Video: Limiting Magnitude in Astrophotography Systems
This video presentation examines multiple factors affecting Astrophotography System sensitivity (i.e. the Limiting Magnitude), and see how much they individually contribute to overall system degradation (actual data in magnitudes).
The presentation quantifies the dependence on Aperture, OTA type, Optics Coatings, Camera QE (with imager comparisons), Seeing, Light pollution, Extinction…
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Astrophotography CAD is inexpensive, and helps users better understand how their Astro-imaging system will perform, what its limits are, and which parameters will enhance the results.
Calculate your system’s Limiting Magnitude, predict SNR and see how changing components will affect it. See the impact of seeing, sky pollution, haze, target and site elevations, aperture, cameras and filters. Find true optimal binning and system F# for best sensitivity. Discover which manufacturer’s camera, OTA or filter will perform best in your system.
The included library contains over 139 Cameras and Imager Sensors, 110 OTA’s and 70 filters from various manufacturers.
• Compare, optimize or design Astro-imaging systems by simulating OTA, Imager and Filter combined performance from 350nm to 1000nm. This is particularly important before significant purchases, such as telescopes and cameras. You will be reasonably assured that the system will really do what you need it to do.
• If you are looking to purchase new camera, OTA, focal reducer or filters, this application will help you make the right decision.
• If you already have an existing imaging system, this application will help you optimize its optical train, and select the correct imaging parameters, such as the sub duration and total exposure length.
• If you have a particular goal in mind, this will help you determine how long of a total exposure time you need, which filters to use etc.
• When designing your system from the available components, or looking to make an upgrade, this application will predict what you can expect from the finished product – before you actually spend the time and money purchasing or making it.
Great - just watched the Intro and have placed an order.
Very educational and I am hoping it will help me better understand my system and its capabilities.
Cheers
Dennis
EDIT: For those with Norton's Protection, after the Download, I ran my Norton Virus Check on the Zip File (before unzipping) and Norton's reported "No threats found".
However, when I extracted the executable file, Norton's intercepted it and removed the .exe deeming it unsafe due to too few users.
I had to then prevent Norton's from intercepting the .exe in order for the zip extraction to work.
Thank you for the EDIT re. Notron AV. Some AV apps are more paranoid than others. That said, here are the results of the EXE scan from 70 AV engines, and 4 sandboxes (sandboxes actually run the EXE, not just scan):
One thing we learned is NOT to upgrade the setup app on the website, but to let the software update itself first time it runs. This gets around the “Too new” application on some engines.
The YouTube video I was referring to is “Limiting Magnitude in Astrophotography Systems”, and not the intro. It is on the same page further down, so you may not have noticed it. We do this because YouTube is blocked in some parts of the world, and our site should redirect those to Panopto server, which is available, say, in China.
We will be adding other tutorials on Sampling, Binning and guider configuration and some use cases very soon, so stay tuned.
Thank you for the purchase, and I do hope you enjoy using the software, and that you will find it as useful as other users (and myself too, because that is how this all started).
We are continuously striving to improve, so any suggestions on added features or new equipment you’d like to see added are welcome.
What generated my interest was a recent image I took of a Quasar BR 1202-0725 in Virgo with z = 4.69.
Whilst trying to establish its position within my image, I identified a star at mag 20.56 and began to ponder what is the faintest star I could reliably identify.
Using "Astrophotography CAD" has helped me understand some of the physics and important HW/SW/Environmental considerations when imaging faint objects, and has likely saved me much trial and error in the field.
Actually, it is just something like that which prompted me to develop my first spreadsheet to try and figure it out. I had been imaging distant galaxy clusters - the splash screen is the very image that started it all . As time went on I wrote an app, and then gave it to my software engineers to enhance it using the same algorithms. So, I can't take full credit, only perhaps 60%.
Couple of things to note:
The Seeing plays a major part in LM determination. If you measure it by looking at the FWFM on your image, it will be wrong because it will also contain the OTA diffraction induced blurring. A way to see what seeing really was, measure it in the image, and then look at the "Focused Star Size" on the System page in aCAD. Move the Seeing slider until it matches your measured FWHM. That was your seeing. In my case, using the C11, the measured FWHM of 3.8" corresponded to seeing of 2.8". We should add a small calculator to assist with that.
