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Northstar Observatory

Telescope operations sheet · Ritchey-Chrétien 1.8 m

Sheet
NS-TEL-OPS-014
Rev
03
Date
14 Aug 2026
Night
26-0814

01 / Observation window

Assigned window · NGC 7000

Tonight’s primary assignment is the west wall of NGC 7000 through the 1.8 m Ritchey-Chrétien. The window is recorded below. Advance the window only after the mount is homed and the alignment solution in section 03 is complete or waived by the duty astronomer.

Target
NGC 7000
Catalogue / North America Nebula · west wall
Instrument
Ritchey-Chrétien 1.8 m
ID / NS-RC-18 · focus f/8 · port A
Window
22:42–01:16
Local · night 26-0814 · LST 19:08 at open
State
READY
Mark / operator · recorded 22:42:00

See observation / 26-0814-A

Command plate records READY → TRACKING → EXPOSING → COMPLETE. Each change writes a timestamp to the window log.

  1. Window assigned · NGC 7000
  2. Thermal soak complete · 18 min
  3. State / READY

02 / Instrument status

Specification · NS-RC-18

Values are read from the instrument bus at the time of last poll. They are not a dashboard. When the observation window advances, selected rows receive a temporary REV mark. Tolerances are from NS-TEL-SPEC-18 Rev 07.

Parameter Value Tolerance State
Primary temp −8.4 °C ± 0.5 °C of set Nominal
Mirror delta 0.12 K Max 0.30 K Nominal
Dome humidity 18 % Max 40 % Nominal
Wind 4.2 m/s Max 12 m/s Nominal
Tracking error 0.18″ Max 0.40″ rms Nominal
Seeing 0.94″ Nom 0.80–1.20″ Nominal

Set point primary −8.5 °C · last poll 22:41:51 · bus NS-INST-02

03 / Alignment procedure

Mount solution · night start

Complete the six steps in order. Mark a step only after the stated check is true. The current step is underlined and labeled CURRENT. Completed steps receive an operator mark and a timestamp. Reset returns the sheet to step 01 without clearing the observation window.

  1. 01

    Home mount

    Drive both axes to encoded home. Confirm azimuth and altitude limit flags are clear before any slew to target.

    Current
  2. 02

    Verify encoders

    Compare tape encoder and motor encoder on each axis. Difference must remain inside 2.0 arcsec after a 5° jog and return.

    Pending
  3. 03

    Acquire reference

    Center TYC 2684-1238-1 on the guider. Record pixel centroid. Do not use NGC 7000 itself as the pointing reference.

    Pending
  4. 04

    Correct offset

    Apply the measured pointing offset to the mount model. Re-center the reference and confirm residual below 0.30″.

    Pending
  5. 05

    Verify track

    Enable sidereal track for 60 s. Guider rms must remain inside 0.40″. If wind exceeds 8 m/s, extend the sample to 90 s.

    Pending
  6. 06

    Record solution

    Write the pointing solution to night 26-0814. Attach the operator ident and the reference star used. Close the procedure.

    Pending

04 / Figure 07

Optical path · Ritchey-Chrétien

Side elevation of NS-RC-18. Select a numbered callout to mark the matching note. Callouts remain on the figure at every width. On a narrow sheet the notes sit below the drawing.

Fig. 07 — Optical path · NS-RC-18 · view / elevation

Line diagram of a Ritchey-Chrétien telescope: incoming beam at the aperture, hyperbolic primary at the base, hyperbolic secondary near the top, Cassegrain path through the primary perforation, and focuser with instrument port below the cell. INCOMING BEAM PRIMARY FOCUSER 01 02 03 04 05

05 / Observation record

Night log · 26-0814 and prior

Select a row to mark it SELECTED. Selection uses a left rule, not a fill. Horizontal scroll is permitted on a narrow sheet. Record 26-0814-A is the current assignment.

