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I have a 130mm (5") diameter Newtonian reflector with a 650mm focal length (f/5). I have collimated my telescope already but when I'm looking at Mars or Jupiter (not a star I'm sure), all I see is a white dot. Even if I use my 6mm with a 2x barlow, Mars still looks like a white dot but with a liiittle bit of a gray shade like a 3/4 moon. Of course I focused my eyepiece before. Why can't I see Mars or any other planet better than that ?

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    $\begingroup$ You might be completely out of phase with the eye piece. Try centering the object in the focuser without the eyepiece inserted. Then with the focus all the way in, insert the eyepiece and attempt to focus the object. Also, are you using a finder scope to align the object? or are you eyeballing it? If the former, you might need to align the finder. $\endgroup$ – LaserYeti Dec 15 '16 at 2:40
  • $\begingroup$ yeah i'm using a laser pointer to align what i want with my telescope, i align the finder scope during the day with a chimney far away. I don't know, maybe i'm missing something. $\endgroup$ – Chargnn Dec 15 '16 at 2:49
  • $\begingroup$ what about saturn? It sounds like the edges of your targets are not clear in view? are the round or blurry? $\endgroup$ – com.prehensible Dec 15 '16 at 8:53
  • $\begingroup$ Mars is very small at the moment - about 6" diameter - so it isn't going to look much more than a small oval shape. It should however be yellow/orange colour. $\endgroup$ – Dr Chuck Dec 15 '16 at 10:02
  • $\begingroup$ What do bright stars look like? are they nice bright points ? How about details on the lunar surface? $\endgroup$ – Wayfaring Stranger Dec 15 '16 at 15:55
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It seems that you haven't align properly your finder (or) laser. You can align at day with a chimney, but at night you must start with the moon and after that you are sure that you are pointing correctly move to a well known feature (like Pleiades cluster in Taurus) and try to find it with the scope (after that you can move to a star (maybe Mizar in Ursa Mayoris or Albireo in Cygnus if you are in the northern hemisphere) after that you must be sure that the finder and laser are pointing correctly.

Other question is that (probably) you are using a very high magnification with that telescope. I have myself a RTF newtonian 114 / 500 and I usually works with 20 mm eyepice (that is 25x), you are using about 216x that is almost the maximum theorically magnification for that aperture. Maybe you should use the 6 mm eyepiece without the barlow (that is 108x more or less) this should be enough but with cheap optics that could be a very high magnification also. I think that you could try with a bigger eyepiece... maybe 15mm plössl (30x and about 1.5º of size)

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