Observing objects nearer the zenith?

[Cuto100200]

Hi 

I was just wondering, how much difference it makes to object quality when observing objects nearer the zenith as opposed to the horizon, I understand less light pollution helps a whole bunch, but I was wondering just how much better visual quality would be, and it is worth staying up til say... 3am, waiting for specific objects to move closer toward the zenith?

Thanks

[MarkAR]

A lot less air to see through, makes seeing better.

[BrendanC]

But, also more difficult to access with an AZ mount!

[Pete Presland]

certainly looking forward to seeing Mars up nearer there later in the year.

[John]

2 minutes ago, Pete Presland said:

certainly looking forward to seeing Mars up nearer there later in the year.

Will Mars actually be anywhere near the zenith this year ? - I thought it would still be pretty low down.

As you near the horizon you get both additional disturbance from looking though more atmosphere and also a thing called atmospheric extinction - a dimming effect.

The higher up in the sky the better, especially when trying for stuff that is challenging.

[Pete Presland]

45 degrees i think in September/October, or i that wishful thinking 🙂 

[Waddensky]

It's all about airmass. When an object is low above the horizon, you have to observe through much more atmosphere than when an object is near the zenith, causing scattering and absorption and turbulence.

Unfortunately, observing near zenith is nearly impossible with horizontal mounts like dobsons, so there is a "golden mean" somewhere.

Edited April 27, 2020 by Waddensky

[John]

Just now, Waddensky said:

It's all about airmass. When an object is low above the horizon, you have to observe through much more atmosphere then when an object is near the zenith, causing scattering and absorption and turbulence.

Unfortunately, observing near zenith is nearly impossible with horizontal mounts like dobsons, so there is a "golden mean" somewhere.

Tracking more challenging with a dob when pointing towards the zenith but it is possible to observe there. M51 is up there currently and I've observed that quite a few times with my 12 inch dob over the past few weeks.

[Waddensky]

2 minutes ago, Pete Presland said:

45 degrees i think in September/October, or i that wishful thinking 🙂 

Correct 🙂

[Waddensky]

1 minute ago, John said:

Tracking more challenging with a dob when pointing towards the zenith but it is possible to observe there. M51 is up there currently and I've observed that quite a few times with my 12 inch dob over the past few weeks.

Yes I agree, I primarily meant finding and tracking. Once found, zenithal observing is certainly possible.

[Pete Presland]

According to Calsky it transits at 43.239 degrees at opposition on the 13th October.

[John]

4 minutes ago, Pete Presland said:

According to Calsky it transits at 43.239 degrees at opposition on the 13th October.

In Pisces I think. So not really near the zenith. Better than last years opposition though.

 

 

[Pete Presland]

1 minute ago, John said:

In Pisces I think. So not really near the zenith. Better than last years opposition though.

 

 

No not really, but in the right direction. Certainly better than the Jupiter and Saturn for the foreseeable future.

[John]

5 minutes ago, Pete Presland said:

No not really, but in the right direction. Certainly better than the Jupiter and Saturn for the foreseeable future.

True - last year we had both a major dust storm on Mars and it was so low it was bouncing along the rooftops here.

 

[ScouseSpaceCadet]

4 hours ago, Cuto100200 said:

Hi 

I was just wondering, how much difference it makes to object quality when observing objects nearer the zenith as opposed to the horizon, I understand less light pollution helps a whole bunch, but I was wondering just how much better visual quality would be, and it is worth staying up til say... 3am, waiting for specific objects to move closer toward the zenith?

Thanks

Living in a light polluted area I tend to observe later at night throughout the year and the zenith is my friend.

If you can afford a nice lie in the next day then those late hours are great. Peaceful and dark(er). Bear in mind the street lights are on, but most small business and residential lights have gone off due to the muggles going to bed. While us creatures of the night feast on the delights the universe has to offer.... Muhahaha 🧐

 

[Pixies]

Quick question regarding the larger planets. This is all based on on more recent interest in observing (bins), so apologies if I have gotten the wrong end of the stick.

Venus is quite high just now and I recall Mars being visible a few years ago even higher in the sky. However, Jupiter and Saturn have both been low in the sky for the past few years. Is their orbital inclination different to the nearer planets? I don't think it is. Is it just that during recent years, the best viewing times have been when they are in opposition during the summer - so low in the sky?

If they were in opposition during the winter, they will be higher? In which case, is there an app or website that shows when they will be higher in the sky?

 

Hmmmm - perhaps it's time for bed

 

[Waddensky]

14 hours ago, Pixies said:

Is it just that during recent years, the best viewing times have been when they are in opposition during the summer - so low in the sky?

Exactly. Planets are always in the vincinity of the ecliptic, and from the northern hemisphere, the ecliptic is low above the horizon in the summer and much higher in the winter night sky. Since the outer planets move relatively slowly in their orbits, it takes a while before their yearly oppositions climb to a higher declination (and therefore higher altitude). On this page is a chart of the declination of Saturn during oppositions between 2000 and 2115.

[miguel87]

Zenith is great and does make a noticeable difference.

I always try to leave it until the end of the session tho because it brings on the dew pretty quick!