Date   

Another newbie question on alignment

Parag Modi
 

Hello,

I have a question on how the multi-point alignment transformation is stored.  My setup includes iEXOS-100, POTH hub with ES driver selected and APT.  I'm using just a plain Nikon D7200 with a Sigma 18-300mm lens and no guiding.  I found a cool script in APT that automates a four point alignment.  Basically it moves my camera to four equal points in AZ/ALT, does a platesolve and sync.  I tried that the other night and it seemed to have worked good since my subsequent GoTo moves were pretty close.  My questions are:
1) Where is the alignment information stored and used?  iEXOS firmware?  POTH hub? or APT?
2) Is there a way to view and save this alignment information in between the sessions (over days) if my mount hasn't moved?

--
Parag Modi

Mounts: ES iEXOS-100
Scopes: APS-C Sigma 18-300 mm
Cameras:  Nikon D7200 (Unmodified)
Misc: Bahtinov Mask, K&F Concept Clear night filter
Software: ExploreStars, Stellarium, APT


locked Re: Connecting EXOS 2 PMC 8 to ASIair Pro #EXOS2 #TECHNICAL

Steve Siedentop
 

Hi Steve -

This is a good place to start.

https://espmc-eight.groups.io/g/MAIN/files/User%20Contributions/iExos%20and%20AsiAir%20-%20Getting%20Started%20Guide%20-%20Aug%2021,%202020.pdf

-Steve
--
Mounts: ES PMC-8 G11 with Ruland Couplers and One Piece Worm Blocks, Skywatcher NEQ-6
Scopes: ES ED127CF FCD100, Orion 6” Mak, Stellarvue SV80EDT, Coronado Solarmax 40
Cameras:  CentralDS CDS-600, CentralDS Astro 60D, Orion Starshoot SSAG
Msc: Moonlite Focusers, Astrozap Dew Straps, Pegasus Ultimate PowerBox
Software: PixInsight, Cartes du Ciel, BackyardEOS, SkySafari


Re: #ASCOM #ASCOM

Jeff Snell
 


Hi Tim,
I had slewing issues when I upgraded last week but slightly different.  I lost pulse guiding for PHD2 and the slow speed slew in CdC (.2083) wouldn’t work.  ASCOM Device Hub may be the issue.  Jerry H stated he wasn’t having any issues but that when he upgraded, he selected the option to keep POTH hub in the download.  I uninstalled 6.5, found an old 6.0 version on line, and reinstalled to get POTH back.  Then I reinstalled 6.5 and elected to keep POTH hub in the download.  All is well now...

Hope this helps.

Jeff

EXOS II GT/PMC-Eight, iOptron Skytracker
ESED80mm APO, Celestron 8” Edge HD, TPO Ultrawide
Polemaster, Canon T5i (modified), ZWO ASI 183mm Pro, Orion 50mm Guidescope
Lenovo Thinkpad 11e, 7 Port USB Hub
ASCOM (using POTH Hub), CdC, PHD2, APT, Backyard EOS
Processing w/Deep Sky Stacker, Photoshop (w/Astrophotography Plug-ins)


On Jan 16, 2021, at 9:05 PM, Tim Huseby <Photographybytjh@...> wrote:

Im not sure if this is the correct place to ask this, I finally upgraded to ascot 6.5 sp1 and am having strange behavior when slewing my mount Exos2-gt pic-8. When I was slewing last night trying to use my PoleMaster for polar alignment. when I said slew east the my scope and camera moved west, I would;d select east again and about 99% of the time it would go west and every blue moon it would go back to the east. I am puzzled and scratching my head. I have looked at all the places to put my location in and I think they are correct. Has anyone else had this issue or have suggestions. I did a complete uninstall and re install of ascom but have not had a chance to test it yet.
--
Tim
Las Vegas
Just starting in this Hobby, I have been doing wildlife and landscape photography. 
Mounts
Exos2-gt  PMC-8, Celestron Alt/Azimuth 

Scopes/Lenses:
Celestron SLT 130, William Optics Star 71II  apo, Olympus 7-14,12-40,40-150 Pro 

Cameras: 
Olymous om-d E-M5 Mkii, SBOG STF8300M


Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Jennifer Shelly
 
Edited

Walter:

You may want to check out this website that has astronomy related calculations.  