Record Target Start Exposure Filter State Rev
26-0814-A NGC 7000 22:42 1800 s Hα Ready —
26-0814-B NGC 7000 23:18 1800 s Hα Queued —
26-0813-C M 31 21:06 900 s V Complete 01
26-0813-D M 31 21:28 900 s B Complete —
26-0813-E NGC 891 22:14 1200 s r Complete 02
26-0812-A SN 2026ie 20:51 600 s V Complete —
26-0812-B SN 2026ie 21:04 2400 s Hα Aborted 03
26-0811-F NGC 6992 23:40 1800 s OIII Complete —
26-0810-A M 13 02:18 300 s V Complete —
26-0809-C IC 1396 22:02 1500 s Hα Complete 01

Selected / 26-0814-A · see note A in section 06

06 / Field note

Operator annotation · 26-0814-A

This note is attached to observation 26-0814-A. It is a working annotation, not a message. Reveal it only when the record is in use.

Attached to / 26-0814-A · NGC 7000 · Hα

07 / Calibration notice

Caution · thermal differential

Caution
04.2

Calibration values invalid after thermal differential exceeds specified tolerance

Flat, dark, and focus solutions taken before the soak are not valid once the primary-to-cell differential exceeds 0.30 K. Do not apply last night’s focus offset. Do not mix calibration frames from 26-0813 with science frames from 26-0814-A.

If MIRROR DELTA in section 02 is marked above the limit, stop the exposure, close the shutter, and wait for the primary to return inside tolerance. Recollect a focus pair on TYC 2684-1238-1 before reopening the window.

Limit Value Action
Mirror delta Max 0.30 K Halt exposure
Primary rate Max 0.08 K / 10 min Hold shutter
Focus offset age Max 40 min Retake pair
Flat set Same night only Do not inherit

08 / About the facility

Northstar Observatory

Northstar Observatory sits on a limestone ridge at 2,847 metres, four hours by road from the nearest town and twelve kilometres from the nearest public trailhead. The site was chosen for a dark western horizon, stable summer seeing, and a wind pattern that usually stays below the dome’s operating limit after dusk. The facility is staffed by a small night team: a duty astronomer, a telescope operator, and an instrument technician on call from the lower camp.

The main telescope is a 1.8 metre Ritchey-Chrétien on an altitude-azimuth mount, commissioned in 2019 and rebuilt in 2024 with a new primary cell and a faster instrument rotator. The optical design keeps a wide, well-corrected field at f/8, which is why the house camera and the visiting spectrograph can share the same port without a corrector change. A 0.4 metre wide-field telescope on the north pier is used for transient confirmation and for photometric standards when the main tube is committed to a long window.

Research program

The standing program is emission-line mapping of nearby star-forming complexes, with a secondary effort on nearby supernovae and other optical transients that need a measured position angle and a clean subtraction frame. NGC 7000, IC 1396, and the east wall of NGC 6992 return each season so that the same filter set and the same rotator convention can be compared year to year. Guest observers are accepted for targets that fit the 1.8 metre’s field and the site’s weather, provided they accept the house calibration rules in section 07.

Data leave the mountain on a delayed microwave link at dawn. The night sheet remains the authoritative record until the archive ingest confirms checksums the following afternoon. Operators are asked to write notes as they would in a paper log: attached to a record, timed, and specific about what must not be mixed with what.

How this sheet is used

This page is the working copy for night 26-0814. Section 01 holds the assigned window. Section 02 is the instrument specification at last poll. Section 03 is the alignment sequence that must be marked before the shutter opens. Figure 07 is the optical path used when baffles or focus are in question. The observation table is the legal log. Note A belongs to 26-0814-A. The caution in 04.2 governs calibration after a thermal excursion.

Nothing here is decorative. If a value changes, it is marked. If a step is done, it is checked. If a row is in use, it is selected. The facility is remote. The document has to stand in for a hallway conversation that cannot happen at 23:00.

Record of change

Rev Date Section Description
01 12 Jun 2026 00 Initial issue of operations sheet
02 28 Jul 2026 02.1 Thermal limits updated after cell rebuild
03 14 Aug 2026 04.2 Calibration caution issued for night 26-0814