CMOS sensors have undergone significant upgrades in recent years, in many cases surpassing CCD sensors. Their high speeds (frame rate) and resolution (number of pixels), their low power consumption and, most recently, their improved noise characteristics, quantum efficiency, and color concepts have opened them up to applications previously reserved for CCD sensors.

The improvements to CMOS technology and the strong price/performance ratio in these sensors make CMOS sensors increasingly attractive for industrial machine vision. In particular, the very high frame rates that can be achieved, almost without any compromise in image quality, are one of the primary hallmarks of the current generation of CMOS.

CMOS development over taking CCD

1. High speeds (frame rates)
2. High resolution (number of pixels)
3. Strong dynamic performance
4. Low power consumption
5. Improved noise performance
6. Improved quantum efficiency
7. Improved color concepts
8. Good price/performance ratio

What is a CMOS sensor?



There are two types of image sensors for industrial cameras on the market: CCD and CMOS sensor. The right sensor for any given job is a case-by-case question. At the same time, the trend seems to be toward CMOS sensor technology as the wave of the future. This should come as no surprise, as CMOS sensors have made major strides in recent years in two important parameters for area and line scan cameras, namely image rate and noise level. Since the beginning of 2015, it has become official that CMOS technology will be the future technology.




My New CMOS Camera

​

​GM2000












My new mount 10Microm GM2000  replaces my old AP 1100, my motivation for the upgrade grew out of the realization that my astrophotography quality needed a with dual decodes which lack the replaced mount. Two things matter to me: avoiding wasted time during an overnight session (caused either by images thrown away due to tracking errors or by time spent repeatedly trying to properly frame the desired variable star), and image quality (which affects photometric – brightness measurement – accuracy). This is a personal expression, but never got the reliability to the point where I could trust it to work during unattended overnight sessions.

​What made the GM2000 so attractive is that it uses absolute encoders on both the declination and RA axes, which virtually eliminates periodic error. The company claims that tracking error is routinely less than 1 arcsecond,  What appealed to me is that 10Micron doesn't sell any version of the GM2000 without absolute encoders, which has permitted them to optimize the entire control system around the use of the encoders.

Installing the GM2000 onto my pier was straightforward, just requiring a few holes and bolts. The most difficult part of the installation was wrestling the 30 KM of mount up onto the pier. The image below is a picture showing the new mount, telescope, and camera.

It then took a couple of weeks  to finish upgrading my software to handle the computer interface to the GM2000 and to build a "mount model" in the GM2000 firmware.

To build a mapping points model there are third parties software , this are ModelCreator or Mount Wizzard. It a be tricky to setup the communication channel , but once you connect it a great program.

The firmware has a very nice polar alignment tool, eventually 5 arcseconds away from perfect. 



This time I used Polemaster to assist me , thou you need first to do a three stars alignment followed by the polar alignment and if you use the mount PL you would need again to do the three stars alignment.



The general "feel" of the mount is wonderful. The GM2000's firmware seems solid. When you execute a goto, the mount does it quickly and accurately, the same every time. When things go wrong, you don't need to cycle power to get the mount working normally again; instead, just fixing the problem makes the mount happy again.


The mount performs "two-axis tracking," with both the declination and RA motors involved in the tracking process. The mount's pointing model is translated by the firmware into both a declination tracking rate and a RA tracking rate. Thus, the two-axis tracking is able to compensate for all of the known elements of small misalignment. I've run the mount last week for the first time given that when setting up the connection to SGP  it platesolving was not aligned with the mount RA/DEC coordination. The issue was the mount software memory stick firmware version, thinking that it was latest in reality its was old, quite old (1.22) when the current update with 1.5. After realizing this and quite annoyed that they sold me a nearly two year old mount (new , but old if you know what i mean) I did a fully automates of five hours overnight sessions, connected and sync to the dome. 

For my exposures (up to about 6 minutes), there is no visible tracking error. Typical star images have FWHM widths of about 1.9 pixels.

