The PC in Mount Wilson had failed. A replacement was built in Birmingham and installed on this trip. A new UPS and mains controller were installed. The effect of the primary mirror position on beam alignment was investigated

Hale, Steven J.

University of Birmingham Research Archive, E-papers Repository

BiSONBirminghamSolar-OscillationsNetworkTECHNICAL REPORT NO. 319New Computer in Mount WilsonSteven J. HaleThe University of Birmingham, Edgbaston, Birmingham B15 2TT2009 May 27This technical report series is published by:SLHigh-Resolution Optical-Spectroscopy GroupSchool of Physics and AstronomyThe University of BirminghamEdgbaston, Birmingham B15 2TT, United KingdomTelephone: +44-121-414-4551 FAX: +44-121-414-1438New Computer in Mount WilsonSteven J. HaleThe University of Birmingham, Edgbaston, Birmingham B15 2TT2009 May 27AbstractThe PC in Mount Wilson had failed. A replacement was built in Birmingham andinstalled on this trip. A new UPS and mains controller were installed. The effect of theprimary mirror position on beam alignment was investigated.1 IntroductionSteven Hale visited Mount Wilson between March 2 and March 12. The main tasks that wereplanned for this trip were:• Replace PC.• Buy UPS.• Install mains controller.• Look at mirror alignment.2 Installation of New PCThe PC in Mount Wilson had failed. The fault appeared to be the usual problem of bulgingcapacitors near the CPU on the motherboard. If this is ever seen on a motherboard, then it’stime to replace the board because failure is likely to be imminent.The new PC was installed on 2009 March 2. Since the new PC had only one serial port, thecomputer now uses one of the 8-way serial port PCI cards. The Temperature Monitor and theGPS are connected to the first two channels, with the remaining six being spare. The operatingsystem is Fedora 10.13 UPS and Mains ControllerA new UPS was purchased on this trip. It is an APC 1500-VA model.All of our hardware is now on the UPS, along with Ed’s main PC also. With everything on,including our monitor, the UPS indicates sixteen minutes of up time. Without the monitor itindicates twenty-five minutes. Without Ed’s PC it indicates thirty-five minutes. The displayindicates the device to be running at 30% load. Hopefully it should help out with the poorpower on the mountain. There have been many brown-outs lately, especially on windy days.A mains controller has been installed, allowing us to power cycle everything remotely.Table 1: Mains Controller ChannelsChannel Device0 Main Crate1 Temperature Controllers2 Temperature Monitor3 Velocity Pockels-Cell Driver4 GPS5 n/c6 n/c7 n/c4 Primary Mirror Position and Beam AlignmentUnlike most of our other sites, the instrument in Mount Wilson sits on a bench and does notswing on an equatorial mount. Here, the sunlight is collected using a cœlostat at the top of asixty-foot tower. The cœlostat has two mirrors. The primary first flat is 546mm in diameterand faces the Sun. The secondary has a diameter of 425mm and reflects the light verticallydownwards through the center of the tower to the observing room below.Normally a cœlostat has two mounts for the second flat, one for the summer where the Sunis generally high in the sky, and another for the winter where the Sun is considerably lower. InMount Wilson the primary mirror is offset from the secondary so that there is no need for awinter mount. However, this does mean that for most of the year a small amount of data is lostwhen the primary is moved from the East position to the West position in the middle of theday. The primary mirror has three basic adjustments, the East/West translation, an up/downtranslation to avoid tilt in declination, and a tilt in right ascension. The primary mirror has asimple tracking motor that makes it follow the Sun throughout the day.The secondary mirror is fixed in position, but can tilt along both axes to ensure the beamis projected down through the tower correctly. Two motors are used to drive these movements,and they are controlled by an auto-guider to lock onto the Sun.At the top of the tower there is an “Ellerman” lens. This was installed by Ferdinand Ellermanin 1905. It is 305mm in diameter, and has a focal length of 60 ft. It is used daily to take adirect-view photographs of the Sun. During normal running, the Ellerman lens is moved outof the way and the secondary is tilted towards the East to center the beam on a different lens2towards the bottom of the tower. This lens is used to send the beam into Ed Rhodes’ instrument.In between Ed’s lens and his instrument is a beam-splitter that picks off a percentage of thelight and sends it towards the auto-guider head.In line with Ed’s lens, but slightly further East, we have two “periscope” mirrors that pick-offpart of the beam. The first periscope mirror directs the beam around one foot sideways, andthe second periscope mirror projects the beam down again. Yet another mirror on the bench atthe bottom of the tower reflects the light into our instrument. In total there are five mirrors inthe system