TheSkySearchers

This is another lecture from a course in Beginner's AP that I have given in the past.

Autoguiding is a vital part of the black art of long exposure astrophotography

First, let's get our terms straight -

• – Goto alignment: From the inputted time and location and (1, 2, or 3) alignment star's altitude and azimuth the telescope mount will know its orientation to the entire sky, so this process lets the mount know where it is pointing so the calculations for tracking speed/rate can be done. Plus now you can then find "goto" any object.
  – Polar alignment: is the process of accurately aligning the polar (Right Ascension or R.A.) axis of your EQ mount with the north (or south) celestial pole.
  – Tracking: this is what the mount does to keep the desired object in the field of view (FOV) of the eyepiece
  – Guiding: this is what YOU and your mount do to keep the desired object absolutely motionless within the FOV (also called manual guiding -- it's insanely difficult!)
  – Autoguiding: this is what a computer AND your mount do to keep the desired object absolutely motionless within the FOV

Tools needed for autoguiding -

• – Telescope, imaging camera, guide camera
  • • Method one: a guide scope for the guide camera
    • Method two: an off-axis guider for the guide camera
  
  – Computer (a laptop is my preference), with:
  • • guiding software - (PHD 2 or Metaguide)
    • mount software (ASCOM - Astronomy Common Object Model - Drivers)
    • camera control software (BYE, APT, Nebulosity, N.I.N.A., SGP, Maxim, etc)
  
  – Cables (lots of them)
  – PATIENCE, PATIENCE, PATIENCE

Below is an older image of an autoguiding setup using a guide scope and guide camera. It is also a depiction of poor cable management!


Hope this helps to understand both the terminology and some of the pieces-parts.

Cheers,
JT

Thanks, JT!

Just getting cranked up on this. Got my guide scope in yesterday. Today saw the addition of a USB hub and a longer cable to go from my hand controller to the laptop.

PHD2 installed and seeing the mount and guide camera (ASI120MM-S). Imaging camera works too. Had to tweak some settings in Win 10 to keep all USB ports open and not shut one down while powering the other.

Now I just need a star to steer her by...

:Clap: Today i learn something new and it's basic of autoguiding... Thank you for brief overview!

"GoTo" alignment:

It's purpose is really to let the mount where it is pointing so the calculations for tracking speed / rate can be done. It really has little to do with the actual 'go to'.

The simplest way to accomplish this is through a plate solve routine. One single good plate solve supersedes all the need for multiple alignment stars. Faster and more accurate. :twocents:

UlteriorModem wrote: ↑Wed Jun 05, 2019 2:03 pm "GoTo" alignment: Its purpose is really to let the mount where it is pointing so the calculations for tracking speed / rate can be done. It really has little to do with the actual 'go to'.

Thanks Tom,

Your words have been incorporated.

Appreciatively,
JT

Thank you JT.
Just starting to figure it out here. It is an... adventure.

Thanks JT - this kind of post is incredibly useful.

Thanks JT! It looks like the guide scope in that picture is my imaging scope... Now I'm sad Just kidding, I'm not; however, I really wish I had an insane amount of money for this hobby!!!

I'm not sure either of these is accurate:

UlteriorModem wrote: ↑Wed Jun 05, 2019 2:03 pm "GoTo" alignment:
It's purpose is really to let the mount where it is pointing so the calculations for tracking speed / rate can be done. It really has little to do with the actual 'go to'.

Star Alignment also allows the Mount to note both the Direction and Distance resulting from it's Slewing Inputs (so that it can calculate how many inputs are required to "Goto" there from here), and other esoterics such as Cone Error and Side of Meridian.

UlteriorModem wrote: ↑Wed Jun 05, 2019 2:03 pm "GoTo" alignment:
The simplest way to accomplish this is through a plate solve routine. One single good plate solve supersedes all the need for multiple alignment stars. Faster and more accurate.

There is little simpler than staring into an Eyepiece (or LCD Screen) and pushing on 4 buttons until the Brightest Star is in the Center of FOV. (Repeat for Next Star).

But, neither Star Alignment nor Plate Solving has a direct bearing on the topic of AutoGuiding...

In annotating your Image of the Scope Equipment, you might want to also point out the Mount (maybe even note the type) and the Wedge.
(These are significant elements in the effort and ability to AutoGuide.)

seigell wrote: ↑Mon Sep 16, 2019 11:43 am
But, neither Star Alignment nor Plate Solving has a direct bearing on the topic of AutoGuiding...