The QHY PoleMaster



The QHY PoleMaster electronic polar scope was designed to make your polar alignment routine easier, although I do have the RAPAS scope by Astro-Physics,  this scope is very versatile and can be use jointly with any other polar alignment software like the SharpCap (which I will talk later) or PoleMaster . One point to mention is no matter which camera tracker or telescope mount you’re using, when it comes to astrophotography, accurate polar alignment is critical.
If you have ever struggled to polar align your telescope mount with the north or south celestial pole, the QHY PoleMaster or SharpCap may just be your new best friends.

The QHY PoleMaster delivered exceptional results for me on my first night out with it. The dedicated polar alignment software was easy to use, and the camera produced a crystal clear image of the star field surrounding the north celestial pole, you just have to be patient as you will need a dark sky before starting.
Polar Alignment speed, accuracy and experience improvements with the QHY PoleMaster:

I can polar align faster, at dusk

I using the PM to improve the current method I use with the RAPAS for alignment which was fast, this one is faster.

I can monitor and confirm my polar alignment at any time

No more 2 or 3-star alignment routines if necessary but again is a personal choose
The spot-on accuracy of the PoleMaster means that my AP mount 1100gto will only need to swell to a star at zero declination (South sky) and once centered on the scope finder or PC do a Recal (press bottom left hand corner button once and press 9). QHY PoleMaster Alignment Camera Specifications:

Field of View: 11 degrees by 8 degrees
Interface: Mini USB 2.0
Resolution: Approximately 30 Arc seconds
Weight: 115 g (0.25 lb)
What’s included in the box .This PoleMaster was sent to me from High Point Scientific for review. The team at High Point made sure to include the necessary adapter for my EQ telescope mount. Here is a look at everything that comes with the PoleMaster:
PoleMaster camera body
Lens cap with a lanyard
Mini USB 2.0 cable
Mount adapter
Mount adaptor cap
M4 hardware for attaching the adaptor
Allen key for lens focus adjustment
Fastening the PoleMaster to your telescope mount

The PoleMaster I am using is for my Astro-Physics 1100GTO EQ mount, and I have fastened it to the mount using the dedicated QHY adapter for this model. The hardware was easy to install, and the materials used and overall finish of this device is attractive.

The adapter for my mount came with a tiny Allen key to adjust tension, so I could securely lock the PoleMaster into the front of the polar axis scope of the mount. The QHY PoleMaster adapter for the AP Mount 9000 & 1100

There are two parts to the mount adapter for the PoleMaster, the camera base disc that attaches to the camera body, and the camera mount ring that you need to secure to the mount. You secure the camera base disc to the mounting ring using a thumb screw.

For the mount adapter I used, there were three tiny grub screws to tighten using the supplied Allen key to lock the adapter into place. 

The device connects to my Hub via a Mini USB 2.0 cable, with miniature locking screws to avoid yanking the cable out by accident. I wish more of my device connectors had this. The manual instructs you to position the USB port of the PoleMaster to the left hand side when looking at the device head on.

I ran the mini USB 2.0 cable from the PoleMaster into my recently Pegasus powered USB hub, which consolidates the various astrophotography devices I have running to a single USB cable into my laptop.

The adapter allows you to take the PoleMaster off of the mount while not in use or in storage, but I think I’ll leave it right where it is. The tiny camera adds no weight to my rig and maintains a low profile.

I’ll just have to make sure I don’t bang anything against the device by accident when setting up. The included lens cap should stay on the PoleMaster when not in use to protect the lens.

Software and Downloads



All of the software and drivers needed to run the PoleMaster device were found on the QHY website. The company has recently updated their site, which lead me on a bit of a wild goose chase.

Rather then using the URL printed on the green card that came with the camera, I simply “Googled “QHY PoleMaster Driver” to find the appropriate section of the QHY website. Here, I downloaded the latest stable driver for the PoleMaster, along with the dedicated software needed to communicate with the camera and control parameters such as gain and exposure length.

