Hercules Globular Cluster Messier M13

Globular Star Cluster, Messier M13, is located in constellation Hercules and about 25.000 ly away from Earth.

Setting : Nikon D7500, TAL200K f/8.5, ISO640 and exposure time of 34x30s 

Use of darks, bias, flats and darkflats

Software : APP, CS4 and DeNoise AI

Caution!

Art - Star Vega and Tri-Bahtinov

 

Looks like art but in reality it is the bright star and a Tri-Bahtinov Mask.

Tri-Bahtinov Mask - First Light

While using a "normal" Bahtinov mask for a long time, I was wondering what about an upgrade and using a Tri-Bahtinov mask. 

I read about the use of a Tri-Bahtinov mask on the website from Joost Drogenberg. Using the Bathinov Mask Drawing Generator - https://satakagi.github.io/tribahtinovWebApps/Tri-Bahtinov.html - I was able to prepare one for my TAL200K f/8.5 telescope. A local company did the lasercutting work based on the svg file. 

This evening I did a comparison test  between both Bahtinov masks on the bright star Vega. With the normal Bahtinov, the centerline is good centered and thus in focus. Using the Tr-Bahtinov mask I get 6 groups of spikes each containing 3 lines. The principle is the same as before: make sure the centerline of each spike group is positioned in the center. According to some forums, the use of tri-bahtinov masks is made for Schmidt Cassegrain scopes to collimate for all axes. 

Upcoming Lectures Studium Generale Maastricht

Some interesting upcoming lectures @ Studium Generale Maastricht:

 

1) 13 okober 20h: Govert Schilling will talk about dark matter "the elephant in the universe". see this link

2) 29 september 20h: dr. Lennart de Groot will talk about earth magnetic field. see this link

Limb Darkening plot using ImageJ

 

Plotting the pixel intensity center to limb using software ImageJ (see link). I used picture of the Sun made earlier in feb 5, 2022 (OIII filter).

The use of ImageJ to make the plot is quit easy and accurate. 

Interesting Software: ImageJ, FIJI and AstroImageJ

I'm still reading about Stellar Astrophysics and more specific on the radiative transfer equation linked to limb darkening and in view of analysing images on exoplanets.

Some literature make reference to some interesting software called ImageJ (or FIJI is Just ImageJ). According to the website the software is able to display, edit, analyze, process, save and print 8-bit, 16-bit and 32-bit images. It can read many image formats including TIFF, GIF, JPEG, BMP, DICOM, FITS and "raw". It supports "stacks", a series of images that share a single window. It is multithreaded, so time-consuming operations such as image file reading can be performed in parallel with other operations.

It can calculate area and pixel value statistics of user-defined selections. It can measure distances and angles. It can create density histograms and line profile plots. It supports standard image processing functions such as contrast manipulation, sharpening, smoothing, edge detection and median filtering.

This is the link to the website for more information.

ImageJ is open source software with many plugin possibilities for astronomy. There is even a package called AstroImageJ - see this link.