David's Astronomy Pages Notes - Session 598.2 (2016-12-30)

Notes (S598.1)

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Notes (S598.3)

	2017 Equipment Plans
	New Equipment Plan for 2017
	Planetary Camera Selection  (ZWO ASI178MC)
	Guide/Imaging Scope Selection (TS Optics 80mm f/6 FPL53 Triplet APO)
	Image Capture / Processing Software

New Equipment Plan for 2017

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 Planetary Camera Selection (ZWO ASI178MC)

- Proposed Camera Use
- Selected Camera (ZWO ASI178 MC)
    Pros / Cons
    Risks & Uncertainties
- Other Options Considered
- Specifications
- Image Scale & FOV
- Links

4)  Medium Field Deep Sky Colour Imaging through 80mm APO refractor, piggy-backed on LX200 SCT
     with option for autoguiding with ST-10 camera through LX200

     Key criteria:
     - small light camera (no filter wheel)
     - high resolution (ie small photosite with good match to 80mm f/6, 1.03 arc sec/pixel )
     - large FOV for imaging extended deep sky objects,  comets, moon etc
     - robust & rigid connection between APO scope and LX200
     - supported by good image capture and processing software

5)  Wide Field Deep Sky Colour Imaging through through Canon camera len(s) piggy-backed on LX200 SCT.
     with option for autoguiding with ST-10 camera through LX200

     Key criteria:
     - small light camera (no filter wheel)
     - high resolution
     - large FOV for imaging extended deep sky objects,  comets, conjunctions etc
     - robust & rigid connection between Camera Mount and LX200
     - supported by good image capture and processing software

6) Super-finder using eithe

7)  AllSky Colour Imaging using 150-170 deg fisheye lens supplied with ZWO camera

    Key criteria:
     - small light camera (no filter wheel)
     - single shot colour camera with good ADC/dynamic range and high resolution

8) Colour Imaging of Stars and Deep Sky Objects through old  8" LX200 Classic

    Key Criteria:
    - small light USB camera (replacing old parallel port ST-7 camera)

Other Options Considered

Monochrome Camera:   ASI 178MM (the monochrome version of the ASI 178MC camera) costs £378 (vs £344), and would require extra costs for ZWO's 5 position electronic filter wheel (£175, 300g) and an LRGB filter set (£72)

Cooled Camera:   ASI178 MC-Cool (the cooled version of the ASI 178MC camera) costs £727 (vs £344), weighs 410g (vs 120g),  is x cm longer, and requires an extra 12V power supply for cooling operations. 

Alternative ZWO colour cameras:  Other colour cameras in the ZWO range where rejected for a number of reasons:
  - ASI034 MC, £112, 8 bit, 5.6 µm, USB2  - rejected due to small chip size, low resolution, lower ADC & absence of USB 3
  - ASI120 MC, £199, 12 bit, 3.75 µm, 4.8 x 3.6mm, USB 3 - rejected due to small chip size/small FOV & lower ADC 
  - ASI224 MC, £268, 12 bit, 3.75 µm, 4.8 x 3.6mm, USB 3 - rejected due to smaller chip size/smaller FOV & lower ADC,
    IR cutoff not built in (+/-)
  - ASI290 MC, £297, 12 bit, 2.9 µm, 5.6 x 3.2mm, USB 3 - rejected due to smaller chip size/smaller FOV & lower ADC,  IR cutoff not built in (+/-)
  - ASI185 MC, £298, 12 bit, 3.75 µm, 7.3 x 4.6mm, USB 3 - rejected due to lower resolution & lower ADC
  - ASI178 MC, £377, 14 bit, 2.40 µm, 7.4 x 5.0mm, USB 3 - selected camera (for info)
  - ASI174 MC, £615, 12 bit, 5.86 µm, 11.3 x 7.1mm, USB 3 - rejected due to lower resolution,  lower ADC & cost
  - ASI1600 MC, £717, 12 bit, 3.80 µm, 17.7 x 13.4mm, USB 3 - rejected due to lower ADC, cost & potential vignetting (large chip)

Prices at Dec 2016 on First Optics Website ( https://www.firstlightoptics.com/zwo-cameras.html), prices went up on 1st Jan 2017.