required to get light into Klaus. All have to be aligned correctly or the light quitesimply goes in the wrong direction.The first task after opening the dome in the morning is to setup the primary mirror. Themount is translated to the East position, and placed as close to the center of the tower aspossible. The mirror is then manually tilted until the light is seen to fall centrally onto thesecondary mirror. The declination adjustment is made every other day and is done by placinga cover with an aperture of approximately three inches diameter over the primary to produce anarrow beam. A rubber band is stretched over the secondary to provide a central line, and theprimary moved up or down until the narrow beam is seen to be central on the rubber band.Finally, the secondary mirror is manually tilted until the beam is roughly centered on Ed’slens. The “track” and “guide” buttons are then hit to switch on all the motors, and the auto-guider pulls in the secondary mirror to achieve guider-lock.Around the middle of the day, just before the secondary mirror mount starts to cast a shadowon the primary, the primary is translated to the West side of the tower and tilted in the oppositedirection. It should be moved to the equal and opposite position, but there are no stops toensure this happens.The problem is this procedure is not particularly accurate or repeatable. The guider willquite happily pull in the alignment so long as the manual positioning is basically correct. Butthe physical position of the primary causes the beam to move around inside the tower from oneday to the next, or indeed from morning to afternoon. This is fine for the lens at the center ofthe beam, but since our periscope mirrors are off to one side it can cause problems if we are tooclose to the edge of the beam.It is also possible that the whole tower moves with changes in ambient temperature as thingsexpand or contract. This makes a procedure for accurate alignment even more critical.With the pier in the normal morning position, East of the secondary, but as close to theshaft as possible, the beam was slightly to the South and East of Ed’s lens. This is very goodfor us, since our periscope mirrors are mounted on the East side of the shaft and to the Southof Ed’s lens.With the pier fully to the East as far as possible, the image moves South a little. This wouldbe good for us, but the increased distance between the primary and the secondary reduces thediameter of the beam and puts us closer to the edge. That is bad.With the pier back in the normal position, we shifted the primary up and down. Wheneverthe mirror was moved away from the point at which the beam is vertically central on thesecondary, the beam in the shaft was pushed slightly South and slightly East, but the differenceis hardly noticeable.It appears that the best position is with the primary as close to the secondary as possible.Although really it doesn’t seem to make a huge difference. It has to be a gross error in positioningfor any major movement of the beam in the shaft.3So unfortunately we haven’t come to any major conclusions. Regardless of positioning, thebeam always appeared well over our periscope mirrors—we weren’t right on the edge of thebeam at all.The alignment of the periscope mirrors was also checked. They appeared to be too closetogether— they overlapped slightly shadowing each other. The “down” mirror was moved furtherto the South to give more clearance, and then adjusted to maximize the light on the bottommirror.Finally the alignment of Klaus was checked by removing the cover and the interference filter,and visually checking the beam through the instrument.5 MiscellaneousThe heating in the tower has failed. Several small fan heaters are being used: three in thecomputer room, two in the observing room, and one in the dark room. They wanted to put twoin the dark room, but the extra one causes the circuit breaker to trip out. There must be over10kW of fan heaters running—that’s quite a few Amps! Glad I don’t have to pay the electricitybill.4

New computer in Mount Wilson

University of Birmingham Research Portal

  New Computer in Mount WilsonHale, StevenLicense:Creative Commons: Attribution-NonCommercial-ShareAlike (CC BY-NC-SA)Document VersionPublisher's PDF, also known as Version of recordCitation for published version (Harvard):Hale, SJ 2009 'New Computer in Mount Wilson' BiSON Technical Report Series, no. 319, Birmingham SolarOscillations Network.Link to publication on Research at Birmingham portalGeneral rightsUnless a licence is specified above, all rights (including copyright and moral rights) in this document are retained by the authors and/or thecopyright holders. The express permission of the copyright holder must be obtained for any use of this material other than for purposespermitted by law.•	Users may freely distribute the URL that is used to identify this publication.•	Users may download and/or print one copy of the publication from the University of Birmingham research portal for the purpose of privatestudy or non-commercial research.