Been trying out astrophotography with my LX90 8" scope on the LX90 alt-az mount. I have been able to take photos up to 1 mins exposure with no noticeable star trails for objects with altitude angle around 50 deg or less. However I'm having problems taking high altitude angle objects, around 70 deg or more, the stars have squiggly lines, seems like the scope is struggling to track the object and bouncing around.
I have tried to reset -> calibrate -> train drive a few times, but that didnt seem to improve.
Is this a limitation of alt-az mounts? or there is a problem with my motor drive? Do I need to get a equatorial wedge?
Yes to the wedge - I can take vertical (zenith) shots of any length - you just need a tiny bit of back weight - otherwise it does the backlash zig zag dance.
I've no idea, I got this from the club - it's not mine and came without any instruction or bits - I had to make the whole thing from scratch vis a vie mounting bolts, adjusters etc.
The wedge looks like mine which is the normal LX 90 wedge (the cheaper one) I am not sure if you can put an LX 90 on an ultra wedge-would love to know as I regard mine as quite unstable which is why I hardly use it
Graham
You probably could put an LX90 on an ultrawedge if you made an adaptor plate or took to it with a drill but I doubt that would solve your stability problems. The fork arms on these scopes (both LX90 and LX200) are not strong enough and the tubes are heavy. I spent ages trying with my LX200, ultrawedge and permenent pier yet even the slightest breeze would get the forks moving and ruin the sub. If you intend to use these long focal length scopes for long exposure AP they really need to be deforked (or buy a seperate OTA) and place it on a high quality EQ mount. The scopes are built to mount alt/az and thats where they perform best. You could always try a de rotator to remove field rotation and mount it alt/az but there is lots of argument about these units and I never had much luck with the meade version. Thats not to say they don't work as some people swear by them, just haven't seen any really good results myself.
One reason why my subs are pretty much 3 minutes and no longer!
The accuracy of the whole thing is less than perfect - it is a viewer rather than a AP scope. I daren't touch the focuser after I use the mask as the thing wobbles like a jelly for about 20 seconds -
Wind? not a chance - go have a cup of cocoa!
Another thing I forgot to mention I was running the mount motor using the D-size batteries, which was running low already at the time. Would this have been the cause, as the power is weak and the mount struggle to keep track of the object?
I will try again with the proper external battery pack.
