SCOPE CONTROL WITH ASTROTORTILLA



SCOPE CONTROL WITH ASTROTORTILLA

This tutorial describes using AstroTortilla (AT) to control your mount and center any desired object in the camera FOV, even if the object is too dim to see in a single exposure. All that is required for the object are accurate RA / Dec coordinates.

INTRODUCTION AND REQUIREMENTS

Very briefly, here are the steps that AstroTortilla goes through to center an object. A computer controlling the camera AND the mount is required.

1. Power up and align the mount.

2. GoTo the desired object using mount software.

3. Start whatever imaging software you use.

4. Start AT

5. Connect AT to the mount

6. Take an image

7. Have AT plate-solve the image

8. AT moves the mount to more closely center the object from #2

9. Repeat 6-8 to desired precision

This tutorial assumes that you are familiar with the installation and basic use of AT. You also must have an ASCOM-compatible mount and have ASCOM installed on the PC that is connected to the mount. You must know how to configure ASCOM or your mount. I can help with this to a point.

The following lists the mounts that have ASCOM drivers, as of Sep 2013.

(ascom-)

Merlin Control ACL

Astro-Physics

Celestron

EQ mounts that have been configured to use EQMOD

Gemini (I am not sure of this works with Gemini 1 or 2 or both.)

Most Meade LX200 series

ServoCat

SkyCommander

Takahashi Temma

Any mount that TheSky can control, e.g. Paramount. TheSky is required

Vixen Skysensor

Vixen Sphinx

iOptron EQ30 and EQ45

This driver is available from iOptron.

Note that some of the above drivers may function properly with other mounts. Also, some mount manufacturers, e.g. iOptron, may have developed ASCOM drivers and keep them on their website.

Finally, you must have software that controls your imaging camera. As I understand, if you have Maxim DL, Nebulosity, or Astro Photography Tool, then the process can be very automatic. I do not have any of these and can’t help with them.

For camera control, I use either Canon EOS Utility or ImagesPlus. The only downside here is that you must capture the image manually and navigate AT to that image on your PC. This takes no time at all.

Then, AT will

1. Plate-solve the image,

2. Calculate the actual error between where the mount thinks it is and where the image says it actually is,

3. Move the scope close to the desired object.

2-3 iterations like this and the desired object will be in the exact (within arc-seconds) center of your image. You can then switch to imaging parameters, e.g. ISO, exposures, number of exposures.

The following expands on the brief 9-step description. This is written for setups that do NOT include Maxim DL, Nebulosity, or AstroPhotography Tool, as I cannot provide details on those.

1. Power up and align the mount.

Your normal procedures

2. GoTo the desired object using mount software.

Your normal procedures

3. Start whatever imaging software you use. Note that this is imaging software, NOT guiding software. Auto-guiding is not initiated until the desired object is centered.

Your normal procedures

4. Start AT

Your normal procedures, including setting Scale Min and Scale Max to values appropriate to the scope and camera.

5. Connect AT to the mount

Use dropdown list to select ASCOM.

ASCOM chooser window will appear. Configure, as needed. It is likely that everything is already set, since ASCOM remembers past settings.

Check Sync to scope

Check Re-slew to target

6. Take an image

Your normal procedures

7. Have AT plate-solve the image

Click Capture and Solve

Navigate to the image that you just captured

Click Open

AT will proceed to plate-solve that image and display the information.

8. AT moves the mount to more closely center the object from #2

9. Repeat to desired precision.

Repeat step 6 and 7.

As an experiment, I have deliberately started 10 degrees from the desired object. AT still moved there within 5 iterations. Normally, you would start much closer and 2-3 iterations are all that are needed. Assuming a few seconds for each exposure and as much as 60 seconds to plate-solve, you are still ‘on target’ within a few minutes. As AT solves each image, it stores the new Scale Min and Scale Max; hence, each solution goes faster and faster, as fewer index files are scanned.

AT has several other camera options that may ease the effort, including an ASCOM camera option. I have not tried these.

TIPS from other users

If possible, use units of arcsecperpix and set the scale low and scale high very close together, e.g. scale min = 1.475 & scale max= 1.480 . This will speed up solves substantially. (astroman2)

Unless you really want the annotated plots, set --noplots. This will also speed up solves. (astroman2)

Using AT for polar alignment.

(brownrb)

Video tutorials (brownrb)





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