Author Topic: Losmandy G-11 PMC-Eight w/ Telescope Drive Master - UNGUIDED 600sec image  (Read 148 times)

Matthew Danielson

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Here is a picture I just took using the Losmandy G-11 PMC-Eight mount program withthe Telescope Drive Master drive corrector.The picture was recorded using a QHY163C TEC CCDmounted onanES 152 EDAPO Carbon Fiber scope at the Mark Slade Remote Observatory (MSRO).  FL = 1214 mm.  This can be a 600 second UNGUIDED picture revealing the operation of the combination.  The goal is magnitude 5.6 star HD100808.  I believe the slight elongation in RA is a result of the fact that I've the TDM chosen to Sidereal Rate vs Average King Rate.
Here is the fits header to the picture:

SIMPLE = T
BITPIX = 16 /8 unsigned int, 16 & 32 int, -32 & -64 real
NAXIS = 2 /number of axes
NAXIS1 = 2328 /fastest changing axis
NAXIS2 = 1760 /next to fastest changing axis
BSCALE = 1.0000000000000000 /physical = BZERO + BSCALE*array_value
BZERO = 32768.000000000000 /physical = BZERO + BSCALE*array_value
DATE-OBS = '2017-03-23T02:59:27' / [ISO 8601] UTC date/time of exposure start
EXPTIME = 6.00000000000E+002 / [sec] Duration of exposure
EXPOSURE = 6.00000000000E+002 / [sec] Duration of exposure
SET-TEMP = -30.000000000000000 /CCD temperature setpoint in C
CCD-TEMP = -30.100000000000001 /CCD temperature at start of exposure in C
XPIXSZ = 7.5999999999999996 /Pixel Width in microns (after binning)
YPIXSZ = 7.5999999999999996 /Pixel Height in microns (after binning)
XBINNING = 2 / Binning degree along the X-axis
YBINNING = 2 / Binning degree along the Y-axis
XORGSUBF = 0 /Subframe X position in binned pixels
YORGSUBF = 0 /Subframe Y position in binned pixels
IMAGETYP = 'Light Frame' / Type of picture
FOCALLEN = 1213.9000244140625 /Focal length of telescope in mm
APTDIA = 152.00000000000000 /Aperture diameter of telescope in mm
APTAREA = 18145.839672088623 /Aperture area of telescope in mm^2
EGAIN = 1.0000000000000000 /Electronic gain in e-/ADU
SBSTDVER = 'SBFITSEXT Version 1.0' /Version of SBFITSEXT standard in effect
SWCREATE = 'MaxIm DL Version 6.13 170127 0N130' /Name of software
SWSERIAL = '0N130-U20T9-WM00W-078S7-UFTQA-WA' /Software serial number
FOCUSPOS = 14610 /Focuser position in steps
FOCUSSSZ = 4.1399999999999997 /Focuser step size in microns
FOCUSTEM = 2.5000000000000000 /Focuser temperature in deg C
OBJCTRA = '11 36 26.00' / [hms J2000] Target right ascension
OBJCTDEC = '+27 46 49.0' / [dms +N J2000] Target declination
OBJCTALT = ' 67.4285' / Nominal altitude of center of picture
OBJCTAZ = '111.0456' / Nominal azimuth of center of picture
OBJCTHA = ' -1.5909' / Nominal hour angle of center of picture
PIERSIDE = 'WEST ' / Negative of pier telescope is on
SITELAT = '38 20 02' / Latitude of the imaging location
SITELONG = '-77 42 38' / Longitude of the imaging location
JD = 2457835.6246180558 /Julian Date at beginning of exposure
JD-HELIO = 2457835.6330857864 /Heliocentric Julian Date at vulnerability midpoint
AIRMASS = 1.09803569639E+000 / Airmass (multiple of zenithal airmass)
OBJECT = ' ' / Target object name
TELESCOP = 'ES 152 ED APO CF' / Telescope name
INSTRUME = 'QHY163C TEC' / Detector tool name
OBSERVER = 'Gerald R. Hubbell' / Observer name
NOTES = ' '
FLIPSTAT = ' '
SWOWNER = 'Gerald R Hubbell' / Licensed owner of software
HISTORY Document was processed by PinPoint 6.1.3 at 2017-03-23T03:10:09
