How can I stop planets drifting out of my telescope's field of view?

BBC Sky at Night Magazine's Scope Doctor Steve Richards solves your practical astronomy ailments.

Catch Jupiter and Mars after 04:00 UT low above the southeast horizon on 20 March (inverted telescope view with south up). Credit: Pete Lawrence
Published: March 17, 2020 at 8:12 am
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When I image planets with my Celestron CPC 925 they disappear from view after a few seconds. I finish my alignment pointing up and right to take out backlash, but what else can I do?

Steve says: "The Celestron CPC 925 is a Schmidt-Cassegrain telescope mounted on a Go-To altazimuth mount, which should be capable of keeping a planet in the field of view for minutes rather than seconds. However, it would appear that the mount is not tracking correctly, if at all.


You already have a strategy in place for taking up backlash but make sure that there isn’t still a lag before the drive takes up the slack.

Next, check your GPS is right and that the correct hemisphere, location, date, time and daylight savings settings are in place.

If these settings are correct then after the mount has confirmed you have located your chosen planet, you could try pressing the ‘Enter’ key again to start the mount tracking as some mounts require this extra step.

These mounts can be susceptible to imbalance in the altitude axis so make sure that the telescope, with camera attached, is balanced correctly by adding weight to the front of the telescope if required."


Email your astronomy queries to Steve at and it could get answered in a future issue of BBC Sky at Night Magazine.


Astronomer Steve Richards
Steve RichardsAstronomer and author

Steve Richards is a DIY astronomy expert and author of Making Every Photon Count: A Beginner’s Guide to Deep Sky Astrophotography.


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