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Open Cluster
Messier 45, Pleiades


M45 open cluster December 5, 2018 (click on the image to get a full resolution photo in a new window)

Almost no image processing.

M45 open cluster December 5, 2018 (click on the image to get a full resolution photo in a new window)

Second edition with back ground flatten.

Coordinates/Direction : RA: 03h47m, DEC: +24o07'
Object size : 110'
Object magnitude : 1.6
Object : M45
Date : 2018-10-05
Time (UT) : 19:12 to 20:57
Mount : Star Adventurer
Guide : -
Lens/telescope : Pentax 67 SMC 165mm f2.8 (set to f2.8)
Corrector/Barlow : -
Filter : none
camera : Canon 6D, controlled by intervallometer
Film/CCD : Raw
Exp. time : 59x20 seconds iso6400, 19x30 seconds iso6400, 31x120 seconds iso1600, tot 1.5 hours
Image process tool : AstroImageJ, Fitswork, IrfanView
Processing : crop, level, flat calibration, dark/bias constant subtracted
Weather : clouds
Site : Sweden, Stockholm, Spirudden
Comment : This time I use my medium format lens, the Pentax 67 165mm at aperture f/2.8. I also used different ISO settings and exposures. The purpose of this you can read about here:
../../tutorials/tutorial-dynamics/tutorial-dynamics.html

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 is 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:
../../projects/project-pentax67-test/project-test-pentax67-lens.html

And this link:
../../projects/project-sigma-pentax-vignetting/project-sigma-vs-pentax.html

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:
../../projects/project-star-adventurer-angled-viewfinder/project-star-adventurer-angled-viewfinder.html
More to know :

Zoom in around the Pleiades:

M45 Pleiades
Coordinates/Direction : RA: 03h47m, DEC: +24o07'
Object size : 110'
Object magnitude : 1.6
Object : M45
Date : 2018-12-05
Time (UT) : 19:12 to 20:57
Comment : 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.
More to know :

M45 open cluster October 14, 2018 (click on the image to get a full resolution photo in a new window)
Coordinates/Direction : RA: 03h47m, DEC: +24o07'
Object size : 110'
Object magnitude : 1.6
Object : M45
Date : 2018-10-14
Time (UT) : 20:53 to 23:05
Mount : Star Adventurer
Guide : -
Lens/telescope : Sigma APO 150mm f2.8 (set to f4.0)
Corrector/Barlow : -
Filter : none
camera : Canon 6D, controlled by intervalometer
Film/CCD : Raw
Exp. time : 62x120 seconds, iso1600
Image process tool : AstroImageJ, Fitswork, IrfanView
Processing : crop, level, dark/bias constant subtracted
Weather : clear
Site : Sweden, Stockholm, Ingaröstrand
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.

In the Exif data I can read that the camera temperature was 12 C degree, the out door temperature about + 2 C degree. The electronics have heated the camera about 10 C Degrees, normally for this camera is 6 C Degrees. I suspect the extra heating comes from the active Wifi. Part of the heating can also come from the dew heater, it has a bit too strong power, 5 Watt, 2 Watt had been enough.
More to know :

Zoom in around the Pleiades:

M45 Pleiades
Coordinates/Direction : RA: 03h47m, DEC: +24o07'
Object size : 110'
Object magnitude : 1.6
Object : M45
Date : 2018-10-14
Time (UT) : 20:53 to 23:05
Comment : 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.
More to know :

M45 open cluster 16 august 2016 (click on the image to get a full resolution photo in a new window)
Coordinates/Direction : RA: 03h47m, DEC: +24o07'
Object size : 110'
Object magnitude : 1.6
Object : M45
Date : 2016-08-26
Time (UT) : 22:30 to 23:14
Mount : Star Adventurer
Guide : -
Lens/telescope : Sigma APO 150mm f2.8 (set to f4.0)
Corrector/Barlow : -
Filter : none
camera : Canon 6D, controlled by intervalometer
Film/CCD : Raw
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
Site : Sweden, Stockholm
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 espected.
More to know : Wikipedia:
https://en.wikipedia.org/ wiki/ Pleiades

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