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Telescope troubleshooting and FAQ

Telescope troubleshooting and frequently asked questions (FAQ) for beginners.

These questions are common for those starting out with a new telescope in astronomy. Some of these are focused on the Celestron Astromaster equatorial models.

Please also check out my getting started with a telescope and other astronomy beginner’s guides.

Eyepieces and optics

Telescope troubleshooting and FAQ relating to eyepieces and optics.

Planets are small targets requiring high power eyepieces and typically the use of a barlow lens. Without this magnification you will see little more than a star-like point or tiny disc.

A 4-6mm eyepiece and 2x barlow is ideal for viewing on the Astromaster 130EQ.

You can check the field of view for your telescope, eyepieces and targets using a FOV calculator. provides a handy free FOV calculator which is very handy while getting started with a telescope.

Planets are small targets and will only appear as star-like dots without a high power eyepiece.

A 4-6mm eyepiece and 2x barlow is a great combination for observing the planets.

For deep sky objects you generally want a low power eyepiece – 20mm or lower, e.g. 25, 32, 40mm eyepieces.

For DSOs you need as much light as possible as they will be very faint to observe. Increasing magnification decreases the brightness of the image that you will see in the eyepiece.

You can check the field of view for your telescope, eyepieces and targets using a FOV calculator. provides a handy free FOV calculator which is very handy while getting started with a telescope.

If you have 1.25″ circular filters, these simply screw onto the bottom of any threaded eyepiece. Place the eyepiece (with filter fitted) into the focus tube and look through the telescope as you usually would.

Yes, you will need a T-adapter for your camera model. These are cheaply available on Amazon, eBay and other outlets.

However, to achieve focus you will need to use a barlow lens or fit a low profile focuser to the tube.

A low-profile focuser will bring the camera closer to the tube to allow it to achieve prime focus.

Without a low-profile focuser, you need to unscrew the lens from a metal-bodied barlow extension tube and screw this directly to the threaded T-adapter. The lens brings the focal point closer and allows many DSLR camera’s to achieve focus – however, it does reduce the field of view.

To achieve focus with a DSLR you will need to either fit a low profile focuser to the tube or use a barlow lens. See “Can I connect a DSLR camera to the 130EQ for astrophotography” above.

This is a focus aid that fits to the aperture (open end) of the telescope. It causes a distinctive diffraction pattern that allows very accurate focusing of the telescope.

  • Check lens and eyepiece caps are removed.
  • Check if you’re not leaning on the telescope or holding the focuser. The stand is delicate – these can cause the image to shake violently or even push the telescope off-target.
  • Check target is not too close. Non-issue for astronomy, but for land-viewing targets must be over ~60m away.
  • Check you have checked throughout the focuser travel.
  • Check that the telescope is on target. The red dot finder scope can be easily knocked out of calibration. A low magnification eyepiece and easy-to-find target (e.g. Moon, Polaris) can be used to realign the finder scope.
  • The image may simply be out of focus. If the target is not focused the light can be dispersed so much that you cannot make out any light in the eyepiece. Do try adjusting through the whole travel of the focuser while looking in the eyepiece.
  • Dim targets may not be visible. The light gathering ability of each telescope is different and poor skies or high level cloud can obscure faint targets completely.
  • Ensure your eyes are acclimatised to the dark – especially for dim targets. Try to find a dark site and turn off any lights you can. Even looking at a phone or camera screen will reduce your ability to see faint targets like galaxies and nebulae.
  • Don’t use the telescope through windows or sky-lights if you can avoid it. This will introduce distortions in your image.

You can leave the main cover over the aperture, but remove the smaller cap to reduce the aperture and brightness of very bright targets, like the Moon.

It is not for looking at the Sun! NEVER direct a telescope towards the Sun without a proper solar filter fitted to the main aperture of any telescope.

CG-3 equatorial mount and controls

Telescope troubleshooting and FAQ relating to equatorial mounts and controls.


  • Check tripod legs, axes and fixings are square, level and tighten them. Be careful not to overtighten.
  • Setup the scope with the legs collapsed to their lowest height – this will lower the centre of gravity for the best stability.
  • Ensure you level the mount and try to use a stable ground like grass.
  • Ensure the telescope is well balanced on the mount.
  • Counterweights should be as close as possible to the optical tube. Position two weights close to the tube rather than one weight at the end of the counterweight bar.
  • Add additional weight to the accessory tray, hung from it or on the legs – e.g. sandbags.
  • Carry out accurate polar alignment.
  • Ensure that you lock the axis thumbscrews tightly.

