Pier + Wedge

[nightsky]

G'Day
Would someone know what advantage if any, would a Wedge attached to a Pier be. Thats if a wedge can be attached to a Pier in the first place?
TIA

[rogerg (Roger)]

I'm not sure exactly what you mean:

- Advantage of having a wedge?
- Advantage of having your wedge & scope on pier vs tripod?

How you attach the wedge to your pier depends entirely on the combination of wedge & pier, but anything is possible, it just might take some drilling and so on.

Roger.

[Dennis]

Hi Nightsky

I’m not sure of what you understand about polar alignment and astrophotography, so excuse me if the following is kid’s stuff for you.

One of the main reasons for having a wedge (on either a pier or a tripod) is to allow for accurate polar alignment. Polar alignment is very important in long exposure astrophotography, to prevent the stars from trailing and the field rotating. If you never plan to take long exposure astrophoto’s, then the need for a wedge lessens.

If your mount tracks the stars (i.e. it is motor driven at the sidereal rate) but the mount is an alt-azimuth mount, then you will experience what is called field rotation. If you place a star in the centre of the field of view (FOV) on an alt-az mounted scope, then whilst the mount may accurately track that star, keeping it centred in the FOV for 30, 60, 90 minutes etc., you will notice that the stars surrounding this central star will actually rotate around it, as the evening progresses, due to the rotation of the Earth. This is okay for visual observing, but no good for long exposure astrophotography.

However, for purely visual observing, a modern GoTo scope fitted on an Alt-Az mount, once aligned will be able to accurately locate (GoTo) 1000’s of celestial objects and track them for hours at a time without the need for an (expensive) wedge.

Cheers

Dennis

[nightsky]

G'Day Roger,
I was thinking that having a wedge on a Pier would make the scope more

secure and much better if I decide to get into photography? are there different types of wedges? and are they worth the money $200 plus for what I would want to use it.

[nightsky]

G'Day Dennis,
I was in the process of sending a reply to Roger when your reply came in lol,you have answered my question, one more thing are there different types of wedges?
Thanks

[Dennis]

Hi Nightsky

Ahah, we crossed somewhere in cyberspace!

I've always used a German Equatorial Mount (GEM) so have only seen wedges on the 'scopes of fellow observers. I do believe that there are "standard" wedges and "heavy duty" wedges, as well as wedges made by third parties.

Some of the "standard" (read lighter or less rigid) wedges seem as if they may not be rigid enough? I think the "heavy duty" wedges would cost between $400 and $1000 at least for say, a 10” or 12” fork mounted SCT?

Cheers

Dennis

[nightsky]

G'Day Dennis,
Wow that's a lot of money for a wedge, as I would only be doing a little and I mean a little photography, I'll check around the online shop's and see what they say regarding the price and type of wedge to suite my needs, thanks a lot m8 for the info.

[g__day (Matthew)]

Nightsky - a very quick summary of the above:

1. Pier set-up properly - fantastic platform for any type of fixed location astronomy - saving time, more secure and robust, more stable, less prone to vibration, no risk of being knocked over.

2. Wedge - one of the two key options needed for fork mounts to avoid star rotation for longer duration astro photography. The other option is a field de-rotator that rotates the eye piece or really a ccd so that star field rotation is counter acted.

So for a fork mount a pier on a wedge or more simply a pier with a top mounting plate machined to an angle of your locations exact longitude would be a great asset - and not too expense or difficult to make for yourself if you do some planning.

[rogerg (Roger)]

Originally Posted by nightsky

G'Day Dennis,
... one more thing are there different types of wedges?
Thanks

There's a large range of wedge's available, and if you know a local engineer it's not hard to have one made up yourself, and probably cheaper if you can be bothered with the hassle.

I wouldn't waste the money on the "standard" wedges, they are simply too flimsy in my mind. But the stronger ones are good... Meade Superwedge, Milburn Wedge, and some others out there. You can find instructions/drawings of how to made one in lots of places on the web, MAPUG is a good place to start, even if you don't havea Meade.

Roger.

[nightsky]

G'Day
Thanks G_day,Roger, and Dennis for your input ,gives me food for thought. I appreciate every one's input.
Thanks