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[jglover]

Set up the scopes this evening as it *appeared* clear. The clear sky clock said everything would be just fine, but just like the local weather forecasts, it was wrong. Clouds and fog rolled in around 10pm, effectivley blotting out everything. I left both the ED80 and the ETx set up just in case. Woke up about 3 am, still overcast but Jupiter was poking through so I plugged it into the system and both scopes slewed right on the planet. Pretty good considered I aligned them at about 7:30 this evening. A quick check showed Io should transit the disk about 3:20am this morning so I decided to stick it out and see if I could pick up the shadow. Nothing, I was about to give up util about 3:30am when....boom...it popped into view. A tiny black dot crossing along the equatorial band. Very cool, I've never seen a shadow transit before! Seeing is only marginal right now, things dance in and out of focus but in those steady moments, it obvious in both scopes. I'm runnign the ETX 105 with a 9mm Nagler at 163x while the ED80 has the 13mm Nagler plus a 2.5x Powermate for at 115x. Actually the shadow is more distinct and sharper in the ED80 at the lower power. Looks like the seeing can only stand about 120x reliably tonite, but still, there are times when things settle down and the ETX view is spectacular.

I did try and get ridiculous and used the Pwoermate on the ETX, but it just would not take 408X....

Anyway, back out to watch a bit more, then it is definitely time to pack it in for the evening.

[Chicago Astronomer - Astro Joe]

John,

That's quite cool to have caught the transit.... . Like you, it was cloudy and I did not even consider a session this morning...perhaps I should have!

Glad to have read your account and thanks for sharing with us.

[timothy]

John
That is great. I was just reading about an Io transit in my magazine in march and marked it down in my got to see calander.

[jglover]

timothy said:

John
That is great. I was just reading about an Io transit in my magazine in march and marked it down in my got to see calander.

Actually, I've seen photos of shadow transits for years but never took the time to really look for one. LAst evening as I was getting ready to put away the scopes, I fired up Starry Night and zoomed into Jupiter. It was just dumb luck i happened to time that right as the transit started.

It does take some doing. It took me several minutes to be able to pick up the shadow, it is VERY small. And you have to have steady seeing. Better contrast helps out too, as the shadow was more easily visible in the ED80 at a lower mag than in the ETX 105. I figure that is due to the refractor's higher image contrast.. Give it a try next time Tomothy, it is pretty cool!

[timothy]

John
Will do, should be right up there with seeing saturn for the first time. in march Io is in front of jupiter too. I wonder if I'll be able to see it.

[jglover]

timothy said:

Will do, should be right up there with seeing saturn for the first time. in march Io is in front of jupiter too. I wonder if I'll be able to see it.

You should be able to pick it out with a 3" scope, as I could spot the shadow just fine in my 80mm. But, dark adaption is really important as I found out. It's also much easier to pick up the shadow when it is near the center of disk, where it is brighter and thus you have better contrast on the planetary disk. It Is *really* little though....

[timothy]

little, gotcha, can't wait

[Chicago Astronomer - Astro Joe]

Also,

Increasing contrast is important to make the shadow darker. I have used different filters...(Yellow, magenta etc...), to bring out different aspects. Some times the overwhelming power of the light bouncing off Jupiter's surface makes it hard to catch the very small dot.

I remember when Hale-Bopp smashed into Jupiter. When the planet spun toward us, showing us the insertion area... I could make out, (just barely), the impact sites. Filtering made them stand out better and clearer.

We should get together for the next transit.

[timothy]

now here is some serious jupiter moon crossing. Compliments of the Hubble.

www.space.com/imageoftheday/image_of_day_041104.html