Project:
EQ6 mount and 300 mm lens setup

Contents:

1. Introduction and first setup
2. Adjusting the extender width of guide lens
3. New powered USB Hub and power cables
4. Mounting bracket for motor focuser
5. Instrument for Volt and Ampere
6. Camera external 12 Volt power
7. Motor focus test and calibration
8. Preparing outdoor test
9. To be continued

Note:
I take no responsibility or liability for what are written here, you use the information on your own risk!

2: Adjusting extender width of guide lens

In this case I use an old Pentax M42 lens as a guide telescope. The camera I connect to it is the QHY5. To have them work together I must adjust the distance between the lens and the camera to get it in correct focus. A Pentax M42 lens has a back focus of 45.46 mm and the QHY5 camera has only 12.5 mm.

List if different cameras back focus:

• https://en.wikipedia.org/ wiki/ Flange focal distance (Flange focal distance)

I have to fill the distance with an extender of 32.96 mm. An old lens like this doesn't have inner focus, when focusing the lens whole the lens packet move as one unit. Then the distance isn't very critical as long I reach focus at infinity. But there are more to it.

Adjusting the guide lens' extender:

The front of the lens. The dew heater band will be mounted on the left side of the arrow. In this case it's a lot of space but the part right to the arrow moves when focusing. I want some distance from the dew heater to the focus ring.

I test focusing at infinity with different extender width, with this setting I got much more space where I can have the dew heater band. This lens don't have a barrel of plastic, aluminum everywhere and the dew heater will transfer its heat efficient. I concentrate the heat to the front lens element. My experience is that I need from 1 to 2 Watt to get the dew away at a lens like this.

An extender of 15 mm had been perfect, but didn't have that in my boxes. The arrow to right point at the T2 to M42 adapter, both has the thread diameter of 42 mm but the thread angle is different. The width of this adapter is 7.5 mm. The arrow to the left point at the extender, the nearest size I had was 11 mm, all together 18.5 mm. Good enough.

My collection of Pentax M42 extenders: 45, 19, 18, 11, 7.5 mm.

Align the cameras:

Next thing to do is to align the main camera. I normally have the long side of the sensor parallel to the DEC axis (along the R.A. coordinates), i.e. landscape mode with the star Polaris at top.

The program PHD2 I use can handle the auto guiding whatever angle the guide camera has. I prefer to have it at the same angle as the main camera and parallel to the the RA axis. If there is a problem it's much easier to solve it then.

On the backside of the Vixen tail I mounted the: EQ6 direct connect adapter, 8 Volt converter, 5 Volt converter.

To the left, by the 5 Volt converter powered USB Hub.

Focuser plan (main camera lens):

The arrow point on the focuser motor. I have not decided yet if I would use that one. Maybe I can control the lens built in focuser motor instead. A friend to me are working on it. It's only the main camera lens I want to have the capability to do remote focus on. My experience is that I have to fine adjust the focus every 45 minutes, because of temperature changes. The guide lens isn't that critical and I only focus it manually once.

If I decide to use the external focuser, an USB-Focus set with the middle size motor. To have it work correct I have to 3D-print a big diameter toothed pulley that clamps around the lens barrel.

This focus motor was left over because it was too weak to use on my big and heavy APO refractor.

Repair of Hub's DC cable:

When I powered up the system I didn't get any power to the USB Hub.

It was my home built DC cable that had got broken. I soldered the socket to the cable again and also added a stronger support to the cable to not let this happen again.

I got this draft from my friend. The idea is to place this between the camera and the lens, With direct access to the lens' focus motor it can be controlled independent of the camera. It couldn't be used to a DSLR because there is no space for an adapter like this. I thinking of a heavy modification of my Canon 6D. Take away the mirror, remove all filters and drill a hole in the camera and connect an external cable inside the camera to the connectors to the lens control. Say goodbye to my old working DSLR.