r/askastronomy • u/Fooad4444 BeginneršŸŒ  • 10h ago

Mount keep moving mid frame

/r/AskAstrophotography/comments/1w4k4i1/mount_keep_moving_mid_frame/

Any help appreciated

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u/ramriot 10h ago

A few things to check or be aware of:-

- There is backlash in the SLT drive system that can partly reduced my mechanical adjustment** & corrected for in firmware.

- If there the system is in balance in certain ways it can wobble on the backlash.

- The weight limit plus imbalance may be a hard mechanical limit for the tiny gears in the drive / the friction plate in the altitude bearing**.

- The amount of field rotation limits due to alt-az use the exposure to 15-30 seconds max.

- Pointing the scope near the zenith has issues because it hits azimuth drive rate limits etc.

- Of you only have one camera I don't think you can guide & image at the same time.

** The SLT backlash increases over time because the maker did not use thread-lock on the internal screws holding the gearboxes in place & the main azimuth gear. Also over time with repeated temperature cycles the lubricant in the gearboxes migrates to the altitude friction plate & changes its friction profile.

Suggestions:-

- If you really need the main telescope, use it for guiding via a small ST4 compible guide camera or similar while using a better astro-camera on a smaller lens (under the total weight limit) for deep imaging. It might even be possible to reverse this.

  • Get or make a Equatorial wedge for the mount & set the controller to Equ tracking mode.

- With the mount as an equatorial if you are not using it, remove the main scope & use a dovetail to fix a camera & lens to it. With perhaps a guide camera (though not as much needed because exposure time can be much longer if properly equatorial aligned) NOTE: to have a slight imbalance & be aware of where it flips so that backlash is always taken up smoothly.

- ALWAYS use an external power source on this mount, the internal batteries are really only for protecting against accidental power loss.

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u/Fooad4444 BeginneršŸŒ  9h ago

Thanks for the info

My mount doesnt have battery

And its a big telescope my st120