NPF Rule


Pin Point Stars NPF exampleIf you have ever went out to take photos of the stars at night with your DSLR  it is likely you have been told or you have researched and found the 500 rule.  Sometimes this rule is called the 600 Rule or the 450 rule. These are simple rules to remember out in the field when you need to quickly calculate the amount of time you need exposure to the night sky to get a good star field without trails.

There was one problem with these rules. As one increased the image size the stars seemed elongated. This is something I have struggled with as I love taking star field pictures whether astro-photography or astroscapes. Images I thought were good always had elongated stars and it was frustrating. Thankfully a man in France found a solution. Before I discuss the NPF rule, lets discuss the 500 Rule.

500 Rule (or 600 or 450)

The 500 rule was a carry over from film photography.  it is a simple solution.  The time to expose the film to the sky was equal to 500 ÷ focal length in mm. So if a person was using a 50mm lens or a zoom lens to 50mm the calculation would be 500 ÷ 50 and the result would be 10 seconds. If you use a 600 Rule or 450 rule the calculation is the same, just replace 500 with 600 or 450. The rule was the golden rule because there was general limitations to film photography. With the advent and popularization of DSLR cameras suddenly the golden rule was appearing to be outdated.  It remains a good standard, but as technology advanced and cameras could capture larger and larger images, the elongated stars became more and more of a problem.

The NPF Rule

The NPF rule was developed by Frédéric Michaud for the Société Astronomique du Havre of France. He explains what NPF means N for aperture, P for Pixel size, F for focal length.The best I can find is that he published his formula for the NPF calculation in 2016. I found an announcement post he created on  Fred, as he signed his name on cloudynights, also has an official website for the NPF rule. I highly suggest opening it in a web browser that can translate whole websites because it is written in French. In a humorous way Google translates the website by also translating the abbreviation to MFN. So son’t be surprised if NPF becomes MFN when you visit the page and translate it.

The NPF rule is very detailed. It takes into account the actual hardware of the camera you are using. Therefore, it creates a very precise measure of time to create the exposure. I have since come to call this the maximum time which one will capture pin point stars. The purpose of this writing is to help you find the numbers you need to calculate this yourself. Why? There are a few tools out there that will provide you data for many camera models. These can range from a couple hundred camera models to a couple thousand camera models. As cool as these tools are, you don;t need the data for that many camera. You just need the data for your collection of cameras.

Lets look at the simplified formula.  This is the basic everyday use formula:

Exposure time = ( (35 x aperture) + (30 x pixel pitch) ) ÷ focal length

Spreadsheet formula  =((35*B1)+(30*B2))/(b3)   

Formula assumes your respective data for aperture, pixel pitch, and focal length or in cells B1, B2, B3.

If you are new to photography your aperture is your F-Stop.  Usually expressed such as f/1.8.  The focal length is expressed in mm. The length of your lens. The item you and some long time photographers may not know is the Pixel pitch.  This is easily found through searching for your camera model followed by pixel pitch on Google.  I use a Canon EOS 40D.  So I searched for “Canon EOS 40D pixel pitch on google and found my pixel pitch is 5.7μm.  You do not need the lettering.  You just need the 5.7 or whatever the pixel pitch is for your camera.

As an example I used the Canon Nifty 50 to shoot a sample picture. I set my aperture at f/2.8.  I then used the formula to find that I needed an exposure of 5.38 seconds. Good news is that is the maximum exposure. So I set my camera exposure timer to 5 seconds. The resulting picture is at the top of this post. To compare this to the 500 rule (or 600 or 450) i made a spreadsheet to show all the different results of the calculations:

Exposure chart
Comparing NPF Rule to the 500 Rule.

For some reason I expressed the 450 rule as 400.  The calculation for 450 results in 9 seconds.

But wait there is more

That is only the simplified calculation. If you want precision pictures head to the NPF page mentioned above.  It gives the simplified result I describe here. Then it goes on to collect data of the exact latitude and longitude you plan to capture pictures and the angle you plan to set your camera. It will then give you the maximum exposure time for each section of the camera grid. This is what it looked like for me with the same settings I used in my spreadsheet calculation.

NPF Expanded
Sourced from

As seen in the above result I should use 2 seconds to have really crisp stars. For a normal picture this setting would not be the best.  However,if you are looking to stack the pictures to create a crisp clean noise free image, then 2 seconds is perfect.