 

--
Sincerely,

Jennifer Shelly
AstroPorch, VA

Mounts
: ES PMC-8 G-11, ES PMC-8 iEXOS-100
Scopes: ES ED127 FCD-100, Askar FRA 400, ES Levy Comet Hunter, ES N208CF, QHY Mini Guide Scope, Solomark F60 Guide Scope
Cameras: QHY600M, QHY128C, QHY168C
Misc: MoonLite CFL 2.5 / High Res Stepper / V2 Mini Controller, Baader SteelTrack NT / SteelDrive II, Baader UFC, Optolong 2" L-Pro / L-eNhance, QHY CFW3-L, Baader 2” LRGBSHO CCD
Imaging Software:  NINA, APT, SharpCap Pro
Processing Software: PixInsight, Lightroom, Premiere Elements


#ASCOM #ASCOM

Tim Huseby
 

Im not sure if this is the correct place to ask this, I finally upgraded to ascot 6.5 sp1 and am having strange behavior when slewing my mount Exos2-gt pic-8. When I was slewing last night trying to use my PoleMaster for polar alignment. when I said slew east the my scope and camera moved west, I would;d select east again and about 99% of the time it would go west and every blue moon it would go back to the east. I am puzzled and scratching my head. I have looked at all the places to put my location in and I think they are correct. Has anyone else had this issue or have suggestions. I did a complete uninstall and re install of ascom but have not had a chance to test it yet.
--
Tim
Las Vegas
Just starting in this Hobby, I have been doing wildlife and landscape photography. 
Mounts
Exos2-gt  PMC-8, Celestron Alt/Azimuth 

Scopes/Lenses:
Celestron SLT 130, William Optics Star 71II  apo, Olympus 7-14,12-40,40-150 Pro 

Cameras: 
Olymous om-d E-M5 Mkii, SBOG STF8300M


Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Leigh Caldwell
 

That's just a scale/unit conversion - the number of arcseconds in a degree (3600) divided by the number of microns in a mm (1000).


Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Doug Doonan
 

Hi Bassliner,
Thanks for the info.
And where does the 3.6 come from?
Doug Doonan



-----Original Message-----
From: Andreas Volz via groups.io <bassliner303@...>
To: MAIN@espmc-eight.groups.io
Sent: Thu, Jan 14, 2021 1:23 pm
Subject: Re: [ESPMC-Eight] 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Hey Doug,

The formula is:
pixel size (microns) x 206.3 /focal length in mm = image scale in arcsec/pixel

206.3 results out of:
3.6 * (180 degrees / pi) = 3600/1000 * (180 degrees / pi) = 206.26

Doug Doonan via groups.io <dougdwd=aol.com@groups.io> schrieb am Do., 14. Jan. 2021, 19:09:
Jerry,
Where does the 206.3 in your formula come from, and what are its units?
Doug



-----Original Message-----
From: Jerry Hubbell - Explore Scientific VP Engineering <jrh@...>
To: MAIN@ESPMC-Eight.groups.io
Sent: Wed, Jan 13, 2021 8:34 am
Subject: Re: [ESPMC-Eight] 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Hi Walter,

Yes, I would suggest a 2x Barlow or tele-extender instead of a 3x. The formula for pixel or plate scale is:

Pixel Scale = (Pixel Size x 206.3) / FL, So for your combination: Pixel Scale = (5.2 um x 206.3) / 162 mm = 6.6 arc-seconds/pixel

BTW,  your calibrations look spot on, no problem there,
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


--

Doug Doonan
HomeBru  6 inch Reflector  f 6.6
HomeBru  85 mm Refractor  f 5.6
PMC-8, EXOS 2
Long retired EE.

