Camera-Guidescope Adapter

[JohnSadlerAstro]

Hi,

So I have just come back from a 2 week holiday, and Saturday night was my 1st opportunity to try out my new autoguiding setup. One of the first things I wanted to do was to make sure my ASI camera could focus in the 50mm finder-guider scope I had been sold on SGL. I soon realized that I am missing a part, but I'm not sure what exactly it is. The guy that sold me the 50mm finder (shout-out to @John78 ) generously put in an extra 3d printed adapter that converted the random sized screw thread inside the finder body into a "standard" size of thread. This thread is the same one as is found on the inside of the ASI cam, which allows attachment of a 150degree lens and 1.25" nose. From the manual, it looks like the thread is an M42, but I cant connect the cam to the finder with this because both are female. 

Is there any adapter ring that will allow me to connect these two together? (Preferably for FLO) It will need to be reasonably small, as the finder's objective can only screw forwards/backwards a small amount for focusing. 

Thanks for looking

John

[Zakalwe]

2 options:

Teleskop Express (and probably others) sell a T2 male-to-male adapter. Basically, it's £35 for a hollow tube that's fully threaded on the outside.

The other option is one of the finderscope adapters that Modern Astronomy sell. https://www.modernastronomy.com/shop/accessories/adapters/sky-watcher-clones-to-t-thread-adapter-for-straight-through-finders/

just make sure that your finderscope is a Skywatcher. I think that the Meade ones have a different thread type.

[swag72]

15 minutes ago, Zakalwe said:

Teleskop Express (and probably others) sell a T2 male-to-male adapter. Basically, it's £35 for a hollow tube that's fully threaded on the outside.

If this is the one you are looking at ..... http://www.teleskop-express.de/shop/product_info.php/info/p7843_TS-Optics-T2-to-T2-Inverter-Ring---continuous-male-T2-thread.html then I would be looking at something else. I was in a position where I had to use one of these and if I'm honest it wasn't the most sturdy or confidence inspiring of solutions! You never really knew how far into the female threads it was threaded on both sides!!

A good call for the adapter, but I'd want something more robust especially for a guiding setup where all sorts of flexure could reasonably occur.

[JohnSadlerAstro]

Hi, 

So is the thread inside an ASI cam a T-thread or M42? 

John

[Zakalwe]

49 minutes ago, JohnSadlerAstro said:

Hi, 

So is the thread inside an ASI cam a T-thread or M42? 

John

They are the same thing. T Thread is M42x0.75. Watch out though- old camera lenses are often referred to as M42, but these are M42x1.

Welcome to the wonderful, frustrating, expensive world of astrophotography.  You will know when you have arrived when you end up with a drawer full of expensive aluminium tubes, half of them stuck permanently together and all of them exactly the wrong size for the job in hand.

[Zakalwe]

21 minutes ago, swag72 said:

 You never really knew how far into the female threads it was threaded on both sides!!

 

 

The trick with those adapters is to make sure that you are not relying on it to support anything. The items should be fully threaded together until their mating surfaces lock. The same as a bolt- you don't rely on the bolts inherent strength to hold things together- the bolt is there to provide a clamping force. its the friction between the items that creates the strength.

[JohnSadlerAstro]

So, I can buy a section of this thread, or an adapter tat goes straight from the weird thread inside the finder to a thread I can screw my cam onto.

I am probably best going for the latter as it is from UK, and will be sturdier. 

John

EDIT: ebay search may help though.

EDIT mk 2: it didn't.

[swag72]

Just now, Zakalwe said:

 

 

The trick with those adapters is to make sure that you are not relying on it to support anything. The items should be fully threaded together until their mating surfaces lock. The same as a bolt- you don't rely on the bolts inherent strength to hold things together- the bolt is there to provide a clamping force. its the friction between the items that creates the strength.

They were fully threaded together and while I used a measuring stick on one end while screwing into one thread I never felt happy that when screwing in the other side the threads didn't move up / down inside the other thread..... Of course I needed it to support a camera weight ultimately.....

[LightBucket]

As stated above, modern astronomy sell a specific adapter for connecting a camera with a female T thread, as you have, directly to the rear female thread of the finderscope, but it needs to be a Skywatcher or clone finder, these are sold as finder guider adapters....

[Zakalwe]

2 minutes ago, JohnSadlerAstro said:

So, I can buy a section of this thread, or an adapter tat goes straight from the weird thread inside the finder to a thread I can screw my cam onto.

I am probably best going for the latter as it is from UK, and will be sturdier. 

John

EDIT: ebay search may help though.

You can do either, though I would personally get the adapter from Modern Astronomy. It'll be a more solid fit.

[JohnSadlerAstro]

2 minutes ago, LightBucket said:

As stated above, modern astronomy sell a specific adapter for connecting a camera with a female T thread, as you have, directly to the rest female thread of the finderscope, but it needs to be a Skywatcher or clone finder, these are sold as finder guider adapters....

 

2 minutes ago, Zakalwe said:

You can do either, though I would personally get the adapter from Modern Astronomy. It'll be a more solid fit.

Good, I will buy that then. My finder is a Skywatcher 9x50 so it should work fine Thanks for the help, folks.  

PS. though for a piece of metal that adapter certainly is expensive!!!

John

 

[LightBucket]

If you get one of these adapters, and at some point change your guide camera, as I did, you can then buy an 1.25” eyepiece holder and screw on the back onto the T thread and then slide a lodestar or such like camera in....

[JohnSadlerAstro]

6 minutes ago, LightBucket said:

If you get one of these adapters, and at some point change your guide camera, as I did, you can then buy an 1.25” eyepiece holder and screw on the back onto the T thread and then slide a lodestar or such like camera in..

Sounds good.

[John78]

On 8/7/2017 at 07:26, JohnSadlerAstro said:

Hi,

So I have just come back from a 2 week holiday, and Saturday night was my 1st opportunity to try out my new autoguiding setup. One of the first things I wanted to do was to make sure my ASI camera could focus in the 50mm finder-guider scope I had been sold on SGL. I soon realized that I am missing a part, but I'm not sure what exactly it is. The guy that sold me the 50mm finder (shout-out to @John78 ) generously put in an extra 3d printed adapter that converted the random sized screw thread inside the finder body into a "standard" size of thread. This thread is the same one as is found on the inside of the ASI cam, which allows attachment of a 150degree lens and 1.25" nose. From the manual, it looks like the thread is an M42, but I cant connect the cam to the finder with this because both are female. 

Is there any adapter ring that will allow me to connect these two together? (Preferably for FLO) It will need to be reasonably small, as the finder's objective can only screw forwards/backwards a small amount for focusing. 

Thanks for looking

John

Sorry, not been on the site for a while - er - all I did was take the all sky lens that comes with the camera and unscrew it from the M42 washer then screw it half into the camera, half into the 3d printed part and you're golden.

[JohnSadlerAstro]

Lol.

Not to worry though, I am ordering the part anyway, as it will be a stronger and more long-lasting attachment system. Thanks for telling me though--I am trying out the full system for the first time tonight!

John