astronomy even as a hobby. I can hardly wait for a high pressure to park itself here and bring calm, clear and cold skies. Especially if the T2-ring would be here, so I could learn more about this thing called astrophotography. A few more skills are still on the to-learn list, such as learning the constellations and star hopping to find the dim deep sky objects with more than just random chance.
Other things that I have planned is to finally update the blog-engine from this ancient MT to something more recent, such as Wordpress or a newer version of MT. Main requirements are ease of use, easy integration with Gallery2 and possibility to update from cellphone with an MMS or e-mail.
February 13, 2006
Panoramic photography explained
When doing panoramic photography with a conventional camera, multiple, slightly-overlapping shots of the overall scene are taken by pivoting the camera in steps, and the images are joined to make a single large-scope image. In order to be able to properly join the images, we must avoid parallax shift between them. To do so, the camera must be pivoted about the camera's center of perspective, which turns out to be the center of the entrance pupil of the lens.
I finally found a good and easy to understand article about rotating (pan and tilt) the camera for panoramic photography. Many guides talk about "nodal point", and they are usually dismissed as being misguided, yet no accurate explanation is given. Sometimes somebody mentions "entrance pupil" as a side note, but offers no explanation as to what it really is.
A recommended read for all.
And btw, I have finally made one panorama available from vacation: Cueva de los Verdes in Lanzarote. It has two rows, with 12 shots each, taken on my home-brew panoramic mount on a ballhead and tripod.
January 21, 2006
Panorama structure
I was trying to figure out the math for covering a spherical panorama with a minimal amount of shots providing sufficient overlap, and realized that I had a tool nearly perfectly made for this: Povray.
The sphericalpano.zip contains three files for povray, but you only need to edit the panostructure.inc that defines the lens focal length, camera sensor dimensions and how you are planning to shoot the panorama. The panosim.ini contains povray settings for input, output and quality, and panosim.pov contains the scene construction. To run, just execute povray panosim.ini and look at the results. If you can see any black or if the overlaps are very small, increase number of shots. The center column has colored frames to help you analyze the results.
March 04, 2004
Pics from Stockholm
I finally managed to get my pics from Stockholm online. Try not to loose you eyesight, they are a bit blurry and grainy, especially the ones taken indoors.