Pier Height, Observatory walls & Trigonometry ARGH !!!

[Earl]

I have been looking at some diagrams and I might have a problem.

The walls of the pulsar Observatory are 133cm high, add on for the dome and the openeing is going to start at 140cm ish

My pier is 77cm tall and the center of the dec axis (parked at horizontal this been the lowest) is 33 cm about this putting my Dec center axis at a total of 110 cm, 30 cm lower than the opening of the dome so its a fair bit lower.

the diameter of the dome is 2.2m

What angle am im looking at for the theoretical minimum viewable angle?

old school maths here and im rusty LOL

Wall maximum - mount minimum is 30cm center of dome to mount center is 110cm

This gives me an angle of around 15 degrees (I think) from the horizontal, which is probably not an issue as i dont want to be imaging that low anyway? I think my minimum horizon is around 30 degress anyway.

Any input / corrections very gratfully recieved

[Earl]

Update:

These caculations do not take into account how far the objective is from the center of the dec axis and center of the observatory.

Its just an extesnion of that line of sight though?

[Earl]

My east to south (ish) horizon at 110mm from the floor

[Earl]

Using two tripods and the top of the tripod been tge bottom of the opening of the shutter on the dome i have done this.

[Scott]

I wouldn't concern yourself too much earl. horisontal viewing/imaging is poor at best. I'd say, give it a go with it as is and if you're not happy with it, either buy or make an extention for the pier. Are you doing visual or imaging?

[JamesF]

Well, if your dome radius is 110cm and the depth below the edge of the dome is 30cm you have the adjacent and opposite sides to the angle you want, in a right-angled triangle.  The tangent of the angle you want is opposite divided by adjacent, so the angle is the inverse tangent of 30 / 100 or 0.3, which makes the angle about 16.7 degrees.

I think  It's been some time since I did trig, too

James

[Earl]

Ugh this gets more complcted....

When putting a mount in an Observatory the Dec axis center is off set to the Pier center in my case its 14cm north.

My opening is 600mm wide as im using a dual bar I also have to work out the amount the dec axis mounting surface shifts from the center or rotation on the RA axis. which is around 20cm.

This lead me to think that the observatory shutter doe not sit at the same angle as the scope is pointg but again offset eithwe east or west depending on which pier side you are....

My heads gone pop...

[Earl]

I wouldn't concern yourself too much earl. horisontal viewing/imaging is poor at best. I'd say, give it a go with it as is and if you're not happy with it, either buy or make an extention for the pier. Are you doing visual or imaging?

Just imaging

[Scott]

Just imaging

It's a very rare night that I image below about 30-35 degrees above the horison. Unless of course you have exeptional skies with no lp.

[Earl]

One conclusion im coming to is that side by side is not the ideal way to setup in a dome but rather over and under. but again also makes the psistion of the slit important if the combined height from the center of the RA axis to the dec surface mouting and the to edge of the scopes sitting on top is close to the maximum width of the slit.

[Earl]

What I think cuases all these issues is due to the alt az nature of a dome and the EQ alignment of a scope.

[just_ed]

You could skip the math I think, since you already have the dimensions but no angles. Use those dimensions to draw, at a fraction of the scale, your setup on graph paper, and use a protractor to find the angle you're looking for.

[Earl]

Looking at the ascom drivers, they look to allow an offset to allow for the distance from the ra axis and the centers of the ota

[CSM]

I have a Pulsar 2.2m with one of the Astro-Engineering piers which is about 102mm tall.  With the NexStar 6SE on a wedge I would set the filter limit at about 12deg.  With your bigger scope you probably gain a little height but in any case imaging horizontally doesn't usually work very well!