Distant galaxies look like stars, but if you measure their FWHM, it is larger than regular stars. So, if that is your goal, increase the Seeing to something like 4 - 6" to get a better idea.
The Seeing plays a major part in LM determination. If you measure it by looking at the FWFM on your image, it will be wrong because it will also contain the OTA diffraction induced blurring. A way to see what seeing really was, measure it in the image, and then look at the "Focused Star Size" on the System page in aCAD. Move the Seeing slider until it matches your measured FWHM. That was your seeing. In my case, using the C11, the measured FWHM of 3.8" corresponded to seeing of 2.8". We should add a small calculator to assist with that.
Distant galaxies look like stars, but if you measure their FWHM, it is larger than regular stars. So, if that is your goal, increase the Seeing to something like 4 - 6" to get a better idea.
FYI, here are the details that I entered into "Astrophotography CAD" for my Takahashi Mewlon 210 F11.5, should you folks want to update the OTA database.
To adjust collimation, this secondary assembly cover can be unscrewed to access the x3 collimation screws.
The diameter of this cover/cap is 70mm (obstruction) and it completely covers the secondary mirror assembly.
Sounds interesting, but the blacklisting of the site makes it impossible to download any of the links (or get around it without turning off my virus protection, which I'm loathe to do in this situation).
We'll add it on next revision, along with Player-One cameras.
Just to make clear, what is the actual diameter of the secondary obstruction, including the holder? The secondary mirror is 65mm, but the structure holding it is 70mm?
I'm sorry you are having the issues with our website. We have been getting reports from users who use Bitdefender regarding the same issue. They seem to be the only one with this problem.
Upon the further investigation we found that BD does not play nice with WordPress websites, and in particular some Woo commerce components. We have contacted BD regarding this issue, but it is hard as, unlike many other companies, they do not seem to have a way to complain regarding false positives. If you Google "bitdefender worldpress problem" you will see lots of posts on the issue.
We'll add it on next revision, along with Player-One cameras.
Just to make clear, what is the actual diameter of the secondary obstruction, including the holder? The secondary mirror is 65mm, but the structure holding it is 70mm?
~Chris
Hi Chris
Here is a photo of the Mewlon 210. The 70mm diameter secondary "screw on/screw off cap" with the Mewlon logo is the first obstruction that the incoming light encounters, even though the secondary mirror is 65 mm in diameter.
Regarding Norton 360 quarantining the .exe file, just for general information should others experience this behaviour:
After I downloaded the SW (zip file) I ran Symantec “Norton 360” then “Scan now” on the freshly downloaded zip file and it reported “No Threats Found”.
When I then tried to “Extract” the .exe, that’s when Norton’s intercepted and quarantined the file based on what appears to be a “How new is this” and “How many users” check.
When I temporarily disabled this Norton AV function and successfully extracted the .exe , I ran Symantec “Norton 360” then “Scan now” on the extracted .exe file and it reported “No Threats Found”.
I then re-enabled the Norton protection and ran the .exe to install the SW.
After I installed the application, I then ran the Symantec “Run Smart Scan,” and it reported no issues.
It was a false positive, and thanks for pointing it out.
We have contacted Avast, and they corrected the issue. Below is their reply. Please do let me know if it is not fixed.
Hello,
Thank you for reporting this false positive.
We have now cleared its reputation in our database based on the findings and removed the detection. This change may take up to 24 hours to take full effect. Please accept our apology for the inconvenience caused.
If the detection persists after 24 hours, update the virus database in Avast anti-virus and reply to this email with the attached files:
1.Take a screenshot of the Avast detection dialog (Threat Secured pop-up with See details - displayed at the bottom).
2.Take a screenshot of the Avast virus database (open Avast antivirus and go to Menu > About).
We hope you have a nice day and stay safe online.
Volodymyr
Avast Malware Analysis Team
Enterprise Office Center, Pikrtova 1737/1a, 140 00, Prague 4, Czech Republic
. As time went on I wrote an app, and then gave it to my software engineers to enhance it using the same algorithms. So, I can't take full credit, only perhaps 60%. 