•	User may use extracts from the document in line with the concept of ‘fair dealing’ under the Copyright, Designs and Patents Act 1988 (?)•	Users may not further distribute the material nor use it for the purposes of commercial gain.Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document.When citing, please reference the published version.Take down policyWhile the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has beenuploaded in error or has been deemed to be commercially or otherwise sensitive.If you believe that this is the case for this document, please contact UBIRA@lists.bham.ac.uk providing details and we will remove access tothe work immediately and investigate.Download date: 01. Feb. 2019BiSONBirminghamSolar-OscillationsNetworkTECHNICAL REPORT NO. 319New Computer in Mount WilsonSteven J. HaleThe University of Birmingham, Edgbaston, Birmingham B15 2TT2009 May 27This technical report series is published by:SLHigh-Resolution Optical-Spectroscopy GroupSchool of Physics and AstronomyThe University of BirminghamEdgbaston, Birmingham B15 2TT, United KingdomTelephone: +44-121-414-4551 FAX: +44-121-414-1438New Computer in Mount WilsonSteven J. HaleThe University of Birmingham, Edgbaston, Birmingham B15 2TT2009 May 27AbstractThe PC in Mount Wilson had failed. A replacement was built in Birmingham andinstalled on this trip. A new UPS and mains controller were installed. The effect of theprimary mirror position on beam alignment was investigated.1 IntroductionSteven Hale visited Mount Wilson between March 2 and March 12. The main tasks that wereplanned for this trip were:• Replace PC.• Buy UPS.• Install mains controller.• Look at mirror alignment.2 Installation of New PCThe PC in Mount Wilson had failed. The fault appeared to be the usual problem of bulgingcapacitors near the CPU on the motherboard. If this is ever seen on a motherboard, then it’stime to replace the board because failure is likely to be imminent.The new PC was installed on 2009 March 2. Since the new PC had only one serial port, thecomputer now uses one of the 8-way serial port PCI cards. The Temperature Monitor and theGPS are connected to the first two channels, with the remaining six being spare. The operatingsystem is Fedora 10.13 UPS and Mains ControllerA new UPS was purchased on this trip. It is an APC 1500-VA model.All of our hardware is now on the UPS, along with Ed’s main PC also. With everything on,including our monitor, the UPS indicates sixteen minutes of up time. Without the monitor itindicates twenty-five minutes. Without Ed’s PC it indicates thirty-five minutes. The displayindicates the device to be running at 30% load. Hopefully it should help out with the poorpower on the mountain. There have been many brown-outs lately, especially on windy days.A mains controller has been installed, allowing us to power cycle everything remotely.Table 1: Mains Controller ChannelsChannel Device0 Main Crate1 Temperature Controllers2 Temperature Monitor3 Velocity Pockels-Cell Driver4 GPS5 n/c6 n/c7 n/c4 Primary Mirror Position and Beam AlignmentUnlike most of our other sites, the instrument in Mount Wilson sits on a bench and does notswing on an equatorial mount. Here, the sunlight is collected using a cœlostat at the top of asixty-foot tower. The cœlostat has two mirrors. The primary first flat is 546mm in diameterand faces the Sun. The secondary has a diameter of 425mm and reflects the light verticallydownwards through the center of the tower to the observing room below.Normally a cœlostat has two mounts for the second flat, one for the summer where the Sunis generally high in the sky, and another for the winter where the Sun is considerably lower. InMount Wilson the primary mirror is offset from the secondary so that there is no need for awinter mount. However, this does mean that for most of the year a small amount of data is lostwhen the primary is moved from the East position to the West position in the middle of theday. The primary mirror has three basic adjustments, the East/West translation, an up/downtranslation to avoid tilt in declination, and a tilt in right ascension. The primary mirror has asimple tracking motor that makes it follow the Sun throughout the day.The secondary mirror is fixed in position, but can tilt along both axes to ensure the beamis projected down through the tower correctly. Two motors are used to drive these movements,and they are controlled by an auto-guider to lock onto the Sun.At the top of the tower there is an “Ellerman” lens. This was installed by Ferdinand Ellermanin 1905. It is 305mm in diameter, and has a focal length of 60 ft. It is used daily to take adirect-view photographs of the Sun. During normal running, the Ellerman lens is moved outof the way and the secondary is tilted towards the East to center the beam on a different lens2towards the bottom of the tower. This lens is used to send the beam into Ed Rhodes’ instrument.In between Ed’s lens and his instrument is a beam-splitter that picks off a percentage of