Using computerised mount for manual tracking

Hi Folks,

Bought new celestron telescope with GoTo computerised mount recently , just got a quik Q. I realise to balance scope against counter weights I need to move scope manually along both axis to balance correctly. However , does using the scope in manual mode :x ( Goto computer switched off) with setting circles damage the gears at all. I'm a little concerned as rotating tube by hand is something I enjoy whilst tracking objects. Many thanks.


Regards,


Eamonn.

Bought new celestron telescope with GoTo computerised mount recently , just got a quik Q. I realise to balance scope against counter weights I need to move scope manually along both axis to balance correctly. However , does using the scope in manual mode :x ( Goto computer switched off) with setting circles damage the gears at all. I'm a little concerned as rotating tube by hand is something I enjoy whilst tracking objects. Eamonn.

Eamonn,

Not exactly sure what you're asking here. Presumably, you are talking about the Advanced CG5 GT mount. As you already know, you can move the mount freely in RA and Dec with the locking clamps released so the gears are not meshing with the motors. However, there are no slow motion controls on this mount (as is the case with most if not all GOTO mounts) so you cannot use it manually with the gears engaged. I should imagine it would be quite difficult to actually do so and you would almost certainly cause damage.

I'm puzzled why you would want to track by moving the scope by hand when you've just bought a very nice GOTO mount with good GOTO accuracy and tracking (see August S & T report).

Gordon

Eamonn,

I've just got a celestron CG5GT mount recently. Not sure what mount you have, perhaps you could enlighten us there. With the cg5 when you loosen the clamps on the ra and dec axis the this allows both axis to rotate freely. However even with the clanps enabled you cannot damage the mount with the CG5. I stress that other mounts may be different. I am only referring to the CG5 here.

The way it works is this. When you clamp an axis a bolt bears against the main gear wheel. This means that when the motors turn the wheel cannot move so the worm (and the entire mount head) can only rotate around the gear weel (because the gear wheel is immobile).

The bolt which bears against the gear wheel has a piece of nylon or teflon stuck to it, so if you do move the mount while it is clamped the nylon pad will allow it to slip thus not damaging anything. I would advise against overtightening these clamps.

I've also noticed that although their seems to be zero backlash on the RA axis, there is significant backlash on the dec axis, no problem for visual use, but a pain for photographic guiding. The anti-backlash feature works well but can result in tiny 'jumps' while the motors take up the backlash.

Yesterday i disassembled the dec axis and managed to make significant improvements by re-adjusting the worm/gear meshing. Although I havent tried the fix under the stars yet, looking at a church steeple way off in the distance seems to suggest the problem is now gone. The S&T reviewer found exactly the same on his mount example.

I am fairly sure that all celestron mounts have locking clamps on bith axes (even alt/az) mounts, With these loosened you can do no damage by moving manually.

does using the scope in manual mode :x ( Goto computer switched off) with setting circles damage the gears at all. I'm a little concerned as rotating tube by hand is something I enjoy whilst tracking objects.

As long as you have the clutch out so you're not forcing anything it should be ok. I like to do this myself on my little ETX70 for some objects. Of course you can always manually track things using the goto handset with the speed on it's lowest, if your Goto is like the one Meade produce.

Hope this helps.

Hi Folks,

My mount is the cg5 GT. The backlash is something I aint to familiar with right now , but will keep an eye on it. Relieved to know that when clamps are released( tube can move freely) it causes no damage to gear system.

regards,

Eamonn.

The backlash is something I aint to familiar with right now , but will keep an eye on it.

Eamonn,

I'd be very interested to hear if your CG5GT exhibits the same backlash as mine (and the S&T reviewers too). In case your not familiar with how it works. Backlash shows as a momentary pause when you press a button to slew the scope. Basically its caused by some mechanical misalignment (usually between the main reduction gears). Heres how to test it. Center a star at moderately high power. Now select a reasonably slow slew rate, rate 4 on the CG5 works well. Move the star continually in both directions on each axis noting if the star moves instantly when you press the buttons or if there is a noticable delay between the moment you press the button and the moment the star begins to move. This would be short typically < 1 second. You will find that the backlash only exhibhits when you change direction. I still havent had an opportunity to test it yet although tonight (Sun) looks promising.

Thanks