Spacer project

[peter_4059]

I've recently purchased an MPCC to trial on the newt (as a comparison to the paracorr) and I've been working on a design for an adjustable spacer.

Here's the blueprints including the steps I'm planning to machine it.

suggestions welcome!

[peter_4059]

I've spent a few more hours planning this and have updated the drawings with more detail. I need to verify the thread length of the T thread on the MPCC and also the OD and length of the collar thread - anyone have these dimensions handy?

[h0ughy]

i know i have a spare one of these lying around. do you want to borrow it peter?

[peter_4059]

Do you mean a spare spacer Dave? Is it adjustable?

[h0ughy]

no i got the spacer kit with my mpcc from Myastroshop when i bought mine - originally to use with the meade 16" light bridge, but i later used it with the vixen r200ss. not sure of the sizes but no they are not adjustable

[h0ughy]

you would almost consider a helical setup?

[peter_4059]

I was thinking about a threaded adjustment however it is a lot more work to make and you still need a way of locking it in place so I'm swaying towards a simple sliding mechanism with two grub screws. I want the MPCC and the spacer to insert into the focuser draw tube so the whole thing has to be max 50.7 OD and cant have anything sticking out.

I'll leave a fixed collar near the QHY8 end as a stop against the end of the draw tube. This gets around the problem with the recess in the MPCC causing tilt as the focuser locking ring will be around the spacer instead.

[Poita]

I'd like to make an adjustable spacer for the Hyperstar too, the spacers from Starizona are $90 + postage, and you need a separate one for each camera.
It soon adds up quickly if you are running multiple cameras with different CCD spacings.

[peter_4059]

I got started tonight on the machining. The outside and end have been cleaned up and the bulk of the boring is done for the first part. Thought I'd take some photos along the way this time....

[h0ughy]

thanks for the show and tell. is the lathe in your garage? you are indeed a man of many tallents, look forward to your result

[alistairsam]

Hi peter,
are you making it adjustable to use the same spacer with either the paracorr or the mpcc?
I bought the custom qhy8 spacer for the mpcc from Peter tan and it works perfectly.
Does look like you have it figured out, but do let me know if you need any measurement or pics.
its midway through here http://tan14.com/Others.htm

[peter_4059]

Yes Dave - I have a small lathe at home for those difficult to find astro spacers and adaptors.



I'm making this one specifically for the MPCC. I have the televue IS spacer system for the Paracorr however this won't work with the MPCC. I am also looking to make something that will fit completely inside the draw tube of the focuser so the draw tube compression ring acts on the spacer rather than the recess on the MPCC. I think Peter Tan's spacers are made for the original QHY8 rather than the pro and the t thread to CCD distance is slightly different between the two models.

[peter_4059]

Got the first half of the spacer done this afternoon. Here's a few images of progress. Second half to do tomorrow....

[alistairsam]

Looks great Peter.
Bet you could make a focuser as well.
a low profile, zeroshift focuser!

[peter_4059]

Think I'd need a mill for that ...:question:

[mikerr]

Peter thanks for posting the machining operations. Is the tool shown a boring tool or is it the inside threading tool?

I would be interested to know the thread details (Diameter, pitch, depth, etc) and the tool/insert details used to cut the threads.

Keep it coming:thumbsup:

Michael.

[peter_4059]

That is the boring tool however the internal thread tool is quite similar except the cutting blade has a sharper tip and has interchangeable ends set for the correct angles: 60 deg for metric thread / 55deg for Whitworth. T threads are M42 with a 0.75 pitch. I tend to measure a few with digital calipers to decide what diameter to start with. For this spacer I bored out the internal part to 41.3mm before cutting the actual thread. The actual thread depth is only fractions of a mm. I do this by trial - ie keep cutting and trying the part until the thread is deep enough.

[peter_4059]

Got all the machining done yesterday. Just need to get some small set screws and blacken the internal parts. Here's how it looks now.

[peter_4059]

And here's how it all goes together

[mikerr]

Nice job Peter.:thumbsup: Thanks for going to the trouble of posting the photos.

I have an AL330A lathe but have only cut a couple of trial threads a few years ago with a tool that I ground myself. Those insert cutters look the way to go, especially for the fine pitches.

Michael.

[peter_4059]

They are from Hare and Forbes - not cheap but work well.

[troypiggo]

Looking good mate! Very neat and tidy.

[RobF]

One of my dreams if I ever get enough time, equipment (and brains) would be to be able to make custom adaptors.

Thanks for showing this Peter - very interesting.

[Poita]

That is slick!

I must get around to making some PST adapters soon.

[peter_4059]

If you want to give it a try some day come over Rob. Al you need is a stick of aluminium (50 or 60mm diameter depending on what you want to make). I get it from Action Aluminium.

[RobF]

Thanks Peter, I appreciate that. Next time I'm stuck just may be asking for help :)

[DavidTrap]

Very impressive - I could have a lot of fun if I had your skills!

DT

[peter_4059]

Got the grub screws this afternoon so after a bit of drilling and tapping and a lick of black paint here is finished product.

[troypiggo]

Mate, that's very schmicko :thumbsup:

[ozstronomer]

Very professional work Peter, looks like it should do the job nicely

[peter_4059]

Finally got a chance to test the spacer with the new MPCC. Following a number of steps from 53mm up, I was surprosed to find the MPCC worked best with 59.5mm spacing vs the advertised 55mm. Overall I am very happy with the way it is working.

Here's the final test image CCD Inspector report, a test shot of NGC3324 and a 100% crop in the top right corner.