Alternative Makes: 
 - QHY5III 178 C (uses the same sony chip as the ASI178 MC) - around same price (£347 vs £344), but offers anti amp-glow control function, supposedly better passive cooling, and slightly wider exposure range, 9 µs to 1200s).  Some people have reported problems with QHY drivers /cameras.

Camera Specifications / Technical Data

Specifications of the ZWO ASI178MC camera are listed here for information. 
(for definitive specifications please visit the ZWO website (see ZWO Links) or the  ZWO ASI 174 Manual )

 

Parameter Name		Parameter Value
Sensor		1/1.8” CMOS IMX178 cm
Resolution		6.4 Mega Pixels 3096*2080
Pixel Size		2.4µm
Sensor Size		7.4mm*5mm
Diagonal		8.92mm
Exposure Range		32µs-1000s
ROI Support		Yes
ST4 Guider Port		Yes
Focus Distance to Sensor		12.5mm
Shutter Type		Rolling Shutter
Protect window		IR-CUT window
Operating System Compatibility		Mac, Windows, Linux
Interface		USB3.0/USB2.0
Bit rate		14bit output(14bit ADC)
Focuser		135 mm from the 2" connection and 170 mm from the female M63 thread
Adaptor		2" / 1.25" / M42X0.75
Dimension		75 mm
Weight		120g or 4.2 ounces (without lens)
Working Temperature		-5°C—45°C
Storage Temperature		-20°C—60°C
Working Relative Humidity		20%—80%
Working Relative Humidity		20%—80%
More Specs on ASI178
Full Well Depth		15,000e (at 0 amplifer gain)
Largest Value with 14bit		Largest Value with 14bit (2^14) = 16384
Unity Gain		-15 (estimated from ASI178 graph)
Gain at 0db		0.9e/ADU (estimated from ASI178 graph),    0.916e/ADU from 15000/16384
Camera Gain		0 (0dB) : 0.9e/ADU
		100 (10dB) : 0.28e/ADU
		200 (20dB) : 0.10e/ADU

Image Scale and FOV

Scale and Field Of View of images taken with ZWO ASI178MC camera through different scopes/lenses are listed below.
(Rows are ordered from shortest to longest focal length, i.e. from wideest view to narrowest view)

Links

ZWO Website (Chinese) : http://zwoasi.com/
ZWO Website (English) : https://astronomy-imaging-camera.com/

ZWO Supplier UK: https://www.firstlightoptics.com/zwo-cameras.html

ZWO Users Forum: http://zwoug.org/  - broken ?

Sam at ZWO :   sam.wen(at)zwoptical.com

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Guide/Imaging Scope Selection (TS Photoline 80mm f/6 FPL53 Triplet APO)

- Proposed Scope Use
- Selected Scope  - TS Photoline 80mm f/6 FPL53 Triplet APO
    Pros / Cons
    Risks & Uncertainties
- Other Scopes Considered
- Other Guiding Setups Considered
- Proposed Mount
- Telescope Specification
- Image Scale & FOV
- Links

Proposed Scope Use

The scope is intended to have a dual role as

1) a guidescope and
2) an alternative imaging scope with a medium field of view.

Both roles would use ZWO ASI178MC as the principal camera when it's not in use for Planetary/Lunar or other imaging through the 12" LX200R main scope. The scope would have a number of other potential uses as well.

1)  Guidescope for 12" LX200R main scope

     Key criteria:
     - reasonably fast scope (~ f/6)  and moderate focal length (~480-500mm) with an image scale (~ 1arc/sec)
       suitable for successful guiding of main scope operating at focal length of 3048mm
     - sufficient field of view with ZWO ASI178MC camera to find a good (sufficiently bright) guide star
     - reasonably small/light (~ 80mm aperature)
     - can be piggy-backed on 12" LX200R without passing andy weight constraints and with impacting tracking on the main scope
     - connection between guidescope / guidecamera and LX200 main scope /ST10 imaging camera is robust & rigid
       (ie no flex between guide and imaging sensors)    
     - easy and quick to put on/take off scope from the 12" LX200
       (there isn't room between top of 12" LX200 and the observatory roof to allow a permanent attachment of the guidescope)
     - good polar alignment.
     - guiding is supported by good guiding software
     - ideally the setup will allow adjustments to be able to centre the guide camera view on the imaging camera (main scope) view
     - an arrangement that can allow auto-guiding on a comet nucleus being imaged in main scope.

