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Using a Canon G10 for Astrophotography

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Offline jwillis84

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Using a Canon G10 for Astrophotography
« on: 14 / October / 2014, 12:59:44 »
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Looking for advice or pointers to help prepare for a trip to Fort Davis mountains in TX (very dark skies)(only 2 days from now, evening of Oct.17).

I have two Canon G10 Power Shot cameras.

f2.8
28mm
CHDK
.. more details in the signature below

1. I'd like to try photographing the Milky Way compensating for the focal length, speed and ISO possibilities of the G10. Recipies would be appreciated!

2. I'd like to try photographing a Time Lapse (or Star Lapse) using Stacker Post Processing to compensate for the focal length, speed and ISO possibilities of the G10.

From what I've read there are the Rule of 600/28mm 500/28mm 400/28mm to calculate the max Exposure time for avoiding motion blur due to Star Travel across the sky. And after that choices really come down to boosting the ISO (using CHDK) but that brings in Thermal noise. (but its high altitude and the ambient outside temperature is pretty cool on top of Mount Locke).

Photographing the Milky Way seems more a matter of aiming in the right direction and raising the ISO at the max Exposure time. And shooting RAW. Stellarium or Mobile Observatory on Android look like my best pointing options.

Photographing the Star Lapse seems more about collecting light and not worring about Star Trails since the Stacker software will de-motion the blur back into points of Light for the video clip. (its early days for me, so please enlighten me if I'm making some fundamental mistakes..) But using an Intervalometer script looks best.. calculating the number of shots. I saw the Meteor script and was thinking of trying to learn how to configure it for my particular camera and use case.. but I'm not sure if its better to start by writing one of my own.

I'm doing the Jungle Gym thing all over the Otto Struve 2.1m that night and plan to stay up late and see what I can catch, Light at Night Fishing is a new hobby to me.

I'll post my successes or failures for anyone to critique or learn from (especially if you have a G10).

Any advice would be greatly appreciated.

Thanks, sincerely

John W.

Brand: Canon
Model: PowerShot G10
MegaPixels: 14.70
Sensor resolution: 4438 x 3312
Max. resolution: 4416 x 3312
Sensor: 1/1.7" (~ 7.53 x 5.64 mm)
Crop factor: 4.6
ISO: Auto, 80, 100, 200, 400, 800, 1600 (without CHDK)
Focal length: 28 - 140 mm
Aperture: f2.8 - f4.5
Min. shutter speed: 15 sec (without CHDK)
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Offline waterwingz

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Re: Using a Canon G10 for Astrophotography
« Reply #1 on: 14 / October / 2014, 14:54:00 »
The G10 is not exactly known for its low light performance unfortunately.  It's a high pixel count sensor but the noise goes up quickly at middle to higher ISO settings.   Still, it's a fun camera.

You might be interested in this wiki page : http://chdk.wikia.com/wiki/Meteor_Intervalometer_with_Dark_Frame_Management and the link to the forum thread that it references.
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Offline jwillis84

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Re: Using a Canon G10 for Astrophotography
« Reply #2 on: 14 / October / 2014, 16:36:16 »
Quote from: waterwingz on 14 / October / 2014, 14:54:00
The G10 is not exactly known for its low light performance unfortunately.  It's a high pixel count sensor but the noise goes up quickly at middle to higher ISO settings.   Still, it's a fun camera.

You might be interested in this wiki page : http://chdk.wikia.com/wiki/Meteor_Intervalometer_with_Dark_Frame_Management and the link to the forum thread that it references.

Thanks for the link pointer.

I was definitely afraid of what you said about the G10 and noise.

But its the only set of cameras I currently have.

I'm going to be there anyway, so i figured "try or try not, there is only do or do not" what have I got to loose?

My expectations are appropriately set, so now its time to Give it Gung ho! and see how far I get, could lead to a better informed position when picking out my next camera.. there is so much I don't know.

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Offline waterwingz

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Re: Using a Canon G10 for Astrophotography
« Reply #3 on: 14 / October / 2014, 17:08:31 »
Experiment a bit.   

