SCT optical/mechanical testing

[matt]

Cheers Mike.

Beat me to it by a minute

[iceman (Mike)]

It would've been 3 minutes but I had to find that image where I used the extension tube

[merlin8r]

Just trying to help. With my 8" I can rarely get above 250X, even though "in theory" it should go to 400X. I would guess that you could only bump up to that kind of power in EXTREMELY still conditions. If you're not happy with the optics, take it back. Problem solved!

[matt]

Appreciate your help.

We're just pointing out the same rules don't apply to magnification between visual and imaging

[matt]

Originally Posted by shredder

Another handy approach is if you still arent satisfied, to loosen the locking ring, line up the scope and by hand turn the corrector until you are happy with the results (mark the new position) and then tighten it all down.

Shredder. Would you carry out this procedure at night, on a star?

What about the four cork shims that are wedged between the corrector and the tube? Would they rotate with the corrector? I imagine their placement is also criticial?

Cheers

[shredder]

Um, well, in short yes, how else are you going to tell if its ok unless you do it at night?

The scopes arent quite as fragile as people seem to make out (at least mine isnt). The cork shims are really quite small and will probably just move with the corrector. Basically I am not saying remove the locking ring, just loosen it a little so that you can rotate the corrector.

I would suggest this:
1. At home take of the locking ring and make sure the alignment marks are there, and aligned, and note the position of the shims.
2. Put back the locking ring.
3. Tighten it up, but not 100% so that with some pressure it can be rotated. But certainly not so loose that it can fall/wobble etc.
4. Take it out at night, sight your star, test it out, rotate it till you think its right.
5. Take it down / inside, and open it up.
6. Note the new position of the alignment marks.
7. Move back the shims to the original position.
8. Tighten back up the locking plate.

An SCT is really not that hard to take apart, and once out of the warrant period well worth doing so you know what people are talking about. Many people wont touch them in case they break but with reasonable care they are ok, I mean after all they survive the postal service from the US to Australia so they are reasonably tough.

But in answer to your question, yes if it really bothered me I would do this, just check the position of everything first in case you make it worse and want to go back to the original position. Oh and the shims are really small, be careful not to take the corrector off at night or you will loose them (they too are also easily replaced). Try it at home first, in the light so you get the feel for what you are doing etc.

And looking over your questions again, no I dont think their (the shims) exact placement is such a big deal, just so long as they are evenly spaced and dont end up all in the one quarter etc.

M

[matt]

Originally Posted by shredder

Um, well, in short yes, how else are you going to tell if its ok unless you do it at night?

Um, well... ever heard of an artificial star?

It's what technicians use 24/7 to check scope collimation etc

Admittedly a real "night time" star is best.

Thanks for the other info

[shredder]

An Artificial star? you mean like Danny Minogue?

Ok so I wasnt thinking so clear when I wrote it. Yes it should work just as well with an artificial star (I dont have one so didnt think of it). Would suggest you check up on how you disassemble your SCT as what I have said is only a rough guide, but its basically accurate.

M

[matt]

Your instructions are very good, shredder.

Much appreciated.

I've got plenty of bookmarked sites on how to disassemble the little beasty. All for a rainy day

However, none of it will be used while the scope's under warranty, for the aforementioned warranty reasons.

Thanks heaps for your suggestions and input.

I'm waiting on good news from the distributors this arvo.

By the way... I cracked up at that Dannii Minogue comment!

[Merlin66 (Ken)]

Caution!!!!
The magnificaton quoted was for photographic imaging NOT visual!!!!!!
The aperture in MM usually give a fair guide to visual maximum magnification, photographic/ CCD well that's another matter!!!!!!!!!!!!!!!!!!

[matt]

That's right