PST Mod begins.

[+Graham]

As anyone who has used a PST will know it has one fundamental drawback.

The focuser.

Now for visual use the basic - ney - primitive prism focuser is fine but for imaging it is best described as agricultural to say the least, especially if like me the scope is on a pier in the obs and the computer screen is in the house next door.

After spending the best part of four hours today trudging back and forth between the scope and the computer screen  trying to focus it I decided that there must be a better way to do this.

After reading a PDF Steve (ibbo) kindly sent me on PST modifications I discovered the one and only unbreakable rule is there must be 200mm between the rear of the Etalon and the eye piece.

 

My solution.

 

Use the Revelation duel speed focuser I have on the back of my 10 inch Meade.

 

This gave me 120mm of image train with the focuser fully extended ( this will allow me to rack the focuser back in so I can use my DSLR ) plus the 35mm taken up by the ERF and Blocking filter which are in the EP side of the PST's image train.

This meant I had to gain another 45mm.

 

I decided to machine up an adapter piece to go between the Etalon and the focuser.

 

My reasoning for this decision was two fold.

First it means I can manufacture a substantial adapter giving all the strength needed to carry the focuser and the OTA.

Second it gives me somewhere to mount a dovetail bar so I can mount the whole thing straight onto my NEQ6.

 

Well the thinking soon turned to making, hell who needs sleep anyway.

This is the results of my labours for tonight.

 

 

The adapter placed in position.

 

 

Fitted in Place.

 

 

Another view.

 

 

The whole thing.

 

 

Tomorrow I will Anodize it black and fit the Dovetail bar.

I will also machine a thread into the end of the 2" to 1.25" reducer so the eye piece section will screw into it.

Lastly I will fit an electronic drive to the focuser so I can focus the scope from my computer.

 

More pics to follow. 

Edited July 5, 2015 by Graham

[+Ibbo]

Thats the ticket Graham

[Johnnyaardvark]

Looking nice that Graham. Look forward to pics taken with a dslr on the end. A great mod!

[Brantuk]

Neat mod - wtg!

[Doc]

Well you are living up to your signature.

 

Nice one Graham.

[philjay]

Thats a nice job there Graham. A simple and elegant solution

[+Graham]

Thanks folks.

Here is the finished article.

 

 

 

 

 

 

 

 

And it works.

Ok so the image is pretty ropey as I took it through the clouds tonight.

Taken with the QHY 5ll

I think it might be a tad bright for the camera as I had to turn all the settings right down and I have a bad case of banding on the image.

Still I am please with the result.

 

[+Ibbo]

good first ha image

 

get yourself a moon filter, ND 0.6 or 0.9 or a variable polarising filter

 

it looks like a case of Newtons rings which may disaapear when the clouds have gone or even the filter

 

if not a slight tilt of the cam may help

[+Graham]

good first ha image

 

get yourself a moon filter, ND 0.6 or 0.9 or a variable polarising filter

 

it looks like a case of Newtons rings which may disaapear when the clouds have gone or even the filter

 

if not a slight tilt of the cam may help

 

Thanks Steve.

Only trouble with a filter is there is nowhere to put it on the QHY5ll.

Might try sticking it in the  EP holder and put the camera in after it.

[+Ibbo]

Thanks Steve.

Only trouble with a filter is there is nowhere to put it on the QHY5ll.

Might try sticking it in the  EP holder and put the camera in after it.

 

 

thats what I do with the 03 or green filters i have used on the recent WL images or try holding it place with a tiny bit of bluetac

Edited July 6, 2015 by Ibbo

[+Graham]

Brilliant stuff Steve I will give it a go next time the sun comes out 

[philjay]

+1 for the polarising filter. Good work Graham