Calibrate Msa Altair 4xr

[Amilcar Labrosse]

MSArecommends calibration at least every six months; however, many countries and/or organizations have their own calibration guidelines. The ALTAIR io 4 calibration interval can be configured to adapt to these requirements.

During zero calibration, the O2 sensor is also span calibrated to 20.8% O2 fresh air, adjusting the calibration curve as needed. During span calibration, the O2 sensor's accuracy is checked against a known oxygen gas concentration without adjusting the calibration curve.

The calibration procedure adjusts the span value for any sensor that passes the calibration test; sensor span values that fail calibration are left unchanged. Since residual gas may be present, the device may briefly go into an exposure alarm after the calibration sequence is completed.

If a calibration is unsuccessful for two subsequent calibrations, the device will communicate an end of sensor life warning to the user. Note that a span calibration can fail for many reasons other than a sensor at the end of its life. If a span calibration failure occurs, factors such as remaining gas in the calibration gas cylinder, gas expiration date, security of the calibration cap, etc. should be verified, and a calibration should be repeated prior to replacing the sensor.

MSA offers a 34L calibration gas aluminum cylinders to calibrate the Altair 4XR and 5X monitor. The 4-gas mixture in the calibration gas cylinders is certified to be prepared gravimetrically, using NIST traceable weights. The lot number and the nominal value of the gas concentrations in volume, percent by mass, ppm, or volume are specified on the cylinder. There is a shelf life or expiration date to let you know when not to use the gas to calibrate or bump test a monitor. MSA also has a calibration gas recycling program that helps a non-profit organization. The cylinder contains sufficient calibration gas for multiple MSA instrument calibrations, and it requires a regulator (sold separately).

Note: This item ships via UPS Ground due to HazMat restrictions and isn't available for expedited shipping. Calibration gas is not returnable. Please check your selection carefully before ordering.

Next step is to correct your spectrum for the effect of the instrument and our atmosphere. You can use your Vega or Altair spectra for this and then use it for other stars provided they are at similar height in the sky. The continuum will then show the same overall shape as your reference spectrum. Doing this for a few known stars and comparing them with professionally measured spectra is a good test of your technique, as I have done here for example using spectra of stars from the MILES database

Re your question regarding how I calibrated - I used my Vega spectrum (hence why I took the spectrum last night) and (because I knew main lines wavelengths on Vega spectra) calibrated CCDSPEC/QHY6 using that - was that OK to do?

A dark subtraction will probably deal with them. (The first step with processing spectrum images is the same as with astro imaging ie bias, dark subtraction, flat field correction) You then make any geometric corrections needed eg slant and tilt, remove the sky background and bin the region containing the spectrum to produce the digital data. You then wavelength calibrate and correct for the instrument response/atmospheric extinction to produce the final fully calibrated spectrum. You can see examples of these steps in the presentation "Low Resolution Slit spectroscopy (ALPY) - Confirming and classifying a Supernova " I gave at a BAA workshop a couple of years back for example.

1. You need to subtract the sky background by selecting areas above and below the spectrum and subtracting them from the region where the spectrum is. It is important how you select these regions. Make sure the region you select for the spectrum is wide enough to cover the full height of the spectrum, turn up the brightness in the image to make sure. Then select regions above and below this for background subtraction, far enough away that there is no contamination from the star spectrum.

You can then divide this by the library spectrum, remove any features which did not exactly cancel and smooth the result to produce your instrument response. As a check you can then apply it to your uncorrected spectrum. The result should look like the library version.

50 sec is an extremely long exposure on such bright stars at this resolution. With my similar resolution ALPY setup and a 280mm aperture, a spectrum of Vega is saturated in about a second or less. Was the star well focused and positioned on the slit? Have you checked that no part of the spectrum image was saturated ?

It is crucial to regularly test and calibrate your portable gas detection device to ensure it is working properly. This can save lives. Bump testing checks whether your portable gas detectors are still working properly. These tests should be carried out before use. In case your gas detector does not pass the bump test, it should be recalibrated. MSA Safety Shop has various calibration stations, such as the MSA Galaxy, with which you can efficiently calibrate and bump test your own equipment. Please contact our specialists for the possibilities.

Well, in that case You don't have precise temperature control built into the camera. AFAIK Altair hypercam has only a cooler, not a precise controlled peltier (like ZWO, QHY) and that is why You cannot get rid of thermal pattern, as temperature changes during photosession.

In this case, the amp glow is not calibrated out with the Adaptive Data Pedestal disabled, because the amp glow simply overpowers the real OIII data on the location of the amp-glow. By enabling the Adaptive Data Pedestal, the amp glow is properly calibrated.

These are the results with and without the Adaptive Data Pedestal enabled in calibration, off course, highly stretched to show the data calibration performance in an integration of 60x180 seconds Hydrogen-Alpha frames (3 hours total exposure time):

What happens without the Adaptive Data Pedestal: the residual amp-glow that you see in the integration without the adaptive data pedestal enabled, is the result of skewed data integration (to the upside) due to black clipping of the light frames after the subtraction of the MasterDark. This means that the provided lights are not sufficiently illuminated for this sensor. This sounds strange perhaps for such a BSI cmos sensor, but the illumination really is not enough to have the light/photon signal overcome the severe amp-glow on the right side of the sensor. The Amp-Glow signal is so strong, that after subtracting a masterdark from the light frames, a lot of pixels are still black clipped... The Hydrogen-Alpha signal (in this case) is too weak to overcome the Amp-Glow. This has a degrading effect on the data, once properly calibrated with the Adaptive Data Pedestal enabled, the image data will always have worse noise characteristics in the areas where the Amp-Glow resides on the sensor.

The Adaptive Data Pedestal is an adaptive algorithm that will prevent the black clipping of pixels after masterdark subtraction and therefore the integration results are no longer skewed to the upside, thus properly removing the amp-glow signal if the provided darks are of the same temperature, same exposure and same gain + offsett as the light frames.

First post your issue in a new forum topic, in the appropriate subforum, and please only try to upload your data when we ask you to do so. Upload details will be provided then. When the upload is approved, please make a folder with your name and issue, like "mabula-register-mosaic". The upload server address is :

Background - The Altair G1 (no digital output) has 8 PEQ bands built in and I use a calibrated measurement microphone (Sonarworks XRef 20) and REW (via my M1 MacBook Air and an Audient iD14 Mk1) to measure and adjust the frequency response at my listening position in the "tightly focussed" Dirac 9-point manner, keeping an eye on time based issues, as well.

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