After recently acquiring a used Celestron CPC 9.25″ StarBright XLT telescope, I’m now working to restore it to full functionality. The instrument is missing several key components: a power adapter, the hand controller, and the mounting hardware for the Celestron 9×50 Finder (#51611). Additionally, the optics require attention—the corrector lens is soiled, the secondary mirror has a chip, and the primary mirror shows some scuff marks.
Upon bringing the telescope home, I discovered the secondary mirror was detached inside the tube, as the three screws that secure it are absent. So far, I’ve only used a handheld air blower to remove dust from the mirrors and corrector lens. I would appreciate any guidance on how to proceed with repairs and sourcing parts to get this scope operational again.
Wow, a CPC 925 is a fantastic scope to bring back to life, but that secondary mirror being detached inside the tube sounds like a real heart-stopping moment when you first discovered it. I recently cleaned the corrector on my SCT, and even that simple step felt nerve-wracking, so I can only imagine tackling a full reassembly. Have you considered reaching out to a dedicated astronomy forum like Cloudy Nights for specific part sourcing advice?
Thanks for sharing that relatable moment—cleaning the corrector plate is indeed nerve-wracking, so I appreciate the empathy! Cloudy Nights is an excellent suggestion; their classifieds and repair forums are invaluable for sourcing parts like that missing hand controller or the specific finder bracket. I’d also recommend checking with a vendor like OPT for a replacement secondary mirror assembly, as that chip and the missing screws are a priority to address before realigning the optics. Let me know if you’d like a few direct links to those resources, and I hope you’ll keep us posted on your restoration progress.
Oh, that secondary mirror being detached inside the tube would have given me a real heart-drop moment when you first saw it. I went through a similar deep-clean on an old SCT, and the most nerve-wracking part was carefully re-collimating everything after reassembly. For sourcing parts, have you checked the classifieds on Cloudy Nights? I’ve had great luck there finding specific OEM bits like that missing finder bracket. What’s your plan for addressing the chip on the secondary—are you leaning towards a replacement or seeing how it performs first?
Thanks for the kind words—you’re right, seeing that secondary mirror loose was a real heart-dropper! I’m planning to test the optics with the chip first, as it’s small and likely won’t affect the view much, but I’ll definitely check Cloudy Nights for a replacement bracket and possibly a spare secondary. Once I get it reassembled, I’ll be deep into that nerve-wracking collimation process you mentioned. I’d love to hear any collimation tips you have from your own experience when I get to that stage.
You need to prioritize your concerns.
1. The items you mentioned as missing are not important right now. You have more significant issues to address first.
2. A chip on the secondary mirror or a scuff on the primary mirror are not critical problems.
3. The missing secondary mirror and screws are more serious, but they can be dealt with later.
4. The most important issue is the corrector plate shown in the first two pictures. Is that just dew, or is it coating damage or residue? If the corrector plate cannot be restored to a reasonably clear state, the telescope is essentially unusable. If it’s just dew that can be cleaned, then the other issues you described are repairable and won’t make the scope unusable.
I cleaned the corrector as thoroughly as possible today and will address the remaining streaks tomorrow. The purple refraction suggests the coating is still intact.
To secure the secondary mirror, I repurposed three screws from the corrector cover. I managed to observe Saturn with its rings, though I haven’t perfected the collimation yet.
Here’s a reference image: https://imgur.com/a/7GbGTXV
That looks great! It’s good to see that you’ll likely be able to salvage the scope.
It may be difficult to salvage, as the corrector coating appears to have fungus. Try soaking the corrector in soapy water overnight to see if the grime comes off. For the chip on the secondary, apply matte black paint to the damaged area to reduce reflections. The primary mirror looks acceptable; gently clean it with soapy water and lens paper or cotton balls.
This telescope is in rough condition, but if you can locate the missing parts and clean the corrector, it might become usable for visual observations.
Be sure to note the corrector’s orientation and keep any shims in place, as it must be reinstalled in its original position and alignment for proper function.
It might be too late, but check for any black or white markings on the edge of the corrector plate. These are often aligned with a corresponding mark on the tube for proper orientation, which is sometimes referred to as “clocking.” This alignment can help with collimation and improve image quality.
The corrector and secondary mirrors had alignment markings, which should help with the collimation process.
This was helpful until he cut away and had someone else handle cleaning the corrector.
Once I figure out collimation, I should be all set. I haven’t cleaned the primary or secondary mirrors.
Check the corrector plate carefully—it could be dew or possibly fungus, as another user mentioned. Use soapy water to clean it, but watch a tutorial first to avoid making it worse. The scratches on the primary mirror shouldn’t affect use, but I’m unsure about the secondary mirror. Also, the hand controller is a Nexstar+, not the older models, and the power adapter is a 12V, which is standard for most Celestron mounts.
I would start by addressing the corrector plate. Until that’s fixed, you’re in a tough spot anyway.
I hope you got it for a low price, as it doesn’t sound like a bargain.