DATE = '23/03/17' / [old format] UTC date of exposure start
TIME-OBS = '02:59:27' / [old format] UTC time of exposure start
UT = '02:59:27' / [old format] UTC time of exposure start
TIMESYS = 'UTC ' / Default time program
RADECSYS = 'FK5 ' / Equatorial coordinate system
RA = '11 36 26.00' / [hms J2000] Target right ascension
DEC = '+27 46 49.0' / [dms +N J2000] Target declination
FWHM = 2.95647350550E+000 / [pixels] Mean Full-Width-Half-Max of picture star
ZMAG = 2.20314193308E+001 / Mag zero point for 1 sec exposure
EQUINOX = 2000.0 / Equatorial coordinates are J2000
EPOCH = 2000.0 / (erroneous but needed by old programs)
PA = 1.82794134802E+002 / [deg, 0-360 CCW] Position angle of plate
CTYPE1 = 'RA--TAN' / X-axis coordinate type
CRVAL1 = 1.74104228900E+002 / X-axis coordinate value
CRPIX1 = 1.16400000000E+003 / X-axis reference pixel
CDELT1 = 3.58776891818E-004 / [deg/pixel] X-axis plate scale
CROTA1 = -2.79413480159E+000 / [deg] Roll angle wrt X-axis
CTYPE2 = 'DEC--TAN' / Y-axis coordinate type
CRVAL2 = 2.77923033362E+001 / Y-axis coordinate value
CRPIX2 = 8.80000000000E+002 / Y-axis reference pixel
CDELT2 = 3.58708671167E-004 / [deg/pixel] Y-Axis Plate scale
CROTA2 = -2.79413480159E+000 / [deg] Roll angle wrt Y-axis
CD1_1 = 3.58350353708E-004 / Change in RA--TAN along X-Axis
CD1_2 = 1.74861598180E-005 / Change in RA--TAN along Y-Axis
CD2_1 = -1.74894854059E-005 / Change in DEC--TAN along X-Axis
CD2_2 = 3.58282214162E-004 / Change in DEC--TAN along Y-Axis
TR1_0 = 1.16399987493E+003 / [private] X-axis distortion coefficients
TR1_1 = 2.32799999024E+003
TR1_2 = -2.19261500317E-001
TR1_3 = 2.45830457336E+000
TR1_4 = -1.51819407262E-001
TR1_5 = 2.21296997271E-001
TR1_6 = -1.36828842680E+000
TR1_7 = 4.11163572209E-001
TR1_8 = -3.33478468879E-001
TR1_9 = -4.15609833254E-001
TR1_10 = -1.01916615517E+001
TR1_11 = 3.35444502704E+000
TR1_12 = -3.54818112567E+000
TR1_13 = -3.09588647636E+000
TR1_14 = 1.10722664432E+000
TR2_0 = 8.80000001403E+002 / [private] Y-axis distortion coefficients
TR2_1 = 1.93912981731E-003
TR2_2 = 1.75999999925E+003
TR2_3 = -9.81715419560E-001
TR2_4 = 3.60546010789E-001
TR2_5 = -1.47947883301E+000
TR2_6 = 4.22173761620E-001
TR2_7 = -3.55620866561E-001
TR2_8 = 3.22936700141E-001
TR2_9 = -2.48605441340E-001
TR2_10 = -4.39613095559E-003
TR2_11 = -3.63832957982E+000
TR2_12 = 4.25775181988E+000
TR2_13 = 5.59856142432E-001
TR2_14 = 3.04379590257E+000
HISTORY WCS added by PinPoint 6.1.3 at 2017-03-23T03:10:09
HISTORY Matched 80 stars from the USNO UCAC4 Catalog
HISTORY Average remaining was 0.18 arc-seconds
PLTSOLVD = T / Plate has been solved by PinPoint
HISTORY Image data was modified, written back to file.
SWMODIFY = 'MaxIm DL Version 6.13 170127 0N130' /Name of software
HISTORY Bias Subtraction (Bias 2, 2328 x 1760, Bin2 x 2, Temp -30C,
HISTORY Exp Time 0ms)
CALSTAT = 'BDF '
HISTORY Dark Subtraction (Dark 3, 2328 x 1760, Bin2 x 2, Temp -30C,
HISTORY Exp Time 60s)
HISTORY Dark-Bias(Bias 2,2328 x 1760,Bin2 x 2,Temp -30C,Exp Time 0ms)
HISTORY Flat Field (Flat 2, 2328 x 1760, Bin2 x 2, Temp -30C,
HISTORY Exp Time 150ms)
HISTORY Flat-Bias(Bias 2,2328 x 1760,Bin2 x 2,Temp -30C,Exp Time 0ms)
HISTORY Flat-Dark (Dark 3,2328 x 1760,Bin2 x 2,Temp -30C,Exp Time 60s)
PEDESTAL = -100 /Correction to include zero-based ADU
CBLACK = 16727 /Initial screen black level in ADUs
CWHITE = 8809 /Initial display white level in ADUs