Now for the fun. If you have not looked at Frédéric Michaud tutorial website yet, then I would like to present to you his full NPF calculation for your enjoyment. I honestly don’t know how to read math. I wrote it out for you:

Full NPF formula
Full NPF formula by Frédéric Michaud

I hope you have learned what you need to know about the NPF formula.  I hope it helps you with your stars in your photographs.

Unique function example

Excel Unique Function

June 16, 2020


Have you wanted to count unique values in Excel? Early this year Microsoft released to all users of Excel new array functions that make using an array A LOT easier in order to do so.  These mainly take the place of Control-Shift-Enter arrays (CSE). If you are a user of LibreOffice, I am afraid these are not yet available to that office suite. I am sure they are on their way though. The new array functions will be able to save you a lot of thinking and math.

Under the old CSE style of arrays you could come up with long and complex formulas.  I believe the longest formula I wrote in a spreadsheet was about 600 characters. Needless to say debugging or adding new considerations in the formula was time consuming and took some time. Depending on what you are trying to calculate, that same type of formula could possibly now be written in about 50 characters.

I am going to keep this simple by discussing only the new UNIQUE function here. First lets take a look at the old way. The way I would evaluate a list uses IFERROR to avoid displaying N/A errors. LOOKUP to do what it suggests, lookup values. Finally COUNTIF to evaluate the lookup data to find the unique values. I made a simple spreadsheet with a fictional employee list as seen below:

CSE style array formula to find unique values.

You can see the formula I used up in the formula bar. Using a binary (1 = yes) type of sort I labelled all the active employees. So now I want to find all the unique names. This example is rather impractical in real life, but that is why it is an example. In a nutshell that ugly formula basically says Lookup and write only once unique names from column B and list them in column D only if the value in Column A is 1.  It lists from bottom up and in column D it fills in the names by comparing the names to the name listed above in column D. I then copied that formula into every cell from D2 through D15, Rather complicated.  It works. Yes there are other ways to do this, however the formula will look just as complicated.

So what happened in 2020?  SOMETHING AMAZING! In fact it will blow you away. It will give you free time. It might win over new fans to Excel and other spreadsheet software programs. Really to be honest, this is likely very familiar to you if you use Google Sheets. Are you ready to see how to rewrite the above formula the new way?

The Unique function

UNIQUE formula with spill results.

There you have it, the new way to count unique Excel entries. To get the same list of unique names from the previous formula, just type =UNIQUE(B2:B15).  The only issue you may have with this is if the column the data spills into finds a cell with data in it.  In which case you will get a spill error. Another benefit is that since you only entered the formula one time and the resulting data “spills” down, you end up with a smaller file size that loads faster.

There you have it, one of the new functions Microsoft added to Excel.  Such a time and frustration saver. 

Photography Basics ISO

So received your first Single-lens reflect camera or (SLR). Since it is 2020, it is likely a Digital variety (DSLR). Whether you purchased it yourself or received as a hand me down or a gift this is an exciting moment.  You take it outside or to a party and take that first picture and then you are disappointed.  “I thought these were supposed to be top tier cameras” you think.  They are, and just like everything in life it is knowing how to use it. There are the automatic modes, but if you really want to unlock the full power of your camera then you will want to use manual mode. Don’t worry phone users, this writing is for you too if your camera has a manual mode option. Lets dive into part one of my mini series: Photography basics ISO.

What is ISO?  Well the acronym is rather boring and refers to the name of the standards organization, The International Organization of Standards. As to its historical purpose it is the speed of the film. This effected the light sensitivity of the camera to the film. So in the world of DLSR’s it is the measure of the light sensitivity of the sensor. So when you change the ISO higher you are making it more sensitive to light.  A lower ISO is less sensitive. Many modern high end DSLR cameras with interchangeable lenses can reach ISO’s in near or beyond 100,000. The main problem with a higher ISO value is noise or grainy pictures. 

An example of grain and noise.

If you are wanting to take everyday photos you will likely use ISO 100.  It is the standard and default. This value collects the most detail information for editing (post processing).  It is because of this detail I suggest setting the camera to save in RAW.  Once you get the image to a the larger screen you will see all the flaws you are unable to see on the small camera. (Unless of course your camera is connected to a desktop or laptop for for previewing and shuttering.) Be aware when you venture into higher ISO’s. Older DSLR models (and crop sensors) often produce grainy or noisy pictures at the higher ISO values while newer models and full frame sensors are less likely to have noise in the pictures. My current Canon 40D is a rather old model now and it also is a crop sensor camera meaning it is highly susceptible to noisy pictures. I have to do a lot of post processing (editing) work to make a halfway decent picture.  Therefore I am also looking to purchase a newer full frame DSLR.

