Dear fellow ABers, this the story of I resurrected an old wreck of a mount to future AP usefulness.
Once upon a time I spotted an advert in the UK Astro Buy&Sell website (https://www.astrobuysell.com/uk/propview.php) of a Meade LXD55 mount selling for around £80. Curiosity got the best of me and I investigated the hardware in question. It turned out to be a turn-of-the-century CG-5 clone (itself a clone of the venerable Vixen GP) with some features like low-res encoderes on both axis and motors that allowed some GOTO capabilities together with the Meade's Autostar handpad. It was supposed to to be able to carry up to a 10" f/4 schmidt-newtonian or a 8" SCT or a 6" f/8 achromat.
The guy listing it made it clear that mount conditions were both unknown and also unknowable as it bought on a whim and soon lost track of what was what (together with the scope it was attached to). He made no gurantees that it was in actual usable conditions and some parts might have been lost on several house moves. What seemed certain was the main body, the Autostar and the tripod were there. As for 80 quid I can actually treat the whole of us 4 in my family a meal at the pub if we go easy on drinks and food the decision was made that I'll attempt to put it back to usefulness.
The mount was picked up and as expectd the 3 main bits were there but the counter-weight bar was one of those bits tragically lost together with the counterweight itself. Back home I managed to remove the motors from the mount body without destroying them (too much). The movements of the RA xis seemed smooth enough (with some backlash) but the Dec axis seems overly stiff. That was something I had to sort out eventually.
I posted an advert on the same website to see whether there was any interest in the Autostar, motors and relative casings with a set of spare optical encoder disks and luckily I fund one eager buyer and for £55 I sold the lot off. So total spend on the mount was now at 25 quid.
Next (well after a long while) I put my hands onto the mount and proceeded on removing and stripping the Dec axis down, remove all the gooey grease and put everything together back again with new lithium grease in place. I also removed the RA body to drill holes in the casings for future use. Cleaned more sticky grease from the Alt joint (which later proved to be an error).
After the clean-up operation of the Dec axis I inspected and cleaned the RA worm and case. Movements of the worm resulted in being quite smooth and therefore there wasn't a call for a replacement of the bearings, I thought.
Next up was buying all the hardware needed to put the mount back in full useable conditions (AP grade, that is), which meant GOTO with Ascom capability. As I already built and tested 2 OnStep controllers this was the obvious port of call. Plus steppers (400 steps), cables, belt, pulleys, stepper drivers, other miscellaneous electronics and aluminum plates to make the required mounting hardware. After a month of machining, sawing, drilling and tapping I had all the required mounting hardware up for use. I also ordered a aluminium enclosure and a plexiglass plate for the mount controller. Finally, after toying with the idea of lathe turning a blank rod into the required counterweight shaft I decided that it was more cost-effective to buy a spanking brand new one (rather than buying the lathe steady and the thread die that I would need for the maching operation).
I haven't exactly quantified the total spend but here is an aproximate list:
Counterweight shaft: £50
OnStep Controller hardware inclusive of 3D printed handpad enclosure: £50 approx
Stepper drivers (2x): £10
Steppers (2x): £36
Pulleys and belts: £20 approx
Other hardware: £30 approx
So the total bill would run at around £200 + £25 for the mount itself.
Here is the final assembled mount with the test scope (80mm f/7.5 APO with 130mm guidescope, for a total of 4.5 kg (9.9 lbs)) mounted on:
Next step was to measure periodic error and have a feeling on the mount behaviour. I added a Canon 1300D (modded) for imaging purposes and tracked a star close to the celestial equator for well over an hour. taking 5s integrations every 10s After a bit of maths on the drift corrections here are the results:
This it was confirmed that the priodc error is in the range of 75" over a 10 minute worm period. I also discovered that I hadn't tightened up the Dec axis flange bolts enough and there is an increasing slop in the amount of PE. I drew comfort from the fact that, despite is rather large amplitude, the error appeared to be quite smooth and ameneable to correction by guiding. On the minus side the tripod feels rather flimsy and prone to vibration so I'll have to devise a system of braces to stiffen it up.
Next, after a proper PA (with less than 1' error) I moved in the actual guided performance for several nights. The tyical PA graph (mid altitudes) reported by PHD2 is the one shown here below:
By comparison this is a typical PE graph from my GEM28 (same worm period of 10 min):
Whilst the GEM28 is tracking with an overall better rms (0.76" vs. 0.84") the resurrected LXD55 has better smoothness and would probably benefit for a more aggressive correction to remove the residual PE. In fact at times it has a very low residual PE when watching the tracking on screen, 0.4" or better!
The results of 1/2 hour worth of imaging (10x180s integration) of a star field near Altair (at around +7 degrees N) is shown here below:
And the 1:1 scale image of the field center:
The image scale is 1.48"/px for a 600mm focal length coupled with the 4.3um pixel pitch of the 1300D.
Overall I'm pretty chuffed with the results so far as this Lazzarus of a mount has shown promise for serious work at short and medium focal lengths.
