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Author Topic: Using Webcams for planetary photography - a quick guide  (Read 10138 times)

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Offline coxellis

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Using Webcams for planetary photography - a quick guide
« on: 15:02:01, 01 December, 2004 »
I was recently asked a question about ep projection vs barlow and I got carried away :roll:  Here's the answer I wrote - perhaps a few others could add some additional details or carry on with the registax bit?

Firstly, the principles of ep projection:

You use an adapter which connects to the end of an eyepiece that sticks out from the focusser - this is normally held in place by a few soft plastic screws, but other methods exist.  The focusser adapter then pushes down inside.  This means that the ccd in the camera will be at least the length of the focusser adapter away from the eyepiece.  It therefore follows that the best results can be achieved with a long eye relief eyepiece.  The best I ever had for this was a 10mm skywatcher super (as is supplied with most of their scopes).  Moving the focusser slightly forwards will increase the magnification a little (after re-focussing) and moving it very slightly backwards, the reverse.

Magnification wise, a 10mm ep will give similar results to a 4x barlow.

A 4x barlow is very hard to bring to focus though good collimation if using a newt and a higher focal ratio, e.g., f7+ will help.  The trick is to either focus on a planets moon (with the brightness and gain turned up high in the webcam's settings) or to focus on the bright limb of the moon and get the focus as accurate as possible using very slight touches (this is the time consuming part of lunar and planetary imaging).

A 2x barlow will give an image half the size (and resolution, so detail is limited), but is easier to focus by a very high degree.

With either method, once you are focussed, turn the gain down to around 60/70% and the brightness as low as it can go without losing contrast.  If the target starts to lose contrast, speed up the exposure time (the frame rate of 5fps should stay the same, but depending on the scope and camera, you may have to go as high as 1/1500th sec on a bright moon shot, 1/500th on a planet).  Balance the brightness and exposure time until you have a greyish preview, but with visible detail, e.g., with saturn, a hint of the cassini division and with jupiter it's storm bands.  If the planet looks too bright at this stage it will wash out during stacking.

For Jupiter, limit the overall time of the shot depending on resolution and the distance the planet is - at it's closest to earth and with very high magnification, more than 40 secs can show movement, blurring the stacked image.  With a 4x barlow, about a minute's worth of shooting (300 frames) is generally playing it safe - it's an idea to try 400 and 500 - you can shoot 1 avi and simply uncheck frames over 300 or 400 etc.  Saturn, being considerably further away shows much less fine detail (and this is the nature of the planet anyway) so a 2,000 frame avi where you select the best 1600 frames can give stunning results.

Then there's using Registax :roll: which is an art unto itself...

Andy
Obs: EQ6 SkyScan; Field: EQ5 SynScan
Scopes: MN76 : Equinox 80
Cams: ART285 : BWSC1 : 1000D : 450D

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Offline synner

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Using Webcams for planetary photography - a quick guide
« Reply #1 on: 15:09:02, 01 December, 2004 »
Nice one Andy :D
Nick
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Offline andyt

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« Reply #2 on: 15:31:29, 01 December, 2004 »
yes brill thanks
its all my fault - you wondered where the clouds had come from didnt you - been speaking to bern about my first cam purchase and picked andy's brain in a PM.
one question, using my kodak which has a video option i held the camera to the eyepeice the other night (i wont post the results :-) ) but the resulting MOV converted to AVI run through registax gives me a very small image - pretty much the size it appears to the eye at 100*
would i be right in assuming that because the CCD of a webcam is much smaller than my digital camera the FOV will be smaller hence the image larger and clearer? or is that wishful thinking?
AndyT
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Offline coxellis

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« Reply #3 on: 15:49:23, 01 December, 2004 »
Size wise, the sensors may not be very different, but with an adapter, the webcam ccd is at least an inch away from the ep - stand back from the ep a bit and the planet will fill the bit you can see as the focal plain diverges to fill your pupil.  In the case of a sensor, that means it covers the sensor not just a point in the centre.

