Star Sense Autoguider

[Wombat (Wayne)]

Hello,
Has anyone been using the celestron star sense autoguider?
I have one and it is a nice bit of gear, the only problem I have is balancing the dec axis. When the mount is balanced in dec and ra the ssag tracking is great in the ra axis, the dec axis has a massive run out leading to star streaks in images and could not work out why.
Then I changed cameras from pentax k3 monochrome to a zwo 533mm camera and forgot to rebalance the dec.
Started tracking and the dec tracking within limits getting good images, for some reason the ra axis balanced, the dec axis nowhere near balanced and getting great images.
Anyone have any comments as to why this would happen?
Regards,
Wombat

[Dave882 (David)]

Hi Wayne yep that’s pretty typical behaviour for guiding any mount that has a substantial amount of backlash in one or both of its axis. By unbalancing the axis slightly you are essentially putting some load on the gears so that it’s not floating in the backlash. It’s generally advised to make the mount a little bit east heavy too

[Wombat (Wayne)]

Hello David,
Before using the SSAG I was using the Star Sense align camera, both the ra and dec had to be well balanced for good guiding. Then around october I did a firmware upgrade on cgx mount and the star sense camera then not long after that the guiding according to phd2 was running out a bit.
Re-balancing the mount would not fix it, but I was getting good images.
Enter the SSAG only to find my problem with guiding running way out.
The dec balancing is off to the camera end which seems to much from my point of view.
As I said I am getting great images, but a well balanced mount should mean very good guiding even when the backlash is taken up.
Regards,

[Tony_ (Tony)]

Hello Wayne,


My CGEM has a lot of backlash in the DEC motor. To compensate I guide in one direction only for DEC. This adjusts for any DEC drift due to polar alignment errors. When your DEC isn't perfectly balanced you'll probably find that your guider may also be guiding in one direction only to take up any drift. When it is well balanced it probably oscillates a bit due to over-guiding and backlash.


Regards,
Tony.