Dithering without guiding

[ZiHao]

I have seen a lot of questions about this topic but didn't get a clear answer. Is there a way that I can dither without guiding using APT and PHD2? I am using ST4 cable now and mounting a DSLR + kit lens on my EQ3 Pro to do normal sidereal tracking (maybe dithering is redundant at short focal length, say 24mm?)

Will disabling the RA and DEC corrections in PHD2 still allow dithering? Because I don't need guiding for the widefield setup and not planning to mount the guidescope on top either.

Thanks in advance.

[symmetal]

PHD2 will not dither without guiding, but APT has the option to dither without guiding. You need to select APT Dithering in the Guiding options. From the manual

Quote

Usually the dithering is made by your guiding program/device and there is no need to make dedicated connection to the telescope in APT if you don't want to use other features that require mount control.

 

APT Dithering is special feature made to provide dithering when there is no guiding because your mount is high-end (ASA, 10Micron and etc.) or when you are using short focal length lens or telescope. APT Dithering uses a mount connection to make the needed random position changes between the exposures.

 

APT Pulse Dithering is other special feature made to provide dithering using pulse guiding commands for self guided mounts like Meade StarLock, self guiding solutions or mounts like SkyWatcher StarAdventure, AstroTrac and etc. In this case the Dithering Distance defines the maximum pulse duration in milliseconds. The value is multiplied by 100. For example Dithering Distance = 5 means up to 500ms pulse.

Alan

[ZiHao]

4 hours ago, symmetal said:

PHD2 will not dither without guiding, but APT has the option to dither without guiding. You need to select APT Dithering in the Guiding options. From the manual

Alan

Tried it, doesn't work. I selected the ZWO USBST4, the slew buttons just don't work. In PHD2 Manual Guide everything is okay as the option 'On Camera' is available. I guess EQDIRECT cable is necessary then.

[symmetal]

9 hours ago, ZiHao said:

Tried it, doesn't work. I selected the ZWO USBST4, the slew buttons just don't work. In PHD2 Manual Guide everything is okay as the option 'On Camera' is available. I guess EQDIRECT cable is necessary then.

Yes, a direct connection is needed to the mount from APT for the APT dithering to work as PHD2 isn't involved. An EQDirect cable would be the neatest solution I would think. It may be possible to use the Synscan handset as a link between the PC and the mount instead and achieve the same thing. I have never used the handsets and have an unused collection sitting in a drawer. 😁  Somebody who uses the handset method instead of EQDirect should be able to confirm.

Alan