PHD and guiding camera alignment

[Guest peepshow]

Someone on another forum asked if it was OK to use a  diagonal between his guiding scope and guiding camera.

The answer was yes even though a diagonal would reverse the image that the guiding camera sees !

 

This got me wondering..........nothing is ever mentioned about how accurate the guiding camera should be

rotation wise . 

Say a QHY5..........it's rotational position doesn't seem important as its never mentioned on forums.

 

It seems as though PHD will compensate for any rotational position  of the guiding camera as long as it doesn't move during guiding. 

 

If you lower your own mount and point your guiding camera  to a distant horizon is the guiding image seen on PHD exactly horizontal or not?  

Would it take longer to calibrate if it wasn't level.

 

Something else for me to worry about.

[xanthic]

As far as I know, it doesn't matter. The calibration steps work out the image angle so you don't have to worry about it.

[Guest peepshow]

 The calibration steps work out the image angle so you don't have to worry about it.

Maybe that's why some folk have too many and long calibration steps ?? .......PHD having to work out  all angles,

especially if one has a slow PC running PHD.

 

If the imaging camera saw the horizon as exactly level then no angular calculations required.

 

Might be an interesting experiment to deliberately slew the imaging camera at an big angle and compare number of calcs compared with exactly horizontal......if one could achieve that.

 

Just a thought or two.

Edited June 22, 2015 by peepshow

[philjay]

Yep, phd calibrates and takes into account the orientation. I used to run guidemaster where you had to do the calibration manually, this was initially a pain until I realised I could put datum marks on the tube and camera so I could position the camera then start guiding straight away, worked a treat. I do miss the simplicity of guidemaster and my mintron as a guidecamera.

[Guest peepshow]

That's interesting Phil, as I never have to move my mount at all.

 

So is there a way of say, calibrating PHD once on a part of the sky and if coming back again the next night to the same sky position to stop PHD from calibrating all over again, and so save valuable imaging time? 

 

I know there is a 'force calibration' but haven't seen a 'miss calibration' facility.

[philjay]

Don't know Richard never really experimented with PHD. PHD seems to need to recalibrate everytime you move across the meridian or even shift to another area of sky, that's because balance will be different and hence backlash I suppose, backlash will change over the meridian particularly so its always wise to recalibrate for more accurate results.

 

My description re guidemaster didn't refer to the mount repositioning just the cameras position and orientation on the guidescope.

 

My set up at the time was particularly different from the norm shall we say, Celestron CGE permanently mounted in observatory, C11 imaging scope and SW 127 Mak guidescope on solid rings. Guidecamera was a Mintron video camera. I should imagine it wouldn't be repeatable with different kit.

 

This set up was ultra sensitive and extremely accurate on guiding, something alas I have not been able to emulate with PHD, ST80 or finderguider and QHY5.

[Guest peepshow]

Phil, thanks for all that.   Since guiding in the last few months I  have always used PHD, never looked at PHD2.

 

BUT, this afternoon I had a look at PHD2.  Under Tools are "Enter Calibration Data" and "Restore calibration Data."

There is also a Meridian flip of data too ! 

 

I Googled this and found on this site..........

 

http://openphdguiding.org/man/Basic_use.htm#Automatic_Calibration

 

the following..........

 

 

"Like all other guide settings, the calibration data is automatically saved as part of your current equipment profile.  If nothing has changed in your configuration from one session to the next - even over an extended time period - you can restore the previous calibration data and start guiding immediately.  This function is located under the 'Tools' menu and is labelled 'Restore Calibration Data.'  Remember, the data are saved whenever a full calibration is completed or when you use the 'flip calibration data' command under the 'Tools' menu (see below)."

 

So Phil this is what I am looking for and it may help you too as there is that meridian flip data too !

 

Maybe there is even a way to save sets of calibration data for different parts of the sky.  

 

Just turn on the mount each night, hit Cal Data Number X and start guiding immediately.