| Object : | M3, Globular Cluster
|
| Coordinates/Direction : | RA: 13h42m, DEC: +28o22' |
| Object size : | 18' |
| Object magnitude : | 6.2 |
| More to know : |
Wikipedia:
https://en.wikipedia.org/ wiki/ Messier 3 |
| Exp. time : | 24x30 seconds, iso1600, dithering mode |
| Image process tool : | Siril, Gimp, Irfanview |
| Processing : | flat calibration, no darks used, synthetic bias, photometric color calibration |
| Weather : | clear sky, temperature 0 C |
| Comment : |
In March from our balcony there are no exiting objects visible.
This time I took a new photo of the globular cluster M3 but now with the short 300 mm focal lens.
Even if M3 is a big globular cluster it need much more magnification which this setup can't deliver.
I used a different method when calibrating the image.
Normally I use darks which is subtracted.
But modern cameras has very low static pattern and sometimes this can be replaced by a synthetic bias.
The remaining static pattern is reduced by the dithering technique used when photographing.
It makes everything much easier because the darks is very time consuming to maintain.
And the random noise will also be lower with this, the bias is just a constant.
Long time ago I always used this synthetic bias when calibrating.
Hot pixels can be a problem to cancel out. |
| Exp. time : | 50x60 seconds, iso1600, dithering mode |
| Image process tool : | Siril, Gimp, Irfanview |
| Processing : | Synthetic bias, flat, phoketric color calibration |
| Weather : | clear short moment and clouds, temperature +3o C |
| Comment : |
Going through old data.
This one was almost trashed because of all dirt on the sensor,
dirty image, many of them are drying stains.
But with Siril and especially Gimp even all these dirt and stains can be handled.
As usually there are a lot of back grounds objects:
M3 plate solved.
It has of course been better to take a new photo with a clean sensor.
But good to practice on this, if it has been a comet, it can take thousand of years until it's back.
If I compare with the one I took 2016 it isn't as sharp as that one.
But it could be that I applied some kind of filter on it. |
| Exp. time : | 6x60 seconds, iso800, only 6 images used of 30, dithering mode |
| Image process tool : | AstroImageJ, Fitswork, Irfanview |
| Processing : | crop, level, flat calibration ,no dark&bias calibration |
| Weather : | clear short moment and clouds |
| Comment : |
It was more then three years ago I took any photo of the globular cluster M3.
When I started it looked good but then as usual the clouds come in and destroyed my night.
Anyway I kept a
few of the photos to have to compare with the old setup. I want to see if my new setup with longer focal length do any difference.
And yes it do, but hard to compare a 6 minute exposure with 56 minutes.
|
| Exp. time : | 28x120 seconds, iso800, dithering mode |
| Image process tool : | Fitswork, Irfanview |
| Processing : | crop, level, no cal dark&bias |
| Weather : | clear |
| Comment : |
A new attempt to catch the M3 globular cluster.
This time wasn't there any moon and a bit darker than normal.
I could use 120 seconds exposures which isn't very common from my place.
This time I also increased the dithering distance, now it was possible to completely eliminate the hot pixel without dark calibration frames.
If the photo is studied in detail it's possibly to see that it's under sampled, a camera with smaller pixels had been an advantage in this case. |
| Exp. time : | 60x60 seconds, iso800, dithering mode |
| Image process tool : | Fitswork, Irfanview |
| Processing : | resize, level, cal dark&bias flat |
| Weather : | clear, moon |
| Comment : |
My astrosystem setup works better and better.
This photo is taken with the temperature focus compensation activated.
The telescope is very sensitive on focus,
just a few degrees change in temperature get it off the perfect focus point. One degree Celsius change correspond to 95 step on focus motor.
The AstroTortilla plate solve software that center the object in the frame let me work much faster, get me more time to sub exposures.
The Canon 6D camera has much lower fixed pattern noise and the next thing to do is to work out a procedure that will not require dark calibrations in future.
Dithering is one of these tools.
Without the dark calibration the random noise will be a bit lower and save me a lot of work and hard disk space. |
| Exp. time : | 60x30 seconds, iso800, dithering mode |
| Image process tool : | Fitswork, Irfanview |
| Processing : | resize, level, cal dark&bias flat |
| Weather : | almost clear, temperature -4o C |
| Comment : |
One of the first photos with my new TS refractor. |
English
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