Someone asked a question about the exposure times on the Slooh.com telescopes, so this post answers that question and provides other details.

As described in my book, Slooh.com is unlike other ‘telescope as a service’ providers in that they don’t give you complete control over the telescope. Slooh.com is designed to be easy to use and provide reasonable results with minimal knowledge. So with that, Slooh.com developed processing presets that, among other things, control each telescope’s exposure time. Users simply pick from a listing of processing presets that match the object they’re imaging.

Presets have names like ‘Bright Star’, ‘Faint Galaxy or Comet’, and ‘Small Bright Nebula’ and they are generally available on each of the telescopes. When picking a preset, a user essentially sets the telescope’s CCD exposure time for the reservation. The presets vary by telescope, so the ‘Bright Star’ preset is not the same on each of the telescopes.

The presets are well-documented at the Slooh.com website and instead of providing you with all of the presets here, I share with you the ‘Generic’ preset for each of the telescopes.

I explain in detail what these settings mean and how you can use these presets to your advantage in order to get longer exposures later in this blog post.

Note that I only list telescopes for which you can reserve missions. There are two telescopes that you cannot reserve for missions: Canary 5 Solar Telescope and Chile 3 Lunar and Planetary Telescope.

 ‘Generic’ Presets For Each Of The Slooh.com Telescopes

For each preset, I provide details about each telescope – it’s aperture, field of view, and resolution at binning 1×1 and I list the filter in use for the exposure, the binning, and number of seconds of exposure time. Except for Canary Three, all other telescopes use either a Clear or Luminance (I specify which), Red, Blue, and Green filter.

After this section, I discuss how to use these presets to your advantage to get longer exposures.

Canary One Half Meter Telescope

Aperture: 508mm, FOV: 0deg 37’ 00” x 0deg 37’ 00” , Resolution 3056×3056

  • Luminance: up to 3×60 seconds, binned at 3×3
  • Red: 1×50 seconds, binned at 3×3
  • Green: 1×50 seconds, binned at 3×3
  • Blue: 1×50 seconds, binned at 3×3

Canary Two Wide-Field Telescope

Aperture: 432mm, FOV: 0deg 43’ 00” x 0deg 43’ 00”, Resolution 4096×4096

  • Luminance: 1×60 seconds, binned at 3×3
  • Red: 1×20 seconds, binned at 3×3
  • Green: 1×20 seconds, binned at 3×3
  • Blue: 1×20 seconds, binned at 3×3

Canary Two Ultra-Wide-Field Telescope

Aperture: 85mm, FOV: 1deg 47’ 06” x 1deg 12’ 12”, Resolution 2184×1472

  • Clear: 1×50 seconds, binned at 2×2
  • Red: 1×20 seconds, binned at 3×3
  • Green: 1×20 seconds, binned at 3×3
  • Blue: 1×20 seconds, binned at 3×3

Canary Three Deep Sky Astrograph Telescope

Aperture: 279mm, FOV: 1deg 39’ 14” x 1deg 14’ 56”, Resolution 3357×2535

Note that this telescope is equipped with a color camera (OSC CCD); therefore, there no filters are used.

  • Exposure: up to 3×90 seconds

Canary Four Solar System Telescope

Aperture: 355mm, FOV: 0deg 15’ 57” x 0deg 12’ 03”, Resolution 3358×2536

  • Luminance: 1×50 seconds, binned at 3×3
  • Red: 1×20 seconds, binned at 3×3
  • Green: 1×20 seconds, binned at 3×3
  • Blue: 1×20 seconds, binned at 3×3

Chile One Wide-Field Telescope

Aperture: 355.6mm, FOV: 0deg 31’ 18” x 0deg 20’ 51”, Resolution 3358×2536

  • Luminance: 1×50 seconds, binned at 3×3
  • Red: 1×25 seconds, binned at 3×3
  • Green: 1×25 seconds, binned at 3×3
  • Blue: 1×25 seconds, binned at 3×3

Chile One Ultra-Wide-Field Telescope

Aperture: 90mm, FOV: 1deg 21’ 49” x 1deg 00’ 22”, Resolution 1600×1200

  • Luminance: up to 1×50 seconds, binned at 2×2
  • Red: 1×25 seconds, binned at 2×2
  • Green: 1×25 seconds, binned at 2×2
  • Blue: 1×25 seconds, binned at 2×2

Chile Two Wide-Field Telescope

Aperture: 432mm, FOV: 0deg 43’ 00” x 0deg 43’ 00”, Resolution 4096×4096

  • Luminance: 1×50 seconds, binned at 3×3
  • Red: 1×20 seconds, binned at 3×3
  • Green: 1×20 seconds, binned at 3×3
  • Blue: 1×20 seconds, binned at 3×3

Other Available Presets

Slooh.com offers other presets that vary exposure time and binning. For example, the ‘Bright Star’ preset on Canary One uses the following settings:

  • Luminance: 2×50 seconds, binned at 2×2
  • Red: 1×50 seconds, binned at 2×2
  • Green: 1×50 seconds, binned at 2×2
  • Blue: 1×50 seconds, binned at 2×2

There are other presets that offer Luminance only images where you can get up to eight, 50-second exposures using only the luminance filter binned at 2×2. Note that these luminance-only presets are available to Astronomer members only.  

Understanding Binning

As discussed in my book about Slooh.com, binning affects the resolution of your final image. Binning essentially reduces resolution in order to provide more light gathering capability. The total number of pixels is divided by the binning factor to essentially make each pixel bigger by trading off resolution.

In the presets I present here, binning is set at 3×3 which means the resolution is essentially divided by three. So, for a telescope with 4096×4096 resolution, the binned resolution would be 1365×1365 at 3×3 binning.

There are other presets that offer 2×2 binning (usually ‘Globular Cluster’, but it varies by telescope), and none that offer 1×1 binning, so bear in mind the binning factor of each preset when you’re considering resolution.

How To Get Longer Exposures

When imaging a deep space object like a quasar, it’s often necessary to get longer exposures since the ‘Generic’ preset is capped at 50seconds for the luminance filter in most cases. So how can you get longer exposure times?

You get longer exposure times by exposing the same object several times using the same processing preset. If you view the reservations for just about any telescope, you’ll see members booking multiple missions to the same target in sequence. Astronomer members can have up to five reservations at any given time and it’s common to see members use these reservations to image a dim target.

If you’re an Apprentice member, you could Join missions if another member is imaging the same target as you are, otherwise, you’d have to book one mission at a time (Apprentice members can have one reservation at a time).

In Pictures: 5-minute Exposure Results

This article shows you what 5-minute exposures look like for magnitude 10.6 and 16.7 objects.

Conclusion

In this post, you learned about the ‘Generic’ preset used by each of the reservable telescopes, you learned about the other processing presets, you learned about binning, and gained an understanding of how to get longer exposures on a target.