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Dome Sync Home and Park Settings

Hope someone can clarify for me.

I need a basic understanding of the Home and Park settings in the ASCOM configuration. I've read the WIKI page and trying to wrap my head around it.

I believe that Home position from true north affects the sync position as it tells the system where true north is in relation to Home. Also, that park should not influence the sync of the dome as it is arbitrary.

In my case my Home and charging position is 345deg from true north. My park can be set to anywhere, but if I want it to park and charge it also should be set to 345deg?

The 4.0 ASCOM version of the NexDome driver has a Park button and with no Home button, but when the Park button is selected the dome moves all the way around to the sensor position and stops

NINA has a Home button and a Park button, but Nina's Home button does the same thing as the ASCOM Park Button and Nina's Park position can be set arbitrarily. So is the ASCOM Park button not really the Park position which is set by degrees elsewhere, but actually it calibrates the Dome Home position?

8 comments

8 Comments

James Myres

Feb 16

So in my case I will make both home and park at 345deg. Or leave the park at 345deg and move thr sensor to 0 azimuth and set home to zero.

I found the poth settings and there is both a home button and a azimuth set button for 0. Does this azimuth set button change the home setting value if different? Does it need to be set or can I just set it in the home value setting?

Rodolphe

Feb 16

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Replying to

There is no reason to change the sensor position. Set them both at 345º and that is all you need to do.

In POTH , the Azimuth set is probably fora goto, not to set the current position as the new Azimuth. Same for the home button, it's probably used to send the dome to its home position.

Rodolphe

Feb 16

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If your charging pads are at 345º , I would set this as the park position. Regarding the home position, this should be the azimuth of the magnet sensor on the bottom part of the dome. This is what defines the offset between the dome 0 tick position (home) and it's position in space (X degree from true north, aka its azimuth).

James Myres

Feb 18

Replying to

When I said aligned with the mount...It was the line of site for the telescope pointing at true north. My park position for my Celestron CGEM with the indexes is at 0 when booting up the scope. My mount is aligned to true north with a RA at about 33deg.

The dome is set for home 345deg and park is 345 deg. The slit of the dome will move to align with the scope line of site when I goto azimuth 0. Regardless of the scope offset settings North, South, East or West...The dome should move to azimuth 0 when the scope is at azimuth 0 and slave to mount is checked. It does not. It moves more east than 0 azimuth.

While the offset settings of the mount in the dome can affect the dome position at any other setting other than 0, at scope 0 azimuth it should be in line with the scope. should also be the same whether the scope is Alt-AZ or Equatorial.

Edited

Rodolphe

Feb 18

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Replying to

In GEM mode the calculation is done using Ra, Dec, not Alt, Az.

IF at park your mount put the OTA straight above it pointing north (like an Alt,Az mount), this is a park position, not a real position. Do a goto something then goto Polaris, your OTA will not move to the park position but off one side of the pier, and the dome should align the slit with it. If your OTA not straight above the mount pointing north when parked, and is off one side (RA 33 ?), then the dome geometry is used to calculate where the slit should be to line up with the OTA.

Can you post a picture ?

This seem to all be related to dome geometry (mount Ra/Dec intersection offset from the center of the dome sphere and OTA offset from the mount).

https://rti-zone-images.s3.amazonaws.com/dome_geo.png

James Myres

Feb 20

Replying to

I thought i had this correct but it appears,very subtle changes in these settings can have a profound affect.

After some carefull adjustments it is pointing close now. I will have to fiddle some to get it perfect. I used the gem offset at the center of the combined apeture of the main scope and guide scope. This seems to be the least sensive setting.

What dome radius is being used? And how is the dome center from the floor being measured?

Edited