Open Cluster
Messier 45
Pleiades / Seven sisters
|
| Object : | M45 (Mel 22) |
| Coordinates/Direction : | RA: 03h47m, DEC: +24o07' |
| Object size : | 120' |
| Apparent magnitude : | 1.6 |
| Distance : | 444 ly |
| No solar mass : | 8e2 |
| Radius : | 20.34 ly |
| Find in constellation : | Taurus |
| More to know : |
Wikipedia:
https://en.wikipedia.org/ wiki/ Pleiades |
| Exp. time : | 72x60 seconds 400iso, dithered every 3rd |
| Image process tool : | Siril, Gimp, IrfanView |
| Processing : | flat, astrometric color calibration |
| Weather : | clouds, temperature +4o C |
| Comment : |
First photo of M45 Pleiades with my new equipment.
Not too bad to be taken at a Bortle 9 environment. |
| Exp. time : | 59x20 seconds iso6400, 19x30 seconds iso6400, 31x120 seconds iso1600, tot 1.5 hours |
| Image process tool : | AstroImageJ, Fitswork, IrfanView |
| Processing : | synthetic bias, flat calibration |
| Weather : | clouds, temperature +6o C |
| Comment : |
This time I use my medium format lens, the Pentax 67 165 mm at aperture f/2.8.
I also used different ISO settings and exposures.
The purpose of this you can read about here:
Tutorial dynamics
The clouds destroyed my attempt this night to get a beautiful image of the M45 nebula.
The exposure time is 1.5 hour compare to the one below that has 2 hours exposure time.
But this image is taken at f/2.8 and the one below is at f/4 so still it has more exposure.
Why I did this? I just found it interesting to compare an once very expensive medium format lens from 1980s with a 30 years newer APO lens.
This lens isn't as sharp as the Sigma APO 150 lens, or?
But the vignetting is very low and I can use it at f/2.8.
The Sigma lens I normally has to use at f/4.
The problem with a non APO lens is that they don't focus all colors at the same focus.
The red and blue color are out of focus.
You see it in the full resolution image as blue and red rings around bright stars.
It doesn't have a built in focus motor either.
It's hard to compare these images because of the clouds I got after one hour into the exposure session.
I did a second variation of this image.
I processed the back ground to be more flat to reduce the effect from clouds.
Note that this image is not cropped more then a few pixels at the edges, a full frame sensor, not bad when looking at the stars at the edges.
You can read more about this medium format lens here:
Project test Pentax67 lens
And this link:
Sigma vs Pentax
This time I did my first test of the angled viewfinder that I connect to the polar scope, what a difference! You can read about it here:
Project Star Adventurer angled viewfinder
|
| Exp. time : | 62x120 seconds, iso1600 |
| Image process tool : | AstroImageJ, Fitswork, IrfanView |
| Processing : | crop, level, dark/bias constant subtracted |
| Weather : | clear |
| Comment : |
A second attempt to catch this object.
This time I have done it in late autumn, then it's darker and I did it also with three times the exposure time.
Now the nebulosity becomes more visible.
A crop around the Pleiades and more intensive processing to get more nebulosity.
It can be processed much more but I prefer to have a mild processing to get it look more natural.
As you notice there is no color of the stars.
It comes from the long exposures that oversaturated the readout device at this high ISO setting.
Next time I will do much shorter sub exposures but more of them.
In the Exif data I can read that the camera temperature was 12 C degree, the out door temperature about + 2 C degree.
|
| Date : | 2018-10-14 + 2018-04-18 |
| Exp. time : | 101x120 seconds, iso1600 |
| Image process tool : | Siril, GraXpert, SyQon, VeraLux, Gimp, IrfanView |
| Processing : | synth bias and flat calibration, color astrometry, dark subtraction, star nebulosity separation, synthetic PSF stars, hypermetric stretch |
| Comment : |
I have some old pictures of M45, that star cluster has some bright stars that tend to bleed into the surroundings.
Here I am experimenting with a new image processing with modern tools (2026).
Among other things, I use Siril's Synthetic Star with PSF function.
Before that I had divided the image into two parts, one with stars and another with nebulosity.
Then I process the two images separately with slightly different parameters.
After that the two images are merged again. |
| Exp. time : | 19x130 seconds, iso1600 (the exif data say 129 sec but it should only had been 60 sec) |
| Image process tool : | Fitswork |
| Processing : | crop, level, cal in camera dark/bias subtracted |
| Weather : | clear |
| Comment : |
M45 is an open clusters, small islands of stars. This one also have a blue nebulosity.
The reason that I took this photo was to do a test of my new light portable mount, a Star Adventurer.
One difficulty is to aim the RA axis for the polar star. I didn't expected much from this photo.
150mm is a long focal length in this case but it worked pretty well.
Take a look of the full resolution photo and look at the stars, they are almost round, not elongated as I expected. |
| Exp. time : | 51x30 seconds, iso1000 |
| Image process tool : | Siril, Gimp, IrfanView |
| Processing : | synthetic bias calibration |
| Weather : | Moon Phase 55%, Temperature +1oC, rel Humidity -% |
| Comment : |
One of few photos I took with my Newton 10 inch telescope.
It's big difference compare to my refractors because of its bigger opening. |
| Date : | 2013-10-12 |
| Exp. time : | 51x30 seconds, iso1000 |
| Image process tool : | Siril, GraXpert, Gimp, IrfanView |
| Processing : | synthetic bias and flat calibration, background subtraction, stretch |
| Comment : |
Tested with the latest image processing tools I have (2026), is it possible to see anything of the reflection nebulosity around the bright stars with these bright stars?
Yes, they came through the darknes and show up. |
English
(click on the image to get a full resolution photo in a new window)
(click on the image to get a full resolution photo in a new window)
(click on the image to get a full resolution photo in a new window)
(click on the image to get a full resolution photo in a new window)
(click on the image to get a full resolution photo in a new window)
(click on the image to get a full resolution photo in a new window)