The G10 is supposed to be fine at low ISO values like 100. Use 100 and take a 5, 10, and 20 second or so exposure with the focus at infinity and the lens wide open and see what you get?   You are going to be stacking anyway so use the script to get periodic dark frames, throw that into the mix,  I'll bet you get some things that will make you happy.   Getting away from light pollution by itself makes the trip worth while.

Post some of your best shots here when you get back?

Update : I'm curious about what you were thinking when you mentioned writing your own script?  What else would you want a "star trails" script to do?  Also, have you worked out how your are going to power the two cameras?  You can get hours of shooting from a fresh battery but it's not unlimited.

« Last Edit: 14 / October / 2014, 17:11:16 by waterwingz »
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Offline jwillis84

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Re: Using a Canon G10 for Astrophotography
« Reply #4 on: 14 / October / 2014, 20:30:39 »
Quote from: waterwingz on 14 / October / 2014, 17:08:31

Post some of your best shots here when you get back?

Update : I'm curious about what you were thinking when you mentioned writing your own script?  What else would you want a "star trails" script to do?  Also, have you worked out how your are going to power the two cameras?  You can get hours of shooting from a fresh battery but it's not unlimited.

I'll post whatever I can get. Critique will be helpful, can't learn if we don't fail sometimes.

Script writing? I was thinking perhaps I needed to go slow and fully understand all the parameters of the script or its defaults might overwhelm me and ruin my chances of getting anything.

The purpose of the existing scripts seems a bit more advanced and specific than what I was hoping for.. I was hoping mainly to catch a lot of stars rotating across the sky as pinpoints of light.. and maybe any drifting clouds that dark at night that might eventually show up.  I'm really not expecting the G10 to be able to catch the Milky Way, but that would be awesome. (I will try anyway.. point it in the right direction.. and see)

The meteor script for example I think was written for the Perseids meteor shower, or Iridium Flares (fast moving objects in the night sky, or satellites.. not something mundane as plain old 'stars').

Another script was written for catching Sunsets and Sunrises, manipulating the Exposure automatically to avoid blow outs or damaging the sensor during long exposures.

I really don't care about those advanced scenarios in my simple learning phase. So I thought the existing scripts might be too advanced for me to tailor them 'downwards' to do simple things.

Power is a concern, I have two DR-50 DC Couplers which take a standard power barrel connector, but I need extra capacity external batteries. And preferably a solderless way to connect them.

They actually came part of a kit the Canon ACK-DC50 which includes the CA-PS700, power cord, a cable with an EMI soft ferrite core and DR-50 DC Coupler

Canon AC Adapter Kit ACK-DC50



Input 100-240v AC 50/60Hz
Output 7.4V at 2.0A


DC Coupler DR-50 for CANON PowerShot G10 Digital Camera, PowerShot G11

DC connector size: 5.5 x 2.1mm
Parameter: 9V/2A

Neg. Collar, Pos. Center - right angle tiny but long female barrel connector

DC Coupler has the corresponding male centered barrel connector

Actually this looks a lot more promising and includes a connector kit will probably connect right up to the DC Coupler with no modifications. The connector polarity is also reversible.

8.4V Pocket-Size Rechargeable Lithium Battery - PM55



Capacity: 21 Watt-hour (5675mAH) lithium polymer
Dimensions: 118 x 86 x 16.5mm (4.6" x 3.4" x 0.6")
Weight: about 191g
Output voltage: DC 5V & 8.4V,
Input voltage: 5V or DC 12 ~ 15V
Max. Output current: 1A for 5V USB port, 2A for 8.4V Port

I don't think I really have the time to acquire these before this Friday, but it might be what I do in the future.

I'm headed up North a few days later.. if the Milky Way is a long shot.. the Aurora Borealis is probably just impossible. But I'm kinda stubborn that way in that I try try and see what sticks.
« Last Edit: 14 / October / 2014, 23:19:16 by jwillis84 »
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Offline waterwingz

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Re: Using a Canon G10 for Astrophotography
« Reply #5 on: 14 / October / 2014, 20:48:08 »
Quote from: jwillis84 on 14 / October / 2014, 20:30:39
The meteor script for example I think was written for the Perseids meteor shower, or Iridium Flares (fast moving objects in the night sky, or satellites.. not something mundane as plain old 'stars').
Those events get all the attention but the script is a lot simpler than that.  Its only function is to take continuous long exposure shots  with occasional "dark frames".  The long exposure times and dark frames are CHDK tricks that you can't do with most conventional cameras (even if they have built-in intervalometers).   Having dark frames lets you post process to remove "amp glow".    Other than that, there is nothing fancy related to meteor showers.
 