thelight and sends it towards the auto-guider head.In line with Ed’s lens, but slightly further East, we have two “periscope” mirrors that pick-offpart of the beam. The first periscope mirror directs the beam around one foot sideways, andthe second periscope mirror projects the beam down again. Yet another mirror on the bench atthe bottom of the tower reflects the light into our instrument. In total there are five mirrors inthe system required to get light into Klaus. All have to be aligned correctly or the light quitesimply goes in the wrong direction.The first task after opening the dome in the morning is to setup the primary mirror. Themount is translated to the East position, and placed as close to the center of the tower aspossible. The mirror is then manually tilted until the light is seen to fall centrally onto thesecondary mirror. The declination adjustment is made every other day and is done by placinga cover with an aperture of approximately three inches diameter over the primary to produce anarrow beam. A rubber band is stretched over the secondary to provide a central line, and theprimary moved up or down until the narrow beam is seen to be central on the rubber band.Finally, the secondary mirror is manually tilted until the beam is roughly centered on Ed’slens. The “track” and “guide” buttons are then hit to switch on all the motors, and the auto-guider pulls in the secondary mirror to achieve guider-lock.Around the middle of the day, just before the secondary mirror mount starts to cast a shadowon the primary, the primary is translated to the West side of the tower and tilted in the oppositedirection. It should be moved to the equal and opposite position, but there are no stops toensure this happens.The problem is this procedure is not particularly accurate or repeatable. The guider willquite happily pull in the alignment so long as the manual positioning is basically correct. Butthe physical position of the primary causes the beam to move around inside the tower from oneday to the next, or indeed from morning to afternoon. This is fine for the lens at the center ofthe beam, but since our periscope mirrors are off to one side it can cause problems if we are tooclose to the edge of the beam.It is also possible that the whole tower moves with changes in ambient temperature as thingsexpand or contract. This makes a procedure for accurate alignment even more critical.With the pier in the normal morning position, East of the secondary, but as close to theshaft as possible, the beam was slightly to the South and East of Ed’s lens. This is very goodfor us, since our periscope mirrors are mounted on the East side of the shaft and to the Southof Ed’s lens.With the pier fully to the East as far as possible, the image moves South a little. This wouldbe good for us, but the increased distance between the primary and the secondary reduces thediameter of the beam and puts us closer to the edge. That is bad.With the pier back in the normal position, we shifted the primary up and down. Wheneverthe mirror was moved away from the point at which the beam is vertically central on thesecondary, the beam in the shaft was pushed slightly South and slightly East, but the differenceis hardly noticeable.It appears that the best position is with the primary as close to the secondary as possible.Although really it doesn’t seem to make a huge difference. It has to be a gross error in positioningfor any major movement of the beam in the shaft.3So unfortunately we haven’t come to any major conclusions. Regardless of positioning, thebeam always appeared well over our periscope mirrors—we weren’t right on the edge of thebeam at all.The alignment of the periscope mirrors was also checked. They appeared to be too closetogether— they overlapped slightly shadowing each other. The “down” mirror was moved furtherto the South to give more clearance, and then adjusted to maximize the light on the bottommirror.Finally the alignment of Klaus was checked by removing the cover and the interference filter,and visually checking the beam through the instrument.5 MiscellaneousThe heating in the tower has failed. Several small fan heaters are being used: three in thecomputer room, two in the observing room, and one in the dark room. They wanted to put twoin the dark room, but the extra one causes the circuit breaker to trip out. There must be over10kW of fan heaters running—that’s quite a few Amps! Glad I don’t have to pay the electricitybill.4

New Computer in Mount Wilson

