Planning my first observatory

[LuckieEddie]

I need an observatory for all the usual reasons. Unfortunately our corner plot only has one suitable location - and it's triangular. I think I'm going to be making a variation on a dome to modify the shed that's already there.

Right now I'm planning the structure but also thinking ahead to future automation. I have a question for anyone using an automated dome:

I assume the dome rotation gets synchronised to the mounts Azimuth co-ordinate via the chosen software/drivers but what happens when the scope changes pier side after a meridian flip? The resulting Azimuth is (almost) unchanged but physically the optical axis is displaced by a significant amount (eg. maybe 0.5 - 0.8m). I'm assuming that the typical dome shutter aperture isn't wide enough to allow for this so is there some offset applied to the dome rotation depending on current pier side?

[Tomatobro]

On a Pulsar dome controller operated by N.I.N.A software there is a whole host of measurements that have to be programmed in in order for the controlling software to position the dome to match the scope position. Steve Richards did a write up and spread sheet to help with the measurements.

I built a controller for a early Pulsar dome which used two lasers mounted either side of the dome aperture which sensed when the scope broke the laser beam and nudged the dome round to re-establish the laser light.

Its also possible to wind a coil round the end of the scope and use a switching circuit to create a alternating magnetic field which can induce a current in a coil of wire looped round the shutter aperture. Electronics sense the rising current as the scope approaches the edge of the aperture and nudges the dome round to null the current.

I built a mock up of this method but settled on the lasers illuminating light dependant resistors as a reliable method. I did have to write a routine that allowed for moths flying through the laser beam in that the beam had to be broken for a number of seconds before the dome got nudged.

[inFINNity Deck]

When you plan to build your own dome, like I did (for automation see here), you can use LesveDomeNet to automate it. Meridian flips are properly dealt with in any imaging software that can handle a dome (e.g. SGP or NINA). However, when you plan to use a side-by-side set-up, you will need to check whether the imaging-software can handle lateral offsets to the imaging scope. I used to use SGP, but that could not handle side-by-side set-ups, nor was that implemented within a year (!) after asking to do so, despite even offering the required algorithm. Another issue with SGP (and perhaps other imaging-software as well) is that it would control the dome during imaging instead of in between integrations (synchronised slewing). As a dome-slew will result in vibrations, that will mess-up your image(s). In the end I felt SGP was a dead end and switched to NINA as that had the lateral offset already implemented. I asked the developer for synchronised dome-slews, which was implemented with a few days.

My imaging scope has a GEM-offset of 430mm and a lateral offset of 180mm and never have issues during nightly sessions where the mount does its meridian flip when using NINA.

Nicolàs

[LuckieEddie]

Thanks for the responses.

Tomatobro - I do like the idea of a "follow me" system controlling the dome from the mount. Genius.

inFINNity Deck - That's a seriously impressive build. Way beyond what I'm hoping to achieve. Thanks for the tips and the links.