ForHosting KIT · Developer Utilities

Star trail stacking calculator

Building long, continuous star trails on a fixed tripod almost always means stacking many shorter frames instead of holding the shutter open for an hour in one go.

● BetaFree · in your browser

Run — free How it works & API

Use it from WebAPIEmailTelegramApp soon

Long single exposures heat the sensor, fill the histogram with noise, and risk a single airplane, cloud, or bump ruining the whole night. This star trail stacking frame count calculator turns two simple numbers — the length of each sub-exposure in seconds and the continuous trail duration you want — into the minimum frame count that covers that open-shutter total, plus optional intervalometer gap time so your session wall-clock is honest. The formula is fully deterministic: frame count equals the ceiling of desired trail seconds divided by single exposure seconds. A thirty-second shutter for a one-hour trail needs one hundred twenty frames; twenty-second frames for forty-five minutes need one hundred thirty-five. Use it free in the browser for field planning, or call the API at $0.002 per successful request when apps, worksheets, or CI fixtures need the same stack size without re-implementing ceiling division by hand.

How to use it

Enter your values in the form above. The tool checks them before calculating and shows the result on the same page.

Check your inputs

Use the labels and units shown next to each field. If something is missing or outside the allowed range, the page points to the field to fix.

Use it again or automate it

Use the browser tool for individual checks and the API when you need the same capability in an automated workflow.

What you can do with it

Get an answer now

Enter one set of values and see the result without building a spreadsheet or script.

Compare scenarios

Change one value at a time and rerun the calculation to understand what affects the result.

Automate repeated work

Use the API when the same calculation needs to run inside your product or workflow.

FAQ

How do I use this capability?

Complete the fields above and run it on this page. The form highlights anything that needs attention.

For developers — API access

Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.

API endpoint

POSThttps://api.kit.forhosting.com/hobby/photo-star-trail-count

Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.

Call it from your stack

curl -X POST https://api.kit.forhosting.com/hobby/photo-star-trail-count \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"single_exposure_seconds":30,"desired_trail_seconds":3600}'

const res = await fetch("https://api.kit.forhosting.com/hobby/photo-star-trail-count", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "single_exposure_seconds": 30,
    "desired_trail_seconds": 3600
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/hobby/photo-star-trail-count",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "single_exposure_seconds": 30,
    "desired_trail_seconds": 3600
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/hobby/photo-star-trail-count", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"single_exposure_seconds":30,"desired_trail_seconds":3600}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"single_exposure_seconds":30,"desired_trail_seconds":3600}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/hobby/photo-star-trail-count", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "single_exposure_seconds": 30,
  "desired_trail_seconds": 3600
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "hobby.photo_star_trail_count",
  "status": "queued",
  "_links": {
    "result": "/tasks/tsk_…/result"
  }
}

The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.

Pricing

Per request$0.002

Published price — no tokens, no invented credits. A failed task is never charged.

Errors

HTTP	Code	Meaning
`401`	`unauthorized`	Missing or invalid API key.
`402`	`insufficient_balance`	Your balance doesn't cover the task price.
`404`	`unknown_type`	That task type doesn't exist.
`429`	`rate_limited`	Too many requests. Use the webhook instead of polling.

Read the full KIT documentation →