With the 2 downloads unpacked and installed, I ran the PoleMaster software on my field laptop with the camera connected. The QHY PoleMaster manual was to-the-point and helpful through this process, and instructed me to click the “connect” button. I heard the reassuring “new device connected” chime on my Windows 10 OS after plugging in the PoleMaster, so I new the camera was successfully recognized by my PC.

After hitting the “connect” button, the PoleMaster delivered a live-view loop of the stars in the northern sky. My mount was already partially polar aligned to my latitude at 36 degrees north, and pointed towards Polaris from my observatory.

The PoleMaster camera lens has an 11 x 6 degree of field of view. This means that the pole star should be visible if the mount has been roughly polar aligned.

Even though it was not completely dark out yet, I could see a formation of stars in the display screen right off the bat. After zooming out to 75% view, the north star, Polaris was obvious.

Using the PoleMaster Software

The PoleMaster software user interface.The first thing you’ll want to do is adjust the gain and exposure settings so that it is easy to identify the pole star and a  of adjacent stars in the field.

The software walks you through a simple process of identifying and confirming the pole star. The process involves matching an overlay of star positions with your current view of Polaris and surrounding stars.
The rotate tool on the left hand sidebar lets you rotate the star pattern overlay using your mouse or using the computer arrows to move the sidebar level.

Then, you are asked to rotate the RA axis of your telescope mount to determine the rotation of the mechanical axis. By rotating your mounts right ascension axis by 15 degrees or more, the software can confirm this value.
This can be confusing the arrow showing on your screen shows an clockwise rotation, the star rotation must be moving anti-clockwise, so when using the Hand_Control/HandPad move the stars anti-clockwise. when the manual clearly states that this must done using the hand controller or mount control software.
Fine tuning my the polar alignment accuracy of my telescope mount using the QHY PoleMaster.
Next the on-screen prompts tell you to confirm the center of rotation. Eventually, you will get to a point where the application displays a small green circle. This is exactly where the pole star needs to be. At this point, the ultra-fine adjustments you make to your polar alignment are far beyond what’s possible with the naked eye.

Atmospheric Refraction

The PoleMaster has an option to enable a feature called atmospheric refraction to further improve your polar alignment accuracy. This feature asks you to input your coordinates, temperature, and pressure. For atmospheric refraction to work correctly, the USB connector on the PoleMaster must be facing east. 

Owners of the PoleMaster have recommended to start the polar alignment routine with your telescope to the west instead of the home position. 2 moves or more than 30 degrees can be difficult from the home position, so if the telescope starts in the west it is not an issue.



If you do not remove the PoleMaster from your telescope mount between astrophotography sessions, you can reuse the centering procedure from your previous polar alignment. However, if you are using the atmospheric refraction feature, you’ll need to remember to adjust the temperature and pressure settings for that night.



SharpCap



Some weeks back I began to hear about Sharpcap’s polar alignment tool. Sharpcap is compatible with just about any camera out there as long as there is an ASCOM driver for it. Best part? Sharpcap is free.

A visit to the Sharpcap website revealed I had everything I needed to give this Polar Alignment Tool a try:  a compatible camera (guess what my QHY polemaster camera!!)  and all I needed was one of those increasingly rare clear nights to give it a try. I read over the instructions a time or two in preparation, but, frankly, there isn't much to the procedure once the camera is connected to Sharpcap. Press an onscreen button a few times, move the mount once, and adjust the polar alignment with the mount’s altitude and azimuth adjusters.

That nice night finally came, and saw me setting up my AP-1100GTo mount. I put the telescope in normal “home” position, that is, pointed north with the counterweight “down.” (NOT Tracking) the QHY polemaster was already was inserted into the guide scope and connected to the Pegasus USB hub/ computer.



First task was getting an image, a focused image.