--
Clear skies,
Andy

Mount: ES PMC-8 EXOS2, ioptron SkyGuider Pro
Scope: SkyWatcher Explorer 150/750 PDS
Cameras: Canon 6D, Canon 7D Mk2
Guiding: ZWO ASI120Mini mono, ZWO 30F4 Guidescope, PHD2
Msc: TS Optics Coma Reducer Corrector 0.95x
Software: N.I.N.A, APT, Pixinsight, DeepSkyStacker, Photoshop

--

Doug Doonan
HomeBru  6 inch Reflector  f 6.6
HomeBru  85 mm Refractor  f 5.6
PMC-8, EXOS 2
Long retired EE.


Re: How to change window size in ASCOM Device Hub? #ASCOM

Marcin Mieszczuk
 

Hi Jerry,

thanks for the information. I will post the question there.

Regards, M.


Re: How to change window size in ASCOM Device Hub? #ASCOM

Jerry Hubbell - Explore Scientific VP Engineering
 

Hi Marcin,

You can find help about the ASCOM Platform and applications (such as Device Hub) on the ASCOM Platform Help Groups.io forum
Help@ASCOMTalk.groups.io | Home

They are a great resource for everything ASCOM
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


How to change window size in ASCOM Device Hub? #ASCOM

Marcin Mieszczuk
 

Hello,

I have upgraded my ASCOM environment to 6.5SP1 and have started using Device Hub instead of POTH. Everything seems to work fine but I have an issue with window size of the application. In Windows 8.1 (1920x1080 resoution) the application opens in the window that is too small to see all the options (eg. Other Actions on "Motion" tab or coordinates' input boxes on "Direct slew" tab).

Does anyone know how to change the size of the application window (I can't figure out how to contact the developer)?

Regards,

Marcin


Re: Occasional erratic behaviour when slewing EXOS2 #EXOS2

Wes Mcdonald
 

Unpowered hubs are notorious for this kind of behavior.  Good this time, not the next.  
Wes

--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


Re: Occasional erratic behaviour when slewing EXOS2 #EXOS2

Leigh Caldwell
 

Thanks for the suggestion Wes - I think time and location are all aligned but I will check.

And I'm sure you're right on the hub, Bob. I got this one because I wanted one less device to draw power if I take the mount away from home. But I do get issues with it, e.g. if I plug in a camera partway through a session, the computer often loses its connection to the mount. A powered hub is one of several items on the shopping list...


Re: Astrophotography Done with the iEXOS-100, EXOS 2, and G11 Post your Pictures and Details! Lets Show What These Mounts Can Do. #G11 #astrophotography #iEXOS-100 #EXOS2

Wes Mcdonald
 

Parag

Yes, there are no limits built into the driver, unless you do a goto.  The driver will slew you around correctly according to the need to do a meridian flip.  But it will allow you to track through meridian, which on the 100 is not a problem I don't think except maybe for balance.  At least not at first.
Can't say why.  Don't know about POTH, but expect not.

Wes.




--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


Re: Occasional erratic behaviour when slewing EXOS2 #EXOS2

Wes Mcdonald
 

Leigh:

Sounds like time or location or both are off for stellarium and ascom driver.  Make sure stellarium location and time are same as the ASCOM driver location.

Wes.


--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Doug Doonan
 

HI Jerry,
This straightens me out on the formula and how it works. Pretty neat. Also, thanks for the chart. It will be handy in my set-up.
Boy, all I can say is that this astronomy stuff is complicated, and people have done the math to analyze it.
Doug D.
 



-----Original Message-----
From: Jerry Hubbell - Explore Scientific VP Engineering <jrh@...>
To: MAIN@ESPMC-Eight.groups.io
Sent: Thu, Jan 14, 2021 1:59 pm
Subject: Re: [ESPMC-Eight] 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

There are 206265 arc-seconds per radian so the formula is the conversion between an angular value to a linear scale at the image plane. The value is 206.3 (rounded 206.265) because of the FL being in mm and the pixel size being in um (microns) a 1000:1 ratio.

