Edge 8 hd cleaning

+1 to Andrea‘s post. 
Also: don’t use a flashlight to look for dust.

If the mirror of a „closed“ scope like this SCT has a dusty mirror, I wonder how the Schmidt-plate would look like.

Dust is irrelevant and so are smudges. They do not impact the workings of the scope (you should see my mirrors!) and while doable with care and attention to details (spacers, shim, position of the corrector plate) I don't think the effort of removing the corrector justify the gain. For the corrector (external or internal) the procedure is to blow out as musg as possible of the dust and the using a cotton swab and isopropylic alcohol drag (but do not push) the swab from center to edge in a spiral fashion. Repeat until clean Don't get carried away, there isn't anything needing polishing there. For mirrors there is plenty of advice either here or elsewhere on the net but all of them require removal of said mirror from the support.

Thanks, that makes sense. Need to clean so I'll try the corrector plate glass first cleaning with the correct cleaning mixture. Then retry imaging see if the infamous dust bunnies disappear. 

Thanks for the reply and info

Hi.
Owner of a C14 here. You can clean both, plate and mirror. Usually, just a thin layer of dust it's not a big deal. But if you have fingerprints, grease or just don't like to see the dust there, there are different distilled water+isopropyl alcohol solutions you can use with the corrector plate. For the mirror, you can use distilled water+neutral soap. That's the cheapest option. I use Baader's Optical Wonder for both or even Purosol Optical. Both works fine for the mirror and the corrector plate but are expensive.  

Now the question is: how do you access the mirror? And that's quite challenging for the C8. There are videos in Youtube showing how to dismantle the tube to access the mirror, but it's something potentially dangerous if you don't have expertise on it. With the C14 I just can introduce my arm through the secondary mirror's aperture and manage to clean the mirror with a cleaning tool, but unfortunately the secondary "hole" in the C8 is too small for that. 

So, if it's just dust, let it there or try to find someone with expertise, or get your own experience but knowing that it could be more problematic that leaving the dust there alone.

Cheers.

No filter, and I've cleaned the camera. So I'm at a loose end if it's not the glass or mirror.

Will do, I binned the images I had. Will wait for the cloud gods to move along.. 🙏

+1 to Björn's comments, if you're seeing dust motes (like defocused donuts) these are not located on the corrector plate, nor the primary mirror, they are almost always in the camera. When they're bad enough, I can remove the camera and see specs on my sensor that line up with their presence in the image. You are almost certainly not seeing the effects of dust on the plate, and even if so, it would be a reduced light throughput, not individually "bunnies". It's also worth noting that timely taken flats should remove dust motes 100% from your images anyways.

Unless you are shooting infrared, or UV, there is no need to clean the corrector (and completely disregard cleaning the mirror, you can really only damage it). Certain cases will warrant cleaning your corrector, like having reduced contrast visibly compared to when you first shot on the scope. I use a ultra-fine (Gold Leaf rated) brush, with methanol to clean my corrector, I've only had to do this once in the last 4 years of owning mine.

*** never had too, mine is now 4 year old and needs a wee clean***

If you have to clean the corrector, get a high pressure aerosol free air gun, or a ultra fine optics brush, and whisk the dust away. Alternatively, methanol and specialized pec pads or optical cleaning swabs work.

Aaron H.:
There are calculators available for determining the location of the dust from the size of its donut:
https://astronomy.tools/calculators/dust_reflection_calculator

You can see from these that any reasonably-sized donut is likely within a few centimetres of the sensor. Any further than that and it would get so large and diffuse it would be almost impossible to spot.

*** I have missed this at astronomy tools, I will look at that.

It's hard to tell how dirty it really is. I do know that most optics look really dirty if you illuminate them with a small bright source like a flashlight or a phone. How does it look in normal daylight or room light?  More importantly, how do the images look. It's not hard to remove and clean the corrector plate, just not sure that you need to.