Once I was close to focus, the sensitive QHY was producing more than enough stars to meet Sharpcap’s requirements in a mere 1 seconds of exposure. To work, the program needs 15 stars within 5-degrees of the pole, and according to the information on the first polar alignment screen, I was getting around 20.

Ready to go, I clicked Sharpcap’s Tools menu and selected “Polar Align.” I was then presented with Screen 1, shown here. Stars marked in yellow are the ones Sharpcap is using for plate solving the star field (figuring out which star is which). I didn’t worry about that, just let the program think for a little while as the frames rolled in. Shortly, the “Next” button was enabled, meaning I was ready for step 2.

After pressing “Next,” screen 2 was presented and I was instructed to rotate the mount 90-degrees in right ascension. I did, so, moving the mount roughly 90-degrees to the east. (remember NOT TO USE the hand-control to rotate the scope).



Sharpcap then studied a few more frames in order to determine where the Celestial Pole was and what I needed to do to aim the mount there. Once it knew these things, the Next button was enabled again.

After pressing Next for a final time, a star was highlighted in yellow and there was a yellow arrow connecting it to a circle, my target . The task was to move the mount in altitude and azimuth so as to position the star in the little circle, not unlike what you do with a polar bore-scope (by the way, you don't need to return the mount to home position before adjusting; leave it rotated 90-degrees). As you move in the proper direction, the yellow arrow gets shorter and shorter and eventually disappears. It is then replaced with a pair of brackets around the target to allow fine tuning. As you center the star in the target circle, the brackets will move closer and closer together.



How easy was this to do? Quite easy AFTER I understood exactly how to do it. In the beginning, I was fairly far from the pole, with the arrow extending off screen. I’d been told that at this stage it was best to adjust while watching the error numbers Sharpcap displays instead of worrying about the arrow.

These numbers (degrees, minutes, and seconds) indicate how far you are from the pole. They aren’t labeled as altitude and azimuth; instead they read “Up/Down” and “Left/ Right.” Sounded easy to me. I’d adjust the mount’s altitude until the Up/Down number got smaller, and the azimuth till the Left/Right went down. Alas, that didn’t work at all.

It turned out there was a catch, and until I understood what it was, I was all at sea. Up/Down does NOT mean the mount’s altitude, and Left/Right does NOT equal azimuth. Instead, these error numbers relate to directions onscreen (that's what I thought, anyway; see the addendum at the end of the article).

In just a minute or two, I had the program indicating my distance from the pole as under a minute (it when from 55sec to 15 sec) showing as an 'excellent' Polar Alignment!!

The accuracy? I swell to a star at zero declination south and just need to move  the star with my hand-control a bit to the centre of the screen to calibrate my AP 1100gto mount.



Advantage above Polemaster

Basically, SharpCap takes two pictures near the pole and analyzes them to judge the accuracy of your Polar Alignment.  SharpCap uses plate solving to scan the images and then tells you how much you need to move your mount to increase the accuracy of your Polar Alignment. It connected to APCC automatically using it plate solve and altitude position.


​

Almost one year after my first try to build an amateur observatory in my  garden  this was unfortunately discarded due to poor location both in light pollution and water log coming form a nearby golf course grounds. The current location is situated in Istan Mountain around 270m from the sea level and away from light pollution. I am installing the observatory using a Pulsar 2.2M (https://www.pulsarastro.com/).


Description


The Pulsar Observatory Dome provides a high quality, secure and practical housing for your telescope. Providing excellent weather protection for you and your telescope, it allows you to have your instrument ready for use at all times. Whether imaging or visual, having the convenience of a permanent set up adds greatly to your enjoyment of exploring the night sky.