  University of BirminghamNew Computer in Mount WilsonHale, Steven J.License:Creative Commons: Attribution-NonCommercial-ShareAlike (CC BY-NC-SA)Document VersionPublisher's PDF, also known as Version of recordCitation for published version (Harvard):Hale, SJ 2009 'New Computer in Mount Wilson' BiSON Technical Report Series, no. 319, Birmingham SolarOscillations Network.Link to publication on Research at Birmingham portalGeneral rightsUnless a licence is specified above, all rights (including copyright and moral rights) in this document are retained by the authors and/or thecopyright holders. The express permission of the copyright holder must be obtained for any use of this material other than for purposespermitted by law.•	Users may freely distribute the URL that is used to identify this publication.•	Users may download and/or print one copy of the publication from the University of Birmingham research portal for the purpose of privatestudy or non-commercial research.•	User may use extracts from the document in line with the concept of ‘fair dealing’ under the Copyright, Designs and Patents Act 1988 (?)•	Users may not further distribute the material nor use it for the purposes of commercial gain.Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document.When citing, please reference the published version.Take down policyWhile the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has beenuploaded in error or has been deemed to be commercially or otherwise sensitive.If you believe that this is the case for this document, please contact UBIRA@lists.bham.ac.uk providing details and we will remove access tothe work immediately and investigate.Download date: 01. Mar. 2020BiSONBirminghamSolar-OscillationsNetworkTECHNICAL REPORT NO. 319New Computer in Mount WilsonSteven J. HaleThe University of Birmingham, Edgbaston, Birmingham B15 2TT2009 May 27This technical report series is published by:SLHigh-Resolution Optical-Spectroscopy GroupSchool of Physics and AstronomyThe University of BirminghamEdgbaston, Birmingham B15 2TT, United KingdomTelephone: +44-121-414-4551 FAX: +44-121-414-1438New Computer in Mount WilsonSteven J. HaleThe University of Birmingham, Edgbaston, Birmingham B15 2TT2009 May 27AbstractThe PC in Mount Wilson had failed. A replacement was built in Birmingham andinstalled on this trip. A new UPS and mains controller were installed. The effect of theprimary mirror position on beam alignment was investigated.1 IntroductionSteven Hale visited Mount Wilson between March 2 and March 12. The main tasks that wereplanned for this trip were:• Replace PC.• Buy UPS.• Install mains controller.• Look at mirror alignment.2 Installation of New PCThe PC in Mount Wilson had failed. The fault appeared to be the usual problem of bulgingcapacitors near the CPU on the motherboard. If this is ever seen on a motherboard, then it’stime to replace the board because failure is likely to be imminent.The new PC was installed on 2009 March 2. Since the new PC had only one serial port, thecomputer now uses one of the 8-way serial port PCI cards. The Temperature Monitor and theGPS are connected to the first two channels, with the remaining six being spare. The operatingsystem is Fedora 10.13 UPS and Mains ControllerA new UPS was purchased on this trip. It is an APC 1500-VA model.All of our hardware is now on the UPS, along with Ed’s main PC also. With everything on,including our monitor, the UPS indicates sixteen minutes of up time. Without the monitor itindicates twenty-five minutes. Without Ed’s PC it indicates thirty-five minutes. The displayindicates the device to be running at 30% load. Hopefully it should help out with the poorpower on the mountain. There have been many brown-outs lately, especially on windy days.A mains controller has been installed, allowing us to power cycle everything remotely.Table 1: Mains Controller ChannelsChannel Device0 Main Crate1 Temperature Controllers2 Temperature Monitor3 Velocity Pockels-Cell Driver4 GPS5 n/c6 n/c7 n/c4 Primary Mirror Position and Beam AlignmentUnlike most of our other sites, the instrument in Mount Wilson sits on a bench and does notswing on an equatorial mount. Here, the sunlight is collected using a cœlostat at the top of asixty-foot tower. The cœlostat has two mirrors. The primary first flat is 546mm in diameterand faces the Sun. The secondary has a diameter of 425mm and reflects the light verticallydownwards through the center of the tower to the observing room below.Normally a cœlostat has two mounts for the second flat, one for the summer where the Sunis generally high in the sky, and another for the winter where the Sun is considerably lower. InMount Wilson the primary mirror is offset from the secondary so that there is no need for awinter mount. However, this does mean that for most of the year a small amount of data is lostwhen the primary is moved from the East position to the West position in the middle of theday. The primary mirror has three basic adjustments, the East/West translation, an up/downtranslation to avoid tilt in declination, and a tilt in right ascension. The primary mirror has asimple tracking motor that makes it follow the Sun throughout the day.The secondary mirror is fixed in position, but can tilt along both axes to ensure the beamis projected down through the tower correctly. Two motors are used to drive these movements,and they are controlled by an auto-guider to lock onto the Sun.At the top of the tower there is an “Ellerman” lens. This was installed by Ferdinand Ellermanin 1905. It is 305mm in diameter, and