Imaging on rise to Meridien or fall to horizon?

[Jonk]

Something I've been thinking of lately is the mechanical difference between imaging a target whilst it rises from the east to the Meridien or sets to the west.

There shouldn't be any difference really apart from balance and mount performance but something tells me imaging on the rise is better?

Is anyone able to convince me otherwise?

The reason is, where I'm moving to has more visible sky to the west than the east due to a few tall trees and therefore more time available on a target as it sets.

[steppenwolf]

I don't think it makes any significant difference mechanically but it could be argued that the effects on the steadiness of the atmosphere of heat release from the ground after the Sun has gone down makes imaging after the meridian a better bet?

I would always try and image when objects are at their highest in the sky and just accept the necessity of a meridian flip as this gives you the minimum of atmosphere to image through. It could well be that even your limited easterly horizon will allow you to do this.

[Jonk]

Thanks Steve, good point about heat as the location of the obsy may have to also point over the house to some degree, so short of moving to Chile I'll have to live with it.

I suppose start imaging as soon as a target is visible in the east, flip then as far down as possible before house or 30 degrees elevation and there won't be any noticeable difference at all?

As I'm looking at 30min subs I'll image the same target on multiple night so beggars can't be choosers I guess.

[steppenwolf]

23 minutes ago, Jonk said:

I suppose start imaging as soon as a target is visible in the east, flip then as far down as possible before house or 30 degrees elevation and there won't be any noticeable difference at all?

That would be the best plan as this way you are making the best use of the object's elevation.

[coatesg]

The mechanical aspect applies for German mounts - those with a worm/gear are generally best when the worm is always driving (ie they are slightly weighted towards the east). The reason is to avoid the scope swimming around in the RA backlash if it was perfectly balanced. This is true either side of the Meridian (and either side of the flip) though.

The way to ensure it's true is to shift the counterweight slightly according to which side you want to be heavy.

[Jonk]

2 minutes ago, coatesg said:

The way to ensure it's true is to shift the counterweight slightly according to which side you want to be heavy.

Yes very true, but that isn't easy when a flip takes place when I'm in bed ?

It's just always made me wonder if imaging on the rise or fall is better.

I think a Mesu is on the cards here!

[steppenwolf]

12 minutes ago, Jonk said:

I think a Mesu is on the cards here!

No doubt about that!

[Jonk]

2 minutes ago, steppenwolf said:

No doubt about that!

It's the 1st thing I'll order once moved!

[iansmith]

On 01/10/2018 at 20:42, Jonk said:

think a Mesu is on the cards here!

Go for it, you won't regret it.

Cheers, Ian (a happy Mesu owner )

[Jonk]

I know... I've read everything I can find on it, including the issues Harry Page has had and I can't think of a better mount to go for.

I also like the idea of imaging a couple of hours aftet the meridian without having to flip so that also helped make my mind up.

Sure I could go balls out and get something stupidly good and expensive but what's the point for a back garden observatory?!

It will be a Christmas present to me!