Mak-mistake

[dawson]

Well, within 24 hours of having my new Mak, I made a big error.

 

I'd read about how the 180 Mak is a bit unsteady on the mount with the supplied SW dovetail.

 

It just so happens I had a fat 11" Losmandy mounting plate at home, which Kim had said I could try on the tatty old Newt.

 

So, it looked easy, two screws in the old dovetail and the holes lined up with the holes on the new mounting plate.

 

As I started to unscrew the screws, I thought "oh, the nuts inside might not be fixed to the tube..."

 

And they weren't. Luckily I realised this before I'd undone the bolts completely so the nuts were still fixed to the bolts.

 

The only option was to take the front corrector plate off the OTA, and access the nuts from inside.

 

The bolts weren't long enough to fit the Losmandy plate, so I put the original one back on. Put the front corrector plate back on in the same position (having marked it with tape), and just preyed collimation hadn't been badly affected.

 

Then I looked at the scope and thought the dovetail looked odd.... I'd put it on the wrong way.

 

Corrector plate off again!

 

It's all back in one piece, but I have no idea how much I'm knackered up collimation. I've looked through in day light at various objects with the same focus in different parts of the visual field and it looks fine, but no idea what will happen at night.

 

I'm not even sure how I'll know if collimation is off.

 

Anyway, watch this space and think ahead before undoing any screws. Learn from my mistake.

 

A pretty stressed James.

 

 

[Doc]

I would imagine everything will be Ok James.

 

As long as you marked the exact position to corrector plate goes back you will be OK. I would be more concerned about finger prints on the corrector plate.

[Guest CodnorPaul]

Any finger prints will come straight off with a bit of wonder fluid and a lot of care

[Doc]

Not if they are inside.

[Guest CodnorPaul]

Very true Mick - that wouldn't be great

[Teslar]

Not to worry i took mine apart. As long as you mark the corrector plate and put it it in the same place. There only four screws after all so easy to get the right place. I took the existing vixen off and used the original screw and plate to fill the holes and used rings to mount the scope

Edited May 7, 2013 by Teslar

[BAZ]

If you don't make mistakes, you don't gain experience.

 

I don't think you have upset it too much, you had the foresight to mark where it came from, and put it back in the same place.

 

You also kept an eye on the nuts, one of those dinking the mirror would have been unpleasant.

Let me know what size bolts you need and I'll see what I have knocking about.

[xanthic]

I've got some panel wipe if you need some high grade degreasing

[Teslar]

Mind you I struggled to get those screws out on mine vi tried a 5/16 spanner but it turned it to by 7mm.....,

[dawson]

I'm looking for rings, but they don't make any so only second hand ones and none around. I'll post a wanted add on ABS sometime.

 

I didn't touch anything inside, and wore gloves.

 

I'm just waiting for Polaris to become viable then going to try and polar align.

 

Thanks for the support, and not for criticizing me.

 

James

[+Graham]

I'm looking for rings, but they don't make any so only second hand ones and none around. I'll post a wanted add on ABS sometime.

 

I didn't touch anything inside, and wore gloves.

 

I'm just waiting for Polaris to become viable then going to try and polar align.

 

Thanks for the support, and not for criticizing me.

 

James

 

What size rings do you need James ??

[dawson]

Graham,

 

Reading elsewhere (like here  http://stargazerslounge.com/topic/119776-skymax-180-pro/page__st__80) it sounds like Orion 216 rings are the ones to go for but which aren't sold anymore. I've just measured the OTA and it's 680mm in circumference and using a calculator I get that to be a diameter of 216mm.

 

So that kind of size.

 

I'll put a wanted add on ABS now and see; the ad is free.

 

James

[Guest ollypenrice]

If you don't notice that collimation is off I'd have to ask whether it would matter!  Anyway, I doubt that it will be and it won't be difficult to correct using a star test. Go for something near the zenith, around mag 2 or 3, and defocus lightly. If your diff circles are round and concentric you're bang on.

 

Nobdy likes fingerprints on their optics but it is also true that nobody could distinguish between the view with a fingerprint and the view without. Have you noticed that rather large opaque thing in the middle of your corrector plate? You can see it from outside the scope but do you see your secondary mirror when you look through the scope? 

 

Olly

[Guest Nightfisher]

Graham,

 

Reading elsewhere (like here  http://stargazerslounge.com/topic/119776-skymax-180-pro/page__st__80) it sounds like Orion 216 rings are the ones to go for but which aren't sold anymore. I've just measured the OTA and it's 680mm in circumference and using a calculator I get that to be a diameter of 216mm.

 

So that kind of size.

 

I'll put a wanted add on ABS now and see; the ad is free.

 

James

strange seeing my thread linked on here lol, re collimation when i took corrector of my mak to fit rings it never shifted at all

[Brantuk]

Yup - you're famous all over the East Midlands Jules lol

[Guest Ely Ellis]

I did a lot of reading about the difference between a Mak and and SCT as I was a bit confused. They both look similar.

From what I remember on the SCT the corrector plate has to be a match to the mirror and if removed must be replaced back in the correct position.

The Mak on the other hand, is not as critical, does not require matching to the mirror and doesn't even need fitting in the exact same position it came off.

I could be wrong, but that is how I understood it.

So with that in mind, I think you are pretty safe James.

 

Cheers

 

Martin

[Rusty Strings]

I can't see why synta can't make the things with some kind if captive nut, after all, changing the dovetail

is a common thing to do.

[dawson]

This issue was over two months ago, just to put things in time perspective.

 

The collimation seems fine post taking the corrector plate off, and putting it back on again. Thought I'm not had it out in June or July, but roll on darker nights and I will again.

 

Yes, in an ideal world it would be ideal not to have to take the corrector plate off when changing the dovetail, but it's probably a cost and weight issue. I'm still waiting for some rings for my Mak, so once I get them, I'll have to go through the process again and plug the holes up with something.

 

Martin, the shapes of the glass at the front of an SCT and a Mak are different (as is the thickness of it), and the central obstruction in the Mak is proportionally smaller, and the shape of the 'secondary' is different too:

 

http://www.cloudynights.com/ubbthreads/attachments/2049385-SCT-Diagram.jpg

 

http://starizona.com/acb/basics/optics/makcass_scope.jpg

 

I don't know anything about the comparison of taking off the corrector plate from the front of the SCT or if that is more likely to mess up collimation than if doing so on the Mak.

 

Thanks.

 

James