Post by Chicago Astronomer - Astro Joe on Jul 14, 2010 4:33:41 GMT -6
Solo at home Test session with the C11
13 July 2010
13 July 2010
I thought I would take advantage of this clear evening by setting up the C11 close to home...and solo. I wanted to test out the Bahtinov Mask and the Extended Dew Shield, (E.D.S.) at my leisure.
I wanted no distractions, so I set up the C11 for the first time, in by my alley walkway gate....but it's so damned big, the beast would not fit comfortably - even having to remove the 60mm Finderscope. Slewing was cramped and vibrations unacceptable.
Not cool...
Grudgingly, I broke it down and set up at my usual spot outside of the garage for this solo session - accepting the curious visitors wanting to see what I was doing.
First off, the Bahtinov Mask test.
I had first tried it out a week ago, but it was a quick test and more to see if it worked. This time, it would be more of a shake out and with pics.
The mask fits nicely in front of the aperture and with Vega high, I tried the mask on that...
Bright and with the mask slots clearly visible, I was ready to play with some starlight from the movie "Contact" .
Starting to focus, the mask deforms into the desired "spikey" form...
An interesting and functional manner of diffraction...and we were in sharp focus...
But were we?
I removed the mask and presented before me were pin point stars...
It works!
I'm satisfied on the properties of the mask and making it...
Details here:
astronomer.proboards.com/index.cgi?board=ATM&action=display&thread=2775
Checking the collimation now...
..it's slightly off.
I think I will buy me some "Bob's Knobs" and maybe a "Hotech" SCT collimator soon....making this a one person job.
Next...the E.D.S...
My alley is brightly lit with the awful orange Mercury vapor blight - pounding my corrector plate, pouring down the tube and washing objects out in feeble contrast.
I still am able to pick out celestial targets despite the glare, but this Extended Dew Shield should be able to minimize this situation somewhat.
And it does...
Glare, that would normally have fallen unimpeded onto my corrector plate, gets swallowed up in the black felt-like material inside the shield.
Excellent!
I also made one for the 9x50mm finderscope...
In comparison with the earlier shot of Vega without the shield, it is apparent that the contrast is much better...
The sickly orange glare is drastically reduced and objects appear in a much darker background. The accumulated starlight on the camera CCD sensor makes Vega's starshine look like a disk.
Nice...
I focused on the "Double Double" in Lyrae and tested if I could split them easier with the sheild...(which is still temporarily secured wit duct tape)...
The lens on the Canon Powershot S3, although is a great all around camera, "bends" the incoming light slightly under high magnification. It's just something I have to live with for the time being...
But, we can already start to see the two different orientations of the four stars to each other. I had thought that an exposure of a few seconds was neccessary to capture the doubles, but not the case. Less time made for better images and started to separate the stars better...
An exposure of 1/8th at 400 ISO and 2.8 f-stop was sufficient.
And...there is also the problem of perfectly centering the axis of both camera and eyepiece, which when off, smears the stars a bit...
But at least we get some images of the separation.
By 12:00 midnight, Jupiter was already 20 degrees high and I slew to it for some shots...
I think the first one is the best of the lot.
I was out for four hours now and ready to call an end to the session, but I wanted a comparison shot of the contrast views - with and without the Extended Dew Shield and Jupiter rises in direct line to a nasty alley street light...
The difference is amazing.
I still need to work on the EDS, adding Velcro strips, some more notches for the control handles and perhaps cut it down to 16". It's now 26".
I can always add on the additional 10" when needed.
A good solo session.