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[Chicago Astronomer - Astro Joe]

Last Minute gathering of three Chicago Astronomers

24 September 2010

Yesterday was a disappointment with all the heavy clouds for the Full Moon Rise session - canceling the event for many. But this evening was clear...and a last moment phone call brought three of out to enjoy the Chicago sky.

Chicago Astronomers Steve, Bill and I met up by the Adler for some goofing around with scopes. I brought the C11, Bill his Vixen and Steve, his refractor.

The area was practically devoid of foot traffic, although we did get a few passerbyers and police to stop by and take a peek. But since it was quiet, I thought to take some astrophotos, even if the wind was gusting at times.

I used Steve's 40mm 2" eyepiece, because it has a threaded adapter that I can connect the Canon Powershot S3 to - but it has a sweet spot and not too easy of a eye relief - hence the secondary mirror shows up on some of the shots.

The first target was the E.T. Star Cluster...

Not bad for a windy night...

Then, with Jupiter high and bright...

And finally, some lunar shots...

Steve playfully suggested that I should pile up the barlows we had on hand.

Don't challenge me, 'cause I'll do it...

Using his 40mm eyepiece coupled with a 1.6X Barlow, and attaching my own 2X Barlow....it worked fairly well....

The magnification difference was quite apparent.

Bill in the meantime was searching for Comet Hartley, acquainting himself with the path of stars it is travelling against, but had no success in locating it. The near full Moon didn't help either, as we all tried to spot it, but nada.

I wanted to tweak the C11 a bit, as I think the images have been rather "soft" and I know could be better. Having done a star test before, the inside & outside focus was acceptable with concentric rings, but I was getting some coma earlier while focusing on the Jovian satellites. So, I tweaked with the help of both Steve and Bill.

With me on the step ladder and Phillips screw driver in hand, I had them concentrate on doing a "Star test" on the Moons of Jupiter, instead of using a star. While out of focus, it was very apparent that a slight coma was biased to one side - with pin point focus....just out of reach. So with trial and error I ever so slowly loosened or tightened the secondary mirror adjustment screws until we all agreed that close to perfect circles were had on the out of focused image.

Now purposely focusing on Jupiter, the views were noticeably sharper. Still not satisfied, I slewed over to Vega to slightly tweak some more, and again with help, got good circles.

Slewing back to Jupiter, the satellites were good out of focused circles and when finally focused, were probably the best images of Jupiter I have observed to date. It will do for now.

There needs to be some more tweaking, with higher power eyepieces, (I want it right on the nose), but time did not permit us to continue and we packed up our gear for another time....which could be as soon as this coming Sunday evening.