I’m having trouble setting up MaxIm DL software for autofocusing. Any advice?

Steve says: "MaxIm DL is a powerful image capture program, but the key to getting the autofocuser routine to work well is ensuring that the equipment settings are accurately entered.


The system needs to know how far your focuser moves for one step of the focus motor, so select View – Observatory Control Window – Focus.

With the focuser set at half its extension, enter 100 in the Incremental box and then click on the ‘Move In’ button to take up any backlash. When the motor stops, measure the extension of the focus tube from the focuser housing in millimetres.

Next, enter '1,000' in the Incremental box and click on the ‘Move In’ button. Re-measure the extension and calculate the distance moved in millimetres.

Click on the ‘Options’ button and enter this value in the Focuser Step Size box – never use the ‘Auto’ button.

Select the Microns radio button and enter your telescope’s focal ratio in the box. In the Target ½ Flux Dia. box enter a value between 7 and 9 as this sets a higher than desirable focus target.

This is required as the measurements are made on either side of focus, not at focus."


Email your astronomy queries to Steve at scopedoctor@skyatnightmagazine.com and they 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.