Pulsar dome and POTH...Help!!!!

[Hallingskies]

The equation for a roll-off roof is a lot easier...

[steppenwolf]

53 minutes ago, Hallingskies said:

The equation for a roll-off roof is a lot easier...

True, 1-1 = 0    where 1 is equal to the roof closed and 0 is equal to no roof apparent........

[tomato]

On 11/08/2018 at 13:21, steppenwolf said:

Here you go - it's quite simple actually

Document 1   and

....... Dome Slit Calculation

I’m charged with sorting the dome control software out when my retirement dome project goes ahead next year.

I did pure and applied maths at A level many, many  moons ago, it will be good to put that trig to good practical use after all this time☺️

[steppenwolf]

3 hours ago, tomato said:

I’m charged with sorting the dome control software out when my retirement dome project goes ahead next year.

I did pure and applied maths at A level many, many  moons ago, it will be good to put that trig to good practical use after all this time☺️

You'll be able to make mincemeat out of it then!

[tomato]

Lets just say I’m glad it’s already all written down....

[Hallingskies]

The thread that refused to go away....

OK.  Dome now synchs with mount, something I couldn't get to happen until I received advice here.  However and despite much entering of different numbers into different places, the dome slit consistently runs about 50 degrees west of where the scope is pointing.  As far as I can tell, I have entered the correct offset values into the POTH set-up screen.  I have also tried entering various values into the POTH goto/synch control screen once the dome is connected, but there seems no rhyme or reason to the value that needs to be used to get the dome running in the right place.

Any ideas anyone?

It's all getting a bit frustrating.  Also, an amusing side effect of all this mucking around is that somehow, I have messed up some setting so that the ASCOM and Pegasus hub software fails to automatically recognise any of the USB devices connected to them. I now have to unplug and re-plug all my USB inputs (hub, dome and mount) into the PC every time after I boot up, before the software can pick them up, even though they are showing up as all present and correct in the Windows 7 device manager.

I'm really beginning to wish I'd left well enough alone...

[steppenwolf]

2 hours ago, Hallingskies said:

As far as I can tell, I have entered the correct offset values into the POTH set-up screen.  I have also tried entering various values into the POTH goto/synch control screen once the dome is connected, but there seems no rhyme or reason to the value that needs to be used to get the dome running in the right place.

Can you please post up a screen shot of your POTH settings that lead to the 50 degree discrepancy? Thanks.

[Hallingskies]

18 hours ago, steppenwolf said:

Can you please post up a screen shot of your POTH settings that lead to the 50 degree discrepancy? Thanks.

Thanks Steve - assume this is what you mean...

These are the measurements as translated into the above...

If I have done something daft then let me know.  I have tried various values for the GEM axis offset, although the 400mm value is the correct one (the distance between the mount RA pivot axis and the common axis of the main scope/guide scope combo).

Whatever number I entered here seems to make no difference to the 50 degree west error on the dome position.

In the ASCOM telescope chooser options, I saw there was an alternative to POTH, called ASCOM Dome Control.  I opened that screen, and it seemed to require the same dome data, only in inches.  The dome site information was already in there, but I left the dome data blank and did not select it this option, sticking with POTH instead.   Just wondered what this did if POTH is the "hub".

[steppenwolf]

OK, none of your entries look outrageous so I think that we can assume that they are more or less correct provided you have ascertained the correct position of the RA centre offset.

Have you tried manually moving the dome slit to the correct position and then taking a night time photograph and plate-solving followed by a SYNC to make sure that the mount is correctly reporting its position? It is just possible that the mount is reporting its position as being 50 degrees off where it is actually pointing!

[Hallingskies]

55 minutes ago, steppenwolf said:

It is just possible that the mount is reporting its position as being 50 degrees off where it is actually pointing!

I don’t have plate solving capability but I can certainly check what mount position is being reported in POTH.  A 50 degree error should be readily seen, even if I point the scope at a target in daylight.

[steppenwolf]

41 minutes ago, Hallingskies said:

I don’t have plate solving capability but I can certainly check what mount position is being reported in POTH.  A 50 degree error should be readily seen, even if I point the scope at a target in daylight.

You cannot rely on the reported position in POTH - that's the point I'm making. You need to be SURE that the telescope is pointing exactly where it reports to be pointing, hence the plate solving requirement.