Friday, June 08, 2012

2012/06/06 Venus Transit


1. Canon 450D + Canon 100-400mm f4.5-5.6L, (Kenko 2x sometimes used) with Baader 3.8
2. Lumenera Lu070M + Tele Vue Ranger + Thousand Oaks Type 2+
3. Gitzo G160 + GOTO Mark-X with DIY motor and mounting accessories

Location: Nam Cheong Playground (南昌公園)

First up is one of those earlier shots, taken with the Ranger setup, the focus is less than perfect since I found that I've to push up the brightness of the display in order to show clearly under strong sunshine despite I was already using an umbrella.  Battery life was greatly reduced in that case, so I'd rather save the energy for 3rd and 4th contact.

2. So we did a fast forward and now it's close to 3rd contact, I've fine tuned the focus this time.

3. This is just a hair before 3rd contact and there is no obvious black drop effect.  I would say black drop effect is not a must and it's probably a combination of suboptimal optics, atmospheric issue (seeing), less than perfect focus, etc.  Even with only 70mm of aperture, the thin line between the planet disc and the solar disc was resolved nicely.

4. This is the 3rd contact.

5. The moment passed 3rd contact, notice that the atmosphere of planet Venus was shown protruding outside the solar disc, I've pushed up the exposure to make it clearer.

6. Venus was getting out further, the atmosphere arc was shown better.

7. The moment just before the 4th contact, I have to add an arrow in order to see the last trace of transit.

8. This is the 4th contact, but it's virtually the same as if there is no more transit, since this is the moment when the planet disc was completely out of the surface of the solar disc.

Second set was taken with my Canon 450D setup, and it's less than perfect as expected.  I should have used the Thousand Oaks filter with this setup in order to optimize the Ranger setup, but I was not smart enough to do so.

1. This is the earliest one, even earlier than the Ranger setup since I can do it handheld without much setup. 

2. Cloud kept rolling in briefly and away, and it's not too bad to have cloud around especially when it's just oh-so-hot!

3. For most of the time it was boring so I've skipped those moments and let's go to where it's closer to 3rd contact.

4. Black drop effect is about to appear...

5. The infamous black drop effect!  I believe it's not the quality of the optics for this particular case, but stacking actually help to eliminate the effect of atmospheric seeing!  That's why those images taken with the Ranger setup is sharper.  Day time seeing is even more unstable.

6. Planet disc was getting away...

7. The moment just before 4th contact.

Finally, I include a few snapshots so as to remind me of the hot moments under the strong sunshine.

There are over 30 passerby who observed and chatted with me on topics like simple planet knowledge, solar physics, cosmology, politics, education system, eschatology, camera, old days of Hong Kong, etc.  Around 5 people spent more than half an hour with me, and 10 of them came back periodically to check up the moment of Venus!

World without strangers for astronomy!

The ballhead side of the Mark-X is not easy to use for 400mm shots, so I will have to re-center it periodically and it's not a good exercise, so I pull it off and use it handheld with a Kenko 2x, since I'm using Baader 3.8 and the sunshine is strong enough even at f/11 with ISO 100, at faster than 1/2000s shutter, handheld is never an issue.

For those who are careful enough, you will see now I've a bigger umbrella and a piece of paper on the floor.  Those were given by those passerby to me!  

 My legs were darkened afterward and it's a nice morning indeed.

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