James Merrill

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Re: Losmandy G-11 PMC-Eight w/ Telescope Drive Master - UNGUIDED 600sec image
« Reply #1 on: December 29, 2017, 02:27:47 AM »
Quote
Here is an image I just took using the Losmandy G-11 PMC-Eight mount system withthe Telescope Drive Master drive corrector.The image was captured with a QHY163C TEC CCDmounted onanES 152 EDAPO Carbon Fiber scope at the Mark Slade Remote Observatory (MSRO). FL = 1214 mm. This is a 600 second UNGUIDED image showing the performance of this combination. The target is magnitude 5.6 star HD100808. I think the slight elongation in RA is due to the fact that I have the TDM selected to Sidereal Rate vs Average King Rate.

HD100808_600sec_G11_TDM_2.jpg

Here is the fits header for the image:

SIMPLE = T
BITPIX = 16 /8 unsigned int, 16 & 32 int, -32 & -64 real
NAXIS = 2 /number of axes
NAXIS1 = 2328 /fastest changing axis
NAXIS2 = 1760 /next to fastest changing axis
BSCALE = 1.0000000000000000 /physical = BZERO + BSCALE*array_value
BZERO = 32768.000000000000 /physical = BZERO + BSCALE*array_value
DATE-OBS = '2017-03-23T02:59:27' / [ISO 8601] UTC date/time of exposure start
EXPTIME = 6.00000000000E+002 / [sec] Duration of exposure
EXPOSURE = 6.00000000000E+002 / [sec] Duration of exposure
SET-TEMP = -30.000000000000000 /CCD temperature setpoint in C
CCD-TEMP = -30.100000000000001 /CCD temperature at start of exposure in C
XPIXSZ = 7.5999999999999996 /Pixel Width in microns (after binning)
YPIXSZ = 7.5999999999999996 /Pixel Height in microns (after binning)
XBINNING = 2 / Binning level along the X-axis
YBINNING = 2 / Binning level along the Y-axis
XORGSUBF = 0 /Subframe X position in binned pixels
YORGSUBF = 0 /Subframe Y position in binned pixels
IMAGETYP = 'Light Frame' / Type of image
FOCALLEN = 1213.9000244140625 /Focal length of telescope in mm
APTDIA = 152.00000000000000 /Aperture diameter of telescope in mm
APTAREA = 18145.839672088623 /Aperture area of telescope in mm^2
EGAIN = 1.0000000000000000 /Electronic gain in e-/ADU
SBSTDVER = 'SBFITSEXT Version 1.0' /Version of SBFITSEXT standard in effect
SWCREATE = 'MaxIm DL Version 6.13 170127 0N130' /Name of software
SWSERIAL = '0N130-U20T9-WM00W-078S7-UFTQA-WA' /Software serial number
FOCUSPOS = 14610 /Focuser position in steps
FOCUSSSZ = 4.1399999999999997 /Focuser step size in microns
FOCUSTEM = 2.5000000000000000 /Focuser temperature in deg C
OBJCTRA = '11 36 26.00' / [hms J2000] Target right ascension
OBJCTDEC = '+27 46 49.0' / [dms +N J2000] Target declination
OBJCTALT = ' 67.4285' / Nominal altitude of center of image
OBJCTAZ = '111.0456' / Nominal azimuth of center of image
OBJCTHA = ' -1.5909' / Nominal hour angle of center of image
PIERSIDE = 'WEST ' / Side of pier telescope is on
SITELAT = '38 20 02' / Latitude of the imaging location
SITELONG = '-77 42 38' / Longitude of the imaging location
JD = 2457835.6246180558 /Julian Date at start of exposure
JD-HELIO = 2457835.6330857864 /Heliocentric Julian Date at exposure midpoint
AIRMASS = 1.09803569639E+000 / Airmass (multiple of zenithal airmass)
OBJECT = ' ' / Target object name
TELESCOP = 'ES 152 ED APO CF' / Telescope name
INSTRUME = 'QHY163C TEC' / Detector instrument name
OBSERVER = 'Gerald R. Hubbell' / Observer name
NOTES = ' '
FLIPSTAT = ' '
SWOWNER = 'Gerald R Hubbell' / Licensed owner of software
HISTORY File was processed by PinPoint 6.1.3 at 2017-03-23T03:10:09
