Why can't I see Mars clearly?

  • I just bought my first telescope - a Celestron CDC 1100. It came with a 40mm lens so with a primary focal length of 2800mm the power should be 70x.



    My problem is that I've looked at Sirius and Mars and they look clearer to my naked eye than with my telescope.



    I am able to focus from way out so I can see the 'blind spot' of the secondary mirror, go through 'focused' and then continue moving the mirror in the same direction until I again see the blind spot. So I know I'm focusing through when it should be 'good'. But, like I said, what I see is a relatively unfocused spot of light that is clearer and steadier with my naked eye.



    Admittedly, my 'seeing conditions' aren't very good since I am looking through my window in a suburban neighborhood where light pollution is pretty bad. That being said, I still see Mars and Sirius quite brightly - it's just that they never come into clear focus - nor are they any larger than when I look using my eyes. And when I move my eye around the eyepiece I see streaks of light in different directions originating from the target.



    There are many stars to be seen, though they are just pinpricks as I would expect given the seeing conditions. What I mean to say is that I cannot see all those stars with my naked eye but can see tens or hundreds more looking through the scope so I know it is gathering plenty of light as an 11" scope should.



    I tried both with and without the diagonal with no discernable difference.



    I have not collimated but supposedly it was collimated before leaving the factory and I would hope that even if it were off a bit from shipping I would still be able to see a sizable though fuzzy image of Mars instead of just a small speck of orangish light.



    Any thoughts as to what I may have done wrong or what may be causing this lack of clarity?


    Did you try it outside, without a window in-between? The window might cause light refraction.

    Are you asking 'Why is Mars fuzzy?' (you are shooting through a window) or is it 'Why isn't Mars bigger in my field of view?'

    @Jeremy, both. It was very small and very fuzzy - even when I thought it should have been in focus. I will add another comment to your answer below.

    Tracy, Where in So. Cal are you? there are lots of good astronomy clubs throughout the southland. I live in OC, and we have one of the best clubs around (The Orange County Astronomers). With around 800 members and a very active outreach and Astroimagers group, not to mention, one of the best dark sky sites of any club (and I've visted a lot). Our site might not be the darkest, but it's pretty good for light polluted So. Cal. as we have a good set of Amenities including a permanently mounted 22" Cassegrain in the clubs observatory, member observatories and Pads, with Electric and Wi-fi througho

    I don't see how to PM you. I am in Irvine. I looked at the OC club web page but didn't go any further than that. It looks like a great club.

    @CraigBob I converted this to a comment as answers should be restricted to just that, answering the question. As for where you guys might want to talk further [chat] may be the best place, we dont have a PM system on stack exchange sites. It does require 50 rep to get into the chat room however

    You definitely need to be outside.

  • Gerald

    Gerald Correct answer

    8 years ago

    Light pollution doesn't disturb the focussing, just the contrast.
    But non-uniform refraction of the window can.



    So try to open the window, if you can, or take a try outside.


    just opening the window won't do all that much, as you're causing a mix of warm and cold air in front of the telescope, but atmospheric blooming at its worst.

    The windows aren't perfectly plane, therefore cause distortions. That's at least my experience with observing sunspots with a solar projector. If temperature differences cause problems, the only other thing I can recommend is trying the telescope under free sky.

    I will be taking it outside tonight and look at the moon and Jupiter. However, I still don't have a good feeling about being able to see Jupiter any more clearly than I can inside. I hope I'm wrong but am a bit pessimistic. I also ordered a lens kit to allow more magnification. I'm hoping this will provide better views of the skies.

License under CC-BY-SA with attribution


Content dated before 7/24/2021 11:53 AM