Once upon a time I spotted an advert in the UK Astro Buy&Sell website (https://www.astrobuysell.com/uk/propview.php) of a Meade LXD55 mount selling for around £80. Curiosity got the best of me and I investigated the hardware in question. It turned out to be a turn-of-the-century CG-5 clone (itself a clone of the venerable Vixen GP) with some features like low-res encoderes on both axis and motors that allowed some GOTO capabilities together with the Meade's Autostar handpad. It was supposed to to be able to carry up to a 10" f/4 schmidt-newtonian or a 8" SCT or a 6" f/8 achromat.
The guy listing it made it clear that mount conditions were both unknown and also unknowable as it bought on a whim and soon lost track of what was what (together with the scope it was attached to). He made no gurantees that it was in actual usable conditions and some parts might have been lost on several house moves. What seemed certain was the main body, the Autostar and the tripod were there. As for 80 quid I can actually treat the whole of us 4 in my family a meal at the pub if we go easy on drinks and food the decision was made that I'll attempt to put it back to usefulness.
The mount was picked up and as expectd the 3 main bits were there but the counter-weight bar was one of those bits tragically lost together with the counterweight itself. Back home I managed to remove the motors from the mount body without destroying them (too much). The movements of the RA xis seemed smooth enough (with some backlash) but the Dec axis seems overly stiff. That was something I had to sort out eventually.
I posted an advert on the same website to see whether there was any interest in the Autostar, motors and relative casings with a set of spare optical encoder disks and luckily I fund one eager buyer and for £55 I sold the lot off. So total spend on the mount was now at 25 quid.
Next (well after a long while) I put my hands onto the mount and proceeded on removing and stripping the Dec axis down, remove all the gooey grease and put everything together back again with new lithium grease in place. I also removed the RA body to drill holes in the casings for future use. Cleaned more sticky grease from the Alt joint (which later proved to be an error).
After the clean-up operation of the Dec axis I inspected and cleaned the RA worm and case. Movements of the worm resulted in being quite smooth and therefore there wasn't a call for a replacement of the bearings, I thought.
Next up was buying all the hardware needed to put the mount back in full useable conditions (AP grade, that is), which meant GOTO with Ascom capability. As I already built and tested 2 OnStep controllers this was the obvious port of call. Plus steppers (400 steps), cables, belt, pulleys, stepper drivers, other miscellaneous electronics and aluminum plates to make the required mounting hardware. After a month of machining, sawing, drilling and tapping I had all the required mounting hardware up for use. I also ordered a aluminium enclosure and a plexiglass plate for the mount controller. Finally, after toying with the idea of lathe turning a blank rod into the required counterweight shaft I decided that it was more cost-effective to buy a spanking brand new one (rather than buying the lathe steady and the thread die that I would need for the maching operation).
I haven't exactly quantified the total spend but here is an aproximate list:
Counterweight shaft: £50
OnStep Controller hardware inclusive of 3D printed handpad enclosure: £50 approx
Stepper drivers (2x): £10
Steppers (2x): £36
Pulleys and belts: £20 approx
Other hardware: £30 approx
So the total bill would run at around £200 + £25 for the mount itself.
Here is the final assembled mount with the test scope (80mm f/7.5 APO with 130mm guidescope, for a total of 4.5 kg (9.9 lbs)) mounted on:
Next step was to measure periodic error and have a feeling on the mount behaviour. I added a Canon 1300D (modded) for imaging purposes and tracked a star close to the celestial equator for well over an hour. taking 5s integrations every 10s After a bit of maths on the drift corrections here are the results:
This it was confirmed that the priodc error is in the range of 75" over a 10 minute worm period. I also discovered that I hadn't tightened up the Dec axis flange bolts enough and there is an increasing slop in the amount of PE. I drew comfort from the fact that, despite is rather large amplitude, the error appeared to be quite smooth and ameneable to correction by guiding. On the minus side the tripod feels rather flimsy and prone to vibration so I'll have to devise a system of braces to stiffen it up.
Next, after a proper PA (with less than 1' error) I moved in the actual guided performance for several nights. The tyical PA graph (mid altitudes) reported by PHD2 is the one shown here below:
By comparison this is a typical PE graph from my GEM28 (same worm period of 10 min):
Whilst the GEM28 is tracking with an overall better rms (0.76" vs. 0.84") the resurrected LXD55 has better smoothness and would probably benefit for a more aggressive correction to remove the residual PE. In fact at times it has a very low residual PE when watching the tracking on screen, 0.4" or better!
The results of 1/2 hour worth of imaging (10x180s integration) of a star field near Altair (at around +7 degrees N) is shown here below:
And the 1:1 scale image of the field center:
The image scale is 1.48"/px for a 600mm focal length coupled with the 4.3um pixel pitch of the 1300D.
Overall I'm pretty chuffed with the results so far as this Lazzarus of a mount has shown promise for serious work at short and medium focal lengths.
