Disassemble a Meade SCT?

[AstralTraveller (David)]

Some folk here in the atmospheric chemistry group are into open-air IR specroscopy. As part of a new setup they are using a Meade 12" SCT. The only part they need is the mirror and cell. So they are trying to seperate the tube from the base section. They have removed all the obvious bolts but the tube doesn't want to detach from the base. They have tried a modicum of force but didn't want to be too heavy-handed.

Has anyone here ever done this? If so, what are they doing wrong?

PS I told them that someone on IIS would certainly know the answer. Please don't embarass me!

[renormalised (Carl)]

The base is glued to the tube, you'd have to cut it off!!!

[AndrewJ]

As noted, the OTA tube is glued to the casting.
One character in the US heated the rear cell on an electric frying pan.
That made the glue soft enough to slowly ooze the tube off

Andrew

[AstralTraveller (David)]

Carl, that is possible, we have a band saw that could do it. Is removing the mirror straight forward?

Edit: Andrew, that might even be better. Once again though, I think the mirror would have to be out first.

[AndrewJ]

I think the mirror would have to be out first.

I think you think right

Removing the mirror is easy enough
Remove the corrector first
Release the mirror lock if fitted
Remove the mirror lock knob ( it just falls out )
Then remove the focusser knob assy
( just remove the 3 screws and then slide it off its pin )
Now remove either grubscrew/circlip at the front of the baffle tube
( stops mirror sled falling off )
Pull off mirror sled and remove assy
You may need to turn the mirror sideways a bit
( enough to get the mirror through the slots in the corrector casting )
Tube is now ready for surgery.

Andrew

[multiweb (Marc)]

As long as you haven't got any part left on the table when you have put it all back together... it's all good.

[FredSnerd (Claude)]

After you've gone through all the steps in Andrew's post you should see 2 wires. A yellow wire and a blue wire. You have to cut one. But you cant cut the wrong one OR KARBOOOM. What you gotta ask yourself is do I feel lucky. Well do ya, Punk!

[Blue Skies (Jacquie)]

Andrew has the right description. The mirror basically sits on the long baffle tube you see inside and you have to slide that out from the back after you have removed the locking clip at the front of it, which means removing the corrector plate to get to it. I have some photos from an old 8" SCT I took apart some years ago but I'm afraid you'll have to wait until tomorrow night before I post them (I've been out tonight and really need to hit the pillow!) But if you're interested I certainly try to get them up for you.

[Blue Skies (Jacquie)]

I've had a chance to look for the pics I took and I hope they give a better idea of how SCT's go together. The first one is the 'clip' you have to remove from the end of the baffle (3rd photo). The baffle/tube slides out the end and if you look at the middle photo you can just see where the focuser is joined onto the mirror cell through the hole in the back. I didn't attempt it, as I was mainly aiming to remove the baffle to get the thread at the back recut so I could fit an adaptor on it in this case, but I guess the focuser also needs to be detached somehow before the mirror can be completely removed.

[AstralTraveller (David)]

The tube has been removed. The blokes asked me to pass on their thanks to everyone who replied. The instructions were great and they loved the jokes. They even cut the right wire!

I might just mention that this scope is already part of a spectrometer, they just wanted to save some weight - something about their aging backs. The last job the spectrometer did was measuring emissions from a feedlot. They obviously got up close and personal with the subject of the experiment because the inside of the tube now smells of bovine byproduct and the mirror has some nasty brown splotches on it.

[Blue Skies (Jacquie)]

Good to hear they got what they wanted, but not so good about the brown stuff. Best they wash it off with some distilled water pronto (but if its been there a while it might be too late!)