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Another script was written for catching Sunsets and Sunrises, manipulating the Exposure automatically to avoid blow outs or damaging the sensor during long exposures.
Those ones don't do much for your sensor - the mostly try to let the exposure change gradually so you don't get sudden jumps as the sun come in & out of the clouds while it decends.

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My "guess" is that 12v auto charger contains the complicated "diode" that prevents power flowing back out the port and the would provide power if I could just come up with a "power barrel connector" to "power barrel connector" to the DR50 DC Coupler.. that or I could "jumper" the diode inside the charger. The end result would be I could still charge it in an outlet, but might want to diode protect the12v autocharger if it isn't already wired with a diode. At worst, I would have to sneak a paper clip into the charger box. And never use the 12v autocharger port except to power the camera. At best, its already wired that way, and I can charge using an outlet or the 12v autocharger port and power the camera.
Hmmm .. not too sure what you are trying to do here.  The 12v charger is designed to safely push a charging current into the camera's NB-7L battery.  I'm not certain it can power the camera directly.
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Offline jwillis84

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Re: Using a Canon G10 for Astrophotography
« Reply #6 on: 14 / October / 2014, 21:22:05 »
The comments about the 'Meteor' Script and the 'Sunset' Script are encouraging.

I will look into them and try to set them up for a test this evening or next.

The larger 7.4v for 3400 mAh battery pack was my 'thought experiment' to go beyond the internal NB-7L battery pack in the camera. The NB-7L says it provides 7.4v for 1050 mAh. I'm not sure how long the smaller internal battery pack will last taking time lapse shots at night.

The larger battery pack would be 3.23 times longer whatever the Unit of time the original battery packs would last, but they will not fit the battery compartment of the camera.

So I was trying to come up with a way of simply charging them, then connecting them to the DC Coupler which fits in the battery compartment. The G10 has a very tiny spring loaded trap door in the side shaped like a little "foot" that a wire from the DC Coupler passes through, rather like a microscopic kitty door in the back door of a house.

G12: AC Adapter Kit





If by chance everything worked out perfectly it would be a fairly water and moisture resistant solution, good enough to fend off any condensation or dew. If I have to go down the path of opening things up and splicing them together.. I run the risk of a less elegant solution.

I guess the most direct answer to your question is "I wanted to use the battery charger and its battery clip/connector (when it was not connected to a 110v outlet for charging) to connect to the 12v autocharger port and then to the camera DC coupler, expecting the battery to then discharge through the 12v adapter port and into the camera to provide it power."

I am aware there is probably some sort of rectifier or diode protection to prevent accidentally discharging in the reverse direction into the automobile electrical system. But Kinda thought or assumed to save money, the manufacturers of the charger might put that extra diode protection in the 12v autocharger component that plugs into the car and leave the 12v port on the main charger unprotected.

[Could be a problem with that simplistic thinking though, without stepping the voltage down from 12v to something closer to the 7.4V the battery is expected to provide.. it might generate a lot of heat while charging.. best estimates I've seen are 12v to 8v measured, that's 4v to dissipate across a resistor or something else.. I'm no electrical engineer.. so I'm not sure what their options are. They might have clever charge bucket bridges to do it these days. If you can use them to step up a voltage, I guess you can use them to step down too.]

But if it is a simple electrical connection from the battery terminals to the 12V port and it discharges at 7.4V (or roughly around that), that would be ideal since I could use that port as the power source for the camera.

Its mostly a thought experiment though, since I don't think I'll be able to get the parts before Friday.

And if I really can't capture anything of worth in shorter intervals, then maybe I shouldn't invest a lot of time in finishing this approach to extending the night time capture length.

I do have the ACK-DC50 adapters. I doubt they will make power ports available at the observatory out there, especially to transient guests. But I'll carry one along anyway.

Pardon my crazy formatted messages and images. I am not familar with BBC code yet and I'm learning as I type.