The Pulsar Observatories 2.2 metre full height dome benefits from the following advanced features:

Finest quality, weather proof GRP finish

High quality locking system

Simple design for self assembly

Motorised dome rotation available

Motorised dome shutters available

Accessory storage bays available

Available in white or sage green (other colours - please call)

Dimensions:

Total Height approx 2.47 metres

Dome Diameter approx 2.2 metres

Door Height approx 1.1 metres

Dome Aperture approx 0.6 metres

Ideal for up to 12" telescopes and a variety of installations.
​
www.pulsarastro.com/

Next Step - Internal Equipment Installation

Dome Drive
​
The mounts will follow the apparent movement of the stars in a smooth arc: ideal for imaging, but through the course of the imaging session, the telescope starts on the west side of the pier pointing east and ends up on the east side of the pier pointing west. 
This non-linear pointing has to be accounted for to ensure that the telescope points through the dome’s aperture at all times, requiring some complex mathematics.
It is the job of the dome control software to do this for you.
However, to do this correctly, the software must know exactly where the telescope is mounted in relation to the centre of the dome, so your first task is to make some careful measurements to obtain the dimensions required.
Using the spreadsheet available below will make it easier to get all the dimensions correct and ready for insertion into your software.
Install the ASCOM software and enter the offsets from your spreadsheet, ensuring the correct signs (positive or negative), into your choice of control software – we used MaxIm DL and POTH (Plain Old Telescope Handset) and my personal choose is Sequence Generator Pro.
Once the above is completed, your telescope and dome aperture will be in sync.
 An example below using my AstroPhysics 1100GTO mount, the dimension is obtained from the mount (see below)

​

​Settings in 10Micron

Keypad and virtual keypad settings
Sync Refines OFF → A 2s ENTER press with object data displayed will SYNC the model on the object coordinates.
Sync Refines ON → A 2s ENTER press with object data displayed will ADD A POINT to the current model, with the object coordinates matched against the encoder readouts.

10micron official ASCOM driver settings meaning
Enable Sync OFF(KeyPad-PC) → All synchronization commands through the driver are disabled, so the model cannot be altered. Basically cannot be used for modelling externally.
Enable Sync ON (Keypad), Use Sync as Refine OFF (in setup PC) → The ASCOM synchronization command will SYNC the model on the given target coordinates.

Enable Sync ON, Use Sync as Refine ON → The ASCOM synchronization command will ADD A POINT to the current model, with the given target coordinates matched against the encoder readouts. (basically will allow model points to the model already model)

Per Frejvall's ASCOM driver settings
Sync behaviour "Syncs append to refine model" → The ASCOM synchronization command will ADD A POINT to the current model, with the given target coordinates matched against the encoder readouts.
Sync behaviour "Syncs align model" → The ASCOM synchronization command will SYNC the model on the given target coordinates.


Which settings should I use?

When building a model with the keypad, you will use the 2-Stars or 3-Stars alignment and Refine Stars functions. These works the same whatever the settings are, so don't worry about them.
1.   Using the HandPad do a 3-Stars alignment
2.   Using the HP do a Polar Alignment.
3.   Using the HP/PC do a new 3-Stars Alignment (given that after the polar Alignment the previous 3-Stars alignment will disappear)
4.   Using the HP/PC do 15 to 20 Refine Stars Alignment.
5.   Using the HP/PC save this model.

When building a model with a model building software such as Model Creator, Model Maker, Mount Wizzard,
6.   Normally you'll set "Enable Sync ON" and "Use Sync as Refine ON" on the 10micron ASCOM driver,

7.   or "Syncs append to refine model" on Per Frejvall's ASCOM driver.

In normal operation, usually you shouldn't resynchronize the model. If you connect to the mount with the 10micron ASCOM driver, you can prevent any synchronization through the driver by unchecking "Enable Sync" in the driver setting (note: this won't disable synchronization with the keypad, or with other software that connects to the mount with another driver).

If you have really to synchronize the model on a single star/object (please read above before deciding to do it), you can do it with the keypad (point at the object, centre it with the keypad, then, leaving the object data displayed, press ENTER for at least 2 seconds). In this case you must have "Sync Refines OFF" in the keypad.