DATE = '23/03/17' / [old format] UTC date of exposure start
TIME-OBS = '02:59:27' / [old format] UTC time of exposure start
UT = '02:59:27' / [old format] UTC time of exposure start
TIMESYS = 'UTC ' / Default time system
RADECSYS = 'FK5 ' / Equatorial coordinate system
RA = '11 36 26.00' / [hms J2000] Target right ascension
DEC = '+27 46 49.0' / [dms +N J2000] Target declination
FWHM = 2.95647350550E+000 / [pixels] Mean Full-Width-Half-Max of image star
ZMAG = 2.20314193308E+001 / Mag zero point for 1 sec exposure
EQUINOX = 2000.0 / Equatorial coordinates are J2000
EPOCH = 2000.0 / (incorrect but needed by old programs)
PA = 1.82794134802E+002 / [deg, 0-360 CCW] Position angle of plate
CTYPE1 = 'RA---TAN' / X-axis coordinate type
CRVAL1 = 1.74104228900E+002 / X-axis coordinate value
CRPIX1 = 1.16400000000E+003 / X-axis reference pixel
CDELT1 = 3.58776891818E-004 / [deg/pixel] X-axis plate scale
CROTA1 = -2.79413480159E+000 / [deg] Roll angle wrt X-axis
CTYPE2 = 'DEC--TAN' / Y-axis coordinate type
CRVAL2 = 2.77923033362E+001 / Y-axis coordinate value
CRPIX2 = 8.80000000000E+002 / Y-axis reference pixel
CDELT2 = 3.58708671167E-004 / [deg/pixel] Y-Axis Plate scale
CROTA2 = -2.79413480159E+000 / [deg] Roll angle wrt Y-axis
CD1_1 = 3.58350353708E-004 / Change in RA---TAN along X-Axis
CD1_2 = 1.74861598180E-005 / Change in RA---TAN along Y-Axis
CD2_1 = -1.74894854059E-005 / Change in DEC--TAN along X-Axis
CD2_2 = 3.58282214162E-004 / Change in DEC--TAN along Y-Axis
TR1_0 = 1.16399987493E+003 / [private] X-axis distortion coefficients
TR1_1 = 2.32799999024E+003
TR1_2 = -2.19261500317E-001
TR1_3 = 2.45830457336E+000
TR1_4 = -1.51819407262E-001
TR1_5 = 2.21296997271E-001
TR1_6 = -1.36828842680E+000
TR1_7 = 4.11163572209E-001
TR1_8 = -3.33478468879E-001
TR1_9 = -4.15609833254E-001
TR1_10 = -1.01916615517E+001
TR1_11 = 3.35444502704E+000
TR1_12 = -3.54818112567E+000
TR1_13 = -3.09588647636E+000
TR1_14 = 1.10722664432E+000
TR2_0 = 8.80000001403E+002 / [private] Y-axis distortion coefficients
TR2_1 = 1.93912981731E-003
TR2_2 = 1.75999999925E+003
TR2_3 = -9.81715419560E-001
TR2_4 = 3.60546010789E-001
TR2_5 = -1.47947883301E+000
TR2_6 = 4.22173761620E-001
TR2_7 = -3.55620866561E-001
TR2_8 = 3.22936700141E-001
TR2_9 = -2.48605441340E-001
TR2_10 = -4.39613095559E-003
TR2_11 = -3.63832957982E+000
TR2_12 = 4.25775181988E+000
TR2_13 = 5.59856142432E-001
TR2_14 = 3.04379590257E+000
HISTORY WCS added by PinPoint 6.1.3 at 2017-03-23T03:10:09
HISTORY Matched 80 stars from the USNO UCAC4 Catalog
HISTORY Average residual was 0.18 arc-seconds
PLTSOLVD = T / Plate has been solved by PinPoint
HISTORY Image data was modified, written back to file.
SWMODIFY = 'MaxIm DL Version 6.13 170127 0N130' /Name of software
HISTORY Bias Subtraction (Bias 2, 2328 x 1760, Bin2 x 2, Temp -30C,
HISTORY Exp Time 0ms)
CALSTAT = 'BDF '
HISTORY Dark Subtraction (Dark 3, 2328 x 1760, Bin2 x 2, Temp -30C,
HISTORY Exp Time 60s)
HISTORY Dark-Bias(Bias 2,2328 x 1760,Bin2 x 2,Temp -30C,Exp Time 0ms)
HISTORY Flat Field (Flat 2, 2328 x 1760, Bin2 x 2, Temp -30C,
HISTORY Exp Time 150ms)
HISTORY Flat-Bias(Bias 2,2328 x 1760,Bin2 x 2,Temp -30C,Exp Time 0ms)
HISTORY Flat-Dark (Dark 3,2328 x 1760,Bin2 x 2,Temp -30C,Exp Time 60s)
PEDESTAL = -100 /Correction to add for zero-based ADU
CBLACK = 16727 /Initial display black level in ADUs
CWHITE = 8809 /Initial display white level in ADUs

