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New setup with a 300 mm lens and a EQ6 mount

astrophotography DIY mount
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#1 Astrofriend

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Posted 04 December 2020 - 03:40 PM

Earlier when I tested my Canon 300 mm L f/4 lens mounted on my Star Adventurer I found the load on the mount too high. Now I 'm adapting it to fit my EQ6 mount and include an auto guiding camera too.

 

Here are drawings and photos of my rainy day project:

http://www.astrofrie...00mm-setup.html

 

/Lars



#2 photoracer18

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Posted 04 December 2020 - 04:17 PM

Well for one thing the 6D will not be able to autofocus on anything except the Moon so at a minimum you will need some kind of Bahtinov mask to manual focus it. Otherwise you may need to add PC controlled autofocus. I have done this with a 300/2.8 using a belt driven Robofocus but not with a 300/4. Might add too much extra weight.

With a serious GEM mount this would be a no-brainer. With the 300/2.8 I was using my Losmandy G11 at the time so the weight was nothing. I put everything on a 17" Losmandy dovetail. I mounted an extra oversize tube ring around the lens bolted to the rail and put the guidescope on top of that on a small Vixen rail. Made a bracket off to the side for the autofocus mechanism. I was using a manual 300/2.8, what was the last new Tamron ADaptall-2 360B model 300/2.8 sold in NA (2006) because a manual lens has a much smoother and wider focusing ring than an AF lens (plus they tend to use rubber on the focusing ring which helps the belt drive). You could do a 300/4 similarly as long as it has a tripod mount on it. Wish I had saved some photos of it.


Edited by photoracer18, 04 December 2020 - 04:54 PM.


#3 Astrofriend

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Posted 05 December 2020 - 06:23 AM

Hi,

Sorry, I see that I missed some words in my text. I never use the Canon's built in autofocus. I have either a PC with APT to control the focus inside the lens or a Raspberry with Indi drivers. None of them can control the lens focus motor as I wish. It's because of Canon's limitations.

 

If I want control the Canon lens motor I can use an Canon Remote app in my smartphone if I enable the WIFI in the Canon 6D. But then the camera can not communicate over the USB. And after it's focused I must switch the lens' button to manual focus again. To have perfect focus during a night I need to refocus about every 45 minutes.

 

But with the Astromechanics adapter (the link on my page) I can separate the camera (other cameras with shorter backfocus) and lens and control the focus independent. There is a way to do it in a similar way with the DSLR also, I have talked with a friend about this.

 

I have updated my page:

http://www.astrofrie...00mm-setup.html

 

A question: When you used the 300mm f/2.8, did you use it at full aperture or stopped it down ?

 

When I compare auto focus lens with manuell lenses I have noticed that auto focus lenses can focus more beyond the infinity which is good for astro use.

 

/Lars



#4 Astrofriend

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Posted 06 December 2020 - 03:25 PM

This evening I have tested out an extender between the guide camera and the Pentax lens.

 

http://www.astrofrie...00mm-setup.html

 

It's ready now for a first test, just have to wait for a clear sky.

 

Lars



#5 Astrofriend

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Posted 12 December 2020 - 11:38 AM

Today I noticed something interesting. My mini PC that have an input terminal for 19 Volts can be powered by much lower voltage. I have also installed an instrument with a Volt and Ampere meter. Now I can have more control of which of the devices that consume most power. Important when on battery power.

 

http://www.astrofrie...00mm-setup.html

 

I need to solve the mechanics of the motor focuser, have ordered some parts for that.

 

/Lars



#6 Astrofriend

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Posted 15 January 2021 - 02:19 PM

Is there something so exiting as when you can test something new that you have built ? I could do my first indoor test of the focus motor with it's 3D printed parts today. It's the USB-Focus and I control it through APT and ASCOM driver. Have a look at page 7:

 

http://www.astrofrie...00mm-setup.html

 

The gear ratio I could achive let me use 30'000 steps of the 65500 availably. There is also an instruction how I calibrate the focuser.

 

/Lars


Edited by Astrofriend, 15 January 2021 - 02:20 PM.


#7 Astrofriend

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Posted 23 January 2021 - 04:56 PM

Today we had a terrific weather with sunshine. I hoped to get a clear sky tonight and prepaired my equipment. Set the angle of cameras and measure the balance point.

 

Have a look at page 8 if it's interesting:

http://www.astrofrie...00mm-setup.html

 

Did I get any photos ? Nope !

 

/Lars




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