You can see I make a lot of mistakes.. lol.

Let's hope I'm also learning a lot.
« Last Edit: 14 / October / 2014, 22:43:02 by jwillis84 »
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Offline waterwingz

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Re: Using a Canon G10 for Astrophotography
« Reply #7 on: 14 / October / 2014, 22:46:47 »
Quote from: jwillis84 on 14 / October / 2014, 21:22:05
The comments about the 'Meteor' Script and the 'Sunset' Script are encouraging. I will look into them and try to set them up for a test this evening or next.
Careful - full disclosure here - it's addicting.

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The larger 7.4v for 3400 mAh battery pack was my 'thought experiment' to go beyond the internal NB-7L battery pack in the camera. The NB-7L says it provides 7.4v for 1050 mAh. I'm not sure how long the smaller internal battery pack will last taking time lapse shots at night.
Depends a lot on the age of the battery and whether its geniune Canon or a elcheapo knock off from Asia.

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The larger battery pack would be 3.23 times longer whatever the Unit of time the original battery packs would last, but they will not fit the battery compartment of the camera.
No kidding.

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So I was trying to come up with a way of simply charging them, then connecting them to the DC Coupler which fits in the battery compartment. The G10 has a very tiny spring loaded trap door in the side shaped like a little "foot" that a wire from the DC Coupler passes through, rather like a microscopic kitty door in the back door of a house. If by chance everything worked out perfectly it would be a fairly water and moisture resistant solution, good enough to fend off any condensation or dew. If I have to go down the path of opening things up and splicing them together.. I run the risk of a less elegant solution.
Splicing the larger battery pack into the DC coupler is the way to go.

Quote
I guess the most direct answer to your question is "I wanted to use the battery charger and its battery clip/connector (when it was not connected to a 110v outlet for charging) to connect to the 12v autocharger port and then to the camera DC coupler, expecting the battery to then discharge through the 12v adapter port and into the camera to provide it power."
If you want to run from a 12V source (e.g. car battery) then a low cost  DC-DC converter is your best bet - again, spliced into the DC Coupler.  Something like this : http://www.pololu.com/product/2103 or any one of the other DC-DC converters from Asia.

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I am aware there is probably some sort of rectifier or diode protection to prevent accidentally discharging in the reverse direction into the automobile electrical system. But Kinda thought or assumed to save money, the manufacturers of the charger might put that extra diode protection in the 12v autocharger component that plugs into the car and leave the 12v port on the main charger unprotected.
There is a lot more circuitry than that as it turns out.  Although it only takes a few chips,  the charger actually needs to measure the current into the battery and adjust voltage on the fly based on that.  And perhaps more importantly, it needs to cut off charging when the battery is fully charged.  Some spectacular fire videos on youtube.com show what happens if it does not do that correctly.

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Could be a problem with that simplistic thinking though, without stepping the voltage down from 12v to something closer to the 7.4V the battery is expected to provide.. it might generate a lot of heat while charging.. best estimates I've seen are 12v to 8v measured, that's 4v to dissipate across a resistor or something else.. I'm no electrical engineer.. so I'm not sure what their options are. They might have clever charge bucket bridges to do it these days. If you can use them to step up a voltage, I guess you can use them to step down too.]
Yup - you are not electrical engineer  :D.  See my previous comment in this post for more guidance.

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Its mostly a thought experiment though, since I don't think I'll be able to get the parts before Friday.
True.  But if you own G10's then this is not your first walk in the park.  There is always a next time.


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And if I really can't capture anything of worth in shorter intervals, then maybe I shouldn't invest a lot of time in finishing this approach to extending the night time capture length.
Define "shorter".   In a couple of hours with a truely dark sky and no clouds you should be able to get some spectacular images !

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I do have the ACK-DC50 adapters. I doubt they will make power ports available at the observatory out there, especially to transient guests. But I'll carry one along anyway.
DC-AC inverter to feed the ACK-DC50? (if you can get them fast enough)

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Pardon my crazy formatted messages and images. I am not familar with BBC code yet and I'm learning as I type.
Huh?  Looks good to me. But this is not exactly my first post.

