To centre spot or not to centre spot

[Littleguy80]

I was going to centre spot the primary mirror on my SkyWatcher Explorer 130 tonight using the guide below:

https://www.cloudynights.com/topic/570729-uh-oh-how-can-i-tell-if-i-dented-or-fractured-my-telescope/?p=7775740

I couldn't figure out how to get the primary mirror assembly off though. I found the thread below:

It's put me off doing it a little bit. I'm worried about damaging the mirror or not being able to get it back on afterwards. Is it worth the effort to centre spot it? Are there better options for collimation? 

[Charic]

The mirror itself is housed in a mirror cell, around the mirror cell on my scope there are some screws which just holds the mirror assembly in place on the scope.
 

Pre-marking the mirror cell against the tube with a marker pen, tape, whatever, and keeping the scope horizontal, undo the screws, and the mirror cell will pull off. With careful handling the mirror could be replaced without upsetting the collimation.

The only issue you have now with the cell removed, you have full access to the face of the mirror? Thats where you need to be careful.

As a side note, I centre spotted my Celestron 127EQ, looked the part, but made no difference to the overall end result! If the scope needed a centre spot, Celestron would have fitted one, I assume the same stands with a Sky-watcher. Its possible its just fallen off, but I've never owned the 130 to check!

Just remember, its the screws around the edge of the mirror cell, the side of the telescope. Try not to tamper, with the adjusters to the rear of the mirror, unless your actually collimating.

[johnfosteruk]

I did the same thing when I took out the cell on my 130 the first time and unscrewed the screws around the OD. Sorted that out though and it was fine. 

You absolutely want to centre spot it, I've found the 130 needs it's collimation tweaking periodically so definitely worth doing. Don't be put off though, just take care with it and as Charic says premark so it goes back where it was after.

[Alan64]

 

3 hours ago, Littleguy80 said:

I was going to centre spot the primary mirror on my SkyWatcher Explorer 130 tonight using the guide below:

https://www.cloudynights.com/topic/570729-uh-oh-how-can-i-tell-if-i-dented-or-fractured-my-telescope/?p=7775740

I couldn't figure out how to get the primary mirror assembly off though. I found the thread below:

It's put me off doing it a little bit. I'm worried about damaging the mirror or not being able to get it back on afterwards. Is it worth the effort to centre spot it? Are there better options for collimation? 

Have at it, it's easy.  First, mark where the cell joins the tube with tape or other.  Then, remove the screws going around the circular side of the cell.  After that's done, gently and carefully wiggle it and work it free from the tube...

You don't need to touch the screws on the rear-facing side, as those are for adjusting the mirror.

Don't worry, you won't break it, I hope.

[Alan64]

"If the scope needed a centre spot, Celestron would have fitted one..."

Celestron is actually and practically no more, and hasn't been for quite a few years.  Synta Optical of China owns the name now, and before that, Tasco owned it.  "Celestron" is only a brand, a marque, now.

Synta owns and manufactures the brands "Orion"(in the U.S.) and Sky-Watcher, too.  Synta centre-spots the primaries of the Orion and Sky-Watcher 130mm f/5 Newtonians, but not the Celestron "AstroMaster" 130mm f/5.  I'd say, rather, that that's a bit neglectful and inconsiderate on Synta's behalf, and nothing more.  

 

[Littleguy80]

I'm committed now! Wish me luck!

[estwing]

Here's mine..

[Ricochet]

I don't like the way that mirror is hanging over the edge there 

[Littleguy80]

Job done  Thank you for all the encouragement and advice!

[estwing]

well done mate...

[laudropb]

Nice job. You are braver than me.

[elliot]

Centre spotted my 5" though probably didn't need it. Anyway, I had the lid of my Sharpie in my mouth an as I took it out managed to flick a tiny blob of spit onto the mirror. Luckily well in the shadow of the secondary so no harm though I know it's there.

[Alan64]

11 hours ago, Littleguy80 said:

Job done  Thank you for all the encouragement and advice!

Splendid!

[Astro Imp]

Well done that man!!!