2) An alternate imaging scope with ZWO ASI178MC camera
     (for extended objects (larger than FOV of 12" LX200R + ST-10), fullmoon lunar imaging,
     and objects benefitting from single shot colour imaging)

     Key criteria:
      - good quality optics
      - apochromatic / very good color correction
      - no flex between the camera on alternate imaging scope and the ST-10 camera on 12" LX200R main scope
       (for cases where LX200R + ST10 is being used to autoguide the imaging on the smaller scope.
      - a reasonably flat field (camera sensor is reasonably small and doesn't challenge the extremes of the scope's
        field of view when centered, but  camera may be placed off-axis for either guide star finding or to colliminate
        centre of view with than in the main scope)

     Other variations on an imaging role is using the scope with a DLSR (Canon EOS 400D (=Digital Rebel XTi ))
    or a future Cooled CMOS camera with a larger sensor  to obtain a wider imaging view.  
    A good flat field (astrograph quality) would be very desirable for this.  
    Potential also to use the scope for white light observations of Sun/Sunspots (with suitable Mylar filters).

3) A super-finder (to aid star centering, understand pointing issues and help locate comets or lunar features)

    Key criteria:
     - moderate focal length (480-500mm) to provide a c. 1 deg field of view through camera
     - scope/camera is setup to centre the guide camera view on the imaging camera (main scope) view

4) Visual observing scope (providing an alternative or break from permanent imaging with LX200R main scope).  

   Key criteria:
      - good quality optics
      - can be used with existing variety of eyepieces
      - potential to be taken and used on a standalone tripod system

Selected Scope - TS Photoline 80mm f/6 FPL53 Triplet APO

Pros
- Apochromatic
  > High-quality Photoline Triplet APO with FPL53 element from Ohara (Japan)
  > Reasonable price compared to more expensive ADO alternates
- Suitable Aperature, Focal Ratio and Focal Length for intended uses
   > 80mm aperture, f/6 and 480mm focal length
   > provides 1 arcsec/pixel when used with ZWO ASI178MC camera at 1x1 binning
- Good Focuser
   > Rack-and-pinion focuser, plain bearing mounted.
   > The support is decoupled from the drawtube drive   
   > Oversized drawtube with 60 mm clear aperture capable of full illumination with full-frame sensors
   > 1:10 dual speed system for ultra-precise focusing
   > Option to mount imaging train directly to focuser using M63 connection, rather than 2" connection with knurled screw

Cons
- As supplied the field is not corrected to keep stars nicely round to the edge of the view - a typical consequence of any fast refractor
  (options exist for 2" or 2.1/2" field correction at an additional cost and with/without focal reduction)

Risks & Uncertainties
- the precise connection to be used between TS 80mm f/6 Triplet APO and the 12" LX200R is not yet finalised.  The TS 80mm f/6 is supplied with high-quality CNC rings and GP style dovetail bar.   The dovetail with be replaced with connection to a planned Losmandy style dovetail bar sitting on the 12" LX200R main scope, but it is not clear what is required to achieve a two bolt connection for each ring (Losmandy / ADM dovetail clamps have 0.5" hole spacing whilst the ring tube is likely to have metric hold spacings)
[ Mitigation is to delay choosing final connection until the CNC rings supplied with scope can be assessed ]

- flex between the guidescope / guidecamera and LX200 main scope /ST10 imaging camera is too high and doesn't provide successful autoguiding for long exposures with the main scope camera (or vice versa). Main risk is probably in the flex in the imaging train on the main scope (heavy CCD camera, filter wheel and AO7 unit, 2" connection with focusser)
[ Mitigation is to use rigid tube rings and heavy duty Losmandy dovetail for connection between guidescope and main scope, double bolt connection between rings & clamps and willingness to experiement / optimise the imaging train on the LX200 to reduce flex(e.g remove A07 unit, use of alternate, self centering compression connectors)

- it is difficult to connect / disconect the TS 80mm f/6 Triplet APO from LX200 in cold & dark
[ Mitigation is to use clamps with large knurled knobs ]

- the TS 80mm f/6 Triplet APO is left piggy back on the LX200R main scope when the observatory roof is closed, resulting in equipment damage. Roof closure is manual but potentially subject to human error, e.g a desire to quickly shut roof if it starts to rain ]
[ Mitigation : adherance to procedure and instill a habit of visual check before final roof closure ]

