Reverse Engineering the Skymax 180

[Altocumulus]

Well I came here to see if anyone had cleaned a Skymax 180 and walk away somewhat overwhelmed!  My Mak displays flakes peeling from the inside of the tube like leprosy, and the main mirror looks like it has black measles!

Still works, to a fashion, but if I have to take the plunge at least I have a bit of a guide unless I can find a decent repair service! 

 

Subscribed for future reference. 

 

[ET_PhoneHome]

Wow, thanks OP, for such a detailed post.  I wanted to ask about collimation.  I see a lot of people saying the large and small screws work in push/pull pairs, but that doesn't seem to be correct.  If I'm understanding things correctly, the way to properly collimate these maks is to first loosen all the small screws (just a bit).  Then, use the 3 larger screws like we'd do with an SCT.  Here's the part I'm not clear on:  when I loosen one large screw, do I need to tighten the large screw across from it, or do they function independently?  Finally, once collimation looks good, snug up the small screws.

The procedure above is what SkyWatcher gives in their official collimation document, so I'm confused as to why people say to do it differently.  Those posts have said to tighten/loosen a large screw, and then the small screw next to it will be looser or tighter.

[Captain Scarlet]

What you’ve described and what SW describe are what I understand as “push/pull”.  IE once finished, one bolt is in tension the other In compression.

What’s going on is that those three big bolts are directly attached to the entire primary mirror assembly inside. By screwing or unscrewing those bolts, you are pointing that mirror assembly, together with the baffle tubes, around the inside of the tube. The smaller screws lock the positions in place. A very small degree of tension is provided by three small rubber rings between the plate inside and the back of the cell (see pics in the thread).

So to collimate, yes you must unscrew the smaller ones to unlock, but all in small increments and not re-checking except when locked back up again. If that makes sense  .

Cheers, Magnus (OP)

[ET_PhoneHome]

3 hours ago, Captain Scarlet said:

What you’ve described and what SW describe are what I understand as “push/pull”.  IE once finished, one bolt is in tension the other In compression.

What’s going on is that those three big bolts are directly attached to the entire primary mirror assembly inside. By screwing or unscrewing those bolts, you are pointing that mirror assembly, together with the baffle tubes, around the inside of the tube. The smaller screws lock the positions in place. A very small degree of tension is provided by three small rubber rings between the plate inside and the back of the cell (see pics in the thread).

So to collimate, yes you must unscrew the smaller ones to unlock, but all in small increments and not re-checking except when locked back up again. If that makes sense  .

Cheers, Magnus (OP)

Thanks, I think that makes sense.  So, the large screws are push/pull?  The posts I saw on other forums said the push/pull action was happening between the large and small screws.  For example, if you loosen one small screw, you'd need to tight the large one right next to it.  That doesn't seem to be the way it works, so that's what confused me.  It seems like only the large screws are push/pull, just like the 3 screws on a typical SCT.  I read that the small screws could have a very minor effect, so might need to be tweaked just a hair at the end, but they're not doing the main work.

[Captain Scarlet]

My understanding is that the term “push-pull” refers to the whole arrangement of a larger “locating” bolt which will end up in tension, and a smaller locking bolt that locks the position of what the larger bolt is threaded through, and which ends up in compression.

As you turn the larger bolt, which you can only do by unscrewing the smaller one to release it and give it room to move, whatever the larger bolt is threaded through (in this case, a plate which supports the baffle tubes and primary mirror assembly) moves up or down the thread of the larger bolt. With three, you can point the assembly around inside the OTA wherever you like. Once happy, the smaller bolts can then be tightened against the internal plate, preventing further movement. In practice, the tightening-up may change things a little, so you have yo anticipate and compensate in the collimation process.

Cheers, M

[ET_PhoneHome]

Thanks, I will keep playing with it.  I think I'm almost there, but the weather sucks here in the northeast.  I got some clear skies the other night, but front meniscus dewed over and froze, so that was the end of that, haha.

[-JFK-]

Hi, 

I want anticipate before start opening. 

On the 180, what is the tool needed to remove this ring? 

Thanks 

[Captain Scarlet]

No tool needed, it’s a rubber ring sitting in a shallow groove, there to provide a stop for outer-baffle-tube movement in case the focus-rod becomes detached, preventing the outer tube falling onto the corrector-plate.

provide a stop for Just “roll” it out using your fingertips. I guess with age there’s a possibility that it will harden and perish at some stage, but shouldn’t be too difficult to replace at a hardware or plumbing shop.

Cheers, Magnus

[-JFK-]

Thanks, 

I have another question.

Still not opened it.

Did those four screws are directly screwed in the OTA tube ?
So, in 1.6mm aluminium ???

Edited October 21, 2023 by -JFK-

[-JFK-]

I plan to peint internal OTA + other parts (see attached) with Musou Black paint, any advice ?

Do you think it worse to disassemble the mirror to paint the back OTA part? 

Edited October 22, 2023 by -JFK-