Beg to differ. A mount that is well aware of where in the sky it is pointing can give more accurate guiding rates. Yes autoguiding helps to 'get around that'. But the less the autoguider has to correct the better.

That might be applicable for an Alt-AZ Mount, but for a GEM the Sidereal Rate (along with Solar and Lunar) is hard-coded into the RA Motor Logic Board.

UlteriorModem wrote: ↑Wed Jun 05, 2019 2:03 pm "GoTo" alignment:

It's purpose is really to let the mount where it is pointing so the calculations for tracking speed / rate can be done. It really has little to do with the actual 'go to'.

UlteriorModem wrote: ↑Mon Sep 16, 2019 6:08 pm A mount that is well aware of where in the sky it is pointing can give more accurate guiding rates.

Is this true?

I can see it needed for Alt Az tracking, and maybe for Planetary/Solar/Lunar tracking, but for DSOs on a GEM? Shouldn't tracking only depend on the speed of the motor (sidereal rate) and the polar alignment?

I am speaking from the point of view of someone who has a RA motor, on a manual mount where the motor drive has absolutely no knowledge of where the mount is pointed to. Would the tracking rate be any different based on where the mount is pointed to?
Or does the alignment somehow compensate for small errors in polar alignment on Goto GEMs?

Hey Gents,

You are all providing great info and a good discussion but I believe we are getting a little off-track here. The basis for this post was almost exclusively to get the basic nomenclature straight and spelled out for those very new to both telescopes and AP. So many times we see folks using the words tracking and guiding interchangeably and the same goes for a goto versus a polar alignment.

If you would like I can make a separate post regarding the "nuts-and-bolts" of mount operation and how it pertains to both AP and autoguiding. Let me know.

Cheers,
JT

And here is that post. I wrote it up as an article in the articles forum. Follow this link. app.php/article/choosing-the-ideal-setu ... hy-journey

Cheers,
JT

JayTee wrote: ↑Wed Jun 05, 2019 4:16 am Tools needed for autoguiding -

• – Telescope, imaging camera, guide camera
  • • Method one: a guide scope for the guide camera
    • Method two: an off-axis guider for the guide camera
  – Computer (a laptop is my preference), with:
  • • guiding software - (PHD 2 or Metaguide)
    • mount software (ASCOM - Astronomy Common Object Model - Drivers)
    • camera control software (BYE, APT, Nebulosity, N.I.N.A., SGP, Maxim, etc)

Sorry but ASCOM and camera control software are not required at all. I autoguide with ST/4 and never used camera control software.

Might be worth a quick mention of WHY we autoguide as misconceptions cause some folks to misinterpret their guiding results.
The primary reason for autoguiding is that tracking is imperfect and causes a star to drift around in the FOV in Right Ascension. This is known as periodic error and every mount exhibits it to some degree. Autoguiding corrects for this periodic error.
The second reason is that imperfect polar alignment causes a start to drift around in the FOV in declination. How much depends on how good or bad the mount is polar aligned.
Atmospheric disturbances and vibration also cause a star to move about in the FOV but this happens too rapidly for autoguiding to correct. In fact, trying to use autoguiding to correct these can be detrimental to your imaging and is referred to as "chasing the seeing".
The various autoguiding algorithms try to avoid chasing the seeing whilst still correcting for drift from periodic error and polar alignment error.

It would help to explain more than "guiding is called manual guiding and it's insanely difficult". This only says that "guiding" without "auto" in front of it is manual guiding, but what does that mean, what does the mount do and what does the user do? Is it really insanely difficult or does it just require perseverance?

When mentioning method 1 and 2 as on-axis and off-axis guiding, it would be helpful to give a hint as to what kind of equipment is needed, how it works and what the differences are. Otherwise this article is not for beginners but for those who already know the matter.

Perhaps mention that this is meant for equatorial motorized mounts, not Alt/Az. If this sounds too obvious, there are parts where you assume that the user is a novice (goto vs. polar alignment vs. tracking vs. guiding) and other parts where you assume that the user knows a lot more (by not explaining manual guiding, on-axis vs. off-axis, for instance). Best to assume that the user is a novice.

Gentleman, [mention]SkyHiker[/mention] [mention]KenGS[/mention]

The title of the article is a brief overview.

If either of you would like to write an article expanding on any of the elements contained within this brief overview, TSS would be very appreciative.

Thanks,
JT

Writing a good overview or introduction takes time and thought. I would like to try it but normally with my job (until 2 days ago, lol) I'm too busy.

For now, I just found this link, maybe this is helpful: https://astrobackyard.com/autoguiding/
I like it as an introduction and overview. I don't think I could improve on that.