Focusing a Telescope: How To Get Better Views Of The Planets

If you’re feeling frustrated with the views you’re getting of planetary details, the following may help. It involves a test, with 12 questions to help solve telescope focus problems and other viewing frustrations.

telescope focus and finder scope on Dobsonian telescope
Focuser and finder on a Dobsonian telescope

Is this your: “I couldn’t see the stars clearly because my telescope is blurry”? Let’s take a dive into what could fix this. We’ll start with getting the object in your view first.

Getting the sky object in clear view

Start with a low magnification eyepiece in your telescope as it will give you a wider field of view.

Use your finderscope to locate the target, e.g. star or planet.

Once your finder scope has the object in its crosshairs, move to look through the telescope eyepiece and to see it centered in your view. The image might be upside down – I wrote about ways to fix this.

With the planet in sight, fine tune your view by rotating the knob on the side of the focuser either way until you see a clear and sharp image.

The focuser should move smoothly. What it does is adjust the distance between the eyepiece and the telescopes lens/mirrors to project a sharper image.

You may need to keep re-adjusting the position ever so slightly as the Earth rotates and the object appears to move across the sky.

A sky map app or guide will give you a good idea of where to find planets visible in your area.

13 reasons you’re not getting the best possible views of planets with your telescope

When there’s seems to be a problem with the focus…run this test on why your views of planets through a telescope aren’t satisfactory. It involves 13 questions.

If you think you’re not getting the best view of the planets through your telescope, ask yourself…

  1. Are you looking at a planet that has little to no detail?
  2. Are you limited by the size of your telescope?
  3. Are you using the appropriate magnification?
  4. What are the atmospheric conditions (bad turbulence?)
  5. Position of planet: Is the planet just too low on the horizon?
  6. Do the optics need collimation?
  7. Are heat sources interfering, e.g. rooftops or air conditioning vents?
  8. Are you indoors looking through a window?
  9. Has the telescope adjusted to the surrounding air temperature?
  10. What’s the quality of your optics?
  11. If using a diagonal, is it in place properly?
  12. Is it the Barlow lens or the eyepiece causing the blurriness?
  13. Do you need a filter to improve contrast?
  14. Is there a defect in the lens? – see my article on astigmatism in refractors.
  15. Are there other aberrations relating to quality of the optics?

Read on for how you might resolve your telescope focus problems or other issues interfering with your views.

Planetary detail

Some planets have little to no detail when looking at them through a telescope. Venus is an example, because Venus has a thick atmosphere. As I wrote in what you can see of Venus through a telescope, that’s all you’ll get to see (unless you’re experienced enough with the right gear to see contrasts in the cloud blanket).

The following, which I wrote, will help you with the details you’ll likely see with certain planets:

Aperture size

How big is your telescope? The size of the aperture determines the light gathering ability of the telescope. Light gathering comes before magnification in terms of telescopic power. I cover this in what to look for in a telescope. For better views of planets, consider at least a 6″ in a reflector.


Magnification to see good details of planets can range from 30x to 300x, depending on the target planet and the viewing conditions. I cover magnification for each planet in my write up on telescopes best suited to planetary views.

You should know that telescopes have a maximum useable magnification (though viewing conditions can limit what can be achieved).

If magnification is the problem, you might need a better quality telescope or an extra eyepiece, depending on your set up.

Atmospheric conditions

Although, planets are bright enough to view with the typical suburban light pollution, a location that’s dark, dry, and elevated will give you the best experience.

See my article on some of the best places to stargaze, which has a link to a tool showing designation dark sky sites.

Apart from pollution, air turbulence, cloud cover, and mist are things that can interfere with views.

What can help? Cloud Forecast – From Clear Outside, will give you the outlook for your local atmospheric conditions, so you can know when conditions are favorable.

Timing & position of planet

Timing: No matter what telescope you use, you will get the best views of planets when the planets are closest to Earth. Sky map apps will keep you up to date with notifications of these events.

For example, Mars, especially its white poles, can appear clearer when it is closest to Earth.

Position: When a planet rises at sunset, wait until it is higher in the sky for the best views (i.e. a few hours later, after sunset).

Collimation & telescope blurry blues

If you are using high magnification for planet viewing, optics being out of alignment will affect the telescope’s performance. 

Are all optical elements aligned on the same axis? 

If not, you might need to collimate your scope. This is especially important for Newtonian reflectors and more so with short focal ratios (< f/6).

This applies less to refracting telescopes – see my article on refractors vs reflectors to find out more.

This is about aligning the optics. In some, it is simply a three-step process. 

  1. Align the main mirror roughly 
  2. Position the secondary mirror 
  3. Fine-tune the alignment of the main mirror 

Still, check the specifics for your individual telescope which are often on the website.

Refracting telescopes and Maksutov Cassegrains rarely need collimation.

Schmidt Cassegrains sometimes need it but the long focal ratios of these scopes mean that small collimation errors are less noticeable. Though, I have a step by step article on collimating an SCT and another on collimating Dobsonians.


The best outdoor gift to yourself is to get some extra eyepieces. Which are the best eyepieces for viewing planets? I cover the features and metrics to consider in my article of what to look for in telescope eyepieces.

But for the ones that you have, do they need cleaning? Check them for smudges or gunk. I have an article covering how to clean eyepieces that includes the dos and don’ts, that will help here.

Barlow lens & star diagonals

If you suspect the problem is your Barlow lens, my article on how to use a Barlow lens might help. In this I also cover where to place the Barlow lens if using a star diagonal if you’re worried that it’s misaligned.

Using filters

Filters can improve what you can see. Red/orange filters should help you view the polar caps and major landmarks like Syrtis Major and Hellas on Mars. This will depend on what side of Mars is facing the Earth.

Getting hold of a good selection of color filters and having an understanding of the landmarks will also help just as much as having the best eyepieces to see details and contrasts on the planet’s surface… Check out my article on explaining the ins and outs of telescope filters.

Final thoughts on improving telescope focus

A sharp focus is what you want when looking through a telescope to view planets. To get better views, there are a few variables to consider in regard with focusing, as I mention. But one main factor that helps improve your night sky views is experience and learning. The more you use your telescope the more confidence you’ll gain with knowing how bet to get those views.