Quote
You can see I make a lot of mistakes.. lol.
That's where the fun starts!
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Offline jwillis84

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Re: Using a Canon G10 for Astrophotography
« Reply #8 on: 16 / October / 2014, 04:17:17 »
I was hoping to ask about the parameters in the meteor2.lau script when it is run.

The options are:

  • Tv exposure (secs)
  • ISO
  • Av (f-stop)
  • ND filter
  • Total shots (0=infinite)
  • Zoom position
  • Enable Raw
  • Focus @ Infinity Mode
  • Dark Frame Mode
  • Shots per Dark Frame
  • Display Off

I can "guess"

Tv exposure is how long the sensor is exposed to light
ISO is how sensitive the sensor is dialed up
Av is the wideness of the Aperture

What are these?

ND Filter?
Shot Interval?
Zoom position?
Focus @ Infinity Mode? (None, AFL, MF)
Dark Frame Mode? (None, Canon, CHDK)
Shots per Dark Frame?

I also read something about disabling Overrides?

Or other settings in the camera

Could you provide any general descriptions that might serve as a guide to me, and anyone else who might be browsing for information?

Thanks
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Offline waterwingz

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Re: Using a Canon G10 for Astrophotography
« Reply #9 on: 16 / October / 2014, 06:34:28 »
Quote from: jwillis84 on 16 / October / 2014, 04:17:17
I also read something about disabling Overrides?
You can override the settings your camera uses for exposure (shutter speed, aperture , sensitivity) and other things (focus, ND filter, flash intensity) using options in the CHDK "Ehanced Photo Operations" menu.   For convenience, you can also disable all the override settings using the Disable Overrides option in that menu.

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Could you provide any general descriptions that might serve as a guide to me, and anyone else who might be browsing for information?
Typically, a good script will override things that need to be overridden to accomplish the purpose of the script.  Other camera settings (e.g. JPG size, white balance)  are up to you.  I can't teach you how every feature in your camera (or CHDK) works in a forum post though - you'll  have to read and experiment on your own. 

Generally speaking, if you put the camera in to "P" mode and leave its settings at the Canon & CHDK defaults you will get good results running most scripts. Exceptions to that statement are usually posted in any of the script's "documentation" (  wiki, readme.txt file, forum posting ).


metero2.lua script options :
  • Tv exposure (secs) : Tv is short for time value and defines how long the camera's shutter stays open
  • ISO : ISO (or Sv for sensitiviy value) is a standard camera term from back in the days of film that defines how sensitive the sensor (or film) is to light.  Higher numbers mean more sensitvity (at the cost of more noise)
  • Av (f-stop): means aperture value - a standard photography term for the ratio of the lens focal length to the diameter of the lens opening - small numbers mean a bigger opening
  • ND filter : most Canon P&S cameras have an internal neutral density filter that can be inserted in the light path. This decreases the amount of light that reaches the camera's image sensor. This can theoretically be useful during long exposures where you wish to record movement (star trails) without overexposing the image.
  • Total shots (0=infinite) : the script will take as many shots (pictures) as you specify with this number.  If you set this nubmber to zero it will shoot until you manually stop the script or you run out of battery power or SD card space
  • Zoom position : your camera has a zoom lens - this setting tells the script where to set the position of that lens
  • Enable Raw : CHDK allows the camera to save RAW or DNG images as well as JPG.  This setting causes the script to enable that feature when the script runs, overriding the setting in the CHDK menus
  • Focus @ Infinity Mode : a camera lens needs to be focusses somewhere,  Normally the Canon firmware does this automatically for you.  This setting overrides the camera firmware and forces the lens focus to be at infinity (i.e. way off in the distance where the stars can usually be found)
  • Dark Frame Mode - tells the script to periodically leave the camera's shutter closed so that no light gets in during a shot. That particular image will only contain sensor noise ( google for "amp glow") and can be used in post processing to remove noise from the other images.
  • Shots per Dark Frame : determines how often the script takes a dark frame image - useful because the noise captured changes over time as the camera's image sensor temperature changes
  • Display Off : turns off the camera's LCD display to save a little battery power and your "night vision"

HTH
« Last Edit: 16 / October / 2014, 06:41:22 by waterwingz »
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