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Stormwatch

Your favourite astro books?

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I have about twenty different Astronomy books, some good, some well above what I can understand.

One of my favorites is quite old "Exploring the moon through Binoculars" by Ernest Cherrington. I've had this for years and love it, although it's very dated. "The Moon" by Patrick Moore is another great fave, and I enjoyed Dava Sorbel's "The Planets".

I have just ordered "Turn Left at Orion" and can't wait for it to arrive. I hope it is as good as you guys say it is.

JV

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The books I have read to date are:

Skywatching by David Levy

Nexstar Users Guide by Mike Swanson

I have recently bought Turn Left at Orion and will no doubt be refering to that while out at the scope this season.

I also buy Sky at night and Astronomy now magazines regularly.

I am now looking to buy a decent book on web cam imaging, if there is such a thing?

Gary

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Hi Gaz,

What was that link to? all I got when I clicked on was that it was missing or off mlimits to me.......... :?

Gary

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Thats strange.....

Heres the post :wink:

Martin Mobberleys "Lunar and Planetary Webcam Users Guide"

These are the notes I made while reading the book, they were purely for my purposes so I've concentrated on aspects releating to my setup/ interests/ knowledge level and as such contains large omissions - particulary in the B/W imaging area (I have a colour Toucam), basic stuff like collimation/ scope and equipment design and the Registax/ K3CCD stuff that I already knew that are covered in the book. Hopefully a few bits and bobs will be helpful to someone.

NOTES FROM A LUNAR AND PLANETARY WEBCAM USERS GUIDE

Actual Exposure Rates for Phillips Toucam:

5 fps 10fps 15 fps

1/25th exposure 1/5th sec 10th sec 15th sec

1/33rd exposure 10th sec 20th sec 30th sec

1/50th exposure 30th sec 50th sec 50th sec

Recommended starting point is 1/25 and 10 fps giving 10th sec exposures. Also try 1/33 and 5 fps for same exposure in better seeing. If the fps is too high the camera is forced to compress the image, this can cause blocky images.

Focussing:

Hartmann mask, moons of Jupiter, Casini division.

Image Scale:

Toucam pixel size is 5.6 microns, so image scale is:

206 * (5.6 / system focal length) given in arc/secs per pixel

Registax:

Initial frame quality assessment – “Gradient”

Wavelets:

1 and 2 enhance or suppress fine details (ie. Noisy pixels)

5 and 6 enhance or suppress larger features.

4 can be used a rough first guide to see how much detail can be enhanced.

Gamma:

Gamma is a number between 0 and 1. When raised by any power, numbers between 0 and 1 will stay between 0 and 1.

Final Pixel Brightness = Original Pixel Brightness^1/Gamma

If gamma is set to 1 then FPB=OPB (no change)

If gamma is set to less than 1 then mid range brightness will be dimmer

If gamma is set to greater than 1 then mid range brightness will increase

In all cases the minimum and maximum values are unaltered, only the mid range is adjusted.

Using the above equation a gamma of 0.7 gives a mid range of 37% and a gamma of 1.3 gives a mid range of 59% (both from the original value of 50%).

Gamma can be used to bring out fine details without ‘whiting out’ other areas. Saturation can also be used to reduce noise in one shot colour images.

Relative Surface Brightness (albedo):

Mercury = 80

Venus = 300

Mars = 15

Jupiter = 3

Saturn = 1 (used as standard)

Uranus = 0.25

Neptune = 0.66

Moon = 3 to 15 (half to full)

Imaging the Moon:

5 minute window before movement of terminator becomes apparent.

More frames are required when attempting to image smaller features than larger ones as signal to noise becomes more important.

Image through red filter for improved results if only B/W data needed.

Imaging Venus:

In UV a Wratten 47 filter can be used with a IR blocking filter to obtain UV images of the Venusian clouds.

Imaging Mars:

Depending on size of planet and resolution of imaging system, the window before rotation causes problems is around 9 mins.

Use deep red filter 25a for luminance channel when using a colour Toucam, split the colours into RGB channels and apply the filtered image as the L channel.

Imaging Jupiter:

Depending on size of planet and resolution of imaging system, the window before rotation causes problems is around 3 mins.

Lower than normal gamma value (0.6 to 1) to avoid the details on the equator washing out.

In colour Toucams, increase the red and decrease the green

Adjust brightness so the brightest part of the globe is almost whiting out, this gives a good dynamic range.

Moons can be used for focussing.

Imaging Saturn:

If seeing is good, aim for 5 fps at 1/25th setting due to low surface brightness.

Depending on size of planet and resolution of imaging system, the window before rotation causes problems is around 6 mins.

Moons can be used for focussing.

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I'm sorry the tone of the post is a bit 'terse' but it was only written as notes as I read the book and then posted straight on here. If you've got any questions about the book that I havn't put in the notes, just ask. :wink:

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I picked up a copy of this book at the recent South West Astronomy Fair. I'm about half way through and I am finding it a very interesting read.

Lee.

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