The declination (DEC) axis control has a limited number of turns. Inspect the mechanism in good light so that you understand the limit of travel.

You will occasionally need to unlock the axis and wind back the control.

Do not overturn the declination (DEC) control as it will damage the thread on the mechanism.

Between the locking thumbscrew and the counterweight bar there should be a small metal pin/bar/slug. Without this the locking thumbscrew will not push and grip against the counterweight bar to hold the counterweight in place.

If you have removed a counterweight and now unable to replace it. Check for a small metal bar (~0.5cm long) around where you were working. A magnet and torch may be helpful.

Unfortunately not. Each time you move the telescope to a new location the mount needs to be polar aligned to the north/south celestial pole.

These are setting circles. They can be used for navigation to different objects once the telescope has been fully polar aligned.

Check that you have not over tighted the mechanism in either direction. The declination control only has a limited number of turns and over turning will cause damage.

Unlock the declination axis and wind back the control occasionally before relocking the axis to ensure you are within the working limits of the mechanism.

If you have a motor drive fitted to your telescope mount then this will prevent you from manually controlling the right ascension axis with the slow motion control.

Instead, unlock the axis and move it manually before relocking the axis – using your aligned finder scope to bring the target into view. You can turn off or vary the speed of the motor to improve targeting once close to the target.

If the lack of movement is not due to a motor drive:

Check the slow motion control is attached to the axis correctly: These usually have a small thumbscrew at the end. The control should be positioned over the axis shaft and the thumbscrew tightened onto a flat cut-out on the shaft to hold the control securely.

Check for and remove any debris on the right ascension (RA) worm gear: where the axis control rod passes through the stand there will be a worm gear that transfers the turning of the control into rotation of the axis. Inspect this and brush or vacuum away any dirt or debris that could be jamming the mechanism.

Celestron customer support is actually very helpful and may be able to organise a replacement for you.

Alternatively, there are a number of 3D printable replacements online, such as this one by Neil19.

Motor drive

Telescope troubleshooting and FAQ relating to motor drive units.

The motor drive moves the scope on the right ascension (RA) axis at an adjustable speed.

Once polar aligned, this means that targets can be tracked across the sky and stay within the eyepiece for long periods of time.

In tandem with polar alignment the motor drive can add significant enjoyment to your experience. It is especially helpful if you intend to carry out any astrophotography.

As a relatively low-cost accessory, the motor drive is definitely worth considering.

See the Celestron website for details on the AstroMaster/PowerSeeker Motor Drive.

Your telescope must be polar aligned in order for the right ascension axis and motor drive to track targets.

If the telescope appears to move away from the target even quicker, check the hemisphere is set correctly (North or South) on the motor drive. A large number of drives have this marked in reverse – so do switch the setting if you are experiencing difficulties.

Red dot finder scope

Telescope troubleshooting and FAQ relating to the celestron starpointer red dot finder scope.

The red-dot “StarPointer” finder scope that comes with the newer/current Celestron Astromaster 130EQ models requires a CR2032 button/cell type battery.

The battery and switch contacts can be intermittent on these scopes. Give them a blow and turn on/off wiggle to check it isn’t a bad contact before you waste money/a perfectly good battery.

  • Check from rear of tube moving eyes up/down/left/right to check for the red dot.
  • Check finder scope is turned on – the smaller dial mid-way along the right of the finder. The contacts on these can play up – so do try turning on/off and vary the brightness.
  • Check the battery is fitted. The contact for this can be quite loose, kitchen foil can be added to pad securely.

Other frequently asked questions

Telescope troubleshooting and FAQ relating to any other topics.

The Celestron Astromaster 130EQ doe not come with the primary mirror centre spotted. This is presumably the case with other Celestron Astromaster models.

Centre spotting is useful in order to carry out alignment and collimation of the telescope’s optics. This will allow you to obtain optimal image quality and pin-point stars.

Unfortunately not. Each time you move the telescope to a new location the mount needs to be polar aligned to the north/south celestial pole.

If you keep the telescope stored properly – dust covers fitted and telescope pointing down – you should not need to clean you scope for 6-12 months. Please follow my mirror removal and cleaning guides if you do need to clean the mirrors.

Please take a look at my other beginner’s astronomy guides, follow my journey or join me on twitter.