Jerry,
 That is an impressive unguided image. Out of curiosity, have you measured the FWHM for any of the stars in the image? Was the mount Drift aligned? Just curious what all went into the prep to capture the image. Thanks!

JMD

grountentaybrig

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Hi, yes, if you look in the FITS header data, the FWHM is about 3 pixels, which is about what you want for critical sampling. It is probably a little over sampled, but only by a slight amount. The TDM only corrects for RA PE, not for declination drift. As you can see in the image, there is virtually no declination drift as we have a near perfect polar alignment. So yes, the answer is we have done a physical polar alignment. No software alignment, and no guide camera. Additionally, I can tell you that the raw pointing with the system can typically place the object within 5 arcmin of the center of the frame, even when slewing across the meridian.

Zachary Tenk

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But how high above the horizon was this taken?

The problem with the TDM and other relative encoders in general is that you can't correct for atmospheric refraction because you don't know the telescope ALT/AZ (from the TDM's perspective).

But in this case since you also own the GoTo controller (the PMC-8) it should be possible to correct for refraction and the King rate. It would require that the GoTo controller read the TDM directly and apply corrections (and not rely on the TDM blindly providing ST4 outputs irrespective of actual telescope ALT/AZ).

Now if that is possible.. it would make the TDM more useful over a wider range of altitudes.

Jerry Dunn

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Hi Orlyandico, as I said in my original post the TDM controller was set to Sidereal rate, versus the Average King rate. I need to switch it and do another image to verify that that is the problem. My TDM recorder program does as you say in pulse guiding mode, but I have to implement pulse guiding in the ASCOM driver. I implemented a PID control scheme to respond to the encoder measurements.

keylozelbou

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No offense, but that image would never make it into one of my stacks. Actually, I think many of us would discard it. (EDIT - Perhaps wait and post one with round stars?)

Why such a push for unguided imaging when the results are mediocre compared to a mount costing 1/5 as much with a $200 autoguider?

Robert Donaldson

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No offense Austin, but I think mediocre is overstating it a bit. I will do some more work to further demonstrate how well this system can perform. I am not going to argue the case any further as I have already done that in plenty of posts over the past few years. I am just trying to show others what is possible with this equipment, nothing more, nothing less. The funny thing is, I agree with you about the cost effectiveness of the system you use, it's just that I hate wasting time babysitting the autoguiding, that's all. For me, personally, my time is more valuable, and worth the extra cost of the encoder based drive corrector.

Harry Smull

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Jerry, what I meant is, even if you are at sidereal or average King rate, if the altitude is below 30-40 degrees atmospheric refraction will ruin the sub anyway.

What needs to be done is to vary the tracking rate depending on how high the object is in the sky. And that can't be done by the TDM alone - you need to know the alt/az (the mount does..) and the mount can then regulate its speed (measured by the TDM) appropriately.

This is why mount modeling is important.

That said, an AP or Paramount can easily achieve under 1" p-p with a proper PEM/PEC training. That's functionally pretty much the same as the TDM and you can also do unguided. The Paramount does better because with ProTrack it does compensate for atmospheric refraction and polar misalignment.

