PHD2 guide scope focal length

[mark skelton]

when setting up an equipment profile in PHD under the scope focal length do we add the extender length to the length of the scope or is it just the length of the scope on its own?

[almcl]

For a Skywatcher StarTravel 80 with just a guide camera attached, you enter the focal length of the scope: 400.  This is to give PHD2 the image scale.

Just to make sure I've understood the question correctly, what extender are you referring to?

[mark skelton]

40 minutes ago, almcl said:

For a Skywatcher StarTravel 80 with just a guide camera attached, you enter the focal length of the scope: 400.  This is to give PHD2 the image scale.

Just to make sure I've understood the question correctly, what extender are you referring to?

https://www.firstlightoptics.com/adapters/flo-80mm-125-focus-extension-tube.html

[michael8554]

Hi Mark

That extension merely helps to place your guidecam at the focal point of the guidescope, the focal length is unchanged at 400mm. 

And 400mm and the camera pixel size 3.75 is what you enter in PHD2 (it will round up the pixel size to 3.8 after you've entered it, no problem). 

Michael 

[mark skelton]

thanks for the reply, phd updated 

[ollypenrice]

Yes, the scope has a very short body to allow the use of a star diagonal for visual observing. The focal length is not the same as the tube length.

Olly

[newbie alert]

13 hours ago, mark skelton said:

when setting up an equipment profile in PHD under the scope focal length do we add the extender length to the length of the scope or is it just the length of the scope on its own?

Focal length is the length that the light travels to come to a focus point.

What guidescope do you have?

[mark skelton]

10 hours ago, newbie alert said:

Focal length is the length that the light travels to come to a focus point.

What guidescope do you have?

At the bottom of my reply's is the list of stuff I use