- the guidescope view can not or cannot easily be centred on the view through the main scope (desirable for certain functions & uses).  This risk is increased by using circular tube rings rather than 3 point tube rings (the latter being unsuitable given the need to put on/take off the secondary scope each session, and the need to have a firm connection between the two scopes for autoguiding.
[ Mitigation is to use a X/Y positional adjuster, and for this purpose the Orion X-Y Guide Star Finder is the chosen solution ]

- although the sensor on the ZWO ASI178MC is of reasonable size compared to many alternative planetary cameras and the focal length of the secondary scope (480mm) is reasonably short, there is a risk that a suitable guide star can not always be found (either too dim or compromises framing on the main imaging camera  (the choice of guide stars with a secondary scope setup is still a lot higher than using the ST-10 secondary guide CCD or an off-axis guide scope)
[ Mitigation is to use a X/Y positional adjuster, and for this purpose the Orion X-Y Guide Star Finder is the chosen solution ]
 
Whilst adjustment can be done with Orion X-Y guide Star Finder without effecting focus the adjustment has to be done manually which requires going out to the observatory/scope ]

- Use of Orion X-Y guide Star Finder introduces flex into the guiding setup.  Risk is low based on reading other users reports online

Online scratch notes:  "My Nikon pixel sizes are 3.9 micron.  The diffraction spot size of the SV80ST with 0.8 reducer is ~5 microns.  That's a good match.  With your 4.3 micron pixel size, that's even better.  Given seeing and tracking, I really don't see how you could get to an under sample condition. "

Other Scopes Considered

   - ASI034 MC, £112, 8 bit, 5.6 µm, USB2  - rejected due to small chip size, low resolution, lower ADC & absence of USB 3
  - TS Photoline ASI120 MC, £199, 12 bit, 3.75 µm, 4.8 x 3.6mm, USB 3 - rejected due to small chip size/small FOV & lower ADC 
  - ASI224 MC, £268, 12 bit, 3.75 µm, 4.8 x 3.6mm, USB 3 - rejected due to smaller chip size/smaller FOV & lower ADC,

Other Guiding Setups Considered

To be written..

Other GuideScope Alignment Options Considered

To be written..

Telescope Specifications

Specifications/technical data for the TS Photoline 80mm f/6 telescope (with 2.5" RAP Focuser) are listed here for information. 
 
For definitive specifications please visit the TS PHOTOLINE 80mm f/6 FPL53 Triplet APO page on the Teleskop Service website.

Other spec on Stellarvue site for

- Tube Rings:  Stellarvue R90SET precision hinged rings.
  Each ring has five 1/4-20 holes top and bottom with one in the center and two spaced 1.5” and 60mm apart.
  Rings on the SV80ST2 have a height of 4 3/4 inch, measured between the two flat sides, one of which is where
  you attach a dovetail.  The maximum width is 5 inches.
  The 1/4-20 mounting screws that Fred refers to applies to all of our clamshells and telescopes that are 5 inch or larger.
  Dual ring mounts for telescopes of less than 5 inch (80 mm - 115 mm) use metric M6 X 1 screws,
  not 1/4-20. We used 6 mm threaded holes on these smaller dual rings since we used to sell the M4 mount that
  came with 6 mm screws. Just FYI

 
- Light Gain:  131x (human eye = 1)
- Theoretical Resolution :  1.5 arc sec (Dawes Limit)
- Weight :  The optical tube assembly weighs about 5.8 lbs. The dual rings weigh about 1.2 pounds total.

Image Scale and FOV

Scale and Field Of View of images taken with ZWO ASI178MC camera through different scopes/lenses are listed below.
(Rows are ordered from shortest to longest focal length, i.e. from wideest view to narrowest view)

Airy Disk Diameter

(from Wilmslow Astro Useful  Formula: http://www.wilmslowastro.com/software/formulae.htm )

Autoguide rates

Using TS Photoline 80mm f/6 (480mm focal length) and AS178MC camera (2.4um)

		Autoguide Rate in pixels/sec
Declination		at Guide Rate   x0.50
0		7.29
10		7.18
30		6.31
45		5.16
60		3.65
75		1.89

Critical Focus Zone

Critical focus zone (length of the zone in which the focused image of a star is smaller than the size of its Airy disk) is around 0.1mm wide using TS Photoline 80mm f/6 & ASI178MC camera.  Fine focusing is therefore important for achieving best quality images.
 
