M45

[saturn5]

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[SteveL]

The stars in M45 appear blue because they are passing through a cloud of gas that reflect blue light. M45 has a lot of nebulosity in it when imaged with longer exposures. 30 seconds is nowhere near "too long", in fact its quite short.

(Take at look at the M45 in my signature image... its the middle one)

[steppenwolf]

As Steve has said, M45 images very blue because of the reflection nebula, however, a 30 second exposure is not really long enough to capture this so I suspect that the brightness of the stars has caused some chromatic aberration giving a purple halo. Was this image taken with an achromatic refractor?

[saturn5]

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[Cloudwatcher]

Hi S5,

You have doubtless checked the image in an enlarged mode on your computer and will have seen the red ring inside the blue halo surrounding the brighter stars. This is usually indicative of overexposure by the achro lens of the camera. This effect is pretty common with any non apro lens regardless of tha camera body to which it is attached. One way around the problem on single frame shots is to underexpose when taking the image and then adjust luminosity,contrast etc in photoshop.

Mind you,I think your missus is right,in some cases a bit of blue here and there makes for an atractive image.

Cheers

CW

[saturn5]

Hi CW,

I'll be really honest and admit i never checked an enlarged image but have now and see what you mean, thanks for that.

I have tried shorter exposure times and still seem to get blue/purple halo effect although it gets less as the exposure time drops,trouble is when i get to a time that doesnt show the halo it hardly shows up any faint stars either.

Still fancy getting a 350D and a laptop,was going to spend around£700/800 on an obsyshed ,but my scope is in the summer house and only need to move it 6ft to the 3 slabs that the tripod sits on(level and marked for north) so maybe the money would be better spent on camera and laptop,decisions,decisions

[Cloudwatcher]

Still fancy getting a 350D and a laptop,was going to spend around£700/800 on an obsyshed ,but my scope is in the summer house and only need to move it 6ft to the 3 slabs that the tripod sits on(level and marked for north) so maybe the money would be better spent on camera and laptop,decisions,decisions

Sounds like you have a comfortable arrangement there S5.

If like me you are only an occasional 'imager' then I think the 350D would be a good choice (await flak from the Nikon Gang) but if you intend to get 'serious' then a dedicated astro camera,laptop etc. is the way to go. You will not be short of advise from the Forum on choices in this connection!

Bye the way I meant to mention before that you are bound to have trouble with a subject like 'The Seven Sisters' because there is such a difference in brightness between the main stars and the rest of those in the FOV.

Just for fun I did a quick 'blue reduction' and minimal enhancement on you M45 piccy and to be honest I think the 'halos' make the image more dramatic in appearance. (Don't tell the wife,she'll get big headed. )

Cheers

CW

[Kaptain Klevtsov]

If like me you are only an occasional 'imager' then I think the 350D would be a good choice (await flak from the Nikon Gang) Cheers

CW

Au contraire my friend. I use a Nikon because I had it before I decided to do astrophotography. Starting new I'd get a Canon.

Kaptain Klevtsov

[saturn5]

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