If you want to synchronize the model on a single star/object (again - please read above before deciding to do it) with an external software via ASCOM, check "Enable Sync" and uncheck "Use Sync as Refine" in the 10micron driver, or set "Syncs align model" in Per Frejvall's driver.

Why synchronization fails?

Usually, the mount won't accept a synchronization or a refinement point if the coordinates that you are trying to synchronize are too far away from the coordinates the mount is believing it is pointing at. The exception is for QCI mounts before the alignment, which accept almost any synchronization except for positions near the meridian, where there is ambiguity on whether the telescope is west or east of the tripod - these positions can be pointed at with two different mechanical configurations. If you encounter such a situation, probably there is something wrong with your model - check that the right ascension axis is pointing at the celestial pole, that the clock is at correct (including timezone and daylight saving), that the site coordinates are correct, that the telescope is mounted in the correct position on the declination flange.
  

• First Step create two more copies of the image /2 new layers

​

With everything in place, I could finally take the mount out for the first time after a very long wait cause by moving house to a better viewing location. 
First, I wanted to try out the rough polar alignment with the green laser pointer on the scope, Although the laser light was weak, but I could see a beam weak but noticeable to align the beam to the North Star.

The 10Micron mount uses simple star alignments for polar alignment (3 stars for a rough alignment, a full model -20 at least for exact polar alignment), always using the hand control to select the stars , DO NOT use at this stage Model Makers or Model Creator.


One point, try to center the Polar Star with a view scope or Computer program like Maxim DL before you start any alignment, if not it will give you headaches. When the mount is not even nearly polar aligned it is difficult through a camera to center a star when it comes to the 3 or 2 star alignment, you will have to use your HC and view-scope to slew near the star.
Before polar alignment, I tried various of the 10Micron functions:

1. Balance check
The mount moves the scope into specific positions and measures on both sides if any creates more or less friction. Measuring in RA was quick and showed that I was only 0.00% off (everything below 0.04% is considered enough for good, stable imaging). For the DEC measurement, it was a bit of by 0.02, I measured the level with a bubble level and it was good, I then moved the weights lightly down measure it again and it was spot on.

2. Orthogonality (cone error)
From the various alignment points, the mount calculates the orthogonality error. In my case it was it was out by 12' 00", I realized that the mount bubble level was not dead center, I centered it by lefting of the tripot legs. Did another test and the Orthogonality error was reduced to 2' 45". Honestly I am not sure if this is within the parameters allowed.

3. The 3 Stars Alignment (prior Polar Alignment)
People say that the  polar alignment was fairly easy, NOT TRUE.

But before a polar alignment its recommended that you do first a 3 star alignment, you do this 3-star alignment from the mount Hand Control the 3 star alignment can be achieved relatively easy if you have certain things done prior.

• Balancing
• Orthogonality
• Rough but relatively pointing to the star
• Correct UTC /Computer time
• GPS or manually input the correct location.

If you have the above correctly input into the mount database then when slewing to the first star the mount position will be very near.

At this stage DO NOT GO TO Polar Alignment yet. The next step is to add more stars after you finish the 3 star alignment (10 is enough) to the pointing model of the mount  through the Hand Control.

4. Polar Alignment
Now is a good time to polar-align.
Pick the Polar Align procedure from the keypad and pick a star from a list. I picked one near the meridian and fairly close to the equator. This time you must not use the hand-pad to center the star, but use the mount alt/az adjustment knobs to do the centering. Press enter when done. That’s very nearly it - but not quite as the pointing model is not that accurate as you moved the mount physically with the adjustments, but not far off. So next step is do another 3 stars alignment.

From the keypad select 2-Star Refine and pick a star from the list, the GM1000 will slew to it, halt and beep when ready and you center the star in the reticule eyepiece or the PC Screen (I use Maxim DL)  continue shooting frames (every second) and center the star.