How do I select an ISO with low Noise?  Simple remember lower ISO is better.  A lot of the high ISO use is reserved for very dark settings such as taking astrophotography pictures as is my hobby. Generally you want to use a high ISO with a low f value ( for a different blog explanation) for a depth of field. A lot of this is easily found through trial an error or through math calculations. I plan to develop a spreadsheet for those who love the images but hate the math.

So when you pick up your camera or switch to manual mode on your cell phone, you now have a better idea what the ISO value is for, being how sensitive to light the image sensor is.

Canon 40D | ISO 800 | 18mm | f/3.5 | 20 sec | Maglite and paper



What is a Manager, Supervisor, and Leader?

What is a Manager, Supervisor, and Leader?  Many places consider these all the same role by default. Many times they are. However, they are actually three separate roles. The lack of understanding is where many in a managerial or supervisory role fail. The leader role is thought to be inherent, but in reality it is earned. It is because it is earn that I I dislike the term Team leader.  So I will discuss these.

First why do I dislike the term Team Leader?  Well, it is a term companies are starting to use to soften the effect of someone  who is a manager or supervisor.  Many people fear those terms because they expect a person to be “bossy.” So the companies use the Team Leader term to create a softer role that is looked to as a leader. There is one problem with that, I believe a Leader role is earned. Why?  The best leaders are ones whom people naturally follow. When people feel forced to do something, they are less likely to be receptive to a leader.

For me a leader is just that, a person who has earned the respect of others and people naturally follow them. Just because a person has the title of leader does not mean they are due respect to be followed.  The true worth of the leader is their ability to have a following that respects them and are able to influence that following with respect. Respect is two ways and it is earned. As I feel a leader values respect then the ability to be a leader must be earned.

So what is a manager then? Manager is a person who has been given the responsibility of controlling an aspect or section of an organization. In short, they manage resources. A Manager is not a Supervisor.  However, being a supervisor is one role that may be assigned to a manager.  In fact, a Manager can very well supervise no employees. AN example an organizational procurement manager may over see all procurements having control over that part of the operation. That person can also be the sole person for the job with no subordinates. A manager ensures that the necessary resources are where they need to be when they are needed. 

What is a Supervisor then?  This is what most people think of when they hear the term Manager.  A supervisor oversees employees.  The supervisor coaches and takes corrective action when necessary.  While a Manager might write an employee schedule, the Supervisor ensures employees adhere to the schedule.

What does a successful person look like who is a Manager with Supervisory roles attached? They may write the schedule and make sure employees adhere to it.  When a customer complains about an item they investigate fairly to determine if it warrants employee corrective action or if a process needs adjusted.  Perhaps the employee or process needs a new tool. If the manager that is a supervisor can balance all this (and perhaps a budget) with the respect of the employees who gladly follow that individual, then that person can also be labelled a leader.

Hopefully, through my opinion based definition you can better understand and answer What is a Manager, Supervisor, and Leader?

An example of the spreadsheet in action.


Make Your Own Credit Card

Many of the frustrations we have as consumers is obtaining a credit card, making the monthly payment and then realizing that only $10 out of the total $55 payment went towards your balance.  Well maybe that is an exaggeration but you know the feeling. What if you could make your own credit card?  That is what I will describe here. This is the page where you candownload this spreadsheet. So lets get to it, make your own credit card.

First things first, if you do not have self control and feel you must spend money that sits in savings, this concept is not for you. As such This will not affect your credit score in anyway. This truly takes self control and dedication. Second, You will need spreadsheet software.  That is not as expensive as you may realize. In fact you can get one for FREE. LibreOffice is an Office suite absolutely free to use. LibreOffice Calc is the spreadsheet program.