(This compares to a critical focus with of 0.25mm using LX200 F/10)

		Colour		Critical Focus Zone
Configuration		Colour Name	Wavelength (nm)	microns		mm
TS Photoline 80mm f/6		Red	650	114		0.11
		Green	510	90		0.09
		Blue	475	83		0.08
TS Photoline 80mm f/4.74		Red	650	71		0.07
(f/6 x0.79)		Green	510	56		0.06
		Blue	475	52		0.05

Using TS Photoline 80mm f/6 (480mm focal length) and AS178MC camera (2.4um)

		Autoguide Rate in pixels/sec
Declination		at Guide Rate   x0.50
0		7.29
10		7.18
30		6.31
45		5.16
60		3.65
75		1.89

Links

Teleskop Service Website (English) : http://www.teleskop-express.de/shop/index.php/language/en
Teleskop Service Telescopes (English) : http://www.teleskop-express.de/shop/index.php/language/en/cat/c4_telescopes_for_astronomy.html

Telescope's web page:  TS PHOTOLINE 80mm f/6 FPL53 Triplet APO page (Teleskop Service website)

Stellarvue Telescope Forum: https://groups.yahoo.com/neo/groups/Stellarvue/info

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Planetary Image Capture / Processing Software

Whilst looking into the software that I could potentially use for capturing and processing images with Zwo camera (including software especially helpful for planetary images) I created the following list - valid as at Jan 2017.  
Of these the only ones that I had used before were RegiStax and CCDSoft.

Please note that the list is not necessarily or intended to be a complete list of all available software.

(Notes made whilst using some of these programs in 2017 with ZWO ASI178MC camera & its acquired images can be found here.)

Free Software - Image Acquistion
- SharpCap, Vn 2.9 (http://www.sharpcap.co.uk/) - Image acqusition incl. ZWO
- Firecapture, Vn 2.5, 64 bit  (http://www.firecapture.de/) - Image acqusition incl. ZWO
- AstroLive  (http://astrolive.io/astroliveusb.html) - Free Version for ZWO cameras only

Free Software - Autoguiding
- PHD 2, Vn 2.6.2 (http://openphdguiding.org/) - Autoguiding
- MetaGuide, Vn 5.2.9 (http://www.astrogeeks.com/Bliss/MetaGuide/) - Autoguiding

Free Software - Processing
- SER Player, Vn 1.6.0 (https://sites.google.com/site/astropipp/) - SER viewer and processing
- FITS Image Grader (http://mainsequencesoftware.com/Products/ImageGrader), FITS review/grading
- DeepSkyStacker, Vn 3.3.2  (http://deepskystacker.free.fr/english/index.html), includes 'DeepSkyStacker Live'
- PIIP, Vn 2.5.8, 64 bit (https://sites.google.com/site/astropipp/)  - Pre-processing planetary images and general image conversion
- AutoStakkert, Vn 2.6.8 (http://www.autostakkert.com/) - Planetary processing
- RegiStax, Vn 6.1 (http://www.astronomie.be/registax/) - Alignment/stacking/processing of images
- WinJUPOS, Vn 10.3.1  (http://jupos.privat.t-online.de/) - Planetary/Solar Surface Position Mapping, Measurement & Computation

- GIMP 2, Vn 2.8.18 (https://www.gimp.org/) - Image manipulation
- Regim, Vn 3.4 (http://www.andreasroerig.de/regim/regim_e.htm) - Image Processing

Free Software - PEC
- PECprep, Vn 2.03 (http://eq-mod.sourceforge.net/pecprep/)  - PEC analysis.

Free Software - Planetarium
- Stellarium, Vn 0.15.1.1 (http://www.stellarium.org/en_GB/) - Desktop Planetarium (Jupiter Moons)

- APT, Astro Photography Tool, Vn 3.20 (http://www.ideiki.com/astro/)   Unlimited Trial, then 18.70 EUR, 1 year support, then 6 EUR per year)

(DARV - Drift Alignment by Robert Vice method)

- IC Capture.AS ?
- FlyCap ?