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Recent 4" Tak Images from last weekend at ARGO
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Julie and Tom Carrico
Hi all,
We had some okay nights at our observatory in central Oregon this last weekend. 3 nights were clear with reasonable seeing, but some high clouds. Two other nights had us chasing holes in the clouds. Still, any night under the stars is wonderful. Continuing to work out all the bugs on the G-11. When it is all tuned up, it works just great. However, it seems to be very sensitive to balance in RA. During guiding, the mount is kept heavy to the east. This means that with the RA clutch loose, the scope will move and you must pay attention when moving from the sky. If it is not that heavy, the RA tracking suffers. I have also found that the tracking rate that works best is 1.3 to 1.5 seconds with a delay between corrections (as set in MaxImCCD) of 0.8 seconds. If the delay is not set or is set too low, the mount seems to chase corrections all over the place. With the mount balanced and the guiding rate and delay properly set, and when used with my 4" Tak (820 mm focal length), the tracking error is usually +/- 0.2 pixels with an occassional flier of .7 or .8 that gets corrected immediately. The camera is an ST-7E. My latest images are: The bubble nebula has been retouched to remove the blooming, as has the cocoon. Tough images that will get another look next month. I have learned that imaging at f/8 just requires lots of exposure. The galaxy images could have used 2x the time I used here. That's also for next month. There will be more images posted later this week. Thanks Tom Carrico |
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Paul Sterngold
Hi Tom,
Very nice images. In the combo shot with 5905 at the center, there appears to be another, bright FFO (galaxy?) close to the bright star that is just to the left and above center of the frame. Is that a deformed star (unlikely), some kind of reflection in the optical train (unlikely), or a legitimate FFO? Cheers, Paul Sterngold --- Julie and Tom Carrico <carrico@...> wrote: Hi all, __________________________________________________ Do You Yahoo!? Kick off your party with Yahoo! Invites. |
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Julie and Tom Carrico
Greg,
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The delay after correction (usually about .8 seconds) is absolutely required. Until I did that, my corrections were always in the .5 to 1 pixel range. The mount was still responding to the prior move when the next guiding exposure was started. If I use a tracking rate of more than 2 seconds, and there is a change in RA and DEC (my minimum move times are usually .2 to .25 seconds), then it can be up to 2+.2+.2+.8+.8 = 4 seconds between corrections. This now starts to get kind of long. I have noticed that the way my drive works is that it hums along pretty well, and then has a jump of .7 or so pixels that is usually guided out on the next correction. If I wait too long between corrections, it will be too long before the error is guided out. I am still working with the drive. Since it is brand new, I have not yet taken it all apart for a cleaning as recommended by so many other G-11 motors. For the most part, I am very satisfied. The DSC are just great and the mount is well built. Tom C Greg Crawford wrote:
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Julie and Tom Carrico
Hi Paul,
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I noticed that fuzzy as well and just assumed it was a galaxy. I checked the Digitized Sky Survey and it shows the galaxy pretty clearly. The ability of these commercial CCDs to pull out these dimmer objects is really amazing. It is one of the things that I really enjoy about this hobby. Thanks Tom C Paul Sterngold wrote:
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Greg Crawford
Tom,
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After another night fine tuning my G11 I still have not achieved your guiding error rate. So I'll keep trying. :-) Two more questions: Do you use the King tracking rate? Do you find that the PEC helps? Greg Crawford -----Original Message----- |
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Julie and Tom Carrico
Hi Greg,
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I do not use the King tracking rate. My impression was it works for low to the horizon shots. Since I do not have a complete understanding of it, I have never tried it. I have not tried the PEC, but I am thinking about giving it a try to see if it provides any help. I am a little bothered by the fact that I would have to retrain it every time I use it, but if it works, it would be worth it. Tom C Greg Crawford wrote:
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