Keep doing this in the 'Refine' to build up say a 12 to 20 star model from stars spaced widely over the sky - you can build a max of 100 stars into your model which is more practical to do (time wise) in a permanent setup. After each additional star you are told what the RMS pointing error is, is everything is working well the RMS will reduce a bit with each Refine star centered.

I experimented in three nights to learn how best to do it and how fast it could be done and how good the results are and if further model building and polar alignment iterations improved things. I performed

1. The optimum solution trading time for accuracy was to 3-star align, then add stars to build at least a 20 star model in the HC/ mount software.
2. Polar align.
3. Then repeat the 3 star align a second time and again go for at least 20 all-over-the-sky stars.
4. Polar align a second time.
5. Finally finish off with a third 3 star align and 12+ "star refine" to build a final model.

I tested the un-guiding without being totally accurate (with an 11 RMS) and unguided with a 900 sec image with prefect round stars. (see below)

5. Tracking precision

Without guiding, I measured the precision of the mount as-is (i.e. no model or such): << 1" !!! 

That's a pretty awesome precision!!!​

​After using Photoshop for some years I always had this urge to try Pixinsight, as I always say, you learn something new everyday, and who knows I might develop my processing and advance further, I am not sure where I am going or what I will achieve, but whatever I lean or not I will recorded each step on the way.

When I open SI and I see all the different processing tools under 'All Process' and those under 'Scrip' and the first impression is wow, where do I start??, while in Photoshop, the frames are coming over already  calibrated (from third party software like PhotoStack2), in SI you have the option to do the calibration as well, or used a third party software to carryout this task and just concentrate on the processing the frame in PI, so this addition of extra menus its a bit intimating.
.
First before I start this adventure I will start off by describing the meaning of 'Image Scale' followed by some useful points about PI , why?, because this awareness will come handy later.


1.    Image Scale 

arcsec/pix=(pix size/focal length)*206.3


Is the angular area of each pixel can see, this is referred as 1 bin, so if we combine 4 pixels into a single pixel the are will increase by 4x = 2bin.


First Setup


A camera / telescope combination. Telescope with 106mm aperture and 530 focal length, this means a F5 (530/106). The camera chip 2750 x 2200 with 4.54 pixel size. The image scale of the pixel is 1.76 arcsecond/pixel and the field of view is of 80.98 x 64.79 arcmin


 Second Setup


Telescope 356mm FL is 2563mm therefore F7.2 will result of an Image Scale of 0.72 arcsec/pixel and Field of View of 48 x 33 arcmin with an FOV in degrees of 0.8.


So the best resolution of both combo is the latter with a 0.72 arcsec/pixel


2.  Loading an Image


When loading an image in PI in 32 bits, the computer will display it in 8 bits, do not reduce from 32bits to 8bit the images. Instead use the STF (Screen Transfer Function) to stretch the images to see it better on the computer screen.


3.   PI is divided into two main sections for processing.


On one side we have the Process and on the other the Scrip. In Process you can find all the tools provided by PI, and in Scrip are third parties software within PI developed by PI users.


4.   On the top screen modules/menus


On the top selections we have : File-Edit-View-Preview-Mask-Process-Script-Workspace-Window-Resources and if you scroll down there are quite a bit of extra menus.


We will skip these menus for now.


5.   Inside PI (whole)

The software is divided into 4 sections - Preprocessing, Linear Post Preprocessing, Nonlinear Post-processing and Special Processing




Part 1

Pre-ProcessingThe processing of an image can be achieved by using the processing tools, if you click on the 'Process' and then <all process> you will open the screen below.






​

















​After a night of imaging you are exacting but also aware that not all the frames would be use for calibration for different reasons, previewing them can be achieved in PixInsight. Most processes can take quite a bit of trial and error to get the right settings and fine tune them for the optimal result. We run these processes on previews so that it is much faster see the effects compared to running it on the complete picture. Furthermore, we can use multiple copies of the same preview and apply the process with different settings so we can really compare the results of our fine tuning in great detail.


