# Smart Telescope Stacking Time Estimator (Integration Time) > Free integration-time estimator for smart telescopes: how long to stack the Orion Nebula, Andromeda or any of 49 deep-sky targets from your Bortle sky, with… - Source: https://smarttelescopereview.com/tools/integration-time/ - Markdown version: https://smarttelescopereview.com/tools/integration-time.md --- - [Home](https://smarttelescopereview.com/) - [Tools](https://smarttelescopereview.com/tools/) - Stacking time estimator # How long should I stack it? Pick a deep-sky target, your Bortle class and a smart telescope. We estimate the total stacking time for a clean, recognizable image, with and without a dual-band filter, and compare every scope side by side. TargetAndromeda Galaxy (M31)Triangulum Galaxy (M33)Whirlpool Galaxy (M51)Bode's Galaxy (M81)Cigar Galaxy (M82)Pinwheel Galaxy (M101)Sombrero Galaxy (M104)Sunflower Galaxy (M63)Black Eye Galaxy (M64)M66 (Leo Triplet) (M66)Virgo A (M87)M106 (M106)Southern Pinwheel (M83)Phantom Galaxy (M74)Sculptor Galaxy (NGC 253)NGC 891 (NGC 891)Needle Galaxy (NGC 4565)Orion Nebula (M42)Lagoon Nebula (M8)Trifid Nebula (M20)Eagle Nebula (M16)Crab Nebula (M1)M78 (M78)North America Nebula (NGC 7000)Pelican Nebula (IC 5070)Eastern Veil Nebula (NGC 6992)Crescent Nebula (NGC 6888)Elephant's Trunk region (IC 1396)Heart Nebula (IC 1805)Soul Nebula (IC 1848)Bubble Nebula (NGC 7635)Rosette Nebula (NGC 2237)California Nebula (NGC 1499)Horsehead Nebula (B33 / IC 434)Dumbbell Nebula (M27)Ring Nebula (M57)Owl Nebula (M97)Helix Nebula (NGC 7293)Eskimo Nebula (NGC 2392)Pleiades (M45)Beehive Cluster (M44)M35 (M35)Wild Duck Cluster (M11)Double Cluster (NGC 869 / NGC 884)Hercules Cluster (M13)M3 (M3)M5 (M5)M22 (M22)Omega Centauri (NGC 5139) TelescopeDWARFLAB Dwarf Mini Smart TelescopeZWO Seestar S30 Plus Smart TelescopeZWO Seestar S30 Pro Smart TelescopeDWARFLAB Dwarf 3 Smart TelescopeZWO Seestar S50 Pro Smart TelescopeVaonis Vespera II Smart TelescopeVaonis Vespera 3 Smart TelescopeVaonis Vespera Pro 2 Smart TelescopeUnistellar Odyssey Smart TelescopeUnistellar Odyssey Pro Smart TelescopeUnistellar eQuinox 2 Smart TelescopeUnistellar eVscope 2 Smart TelescopeCelestron Origin Mark II Intelligent Home Observatory Your sky: Bortle 6 Filter Dual-band filter on emission nebulae How a smart telescope builds an image Every smart scope here follows the same loop; the differences are optics, sensor and software polish. 1. Plate-solveThe camera takes a short frame, matches the star pattern to a catalog and works out exactly where it's pointing. No star alignment, no finder scope. 2. GoTo & trackMotors slew to your target and follow it as the Earth turns. Alt-az mounts also rotate the image slowly, which the software corrects. 3. Short exposuresInstead of one long exposure, the scope takes many 10–30 s frames. Frames spoiled by clouds, wind or bumps are rejected. 4. Live stackingEach new frame is aligned and averaged into the running image, so noise drops and faint detail appears as you watch: roughly √N better signal-to-noise after N frames. 5. Stretch & shareThe app stretches the faint data, removes gradients and denoises, then saves a JPEG (and often FITS/TIFF) to your phone. See it applied to your sky in the [stacking time estimator](https://smarttelescopereview.com/tools/integration-time/). ## The method, in plain numbers We start from a baseline time for each target's editorial difficulty tier at a Bortle 4 sky with f/5 optics and 2.9 µm pixels: about 5 minutes for showpieces, 20 for easy targets, an hour for moderate ones, 2.5 hours for hard ones and 6 hours for very faint ones. Then: - **Sky brightness.** Background light grows by about 2.5× per magnitude of skyglow. For faint targets the time scales with it; for bright targets (tiers 1–3) we soften the penalty, because they're less background-limited. Bortle class sky brightness comes from the commonly cited Bortle-scale table (22 mag/arcsec² at class 1, 17.8 at class 9). - **Dual-band filter.** On emission nebulae, the sky penalty is cut sharply (we raise it to the power 0.35), reflecting how much skyglow H-alpha/OIII filters reject. - **Optics.** Per-pixel signal scales with (pixel size ÷ focal ratio)². Faster optics such as the Origin's f/2.2 RASA need much less time; we count pixel size at half weight because small-pixel images are usually viewed downscaled. - **Small, faint targets** get an aperture adjustment, since resolving them needs more aperture as well as time. The result is a planning estimate, not a prediction. Moonlight, haze, a low target, dew and the app's frame rejection all add time, and "clean" is subjective. Use it to decide whether a target is a one-evening job or a project. ## A worked example The Rosette Nebula from a Bortle 7 suburb: on a Seestar S50 Pro with its built-in dual-band filter, the estimate stays within a single long evening. Untick the filter and it climbs into multi-night territory, because the faint red nebulosity is buried in skyglow. Switch the target to the Pinwheel Galaxy (M101): the filter makes no difference (galaxies aren't emission targets), and from Bortle 7 it runs past ten hours on a 50 mm Seestar. On the Celestron Origin's f/2.2 optics the same galaxy drops to about a quarter of that, still a multi-night project but a realistic one, which is the real reason that 41.6 lb telescope exists. See every target at once in the [sky target checker](https://smarttelescopereview.com/tools/sky-target-checker/), or read how to get more from a bright sky in [smart telescopes and light pollution](https://smarttelescopereview.com/posts/smart-telescopes-light-pollution-city/). ## Frequently asked questions ### What is integration time? The total exposure time stacked into a final image: 120 ten-second frames is 20 minutes of integration. Signal grows in proportion to time while random noise grows with its square root, so doubling the time improves signal-to-noise by about 1.4×. That's why faint targets need hours, not minutes. ### How much does light pollution increase stacking time? For faint targets, roughly in proportion to sky brightness. Each magnitude per square arcsecond of extra skyglow is about 2.5× more background light, so moving from a Bortle 4 sky (about 21.1 mag/arcsec²) to a Bortle 8 sky (about 18.2) means roughly 14× more background and, in the background-limited case, roughly 14× the time for the same result. Bright targets are less affected. ### Does a dual-band filter really save time? On emission nebulae, yes, a lot: it passes the H-alpha and OIII light those nebulae emit and blocks most of the skyglow around them. On galaxies, clusters and reflection nebulae it removes signal along with the skyglow, so leave it out. The estimator applies the filter only to targets where it helps. ### Can I stack over several nights? Yes. Vaonis' Vespera 3 and Pro 2 resume a stack automatically across nights; with other scopes you can save the raw frames (FITS) and stack them together on a computer in free software such as Siril. Multi-night projects are how owners reach the multi-hour totals faint galaxies need from suburbs.