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Krisko

Black dots while observings planets

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Hello everyone!


Last night i went to observe planets with my Celestron AstroMaster 90EQ.I tried to look at Jupiter,Venus and Mars.All of them were really bright,there was no big difference in color quality.Venus and Jupiter had same colors (bright color,something like white), only Mars was red.While observing all of them, there were black dots in the eyepiece, i think its inside the scope, maybe dust inside the scope ? Also, the quallity is not good , i cant see any details.

 

P.S the sky was clear (only at the end of horizonts there have been clouds)

Edited by Krisko

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I suspect that you have not achieved proper focus with your telescope which is allowing some internal dust to become apparent - the planets will appear quite small in your telescope but you should see quite different colours between Venus and Jupiter.

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I believe you did not focus your telescope properly.

Only time you should be able to see dust particles (and there are going to be some most of the time) - is when you don't focus your telescope at infinity.

What sort of eyepiece did you use? With supplied eyepieces (10mm one), planets are going to look like a pea held at arms length (more or less - Jupiter will be about that large, Mars about two times smaller, and Venus at this time should be smaller than the mars). If planets were larger than this in your eyepiece and showing no features at all - you did not focus properly.

Another sign to tell you if you had proper focus is to remember what the Venus looked like - it should have looked like Moon past quarter phase - Venus is now positioned so that it is not fully illuminated and you should see that part is "missing".

Here is what it should look like:

image.png.570a65ac5b88979877a256619801e5fe.png

If you did focus your telescope properly and still seeing dust particles - you might be experiencing "floaters". This is impurity in your eyes that you don't normally see during the day. These are easy to recognize because they don't stay in fixed spot - as you move your eye around they seem to float in front of you (hence the name - floaters).

As for floaters - not much you can do about those - learn to look past them, and they tend to be seen only on very high magnifications (actually more related to small exit pupil, rather than magnification, but those two are connected).

 

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10 minutes ago, vlaiv said:

I believe you did not focus your telescope properly.

Only time you should be able to see dust particles (and there are going to be some most of the time) - is when you don't focus your telescope at infinity.

What sort of eyepiece did you use? With supplied eyepieces (10mm one), planets are going to look like a pea held at arms length (more or less - Jupiter will be about that large, Mars about two times smaller, and Venus at this time should be smaller than the mars). If planets were larger than this in your eyepiece and showing no features at all - you did not focus properly.

Another sign to tell you if you had proper focus is to remember what the Venus looked like - it should have looked like Moon past quarter phase - Venus is now positioned so that it is not fully illuminated and you should see that part is "missing".

Here is what it should look like:

image.png.570a65ac5b88979877a256619801e5fe.png

If you did focus your telescope properly and still seeing dust particles - you might be experiencing "floaters". This is impurity in your eyes that you don't normally see during the day. These are easy to recognize because they don't stay in fixed spot - as you move your eye around they seem to float in front of you (hence the name - floaters).

As for floaters - not much you can do about those - learn to look past them, and they tend to be seen only on very high magnifications (actually more related to small exit pupil, rather than magnification, but those two are connected).

 

Thanks for answer. The image you show is not like my view. I observe it bigger thank this, with 20mm eyepiece. What do you mean with 'focus your scope' ? I paste it on the ground, and position it to the planet, after that i search it direct with the 20mm eyepiece. Also, all of my friends also see black dots, some says they see horizontal lines on the planets

Edited by Krisko

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When you insert your eyepiece and point scope to the sky (not necessarily to a planet, but you can point to planet as well) - you need to turn this knob:

image.png.a2094801669646a380a786ca88e1d9c5.png

until you can see stars as little dots, or clear view of the planet.

As you turn that knob, prism and eyepiece will move in / out the tube finding exact position where view is sharp - stars will appear as circles of changing size - you want your stars to get so small that they turn into sharp dots - just turn the knob in direction where stars are getting smaller until they become virtually points of light - this is good focus.

Then observe planet and adjust focus for best sharpness of features. At this time only features that you will see will be on Jupiter and Saturn. Mars is under global storm so it will appear smooth red. Venus appears smooth milky white most of the time (after a while you might be able to discern slight shadings across the surface, but that takes a lot of practice, but you will be able to see the shape as in above image and observe the phases of Venus).

Edited by vlaiv
typo ...
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4 minutes ago, vlaiv said:

When you insert your eyepiece and point scope to the sky (not necessarily to a planet, but you can point to planet as well) - you need to turn this knob:

image.png.a2094801669646a380a786ca88e1d9c5.png

until you can see stars as little dots, or clear view of the planet.

As you turn that knob, prism and eyepiece will move in / out the tube finding exact position where view is sharp - stars will appear as circles of changing size - you want your stars to get so small that they turn into sharp dots - just turn the knob in direction where stars are getting smaller until they become virtually points of light - this is good focus.

Then observe planet and adjust focus for best sharpness of features. At this time only features that you will see will be on Jupiter and Saturn. Mars is under global storm so it will appear smooth red. Venus appears smooth milky white most of the time (after a while you might be able to discern slight shadings across the surface, but that takes a lot of practice, but you will be able to see the shape as in above image and observe the phases of Venus).

Well, thank you very much ! I didnt know about this knob. Next time i will use it , and hope i will see them with more details and clearly :) THANK YOUUUU ❤️

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