Drift aligment

[alexV]

Hello all

When doing drift alignment should I configure my Synscan as well
Iam Not talking about setting the date, coordinates etc but things like tracking speed, solar rate or siderale rate

It also gives all diferent rates of speed but I don't think that manual realy explained that well

Can I just choose any speed and try to adjust my drift allighment to it?

Thank you :thumbsup:
Alex
A & F painting
www.anfpaintingservices.com.au

[Jeffkop]

Select sidereal rate Alex .. thats the rate that moves the mount exactly the same speed as the earths rotation but of course in the opposite direction

[alexV]

Jeff what about tracking speed should that be on at any time and if yes how do i know which is the right speed

SynScan gives you few options cant remember exactly but something like x0.5, x025 and so on

Thank you

[Jeffkop]

Not sure about the synscan options Alex, however the tracking speed for deep space objects etc is sidereal. Other speeds like planetary or lunar are obviously for those type of objects ... as far as .5 etc I would select normal sidereal or x1.0 etc to start with and see how it goes. Ive never had a mount that I have had to run it at .5 ... others may wish to comment if they have. Good luck

[alexV]

thank you for your help

[ZeroID]

Hey Alex, if I remember correctly the 'tracking speed' you are referring to to are the correction rates that would be applied if you were running an autoguider scope. It more or less specifies the step size that any correction would make. The more accurate your alignment is the smaller and better the step needs to be but if your alignment is well off then the correction step may be insufficient to maintain the target in FOV and bigger steps may introduce some degree of image movement and poor resolution.
The Holy Grail would be to have a perfect alignment and perfect sidereal rate and not need any corrections from a guide scope but .... I think I just saw pig fly past ...

Basically unless you are running a guide scope system it has no relevance to your normal operation at sidereal rate for stars etc.
(The other rates will be for Solar and Lunar Tracking to allow for their differing rates of travel and some PEC rates IIRC )

[ZeroID]

Just checked the SynScan Manual and the actual wording is :


Auto Guide Speed -
When using an autoguider, this sets the guiding speed to 1X, 0.75X,0.5X, 0.25X, or 0.125X sidereal rate.

So ignore unless guiding.

Here are the other rates available with explanations from the manual:

SET TRACKING
Sid. Rate: This activates tracking in Sidereal rate (R.A. Tracking).
Lunar Rate: This activates tracking in Lunar rate (R.A. Tracking).
Solar Rate: This activates tracking in Solar rate (R.A. Tracking).
PEC + Sidereal Rate: Sidereal rate with Periodic Error Compensation.
Stop Tracking: This stops the tracking instantly.

[gary]

Hi Brent,

At last October's IceInSpace Astro Camp which is held north of Sydney, I gave a
presentation on 'Busting the Myth of the Perfect Polar Alignment'.

In a nutshell there is no magic point in the sky to which you can align the RA
axis of the scope and achieve no field rotation.

Likewise, there is no magic single constant rate at which you can drive the scope
and achieve perfect tracking.

Strangely enough this was well understood by the very first professional
astrophotographers as far back as 1893 but is still commonly misunderstood
by many amateurs today, even many accomplished ones.

The reason the Holy Grail is a myth is, of course, due to the distorting effects of atmospheric refraction.

The details are surprisingly complex but the practical realities are that for many
parts of the sky in which people image nearer the zenith, if the mount is aligned to
the refracted pole rather than the true pole, a constant sidereal rate is used and
the exposure time kept short enough, then the field rotation can often be kept small
enough to be acceptable.

But these very issues plagued practitioners in the late 1800's and early 1900's
using emulsion plates and one of the technical challenges they had to contend
with was that whereas we take variable time keeping under computer control
for granted, they had to do this by purely mechanical means.

The other philosophical upshot of all of this are that equatorial mounts are
really just engineering compromises. Without additional facility to change
their elevation dynamically, from a theoretical point of view, they just provide
an approximation of the ideal.

What I like to call "God's Equatorial Mount" would have exactly the same limitations and also suffer from field rotation.

That does not mean in practice equatorial mounts can't work well enough to
exceed user's requirements. But from an engineering standpoint, there is nothing
intrinsically "magical" about their design that gives them zero field rotation,
irrespective of how they are aligned.

Best Regards

Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place, Mount Kuring-Gai
NSW. 2080. Australia
Phone +61-2-9457-9049
Fax +61-2-9457-9593
sales@wildcard-innovations.com.au
http://www.wildcard-innovations.com.au

[seeker372011]

Gary is your presentation available anywhere on the Internet?

As one who didn't make it to the star party?
Narayan

[seeker372011]

Gary is your presentation available anywhere on the Internet?

As one who didn't make it to the star party?
Narayan

[RobF]

What I find most interesting is people with high end mounts raving about 15-20min unguided exposures with their latest "mega-mount". Presumably these people have been lucky enough to track/image an object in a sector of the sky where the various issues that can conspire to throw out careful polar alignment cancel each other out? (expecting of course the errors will have been minimised by top shelf engineering and careful optimisation of alignment)

[gary]

Hi Narayan,

Thanks for the interest.

It was a Powerpoint Presentation so I will publish it as a PDF, put it on our web
server and post the link.

Best regards

Gary

[alexV]

Thanks to everyone's input
Alex