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How do I measure the UP distance in the Dome Slave settings?

2 months 4 days ago
PK
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How do I measure the UP distance in the Dome Slave settings? #60632
I am entering the various Slave settings in the Dome driver and one is for the UP distance. From where do I measure from and where do I measure to? I don’t understand what I am measuring.

Thanks!

Peter


iOptron CEM25P
William Optics Star71
ASI 1600Mm Pro
Moonlight motorfocus
LodeStar X2 and ZWO OAG
DewBuster
NANO PC-T4

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2 months 4 days ago 2 months 3 days ago by xthestreams.
xthestreams
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How do I measure the UP distance in the Dome Slave settings? #60637
Essentially you are aiming to establish the distance from the intersection (pivot point) of the Dec/RA axis relative to the dome "origin" (0,0,0) - where the dome is a hemisphere (ie: assume the walls don’t exist) - this also assumes your mount is polar aligned and facing north or south depending on your latitude.

It’s something of a dark art and I’ll point you to a better thread shortly, but in essence if your counterweights are horizontal, how far up/down in millimeters is the point around which RA and Dec “meet”/intersect relative to the bottom lip of the dome - up being a positive and down a negative number.

Having been through this a few times, I WILL write something up about this as it’s horribly confusing to everyone.

Same idea for north/south offsets as well as east/west - the ease with which you can determine these through measurements is a function of your mount, though you may get luck and find drawings which help you derive them through trig.

NOTE: these offsets are NOT the pier position, which can itself ALSO be different, you are concerned only with where the key axis intersect in 3D space.

Because nothing is ever as simple as it seems in astronomy, there is a FOURTH dimension, being the OTA offset - this is essentially how “wide” is the farthest optical point of your OTA tube is from the same pivot point. To be honest I am not entirely clear I understand this myself but have found that generally if I use the aperture plus the offset from teh RA/DEC pivot point to the saddle plate I generally get it about right.

Chris Rowland has a rather more empirical method here ( indilib.org/forum/general/7125-problem-s...-indi-maxdomeii.html ) but note that he does not have a silver bullet for the Z (up/down) axis.

A decent tape measure will generally do the job.

As you will learn army my own challenges, this all depends on the mount reporting pier side correctly to INDI, the news is not good if you are using a Paramount sadly, the Paramount driver either can't or is incorrectly reporting the pier side so in my case I have had to use TheSkyX to control the dome slaving.... but you’re not, so all good.

GSO Ritchey Chretien 12" Truss | SkyWatcher ED72 | Celestron C14
ZWO ASI 183MC Pro | ZWO ASI290MM | ZWO ASI224MC all-sky | ZEO EFW | ZWO OAG
Moonlite V2 CSL | DeepSkyDad AF3
EQ8-R | Paramount ME (needs some loving)
Nexdome | SQM LE | Ultimate Power Box V2 | Spike-a-Flat
Angry missus
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2 months 3 days ago
knro
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How do I measure the UP distance in the Dome Slave settings? #60641
Please let me know once you have the write-up ready and I'll add it to the dome documentation!

Jasem Mutlaq
Support INDI & Ekos; Get StellarMate Astrophotography Gadget.
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2 months 3 days ago
xthestreams
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How do I measure the UP distance in the Dome Slave settings? #60652
any format you prefer it in Jassem?

GSO Ritchey Chretien 12" Truss | SkyWatcher ED72 | Celestron C14
ZWO ASI 183MC Pro | ZWO ASI290MM | ZWO ASI224MC all-sky | ZEO EFW | ZWO OAG
Moonlite V2 CSL | DeepSkyDad AF3
EQ8-R | Paramount ME (needs some loving)
Nexdome | SQM LE | Ultimate Power Box V2 | Spike-a-Flat
Angry missus

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2 months 2 days ago
knro
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How do I measure the UP distance in the Dome Slave settings? #60711
You just respond here and I'll format it later, the content is what matter!

Jasem Mutlaq
Support INDI & Ekos; Get StellarMate Astrophotography Gadget.
How to Submit Logs when you have problems?
Add your observatory info
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