Observation by Mike Foylan: Carbon Star U-Lyrae

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Mike Foylan


Mike Foylan


2016 Mar 17 - 10:01


2018 Oct 28 - 10:42


Variable star

Planetarium overlay



Field centre

RA: 19h20m
Dec: +37°49'
Position angle: +85°30'

Field size

0°50' × 0°35'

  • SBIG STL 1301E CCD
  • Celestron CG5-GT EQ Mount
  • Photometric Filters BVR
  • 0.2-m SCT
  • Optec TCFS Focuser

R-Filter: 20s x5, G-Filter: 39s x5, B-Filter: 86s x5. All images flat fielded, aligned and median combined


Cherryvalley Observatory (I83) Ireland

Target name

U-Lyrae (GSC 3134:1708)


Carbon Star U-Lyrae

About this image

In the center of this image is Carbon Star U-Lyrae, it is a Mira type variable. In order to capture accurate colour representation of Carbon Stars Cherryvalley Observatory was required to calibrate or match the colour separation photometric filters to CCD as best as possible. This was achieved by using a simple process of using a white (G2V type Star which was well placed and at a high elevation) selected from the Hipparcos catalogue (in this case HIP 43882) using the same exposure time for each filter (but not saturating the star) and taking approximately ten images for each filter and median combine them. Then the flux was measured for each channel and using the highest value number (in this case the R channel) which was then set to 1, the G and B channels were found by dividing into R which gave the result of G-channel = 1.9 and B-channel = 4.1. These values can vary slightly depending on elevation of target object.

We can also see the faint open star cluster of NGC 6791 (upper left) at a distance of ~14,000 light years, also in the Lyra constellation. At roughly 8 billion years old, and with an Iron to Hydrogen abundance ratio that is more than twice that of the Sun, it is one of the oldest and most metal-rich clusters in the Milky Way. It is also one of the largest open clusters known within our Galaxy. 

CCD Operating Temperature: -33 Degrees Centigrade 
Field of View: 46 x 37 arcmins
Pixel Array: 1280 x 1024
Pixel Size: 16um x 16 um
Plate Scale: 2.17 arcsec/pixel
0.2-m SCT+SBIG STL 1301E CCD
f/ratio: 7.6

Star Details: U Lyrae (GSC 3134:1708), Magnitude Range: +8.3 to +13.0, B-V Colour Index: +3.5, Period: ~452 days, R.A. & DEC: 19 20 09 +37 52 40

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