Lets open the file I created.
Lets start with the basics. In cell B1 You set your own Credit Limit. Cell B2 cannot be edited and will tell you your current available to use balance.  In Cell E1 you can set your own Interest Rate. What does all this mean? Well you do not need any money up front to start using this spreadsheet. In fact you can start using it in a maxed out state in order to start saving money for purchases. You can go ahead and set any credit limit you would like. Be mindful, that you still have to make payments (to yourself) and they have to be big enough to cover your interest costs. Here is the cool part, the Interest Rate. This becomes your savings plan.  You can set your rate as high or low as you want.  I suggest setting an obscene rate like I have done. After all you are not giving that money to a bank, you are keeping it for yourself. So if you are broke, you may want to do yourself a favor and start with a $200 limit and low interest rate so you can get your self some cash to use for purchases on your self credit account.

The payments area and you can only edit the Payment column (Column B).  First this is where you will find out how much you can afford to set up. Go ahead and type in what you would like to pay each month.  Then go back to the top and adjust your limit until you are comfortable with the amount you will be paying to the balance each month. In the above example I have $200 available to spend now. So I entered a payment and found that the interest charge is $7.23. If you are fully funded to start each year you can either pay the interest to your savings (like an annual fee) or just ignore it. The next month I used the credit and made a purchase.  It charges me interest against the previous balance of $0 so I opt to pay just $15 to allow myself to earn an interest charge (because that means I will be saving money) and I am left with a balance of $17.49. I continue then with $25 payments while using my credit until I have everything paid down in the 10th month. What happens after the 12 month?  We roll over and clear out the month 1-12. After a full year write down your available balance and delete all the payments in Column B. We will discuss this written down balance after the next section where you track your purchases.

Before then, you likely have one important question.  How and where do I make my payments too.  Well that is up to you.  You can use your own checking and savings. Keep the payments in your checking and then transfer your interest charge to your savings account.  You could also get creative with online banking options like I did.  I use CashApp for my “Credit Account” and ordered a physical card. I recommend finding an online financial institution that will give you a debit card so that you can make your own credit card. Therefore I issued myself an actual physical “credit card.” It also has cool engraving options. Then I transfer my interest to savings.  Then I earn interest to grow my savings. Remember this requires you to be very vigilant and have self control over your own cash.  If you don;t have self control over keeping money in savings or having money sitting in an account for a card then you may want to leave this whole process up to the professionals…

The above is where you track your monthly spending. I left 5 rows for each month (Numbered at the top of each column) for spending.  A handful of rows as you should be using any credit account as little as possible or for large purchases. You will notice in the first month the total is ($200). This is because I entered -$200 in order to have a full $200 to start with. Remember in the previous section I said to write down the available balance at the end of Month 12, this is where you will enter that to start the new credit year. Keep track of your spending for each month and everything will auto calculate when you make the next months payment. As will the payments, after 12 months you will need to delete all your entries. This time entering the ending available balance as a negative in the 1st line of Column H in Month 1. So you want to increase your credit limit? Lets look at that magical section.

This is what this little section is for.  This keeps track of the total interest, er um, your total savings for the year. In this case $20.90.  The next line rounds that down. Why?  Well, my thinking is use the save money to create a higher credit limit and make it immediately available to use. Round up, would mean using funds that don;t exist. So in this case, I would have saved $20.90 over the past year and I could then use a $20 self made credit increase. My new limit could become anything between $200 – $220.


I hope this has been helpful and insightful and you learned how to make your own credit card.

Back to the site

Hello, I’M BACK. Back to the site.  Chances are you never knew that I was here before.  I actually launched this website a few years back.  I was more naive and just wrote and made suggestions to an audience that would never discover the site to ever read it.  Why? Because I thought I knew what Search Engine Optimization (SEO) was, but truly I did not.  Who knew there is a an entire host of tools and knowledge out there to help you.

Not only that but I found an awesome web host provider. I had looked at this provider many years ago for another site I was working on for a company. I had never considered it for myself. Dreamhost is a gem in a sea of web hosting providers. If you are looking to start your own website, I strongly recommend this hosting company.

I am wanting to make this a full income site to help me supplement my income.  Over the course of the next few weeks you will see advertising coming, referral links, and other typical web marketing and income creating items.  I will also launch  a web store where you will find everything I recommend in my blog posts in 1 location in case you lose the post that recommended the item.

I hope you find inspiration and a place you can find ideas for your own life, business, internet, or photography journey’s. I am just highlighting the topics that dominate my life. That truly is the ultimate key to success for any individual, find your passion and just exemplify it. I challenge you to be inspired by me and to go out follow your passions and grow.

I am driven.  I have to make this work. I want to make this work.  So let the journey begin and I invite you to follow along.