John Daniels

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I agree Orly, tracking rate adjustment via TPoint (specifically ProTrack) is a viable method of achieving unguided images. But it appears that a similar approach could be developed to be used with the PMC-Eight controller and TDM encoder which would allow a system that could be used on a wide range of mounts. I really like the open approach and hope that the development of the PMC-Eight will mature to include more advanced features in the future. Exciting stuff!
Clear skies,
Bill

byhodete

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Dual-axis tracking is not rocket science; it took me a few hours to build a prototype for my Mach1 (AP mounts do have dual-axis tracking so the trick is finding the correct RA and DEC rates which I did using multiple images and plate-solving; Paramounts do it using the mount model). APCC Pro also does this, for AP mounts.

So dual-axis tracking is not something exclusive to Paramount (or 10Micron) and it does not require encoders.

My points were..

- the TDM alone won't allow unguided imaging at a wide range of ALT/AZ because of atmospheric refraction and because it only corrects PE; using an average tracking rate only works at high altitudes (above 45 degrees or so) where atmospheric refraction effects on the tracking rate are minimal
- there are mounts that, with proper PEM training, can achieve PE of the same level as the TDM, and can even do better (dual-axis tracking)

Christopher Bryant

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Re: Losmandy G-11 PMC-Eight w/ Telescope Drive Master - UNGUIDED 600sec image
« Reply #10 on: January 12, 2018, 12:01:49 PM »
Hi Orly,
The advantages of tracking rate adjustment are well known and have been in use for for many years in large and small installations. I'm a Paramount user and appreciate the ease of use that Patrick and the Bisques have built into their solution, it's absolutely wonderful. My mount also has 3" of native periodic error which corrects to less than 1" or below my local seeing. Plus all the other goodness that comes with it. Standing right here in the choir.
The PMC-Eight appears to be a well designed control system which *could* be leveraged to incorporate tracking rate corrections in both axes. Time will tell and obviously an engineering effort will be required. The same could be said for integrating the TDM feedback with a more sophisticated control system as opposed to traditional mechanical drivetrains to reduce cost.
I'm not as dismissive. It's very early on and there's plenty of conjecture on my part for possible future development. But it sure does look like a good value if it gains traction and matures. There's a lot of promise and I find Jerry's open discussion refreshing.
Clear skies,
Bill

breakinnocor

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Re: Losmandy G-11 PMC-Eight w/ Telescope Drive Master - UNGUIDED 600sec image
« Reply #11 on: January 13, 2018, 02:53:55 AM »
Quote
Hi Orly,
The advantages of tracking rate adjustment are well known and have been in use for for many years in large and small installations. I'm a Paramount user and appreciate the ease of use that Patrick and the Bisques have built into their solution, it's absolutely wonderful. My mount also has 3" of native periodic error which corrects to less than 1" or below my local seeing. Plus all the other goodness that comes with it. Standing right here in the choir.
The PMC-Eight appears to be a well designed control system which *could* be leveraged to incorporate tracking rate corrections in both axes. Time will tell and obviously an engineering effort will be required. The same could be said for integrating the TDM feedback with a more sophisticated control system as opposed to traditional mechanical drivetrains to reduce cost.
I'm not as dismissive. It's very early on and there's plenty of conjecture on my part for possible future development. But it sure does look like a good value if it gains traction and matures. There's a lot of promise and I find Jerry's open discussion refreshing.
Clear skies,
Bill

I agree with this last sentiment and have followed a number of Jerry's threads detailing his experiments with this mount and unguided imaging.  Given the constraints that he placed on obtaining the image above, it looks quite good for a 5 minute exposure. The work that is done by people who are dedicated to long duration exposure astrophotography using guiding is inspiring, and I think Jerry and most of the others that chime in on these discussions understand that longer exposures, using a mount with a low native PEC and guiding will give you the best possible results, and that using encoders by themselves, whether it be the TDM or the ones offered by AP, 10 Micron, ASA etc....., are not a cure all for all the issues that contribute to messing up ones image.

The fact that we have the technology to do auto guiding and do it cheaply is a great thing. But it adds another layer of complexity with respect to gear, skill, and cost that can be daunting to someone just getting started. Personally I find the idea having to use two cameras and two scopes to capture one image just plain frustrating.  This is due to the constraints I have with respect to facilities and time allotted for observing. On a good night, I might have 4 hours to get things up and running and make my rounds for either visual or photographic observation.  When I get my dedicated facility, where I can leave my rig assembled, that opinion may very well change. For the time being, not so much.  Admittedly, I fall into the category of what I call the photo Tourist imager.  My goal is just to capture a nice little image of what I see at the time. The equivalent of the Polaroid One-Step (check everyones age with that reference:-), as opposed to DLSR imaging.  Extra time setting up other cameras, is time taken away from actual astronomy. Time spent learning to optimize the feedback loop of the guide camera is technically interesting to me, but detracts from my observation time at this stage in my life. That will certainly change over time, as the kids grow up, and at that point I could see myself doing some longer duration imaging.

