I feel sorry my first post here will be a bit long long. I found some help in other topics here. My goal is to summarize every tip and tricks regarding fixing the many issues I had with my stock Celstron Nexstar 6 SLT. Some issues I am still facing, others, fixed.
- Nexstar 6 SLT
- Celestron focus motor V2
- ZWO ASI290MC
- ASCOM platform 65
The issues from stock:
- Very bad stock collimation
- Poor tracking
- Huge backlash
- Broken quick finder
- Too sensitive focus knob (I know it's cheap mount)
Issues with aftermarket:
- Wobbly focus motor
Let's start with the collimation. To fix it, I pointed at Polaris, went out of focus and performed collimation. Made it easier with a laptop and my astro cam so I don't need to come and go each time I turned a screw. This was the easiest fix after all. There are plenty of material explaining how to collimate SCT OTA so I won't dwelve on it further.
Poor tracking, is still on going. I'm now sure it's not a mount level issue. As for weigh limit, that maybe the case since I have starsense, astro cam + focus motor at the back. But yesterday I noticed that when I lose connectivity with the HC through CPWI, the tracking magically become much much better. Very weird indeed. I'm using a 5m USB cable. I wonder if anybody witnessed such behavior with their SLT coupled with CPWI. I plan to use HC only next time and see if I have better tracking than with CPWI. For reference, I can't go past 4s exposure withtout seeing star drift. I read here that SLT mount perform usually good for 20 to 30s exposure. My mount is wayyy under that.
The backlash on this mount was crazy. In speed 4, I clocked at 121 seconds before the mount moves going from positive to negative (and vice-versa) Az. No backlash on Alt though. I stricly followed the procedure in Nexstar Guide II from Author Michael Swamson, withtout success. I found the answer, again, here on cloudy nights: https://www.cloudyni...problem-solved/ Indeed, my 2 screws were loose. So loose I could move by hand the gear about 2mm back and forth. I screwed it in properly. And voilà. No more huge backlash, only 1 sec. I need to tweak it a bit because it's a bit jumpy when changing direction. I'll follow the Nexstar Guide II once more. Also, it might play in my bad star tracking so I need it to be set perfectly for the sake of plugging all the wholes in understanding why my mount have such bad tracking performances. BEWARE: this procedure will void warranty.
The given quick finder had it's base broken, making it impossible to align to quicksearch. That's why I got a starsense, to fasten the alignment procedure but I got many crashes with CPWI which always make me redo the full alignment procedure. such a pain...
The focus knob on this OTA + mount is very very sensitive. Making reaching good focus really hard. I "fixed" that getting the aftermarket celestron focus motor. It's a nice device, only if Celestron made if easier to install with better quality plates, in my humble opinion.
Installing the focus motor is quite a challenge. If you follow strictly the celestron manual, you will fail. It's impossible for me to align // the focus motor with the focus motor plate. If I screw it in place, it tilts inward and makes my mirror very wobbly (and not just the normal shift) when the motor rotates. I just can't let this appliance loose. I don't like loose screws anywhere.
I partially fixed it following the instructions here, the going full clockwise untill you reach max was of great help and isn't in the celestron manual: https://www.cloudyni...-focuser-on-c6/ + adding the original plate on top of the one provided with the motor focus providing support and thus limiting the inward tilt while tightening the screws. I find the wobble quite acceptable now.
So I'm still facing bad sideral tracking. I leveld the mount carefully during daylight. Balanced the OTA (and it was off indeed, it was going upward on itself. Too heavy on it's back, since the fork can be tilted by hand very easily) I just can't believe it's normal. Even with the aftermarkets + astro cam on it's back because sideral tracking is way under what speed the mount can achieve. And, again, when I had a bug the other night and lost connectivity to the HC with CPWI, the tracking was improved greatly. How weird is that! Still got to fine tune the Azimut backlash setting but I'll be quickly out of options if these few things left do not solve the issue. I tried positive and negative Go-To's withtout change to this behavior.
Any suggestion on how to fix the sideral performance is very welcome!
Clear skies to all!