Autoguiding

Guide Scopes, Off-Axis Guiders and Guide Cameras

All guiding does the same thing. The difference between methods is where the guide star comes from, and that determines whether flexure between two optical paths can corrupt your corrections.

• Guide scopes: A small separate telescope with its own camera. Simple, easy to find stars with, and entirely adequate below roughly 800 mm focal length.
• Off-axis guiders: A small prism picks a star from the edge of the main telescope's field, so guide and imaging paths are identical and differential flexure is eliminated.
• Guide cameras: Small, sensitive sensors read out once or twice per second. Sensitivity matters most with an off-axis guider, where the available stars are dim and few.
• Guiding rate and aggressiveness: Software settings that determine how strongly corrections are applied. Over-correction chases seeing and makes stars worse, not better.
• Mounting rigidity: A guide scope on a soft bracket flexes, and guiding faithfully corrects for a shift that never happened. Rigid mounting is not optional.
• Dithering: Shifting the frame slightly between exposures so that fixed-pattern sensor noise averages out during stacking — a guiding feature that visibly improves final images.

Why Choose David Astro for Autoguiding

Guiding problems are usually mechanical problems wearing a software costume. We start with the mechanics.

• Method chosen by focal length: We recommend guide scope or off-axis guider based on your imaging focal length and mount, rather than defaulting to whichever is cheaper.
• Flexure diagnosis: If your guiding numbers look good but your stars are elongated, that is differential flexure and we will help you find it.
• Guide camera matched to method: Off-axis guiding needs a more sensitive sensor than guide scope work, because you cannot choose your star.
• Authorized dealer: Genuine products with full manufacturer warranty, in Canadian stock.
• Setup support: Help with calibration, guiding settings and dithering configuration after the sale.

Autoguiding in Canada — Frequently Asked Questions

Guide scope or off-axis guider?

Guide scope below about 800 mm focal length. Above that, differential flexure between two tubes typically exceeds your guiding tolerance and an off-axis guider becomes the reliable choice.

My guiding graph looks good but stars are elongated. Why?

Almost certainly flexure between guide and imaging paths, or in the imaging train itself. The guider corrects what it sees, and if the guide scope moved relative to the main scope, those corrections actively hurt.

What guiding RMS should I aim for?

Below roughly half your imaging pixel scale in arcseconds. If you image at 1.5 arcseconds per pixel, total RMS under about 0.7 arcseconds keeps stars tight.

Is dithering necessary?

It is one of the highest-value settings you can enable. Shifting a few pixels between subs breaks up fixed pattern noise and walking noise, and costs only a few seconds per exposure.

Setting up guiding?

Tell us your focal length and mount and we will recommend the method and hardware. Ships from Canada.