Determining Scale of the Earth

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Starry Jack
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Determining Scale of the Earth

Post by Starry Jack » Sun Mar 06, 2016 8:07 pm

I'm thrilled to be finally making what I consider good progress on my Solar. I'm just learning about post-processing and will be looking for advice in another thread.

In this thread I'm asking for how to determine the relative size of the earth in my rig.

These images are:
-PST 100 Stage One Mod
-one is f10 straight
-one is f10 with .5x Barlow (I unscrewed the lens off of a 2x Barlow and put it directly on the nose piece of my camera so I am ESTIMATING it's about .5 now (I don't know for certain).

I use a Mallincam SLP (do you need data on the chip?)

Sun 2-15-16 Small.png
f10 no Barlow
Attachments
Sun 2-28-16 4b Small.png
f10 + .5x Barlow

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GreatAttractor
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Re: Determining Scale of the Earth

Post by GreatAttractor » Sun Mar 13, 2016 9:19 am

My method: open the image in GIMP (or most any other bitmap or vector graphics editor), create a circular selection that exactly fits the limb's curve. Divide the selection's diameter by 109 and you get the corresponding Earth diameter in pixels.
My software:
Stackistry — an open-source cross-platform image stacker
ImPPG — stack post-processing and animation alignment
My images

SW Mak-Cass 127, ATM Hα scope (D=90 mm, LS50 etalon), Lunt LS50THa, ATM SSM, ATM Newt 300/1500 mm, PGR Chameleon 3 mono (ICX445)

Starry Jack
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Re: Determining Scale of the Earth

Post by Starry Jack » Mon Mar 14, 2016 3:58 am

GreatAttractor,
This was a fascinating answer on several fronts.

First of all, I now know about GIMP and am learning to use it. Seems like a PhotoShop replacement to me and that's EXCELLENT news.

I've calculated the two diameters as you describe and in the one image I get 3000 px and the other I get 1675 px. This gives me Earths of 27px (3000 / 109) and 15px (1675 / 109).

I've attached the two images again with my Earths. Does it look like I've done the math correctly?
Sun 2-15-16 Small with Earth.png
VERY Pleased for your help,
Starry Jack
Attachments
Sun 2-28-16 4b Small with Earth.png

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marktownley
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Re: Determining Scale of the Earth

Post by marktownley » Mon Mar 14, 2016 6:30 am

Looks right to me!
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

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GreatAttractor
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Re: Determining Scale of the Earth

Post by GreatAttractor » Mon Mar 14, 2016 1:54 pm

Yup, looks fine.
I now know about GIMP and am learning to use it. Seems like a PhotoShop replacement to me and that's EXCELLENT news.
Additionally, in the not-too-distant future there's finally going to be a version with high bit-depth support (there are already experimental builds of version 2.9 available).
My software:
Stackistry — an open-source cross-platform image stacker
ImPPG — stack post-processing and animation alignment
My images

SW Mak-Cass 127, ATM Hα scope (D=90 mm, LS50 etalon), Lunt LS50THa, ATM SSM, ATM Newt 300/1500 mm, PGR Chameleon 3 mono (ICX445)

Starry Jack
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Re: Determining Scale of the Earth

Post by Starry Jack » Mon Mar 14, 2016 4:25 pm

Thank you gentlemen.

Jack

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nickatnight
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Re: Determining Scale of the Earth

Post by nickatnight » Tue Mar 15, 2016 10:09 am

Thanks for asking the question Starry Jack. Been wondering that myself.

Starry Jack
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Re: Determining Scale of the Earth

Post by Starry Jack » Tue Mar 15, 2016 5:01 pm

My ignorance is here to serve you! ;)

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