has a focal length of 60 ft. It is used daily to take adirect-view photographs of the Sun. During normal running, the Ellerman lens is moved outof the way and the secondary is tilted towards the East to center the beam on a different lens2towards the bottom of the tower. This lens is used to send the beam into Ed Rhodes’ instrument.In between Ed’s lens and his instrument is a beam-splitter that picks off a percentage of thelight and sends it towards the auto-guider head.In line with Ed’s lens, but slightly further East, we have two “periscope” mirrors that pick-offpart of the beam. The first periscope mirror directs the beam around one foot sideways, andthe second periscope mirror projects the beam down again. Yet another mirror on the bench atthe bottom of the tower reflects the light into our instrument. In total there are five mirrors inthe system required to get light into Klaus. All have to be aligned correctly or the light quitesimply goes in the wrong direction.The first task after opening the dome in the morning is to setup the primary mirror. Themount is translated to the East position, and placed as close to the center of the tower aspossible. The mirror is then manually tilted until the light is seen to fall centrally onto thesecondary mirror. The declination adjustment is made every other day and is done by placinga cover with an aperture of approximately three inches diameter over the primary to produce anarrow beam. A rubber band is stretched over the secondary to provide a central line, and theprimary moved up or down until the narrow beam is seen to be central on the rubber band.Finally, the secondary mirror is manually tilted until the beam is roughly centered on Ed’slens. The “track” and “guide” buttons are then hit to switch on all the motors, and the auto-guider pulls in the secondary mirror to achieve guider-lock.Around the middle of the day, just before the secondary mirror mount starts to cast a shadowon the primary, the primary is translated to the West side of the tower and tilted in the oppositedirection. It should be moved to the equal and opposite position, but there are no stops toensure this happens.The problem is this procedure is not particularly accurate or repeatable. The guider willquite happily pull in the alignment so long as the manual positioning is basically correct. Butthe physical position of the primary causes the beam to move around inside the tower from oneday to the next, or indeed from morning to afternoon. This is fine for the lens at the center ofthe beam, but since our periscope mirrors are off to one side it can cause problems if we are tooclose to the edge of the beam.It is also possible that the whole tower moves with changes in ambient temperature as thingsexpand or contract. This makes a procedure for accurate alignment even more critical.With the pier in the normal morning position, East of the secondary, but as close to theshaft as possible, the beam was slightly to the South and East of Ed’s lens. This is very goodfor us, since our periscope mirrors are mounted on the East side of the shaft and to the Southof Ed’s lens.With the pier fully to the East as far as possible, the image moves South a little. This wouldbe good for us, but the increased distance between the primary and the secondary reduces thediameter of the beam and puts us closer to the edge. That is bad.With the pier back in the normal position, we shifted the primary up and down. Wheneverthe mirror was moved away from the point at which the beam is vertically central on thesecondary, the beam in the shaft was pushed slightly South and slightly East, but the differenceis hardly noticeable.It appears that the best position is with the primary as close to the secondary as possible.Although really it doesn’t seem to make a huge difference. It has to be a gross error in positioningfor any major movement of the beam in the shaft.3So unfortunately we haven’t come to any major conclusions. Regardless of positioning, thebeam always appeared well over our periscope mirrors—we weren’t right on the edge of thebeam at all.The alignment of the periscope mirrors was also checked. They appeared to be too closetogether— they overlapped slightly shadowing each other. The “down” mirror was moved furtherto the South to give more clearance, and then adjusted to maximize the light on the bottommirror.Finally the alignment of Klaus was checked by removing the cover and the interference filter,and visually checking the beam through the instrument.5 MiscellaneousThe heating in the tower has failed. Several small fan heaters are being used: three in thecomputer room, two in the observing room, and one in the dark room. They wanted to put twoin the dark room, but the extra one causes the circuit breaker to trip out. There must be over10kW of fan heaters running—that’s quite a few Amps! Glad I don’t have to pay the electricitybill.4

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New computer in Mount Wilson

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