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Astrophotography and Sketching >> Beginning and Intermediate Imaging

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Jersey Star Man
sage


Reged: 05/08/10

Loc: Seaville, New Jersey
Total Beginner in need of HELP !
      #5600222 - 01/01/13 07:49 PM

Hello everybody,
I have some questions and need some advice on a project I offered to help my daughter with. For her 7th grade science fair project she decided on light pollution as her subject. Our idea is to take one of our telescopes to multiple areas with skies that have different light pollution. On nights with no moon interference, we plan to center telescope on Polaris and take a picture using identical camera settings, and eye piece at each location.
By doing so we hope to capture a view of how many stars are visible in the same field of view, with light pollution being the only variable.
Now, I need to connect my Canon G10 camera to the focuser of one of our scopes. I have nothing at all in this area.. no equipment, no experience. Hoping to do this the easiest, most economical way possible. I have seen some adapters at a CNC website, as well as on eBay. I thought coming here I could get some great advice before I spend any money.. (trying something new for 2013)
Thank you in advance for any advice, thoughts, links....
Happy New Year !


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nemo129
Post Laureate
*****

Reged: 01/03/10

Loc: WMass
Re: Total Beginner in need of HELP ! new [Re: Jersey Star Man]
      #5600254 - 01/01/13 08:09 PM

If you cannot get the picture method to work. I think you will need to do afocal with that camera using something like this, you could always use the skyfog measurement to quantify light pollution in different areas. Here is one method of calculating the skyfog value using a camera.

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RedLionNJ
scholastic sledgehammer


Reged: 12/29/09

Loc: Red Lion, NJ, USA
Re: Total Beginner in need of HELP ! new [Re: nemo129]
      #5600346 - 01/01/13 09:11 PM

Cool project, but would be so much easier (from a technical perspective) with a DSLR at prime focus. There are approximately three dozen stars of mag 15 or brighter within 8 arcmin of Polaris (just a guess at likely field size using afocal).

When reducing data, however, make sure to remember sky transparency and seeing are also going to be significant factors in how many stars are recorded. Poor transparency can be mistaken for light pollution and poor seeing can blur images of faint stars over a sufficient number of pixels so as to make the stars invisible to the sensor. Ideally, you'd want to estimate both these factors when taking each exposure and somehow factor them in when reducing the data.

Good luck!

Grant


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shawnhar
Postmaster
*****

Reged: 06/25/10

Loc: Knoxville, TN
Re: Total Beginner in need of HELP ! new [Re: RedLionNJ]
      #5600500 - 01/01/13 10:56 PM

I think you would show the effects of light pollution much better just using the camera and a tripod. Use the TV mode and 15 second exposures, no zoom. Take 40 exposures and stack them in Deep Sky Stacker, do that for each location and process them in Photoshop or free software like Gimp or Paint.net using the same settings.

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Pauls72
professor emeritus
*****

Reged: 10/28/07

Loc: LaPorte, IN
Re: Total Beginner in need of HELP ! new [Re: shawnhar]
      #5600563 - 01/01/13 11:57 PM

On of the members of our club was the driving force behind this project. It might give you some idea's.
http://www.lettherebenight.com/

Set you camera on a tripod pointed at Polaris with the camera settings the same every night use either a cable release, remote release or the camera timer to trip the shutter. Put the camera on manual with roughly a 30 second exposure and ISO 1600.

An even better way would be to get a Sky Quality Meter and take readings at each site.
http://agenaastro.com/unihedron-sky-quality-meter-sqm.html


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Jersey Star Man
sage


Reged: 05/08/10

Loc: Seaville, New Jersey
Re: Total Beginner in need of HELP ! new [Re: Pauls72]
      #5606954 - 01/05/13 04:54 PM

Thank you for the replies! I put my G10 on my Zhumell tripod last night and started to try it out. Not sure what I did to make this work as I am just a point and shoot guy. got out the book for my camera and was amazed at what all it can do.. found the 1600 ISO easy enough, it was the shutter speed I had a bit of trouble finding and understanding. After the fact the details of the photo shows I had the shutter speed at 15.0 . aperture is f2.8
Any other hints or tips? Seems grainy or something ? Thanks for the help so far and any other recommendations you could offer up.


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terry59
Post Laureate
*****

Reged: 07/18/11

Loc: Colorado, USA
Re: Total Beginner in need of HELP ! new [Re: Jersey Star Man]
      #5607073 - 01/05/13 06:09 PM

The compression required to post images here makes it difficult to provide a good assessment. Create an account at astrobin and post full size images.

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Pauls72
professor emeritus
*****

Reged: 10/28/07

Loc: LaPorte, IN
Re: Total Beginner in need of HELP ! new [Re: terry59]
      #5607643 - 01/06/13 12:50 AM

Quote:

The compression required to post images here makes it difficult to provide a good assessment. Create an account at astrobin and post full size images.




You camera has multiple ways to save the image to the memory card. Use the "RAW" mode. RAW is an uncompressed image and has a lot more detail than you can see visually. When you save your images in one of the default modes they are saved in JPEG. In the JPEG format the camera compresses the image and a lot of the detail is lost.


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Phil Sherman
Pooh-Bah


Reged: 12/07/10

Loc: Cleveland, Ohio
Re: Total Beginner in need of HELP ! new [Re: Pauls72]
      #5612114 - 01/08/13 02:54 PM

If you're looking at light pollution, you might consider looking at the average brightness level of the image. All images taken with the same equipment and exposure should have an average pixel value that's primarily dependent on the background sky brightness. This eliminates the effects of seeing but not sky transparency.

I've seen this effect when imaging from home, a club observatory, and a truly dark site. For all but the dark site, maximum imaging time is limited by sky brightness, which shows up as the average pixel value in an image.

Phil


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Jersey Star Man
sage


Reged: 05/08/10

Loc: Seaville, New Jersey
Re: Total Beginner in need of HELP ! new [Re: terry59]
      #5612441 - 01/08/13 06:18 PM

Quote:

The compression required to post images here makes it difficult to provide a good assessment. Create an account at astrobin and post full size images.




http://astrob.in/29399/ <There it is...


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shawnhar
Postmaster
*****

Reged: 06/25/10

Loc: Knoxville, TN
Re: Total Beginner in need of HELP ! new [Re: Jersey Star Man]
      #5612647 - 01/08/13 08:26 PM

It's a singe 15 second exposure at iso 1600 with a point n shoot at F2.8...
It's gonna be grainy/noisy, that's just the way it is, point n shoot cameras have a lot of digital noise, but, like I said, take 40 of them, put them in Deep Sky Stacker, then use software like Photoshop, Gimp, Fitswork, etc to process the picture and you will reduce the noise exponetially.
But there is a steep learning curve to all that, don't know if you want to spend that much energy on this project. You COULD just use a noise filter on your single exposures to make it a "little" better and go with that. Lower ISO will have less noise but show less stars n stuff.
Careful, your kid's project may lead you to the "dark side" of astro imaging.


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