Right now, I use an Orion Atlas with a Mallincam camera, and can get up to 2 minute exposures with results that I find acceptable. My bar is low.  I just need my kids and my wife to light up when they see it. It does not have to be APOD worthy.  I am looking to upgrade my mount and would like to have something that can give my ~5 minute unguided images of the quality posted here. Which is why I find what Jerry is doing interesting and informative, and why I am probably the kind of guy that this technology would be targeting.

FWIW, My own research has lead me to the conclusion expressed by a couple others, which is that at this time the cost of the system Jerry is using to generate that image, puts it in to the class of higher end mounts that can achieve similar results via good polar alignment and optimized PPEC, certainly on the used market if not retail. I find that as an add on to an EQ6 or similar class mount, the cost of the TDM to be a bit much for my wallet, and I would be better off upgrading to a better mount overall. IMO, that has been the challenge with the TDM technology, It costs a significant fraction of the cost of the mounts its target audience owns.  That said, if I already owned a G11, that equation would very likely change.

Like Bill, I appreciate that Jerry is sharing his results with this technology and never felt he was particularly pushing anything, but rather addressing an interest of mine, that I think is shared more widely than what is recognized.  I also appreciate that the core of the system he is using is a 100% American made product in the G11. It will be interesting to see what fruits are born down the road from this experiment.

Just thinking out loud....

Cheers!

JMD

Eric Castillo

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Re: Losmandy G-11 PMC-Eight w/ Telescope Drive Master - UNGUIDED 600sec image
« Reply #12 on: January 13, 2018, 03:36:03 AM »
If you download and look at the "PMC-Eight Programmer's Reference" you will find that the PMC-Eight command language and firmware/hardware support fine adjustment of the axis rate value to a resolution of 0.04 micro-steps/second. Using the "Set Tracking Rate" command sets the fine rate value". Using the "Set Slew Rate" command sets the course rate value.

To put this in perspective, the Sidereal rate for the G-11 gear scaling is a nominal 53.33 micro-steps/second. This number can be adjusted as needed in the ExploreStars application to set any tracking rate you like. The controller allows you to adjust the fine rate from 0 to 1600.00 micro-steps/second which is equal to 450 arc-seconds/second or 7.5 arc-minutes/second. The motor count scaling for the G-11 is 0.28125 arc-seconds/micro-step, for a total count of 4,608,000 for both the RA and DEC axis.

The course rate setting allows slewing up to 25 times this value, or 3.125 degrees/second on the G-11. So it would support the fine rate control needed to tweak the nominal Sidereal rate due to changes from refractive error or any other analytically derived or measurable error. It is only a "Simple Matter of Programming" (SMoP)

Michael Robinson

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Re: Losmandy G-11 PMC-Eight w/ Telescope Drive Master - UNGUIDED 600sec image
« Reply #13 on: January 13, 2018, 04:47:59 AM »
Quote
The course rate setting allows slewing up to 25 times this value, or 3.125 degrees/second on the G-11. So it would support the fine rate control needed to tweak the nominal Sidereal rate due to changes from refractive error or any other analytically derived or measurable error. It is only a "Simple Matter of Programming" (SMoP)

How hard can that be? It's just typing right?Shawn

Christopher Patel

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Re: Losmandy G-11 PMC-Eight w/ Telescope Drive Master - UNGUIDED 600sec image
« Reply #14 on: January 15, 2018, 11:12:28 AM »
Jerry, I have no doubt this is possible.

I was pointing out that the TDM + variable rate tracking would be <strong class="bbc">way[/b] more useful.

I believe the TDM has a serial port, so the mount computer can talk to it (instead of relying on ST4 inputs from it). So it should be possible to pre-calculate the required tracking rate on the mount computer, then validate (via the TDM) that this tracking rate is being achieved.

Only a matter of programming

Since tracking is at 15 degrees/hour, even if you re-calculate the tracking rate every 5 minutes, that should be plenty. Mel Bartels has a nice simplified equation for determining the refraction-corrected tracking rate.