Topics

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


Walter Vinci
 

Hi Everyone,

I am pretty new to the hobby, jus went out a few times with my EXOS2-GT PMC-eight. My first struggle with this mount was a ~ 3-4" wiggling in RA I could not get rid of. RA basically kept jumping up and down by about that much every few seconds, with and without DEC guiding. Can seeing be so bad to cause that much error? Or is it more likely a mechanical problem with the worm gear? I have attached the PHD2 logs, hopefully it gives some hints and you can help me learn how to diagnose the logs (the logs contain multiple calibration and guiding sections, probably best to have a look at the latest data).

Thank for the help,
Walter


Jerry Hubbell - Explore Scientific VP Engineering
 

Hi Walter,

I am just starting to look at your guide log, but I did notice that your guide camera (an Orion Starshoot Autoguider) with a 5.8 um pixel coupled with your very short focal length guide scope (162 mm) makes you image scale very large at 6.6 arc-sec/pixel. This is a big problem if you are trying to auto guide to < 2-3 arc-seconds and is very difficult to get any better performance. This will especially the case if you seeing is poor. 

I will spend some more time looking at your guide log to see if I see anything else.
--
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
 

Hi Jerry and Walter,
Would it be possible to use a 3X Barlow in the guiding scope to increase the guiding to  the 2 to3 arc-seconds you suggest?
Doug Doonan



-----Original Message-----
From: Jerry Hubbell - Explore Scientific VP Engineering <jrh@...>
To: MAIN@ESPMC-Eight.groups.io
Sent: Tue, Jan 12, 2021 2:11 pm
Subject: Re: [ESPMC-Eight] 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Hi Walter,

I am just starting to look at your guide log, but I did notice that your guide camera (an Orion Starshoot Autoguider) with a 5.8 um pixel coupled with your very short focal length guide scope (162 mm) makes you image scale very large at 6.6 arc-sec/pixel. This is a big problem if you are trying to auto guide to < 2-3 arc-seconds and is very difficult to get any better performance. This will especially the case if you seeing is poor. 

I will spend some more time looking at your guide log to see if I see anything else.
--
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.


Walter Vinci
 

Hi Jerry,

Thanks for looking at the logs. I went for the Orion guiding package because of its popularity. I thought it would be more than enough to guide my ED 80 at a 2 arc-sec/pixel imaging scale, but this seems will not be easy according to your comment.

I should then use a Barlow lens as Doug suggest or use a guiding camera with smaller pixels if I wanted to push guiding to seeing/mount limits?

Walter

On Jan 12, 2021, at 8:35 PM, Doug Doonan via groups.io <dougdwd@...> wrote:


Hi Jerry and Walter,
Would it be possible to use a 3X Barlow in the guiding scope to increase the guiding to  the 2 to3 arc-seconds you suggest?
Doug Doonan



-----Original Message-----
From: Jerry Hubbell - Explore Scientific VP Engineering <jrh@...>
To: MAIN@ESPMC-Eight.groups.io
Sent: Tue, Jan 12, 2021 2:11 pm
Subject: Re: [ESPMC-Eight] 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Hi Walter,

I am just starting to look at your guide log, but I did notice that your guide camera (an Orion Starshoot Autoguider) with a 5.8 um pixel coupled with your very short focal length guide scope (162 mm) makes you image scale very large at 6.6 arc-sec/pixel. This is a big problem if you are trying to auto guide to < 2-3 arc-seconds and is very difficult to get any better performance. This will especially the case if you seeing is poor. 

I will spend some more time looking at your guide log to see if I see anything else.
--
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.


Jerry Hubbell - Explore Scientific VP Engineering
 

Hi Doug,

That would work if you get get the camera to the focus position with the Barlow or tele-extender. I would suggest trying it at 2x instead of 3x.
--
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!


Jerry Hubbell - Explore Scientific VP Engineering
 

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
 

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.


Andreas Volz
 

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


Walter Vinci
 

Thank you all for your help,

I will try switch guiding from my guide scope (162 mm) to my imaging scope (480) and see if guiding improves next time I have clear skies. That will give my a pixel scale of about 2.2 arc-seconds.

Best,
Walter


On Jan 14, 2021, at 11:23 AM, Andreas Volz via groups.io <bassliner303@...> wrote:

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



Harry
 

Doug, here is a table that might help. Otherwise Peter Zelinka on You Tube explains the formula in his video choosing your first dedicated astronomy camera.

--
Harry
Vero Beach, FL

Mounts: ES iExos 100-PMC Eight
Scopes: ES  ED80CF, ES AR102,  Meade ETX 90 EC (Deforked)
Guide: ZWO 30mm Mini, ZWO ASI120MM-Mini
Software: ASIair Pro, iPad Pro, MacOS, Starry Sky Stacker, Affinity Photo, Lightroom,  SkySafari Plus
Cameras: Nikon D600, D5500
Misc: ES USB Power Bank, Rigel QuikFinder, 0.8x Focal Reducer
Filters:  Optolong L-Pro, L-eNhance






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!


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.


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.


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).


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