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20 minute unguided test shot of Monkey Head nebula

GordonH

By GordonH
in Imaging - Deep Sky

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GordonH

GordonH

Posted
Posted

Hi all

After finishing doing the data for OIII and SII channels of my colour Horsehead image there was just enough light left for me to try a test shot of the monkey head nebula in Orion. I've always wanted to see just how far I could push the Paramount ME before it showed trailing on the stars and I think it may still take me a bit longer to find out. I set the exposure to 20 minutes and let it run while I made some coffee. The resulting image below is from a single unguided 20 minute subframe with a Ha filter, the only processing was to some sharpening using Noel's tools, some noise reduction as the image was very noisy due to daylight, no dark subtraction and only one frame, minor curves and levels were used to help show some detail. The polar alignment was within 0.2 arcmin (12 arcsec) of the celestial pole. I thought 10 minutes unguided was fantastic but this is just ridiculous. No PEC training or second party software was used to increase the accuracy of the tracking, essentially the Paramount is still being used as it came out of the box.

Best wishes

Gordon

:) :) :D :D :(

post-13589-13387734907_thumb.jpg

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CELESCOPE

CELESCOPE

Posted
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Lovely one Gordon always one i love to do as it processes so nicely , i have taken a few of this new , starnge last night i just done 60sec sub on this one as it popped over the roof , no intention of imaging it , but i noticed that fine object to the right , cant say i have never seen it before ,mainly cus i guess of the wider field i,m using, so does anyone know what it is , no time to look as i,m off now to Suffolk ,

Great image Gordon

Rog

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MartinB

MartinB

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A great monkey's head Gordon. If you can go round the worm cycle once without trailing you can go round umpteen times. The only issue then is the quality of your polar alignment rather than the mount. Polar alignment obviously spot on although things might look different at 2000mm focal length which is a more realistic test for a mount in this price bracket.

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GordonH

GordonH

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Hi John

You have me stumped on both questions

1. I don't know what King tracking is

2. True pole or refracted pole - I go by what the information tells me in the T-Point mapping software and this indicates how far away from the pole after each mapping run, also after each mapping run the software tells you how much of an adjustment to make to the mount

Regards

Gordon

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winfij

winfij

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The King tracking rate uses an algorithm which dynamically adjusts the mount tracking rate to compensate for the effects of atmospheric refraction.

Otherwise, even perfect mechanical tracking will show some image drift over time, as the atmosphere refracts the light, changing the apparent position of the target. It's really only a problem with lower elevations though.

John

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winfij

winfij

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A quick look on the web shows that T-Point is correcting to the true pole, not the refracted pole.

If you were to use ProTrack, that includes refraction correction.

The ME doesn't include King rate tracking, but they do have instructions on the web site for making the offset adjustment to the refracted pole, which is the next best thing, although ProTrack is even better than King rate, since it compensates for a lot of other factors as well.

John

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GordonH

GordonH

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A quick look on the web shows that T-Point is correcting to the true pole, not the refracted pole.

If you were to use ProTrack, that includes refraction correction.

The ME doesn't include King rate tracking, but they do have instructions on the web site for making the offset adjustment to the refracted pole, which is the next best thing, although ProTrack is even better than King rate, since it compensates for a lot of other factors as well.

John

Hi John

Thanks for that very useful information, I am sure I read somewhere that the Paramount can be trained to compensate for atmospheric turbulance, tube flexure, etc. I think you have just explained how

Thanks again

Best wishes

Gordon

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winfij

winfij

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Oh nooo!!! A whole new problem to worry about. Well thanks a lot John :D:)

LOL, well, it's all unimportant if you're guiding, since that will keep the target centered and the amount of image rotation you'll get by being aligned to the true pole rather than the refracted pole is probably the least of your worries :)

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