Andy
Obs: EQ6 SkyScan; Field: EQ5 SynScan
Scopes: MN76 : Equinox 80
Cams: ART285 : BWSC1 : 1000D : 450D

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Offline coxellis

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« Reply #4 on: 15:51:14, 01 December, 2004 »
owww carp - summat like that anyway - read it back and it doesn't seem quite right, but something along those lines :roll:
Obs: EQ6 SkyScan; Field: EQ5 SynScan
Scopes: MN76 : Equinox 80
Cams: ART285 : BWSC1 : 1000D : 450D

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Offline andyt

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« Reply #5 on: 15:56:31, 01 December, 2004 »
no that kinda makes sense.. thanks
bern is posting the cam today so once the clouds go i can start playing and learning
AndyT
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Offline dizzytart

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« Reply #6 on: 23:27:39, 28 December, 2004 »
well, that lot went way over my bloody head!! :shock:
A proper dizzytart!!

sky watcher 130P (f/5), EQ2
( newbie to the astro' world!)

Offline PaulB

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« Reply #7 on: 10:27:08, 24 December, 2005 »
Hi Andy.

Thanks for that. I've been thinking about ep projection as I've got a 12" F/4 Newt and was considering using my 18mm Ortho, this eyepiece is the only widefield ep I've got. I also have a 12.5mm s4000 plossl from orion optics and a 10mm Kelner . I'll have to play around and see which works best for Saturn and the Moon.

There is one problem, how the devil do you work out the focal length when your using a 12.5 mm plossl and 12" F/4 and Toucam Pro?.

Rgs
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Offline the fordster

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Using Webcams for planetary photography - a quick guide
« Reply #8 on: 00:53:29, 26 December, 2005 »
Nice work Andy!!!

Offline coxellis

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« Reply #9 on: 10:30:25, 26 December, 2005 »
Quote from: PaulB
There is one problem, how the devil do you work out the focal length when your using a 12.5 mm plossl and 12" F/4 and Toucam Pro?.


Hi Paul - no real answer to that question - the closer the ccd in the toucam is to the ep and the eye relief of the ep will effect the image scale.  I always used a 10mm LER plossl and got good results - you'll have to try them out and see which works best.  These days (I wrote this over a year ago now) I use a 5x TV PowerMate to give an effective fl of 5.6m

Andy
Obs: EQ6 SkyScan; Field: EQ5 SynScan
Scopes: MN76 : Equinox 80
Cams: ART285 : BWSC1 : 1000D : 450D

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Offline Paul J

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Using Webcams for planetary photography - a quick guide
« Reply #10 on: 10:52:56, 26 December, 2005 »
as a newbie (been doing this 2months) i've just been searching the net and finally worked out what ep projection is.....i know that might sounds daft but as a newbie with little experience 'everything' is a learning curve.

regards ep projection this is all i have tried so far, my 'good' results have come from the moon only, to get planetary images in focus i really need a remote focuser (have nearly finished it using a R/C servo).

i built an adapter for my toucam from a piece of water pipe and use an elastic band to hold it in place, not ideal i know but it works
Paul

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Offline spaismunky

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Re: Using Webcams for planetary photography - a quick guide
« Reply #11 on: 12:18:29, 11 February, 2006 »
I'm a complete newbie and I have no idea what you mean by ep projection. My toucam came with a screw-in adaptor that I put directly into the eyepiece holder. Is that what you mean? What's all this about a focuser, and how do I attach an eyepiece to it please? In english please?  :oops:
mojo
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Offline coxellis

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Re: Using Webcams for planetary photography - a quick guide
« Reply #12 on: 14:07:53, 11 February, 2006 »
Obs: EQ6 SkyScan; Field: EQ5 SynScan
Scopes: MN76 : Equinox 80
Cams: ART285 : BWSC1 : 1000D : 450D

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ambermile

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Re: Using Webcams for planetary photography - a quick guide
« Reply #13 on: 14:30:18, 11 February, 2006 »
... and with the original lens on the camera?

Offline coxellis

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Re: Using Webcams for planetary photography - a quick guide
« Reply #14 on: 14:55:24, 11 February, 2006 »
:roll:
Obs: EQ6 SkyScan; Field: EQ5 SynScan
Scopes: MN76 : Equinox 80
Cams: ART285 : BWSC1 : 1000D : 450D

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