Author Topic: first star photo  (Read 559 times)

coachroninil

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first star photo
« on: December 29, 2017, 05:28:02 AM »
Hi
I connected my old d40 to the telescope last night and did an exposure of the double cluster. I attach the snap. I had to jpg and resize it to be able to upload. I'm quite pleased (especially with the nef which has more stars), but I wonder about the colours. I expected false colour but what I can't understand is it's direction; toward the edge it gets 'pushed' inwards.

Any explanations, advice and tips would be great. TIA.




Ryan Miller

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Re: first star photo
« Reply #1 on: December 30, 2017, 02:34:33 AM »
It would help if you stated what equipment you were using.

unmoharib

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Re: first star photo
« Reply #2 on: December 31, 2017, 12:32:14 AM »
Looks pretty nice!

Marquise Nation

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Re: first star photo
« Reply #3 on: December 31, 2017, 12:45:17 AM »
Quote
It would help if you stated what equipment you were using.

Hi Jim
Thanks for the reply.

If I mention equipment, the thread rapidly just turns into a discussion about each other's telescopes!

I just wondered why some of the stars had the false colour stretching toward the centre of the image. Beginner-level/Optically/scietifically/simple.

I've googled, but can't get it, mainly because I'm looking for a scientific term; 'false colour stretching toward the centre of the image...'. No amount of astro, camera, telescope gets me there.

Jeremy Butler

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Re: first star photo
« Reply #4 on: December 31, 2017, 05:07:48 AM »
Quote
Quote

It would help if you stated what equipment you were using.

Hi Jim
Thanks for the reply.

If I mention equipment, the thread rapidly just turns into a discussion about each other's telescopes!

I just wondered why some of the stars had the false colour stretching toward the centre of the image. Beginner-level/Optically/scietifically/simple.

I've googled, but can't get it, mainly because I'm looking for a scientific term; 'false colour stretching toward the centre of the image...'. No amount of astro, camera, telescope gets me there.
Not if you you keep your questions specific. Having the correct info on equipment and processing can only help guide our replies.Grey

Duane Berhane

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Re: first star photo
« Reply #5 on: January 01, 2018, 07:09:13 AM »
Quote
Hi
I connected my old d40 to the telescope last night and did an exposure of the double cluster. I attach the snap. I had to jpg and resize it to be able to upload. I'm quite pleased (especially with the nef which has more stars), but I wonder about the colours. I expected false colour but what I can't understand is it's direction; toward the edge it gets 'pushed' inwards.

Any explanations, advice and tips would be great. TIA.

DSC_0384-resize.JPG

Is this shot from the scope? Like using the scope as the lens, so it would be like a telephoto camera lens? Is it just one exposure and how long was it? That cluster has some orange stars in it and is pretty colorful overall.

geblusandde

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Re: first star photo
« Reply #6 on: January 04, 2018, 02:21:48 PM »
https://en.wikipedia...ical_aberration

See Coma and Field Curvature.

Leon Ware

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Re: first star photo
« Reply #7 on: January 08, 2018, 12:44:50 PM »
Quote
Quote

Hi
I connected my old d40 to the telescope last night and did an exposure of the double cluster. I attach the snap. I had to jpg and resize it to be able to upload. I'm quite pleased (especially with the nef which has more stars), but I wonder about the colours. I expected false colour but what I can't understand is it's direction; toward the edge it gets 'pushed' inwards.

Any explanations, advice and tips would be great. TIA.

DSC_0384-resize.JPG

Is this shot from the scope? Like using the scope as the lens, so it would be like a telephoto camera lens? Is it just one exposure and how long was it? That cluster has some orange stars in it and is pretty colorful overall.
Hi
I removed the lens from the camera and attached it to the telescope so yes, I'm using the telescope just as a telephoto lens. It is one exposure, maybe 2 seconds (?).

olexecin

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Re: first star photo
« Reply #8 on: January 10, 2018, 07:19:56 AM »
I have taken some decent shots with just my Canon T2i and a mild zoom telephoto up to 15-20 second exposures at ISO 11600 on a tripod without star movement.

Do you have a tracking telescope?

bescoldsearchroom

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Re: first star photo
« Reply #9 on: January 10, 2018, 03:23:24 PM »
Quote
https://en.wikipedia...ical_aberration

See Coma and Field Curvature.

Thanks
Ah, OK. So it's one of those. The stars are in focus across the photo. I take that to mean that they are the same small circles. This is not field curvature (?), so it must be coma? It links to this:
http://www.ctio.noao...eng/coma_PF.gif
which is what I'm seeing, but only on photos. Also if it is coma, does coma only affect the blue light?

Damon Brigham

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Re: first star photo
« Reply #10 on: January 11, 2018, 07:26:07 AM »
Are you using a reflector or refractor? If a refractor, is it a doublet or triplet?

bumabbefat

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Re: first star photo
« Reply #11 on: January 12, 2018, 04:37:06 AM »
Hi everyone
Do we agree with the coma diagnosis?
TIA

Michael Robinson

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Re: first star photo
« Reply #12 on: January 13, 2018, 09:29:40 PM »
Quote
Hi everyone
Do we agree with the coma diagnosis?
TIA


I do NOT agree. I see hardly any coma, but I do see what is called Lateral Color (chromatic splitting of point source off axis), it is for example a common eyepiece aberration that is prevalent in some eyepieces (e.g. Radian MK1).

Regards,

Alistair G.

John Wilson

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Re: first star photo
« Reply #13 on: January 15, 2018, 02:51:24 PM »
I am no expert, but congrats on your first photo. I see some minor coma at the extreme edges but nothing too distracting.

tiostaralzo

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Re: first star photo
« Reply #14 on: January 18, 2018, 05:17:07 AM »
Quote
Quote

Hi everyone
Do we agree with the coma diagnosis?
TIA


I do NOT agree. I see hardly any coma, but I do see what is called Lateral Color (chromatic splitting of point source off axis), it is for example a common eyepiece aberration that is prevalent in some eyepieces (e.g. Radian MK1).

Regards,

Alistair G.
Hi
To connect the camera I had to remove the eyepiece.