I hope that makes sense.
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


--

Doug Doonan
HomeBru  6 inch Reflector  f 6.6
HomeBru  85 mm Refractor  f 5.6
PMC-8, EXOS 2
Long retired EE.


Re: Occasional erratic behaviour when slewing EXOS2 #EXOS2

 

Leigh,

Whatever else is going on, you might want to pre-emptively switch that unpowered USB hub out for a powered one...
Lots of tales of woe over on CloudyNights from folks who experienced various forms of flakiness from unpowered hubs, remedied by switching to powered.
 
FWIW...

- Bob 

On Thu, Jan 14, 2021, at 16:37, Leigh Caldwell wrote:
Hi all

Thanks for the always-interesting discussions in this forum! I am a relative beginner but starting to get the hang of the PMC-8 EXOS2 mount and my imaging setup.

Occasionally, I will press the slew button (in Stellarium, connected to ASCOM Device Hub) and the mount seems to go off on a journey to nowhere. Most recently, I tried to slew from M42 to Mars and the mount started turning on DEC axis, no movement at all in RA, and kept going and going, I'd guess 240 degrees of motion until the scope was almost pointing at the floor. At first I thought it was just going around the meridian in a roundabout way, but at some point I realised it was all going wrong and managed to stop it manually. (The objects may have been on opposite sides of the meridian - I didn't notice at the time but it's plausible given when this happened). The RA clutch was tightened normally and slewing had been working fine a little earlier (and tracking correctly too).

On two or three earlier occasions, I started out with an approximate slew to a target, then identified the actual location I ended up pointing at, and used the Sync button in Stellarium to sync the mount. I then attempted to slew by no more than 5 degrees to get to my original target, and the mount went on a trek halfway across the sky until I stopped it manually. On that occasion I didn't notice whether it was the DEC motor, RA or both that were moving.

I do have a challenge with a very restricted viewing angle in my location (a south-facing balcony in London) which means I can't do an accurate polar alignment nor a 2- or 3-star alignment, so I have to rely on either the sync in Stellarium or plate solving in Sharpcap. I have previously managed to do a polar alignment from a different location and locked the Alt levers in a good position, and by carefully measuring out my Az angle and mount position I think I have got an acceptable PA - my tracking is good enough for 30-second shots at 1000mm focal length. But is it possible that not doing a proper star alignment has confused either the ASCOM driver or the mount electronics?

Most of the time everything works fine (especially now that I got Sharpcap plate solve working), it's only occasionally that it shows this bizarre behaviour. Has anyone seen something like this happening?

I am not sure if I have any ASCOM or Stellarium logs from these events, but if that would be useful I'll make sure logging is turned on and post them if this happens again.

Other info:
 - Mount is on AC power
 - Connected to PC via serial through an unpowered USB hub
 - Sky-Watcher 200PDS scope (f/4.9)
 - ZWO ASI294MC-Pro
 - PHD2 + Mini Astro Essentials guide scope with Altair GP-CAM 290C guide camera (although I was not guiding when this happened)
Total equipment weight is somewhere around 10kg/22lbs which I think should be OK on this mount?

(I have a different problem with guiding and a few mm of wiggling in RA but I'll leave that for another post!)

Thanks for any advice you can give (even if it's just "don't worry about it, these things happen")
     Leigh.


--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2 290M
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


Occasional erratic behaviour when slewing EXOS2 #EXOS2

Leigh Caldwell
 

Hi all

Thanks for the always-interesting discussions in this forum! I am a relative beginner but starting to get the hang of the PMC-8 EXOS2 mount and my imaging setup.

