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Celestron AVX mount - How to fix tight RA / Dec axis
ChrisEll replied to ChrisEll's topic in Discussions - Mounts
For those wishing to tune their AVX further check out my other mod: -
Celestron AVX mount - How to fix tight RA / Dec axis
ChrisEll replied to ChrisEll's topic in Discussions - Mounts
That's a big scope for imaging on the AVX... I had a 8" SCT and it was a struggle! I then got a SW ED80 refractor which was an improvement, being lighter and having a shorter focal length. -
Celestron AVX mount - How to fix tight RA / Dec axis
ChrisEll replied to ChrisEll's topic in Discussions - Mounts
That sounds fine to me. Yes I got addicted to imaging but now finished my journey. The AVX is capable of good results, just needs some tweaking which is probably true of all of the cheaper GOTO mounts. -
Celestron AVX mount - How to fix tight RA / Dec axis
ChrisEll replied to ChrisEll's topic in Discussions - Mounts
There are many reasons not to have the axes too tight... you will be able to balance better, less stress and load on the motors, gears, and bearings and yes it may improve guiding. -
Another thought: only operate the mount when the mount is properly balanced otherwise you will overly stress the motors and gears.
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You probably have to buy a whole motor replacement for each... i've not come across any gearboxes which are the same as the ones for the those motors. The broken teeth seem to suggest the RA and Dec axes are far too tight... the axes are not well assembled and tend to be overly tight. They can be easily corrected.
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I had problems removing an M42 adapter off a filter wheel yesterday, tried rubber gloves and WD40 but no good. In the end I used my trusty plumber's pliers, taking care to mask off the area with masking tape to avoid scuffing. If you're not familiar with this tool one arm slides over the other until you get a decent purchase on the thing you want to grip... a very useful tool!
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A similar issue with an EQ3 Pro mount
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How to guide with a telephoto camera lens?
ChrisEll replied to smr's topic in Discussions - Scopes / Whole setups
Interesting device but I would be concerned about flexure with that. -
How to guide with a telephoto camera lens?
ChrisEll replied to smr's topic in Discussions - Scopes / Whole setups
Perhaps some kind of vixen saddle bar that has 2 attachments, one for the DSLR and one for the guide scope. This link is probably not what you need but gives you an idea. https://www.firstlightoptics.com/adm-vixen-type-v-series/adm-v-series-side-by-side-mounting-system.html However rather than waste money on one of those consider a small ED refractor that can be had for around £200. -
I bought mine here: http://www.dancingwingshobby.com/free-shipping-rc-model-metal-pinion-gear-04m-23mmhole-diameter-8t-9t-10t-12t-13t-14t-15t-18t-20t-24t-height5mm-10mm-12mm_p0558.html Takes about 2 weeks. They come in fives, so I have some spare, so PM me and I'll pop one in the post if you like Anyway have a look first and see if your pinion does run off-centre... I thought you said it was all ok?
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My AVX motor pinion replacement finally arrived. The only suitable gear I found were 5mm in height with no boss or grub screw. This meant bonding the new gear to the motor with glue. First job was to check it's the right diameter bore, so I removed the optical wheel off the back end of the motor and tried the gear there... perfect fit. I removed the RA motor, PEC sensor and control panel all as one piece, much easier than removing the motor from the control PCB. Also you can spin the motor using the handset. So the motor went in the vice and after many failed attempts to lever off the pinion with a screwdriver I eventually removed it by gripping the motor in my left hand rather than the vice. The pinion was hammered on very tight and was only held in place by friction... no keying or splines. Next to prep the bonding surfaces... I scored some lines inside the gear hole to give the glue something to grip onto, ditto the motor shaft. Quick clean then I put a small piece of masking tape at the base of the motor shaft (make sure the gearbox base can sit back on the motor without the masking tape interfering). This prevents any wayward glue entering the motor and also I can use it to help position the new pinion at the correct height. I put the gearbox base back on with the 2nd gear to get the correct height - I jiggled the masking tape accordingly. The new pinion is 5mm in height so only 3mm of it will actually bond to the motor shaft, not ideal but hopefully enough. Now to glue it on. I used Loctite 638, a "high strength retaining compound". I smeared some onto the motor shaft and inside the pinion using a tiny screwdriver, then a small blob into the hole and fitted the gear to the required height. I expected to have a bit of time to jiggle it and double check the height but the glue set very quickly and I was not able to move it. Luckily it was at the right height. I spun the motor using the handset to check the gear ran true which it did, much better than the original pinion. I left it for an hour and then scooped out the small pool of residual glue from the top of the pinion... this is not going to set and it's good to get rid of it now to help the curing process (Loctite only cures in small spaces in the absence of air). Left overnight. Next day I reassembled everything and switched on the mount. I could see the RA gears start to turn very slowly. I manually slewed the mount in ever increasing speeds, finally reaching 9... it worked fine. More slewing and then I left it on for the day at sidereal speed. I also loaded the mount with scope, camera, etc. (this is only a 5kg payload, the AVX can handle up to 16kg... I should test with a max payload sometime). So after all that here are the results. The high frequency periodic error is gone and the RA RMS has dropped considerably. Success! N.B. In case you need to remove the gear for any reason here's how: you need to apply heat to the Loctite, so hold the gear in a match flame for about 3 seconds then pull the gear off immediately. N.B.B. No need to do this mod on the Dec motor.
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Star Adventurer and PHD2 guiding
ChrisEll replied to chris-32's topic in Getting Started With Imaging
Dithering randomly nudges the scope position very slightly inbetween exposures... this means the sensor is not sitting over the same bit of sky all the time and so sensor noise can be removed more effectively. I use DigicamControl and you can tell it to dither between shots, handy!- 19 replies
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- star adventurer
- guiding
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