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Stargazing Viewing Saturn from a 6 telescope

  1. Feb 17, 2008 #1
    Viewing Saturn from a 6" telescope

    Hello

    I am not quite sure what resolution i am suppose to see if i look through saturn in my Orion 6" newtonian reflector at 300X. Can anyone show me a picture of saturn from a 6" telescope that is not editted? Thank You

    Scott
     
  2. jcsd
  3. Feb 17, 2008 #2
    You'll know Saturn when you see it. It won't be very large in your field of view; fairly small infact... a dull yellow in color. The rings will be obvious at times and much more difficult to see if the viewing angle is edge on. I don't know what the current angle is relative to Earth.
     

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  4. Feb 17, 2008 #3

    russ_watters

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    At 300x, it's much bigger than that. More like this:

    That's a simulation based on an image I took with a 4" telescope and a webcam. I desaturated it, lowered the contrast, and blurred it. So you should be able to see it at least as well. Some things to look for to make sure you are seeing what you should: the Cassini division (the division between the rings) and banding on the planet surface.

    Btw, I calculated that pic to be 300x magnification based on an 18" viewing distance from a standard monitor.
     

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    Last edited: Feb 17, 2008
  5. Feb 18, 2008 #4
    Wow, nice picture.

    I can see something similar to the picture above but i can't manage to take a picture like that. All my pictures comes out tiny and an example is the picture below. What settings do I need for the picture and do i need a motorized scope to take pictures?

    P.S. - The picture i took is from a digital camera and the exposture is set at 1/8 sec. The scope is not a motorized scope.
     

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  6. Feb 18, 2008 #5

    russ_watters

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    My pic above was taken with a webcam. Webcams actually get better results than regular digital camers because the technique is to take a large number of frames and stack them with software such as Registax.
     
  7. Feb 18, 2008 #6
    In order to stack lots of frames, the saturn must stay in the same spot within my eyepiece? So do i need a RA motor for that?
     
  8. Feb 19, 2008 #7

    russ_watters

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    No, but it helps. There are people who are able to get a webcam to snap a few dozen frames while it crosses the field of view. Trying to track manually can work too, but it can also make it jump around. Registax will follow the planet around and line-up the separate frames, but there is a limit to the "jumpiness" it can handle. You can also align them manually, but that can take a while if you have a lot.
     
  9. Feb 19, 2008 #8
    Thank you for the reply.

    I used registax as you suggested (aligned and stacked some pictures together). Below is the picture of saturn after registax. The image certainly looks better than before but is still much inferior than other 6" pictures. I can see good quality images from my telescope but I can't manage to capture the quality images... Is this because of my digital camera or is it because I only used 1/8 sec exposture? Furthermore, is there anything I should note when taking a picutre of saturn?
     

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  10. Feb 19, 2008 #9

    russ_watters

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    Exposure is fine, magnification could be higher though (try a barlow). The problem is that you probably only stacked a small handful while with a webcam you can integrate hundreds of pictures and that's how you get the more detailed pics. You should be able to do better than the pic I posted above - your telescope is better than the one I used to take that pic (plus, like I said, I lowered the quality a little before posting it here).
     
  11. Feb 20, 2008 #10
    Thank You for the reply.

    I did stack around 200 frames to get this. But am i allowed to have extra magnification? I thought the therotical maximum limit to a 6" telescope is 300X magnification. I tried looking through 600X and it looks slightly blur.
     
  12. Feb 20, 2008 #11

    russ_watters

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    The theoretical max is about 300x, but that photo you posted is not 300x magnification, it's more like 150. What method did you use to take it and what kind of camera did you use? Eyepiece? Barlow?

    Most decent astrophotos are taken with a camera that has no lenses and no eyepiece on the scope. The telescope's objective lens (and a barlow) is all there is and the camera is located at its prime focus.
     
  13. Feb 21, 2008 #12
    I just placed the camera to the eyepiece (I think its called the afocal method, but i am not too sure...). But i used a 2X barlow and a 5mm eyepiece. The camera i used was a normal digital camera for daily use (lumix fx8).

    I can't really pull the lenses off the digital camera, does this mean that i need to buy a camera that allows me to do that?
     
    Last edited: Feb 21, 2008
  14. Feb 21, 2008 #13

    russ_watters

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    That's what's great about webcams - it's easy to pull the lens off and modify them for astrophotography.

    Among the problems with the afocal method, is the more glass you have between your sensor and your subject, the more distortion and lost light you get. With prime focus, it's just the mirror and the sensor (+ a barlow). Your results are actually pretty good for afocal.
     
  15. Feb 21, 2008 #14
    I read from a website that using prime focus, the magnification is around your focal length divided by 50. Thats 750/50=15 for me. Even with a 2X barlow, thats only 30X. I don't think you can actually see saturn that well with 30X. Does this mean I have to get a 10X barlow lens or something? Or can i just zoom with my camera?

    P.S. - Can any webcam work? Can one of those cheap webcams used for MSN conversations work?
     
  16. Feb 21, 2008 #15

    russ_watters

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    Not sure what website that was, but at prime focus, the magnification depends on the size of the camera's sensor. Here's a calculator: http://www.thecgo.com/id28.html. Typical pixel sizes are 6x4um, but I'm not sure what the SPC is.

    Still, you'd want to use a 5x barlow if you can find one. People also stack them.

    Better webcams do work better. The Phillips SPC900 is the favorite of photographers.
     
    Last edited: Feb 21, 2008
  17. Feb 24, 2008 #16
    I would also like to ask if 0.5seconds is the correct shutter speed for saturn? Does stacking two 0.25 seconds photo make the photo 0.5 seconds?
     
  18. Feb 24, 2008 #17

    russ_watters

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    It really depends on your camera, but generally .5 is too high. Also, no, stacking averages frames, so they don't increase in brightness much, just in signal to noise ratio.
     
  19. Feb 26, 2008 #18
    Thanks for your reply

    I went into registax and randomly played with the wavelet filter bars, and the resultant image is actually better than before (picture attached below). I would like to ask if there is a definite setting that i should use for the wavelet filiter or is it trail and error?
     

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  20. Feb 26, 2008 #19

    russ_watters

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    Wavelets have been trial and error for me. They usually look like a bell curve when I'm done. Btw, try the "colorweight" settings in the "histogram" tab to balance the color...

    I also have a Registax tutorial on my website that may be helpful: http://www.russsscope.net/staxtutorial.htm
     
  21. Mar 20, 2009 #20
    Re: Viewing Saturn from a 6" telescope

    Awesome! How do I hook my webcam up to my telescope? My webcam has a USB type cord and I don't see anywhere I can plug that into my telescope.
     
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