Occasionally, I will press the slew button (in Stellarium, connected to ASCOM Device Hub) and the mount seems to go off on a journey to nowhere. Most recently, I tried to slew from M42 to Mars and the mount started turning on DEC axis, no movement at all in RA, and kept going and going, I'd guess 240 degrees of motion until the scope was almost pointing at the floor. At first I thought it was just going around the meridian in a roundabout way, but at some point I realised it was all going wrong and managed to stop it manually. (The objects may have been on opposite sides of the meridian - I didn't notice at the time but it's plausible given when this happened). The RA clutch was tightened normally and slewing had been working fine a little earlier (and tracking correctly too).

On two or three earlier occasions, I started out with an approximate slew to a target, then identified the actual location I ended up pointing at, and used the Sync button in Stellarium to sync the mount. I then attempted to slew by no more than 5 degrees to get to my original target, and the mount went on a trek halfway across the sky until I stopped it manually. On that occasion I didn't notice whether it was the DEC motor, RA or both that were moving.

I do have a challenge with a very restricted viewing angle in my location (a south-facing balcony in London) which means I can't do an accurate polar alignment nor a 2- or 3-star alignment, so I have to rely on either the sync in Stellarium or plate solving in Sharpcap. I have previously managed to do a polar alignment from a different location and locked the Alt levers in a good position, and by carefully measuring out my Az angle and mount position I think I have got an acceptable PA - my tracking is good enough for 30-second shots at 1000mm focal length. But is it possible that not doing a proper star alignment has confused either the ASCOM driver or the mount electronics?

Most of the time everything works fine (especially now that I got Sharpcap plate solve working), it's only occasionally that it shows this bizarre behaviour. Has anyone seen something like this happening?

I am not sure if I have any ASCOM or Stellarium logs from these events, but if that would be useful I'll make sure logging is turned on and post them if this happens again.

Other info:
 - Mount is on AC power
 - Connected to PC via serial through an unpowered USB hub
 - Sky-Watcher 200PDS scope (f/4.9)
 - ZWO ASI294MC-Pro
 - PHD2 + Mini Astro Essentials guide scope with Altair GP-CAM 290C guide camera (although I was not guiding when this happened)
Total equipment weight is somewhere around 10kg/22lbs which I think should be OK on this mount?

(I have a different problem with guiding and a few mm of wiggling in RA but I'll leave that for another post!)

Thanks for any advice you can give (even if it's just "don't worry about it, these things happen")
     Leigh.


Re: Astrophotography Done with the iEXOS-100, EXOS 2, and G11 Post your Pictures and Details! Lets Show What These Mounts Can Do. #G11 #astrophotography #iEXOS-100 #EXOS2

Parag Modi
 

Wes,

I don't use auto meridian flip feature of ATP and therefore should have continued tracking (in fact it executed my full 75 image plan as expected).  When I platesolve the last 20 images, they are just left of the meridian.  According to APT Forums, there maybe some safety limits active in the software downstream.  I looked at POTH HUB settings and PMC-8 ASCOM driver settings and did not see anything that resembles a safety limit.
--
Parag Modi

Mounts: ES iEXOS-100
Scopes: APS-C Sigma 18-300 mm
Cameras:  Nikon D7200 (Unmodified)
Misc: Bahtinov Mask, K&F Concept Clear night filter
Software: ExploreStars, Stellarium, APT


Re: Slew Speed while using Stellarium (Serial) #ASCOM #EXOS2

Wes Mcdonald
 

I see.  WEll perhaps Jerry would consider having a "quiet" mode slew.  But honestly, the sound is low enough that in my experience, the sound is compatible with star parties.

Slewing more quietly though implies a bit slower, so you have that aspect to consider.

Wes.



--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Jerry Hubbell - Explore Scientific VP Engineering
 

There are 206265 arc-seconds per radian so the formula is the conversion between an angular value to a linear scale at the image plane. The value is 206.3 (rounded 206.265) because of the FL being in mm and the pixel size being in um (microns) a 1000:1 ratio.

I hope that makes sense.
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!

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