Star HD 84406
- Constellation: Ursa Major
- Right Ascension: 09h 47m 30.71
- Declination: +63° 14` 53.3
- Distance: 246 ly
- Apparent Magnitude: 6.94
HD 84406 is located in the constellation of Ursa Major, and a yellow star of spectral type G, and shines at a magnitude of 6.9, just dimmer than a person can see without optical aid.
What is special about HD 84406? Actually not too much as stars go, but that is a good thing as it was used for the initial focusing of the new James Webb space telescope.
Some of the constraints were the star would have to be in the field of view for the telescope for the entire collimation of the mirrors. The star couldn't be too bright which would cause issues with the sensors. Also the star needed to be in an uncrowded area by other stars. And of course the star needs to be stable with a constant magnitude.
- Details
- Category: Stars
- Telescope: GSO RC10
- Camera: ZWO 2600 MM
Trio of Messier Open Clusters
One classification of open clusters is the Trumpler classification. It consists of 3 parameters, the first is the degree of concentration.
I - Detached clusters with strong central concentration.
II - Detached clusters with little central concentration.
III - Detached cluster with no noticeable concentration.
IV - Clusters not well detached, but has a strong field concentration.
The second parameter is the range of brightness.
1 - Most of the cluster stars are nearly the same apparent brightness.
2 - A medium range of brightness between the stars in the cluster.
3 - Cluster is composed of bright and faint stars.
The last parameter categorizes the number of stars in the cluster.
p - Poor clusters with less than 50 stars.
m - Medium rich cluster with 50-100 stars.
r - Rich clusters with over 100 stars.
If the cluster any type of nebulosity, the letter "n" is added to the last parameter.
First up is Messier 34, located in the constellation of Perseus. Consisting of over 100 stars, in a space of a diameter of 14 light years. It is some 1,500 light years distance and shines at an apparent magnitude of 5.5 at an estimated age of 200 million years.
- Details
- Category: Open Clusters
- Telescope: GSO RC10
- Camera: ZWO 2600 MM
Page 4 of 4