One of tools that unable preview your frames is 'Blink', it will preview a set of images. Open the images with the small folder in the Blink dialog window.

If your are setting the Star Detection and Fitting and these settings are inadequate, the console will report failure, leave the setting as default it works perfectly, but before hitting the  measure button, if you feel that you can enter a formula into Expressions/Approval to automate the grading process, do so, if not do not worry. Finally click measure, and the  Process Console   will appear as the script does its calculations.

Tables


The Table at the bottom , shows the finding calculation Note, you can change the field of interest, three of the main and basically used by many astrophotography are: the images’ signal to noise  ratios  , choose SNRWeight (noise), and in descending, if the SNR reading is higher-this is a good thing. 

If your choose on the Full Width at Half Maximum (FWHM) of the stars in the images, remember if the file at the top of the list would have the highest FWHM value—this is a bad thing. You might therefore switch to ascending order, placing the file with the smallest/best FWHM on top to make that category easier to read. 


FWHM measures star size/spread whereas eccentricity measures shape in terms of how out of round the star are.


Formula into Expressions/Approval 


Limits -Minimum and Maximum settings 


Eccentricity 
For eccentricity <=0.4 is considered 'round', if anything  from 0.4 to 0.49 will be acceptable,  if generally stack anything <0.55 and  above 0.55 and start to get picky and choose, it all depends how many frames you have to play with. For example if they're mostly 0.4 to 0.5 you can select with assurance and toss away any outliers that are above that, I would reject anything above 0.6.




FWHM
FWHM is a lot harder to be so absolute about, as it largely a factor of the seeing. On a really good night a seeing <3", but a 5" is considered poor. As such, for FWHM I tend to work in relative terms within the available frames I have for a target rather than absolutes. FWHMSigma is a good approval term to use for this and I'll typical approve frames that lie within 2 sigma, so an approval term of FWHMSigma < 2.

To sum up a typical approval expression I'll use for these factors in SubframeSelector will be:
Eccentricity < 0.5 && FWHMSigma < 2


[What I am saying here is I will only accept those frames with FWHS that lies with 2" and Eccentricity with a 0.5 value or below, any frame above any of these two parameters will be automatically rejected.]

• Smaller FWHM values are better.  I’ve also restricted the list by the Eccentricity and Noise metrics.  
• Noise is fairly straight forward, the higher the noise level the more difficult it is to discern your target, so again, lower values are better.  
• Eccentricity is a measure of how far from round a star is.  If a star is very elongated it will have a higher Eccentricity value, so it is also better to have lower values here.

The weighting is more complicated. Basically its means that you need to use one of the three weighting (SNR-FWHM or ECCEN). When applying the weighting to one of the three, first it will be based upon it own parameters--if you use FWHM as your most important factor to build the expression. If Eccentricity is more important to you than FWHM you can change the weightings in the formula.  

If we take the expression below (provided by....) and we take my reading below under FWHM its ranges from 3.05 to 3.6, so I  want to use a maximum value of 3.05 (<3.05) not further then this, so I put in the first part of the expression (3.6-3.05). For the Eccentricity range 0.534 to 0.511, and for the Noise its 0.736 to 0.707.


The numbers in front of each factor is based on 50 (50 frames), if you are interested in having a good FWHM (better resolution to rounded stars) you will have a higher value (30) in front of the equation. This is what the 30, 5 & 15 values are for.  If you were less concerned with resolution and wanted rounder stars with a better SNR then you might weight FWHM lower and Eccentricity and Noise higher.
  
            Most important                          Second most important                     lease important
(30*(1-(3.6-3.05)/(3.60-3.05)) + 5*(1-(0.534-0.511)/(0.534-0.511)) + 15*(1-(0.736-0.707)/(0.736-0.707)))

This expression will be reduced to:


(30x(1-(1))+5x(1-(1))+15x(1-(1)) = 30+5+15=50