Determining Scale of the Earth

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Starry Jack
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Determining Scale of the Earth

Post by Starry Jack »

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?)

f10 no Barlow
f10 no Barlow
Attachments
f10 + .5x Barlow
f10 + .5x Barlow


Explore Scientific 152mm f6.5 achromat
Aeries D-ERF
Quark Chromosphere f27 native, (f14 when focal reduced)
Mallincam .5x focal reducer (large format)
12nm Filter
ZWO174 (IMX249 chip 5um)
Huge Sense of Adventure Viewing Creation
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GreatAttractor
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Re: Determining Scale of the Earth

Post by GreatAttractor »

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 scopes (90 mm, 200 mm), Lunt LS50THa, ATM SSM, ATM Newt 300/1500 mm, PGR Chameleon 3 mono (ICX445)
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Re: Determining Scale of the Earth

Post by Starry Jack »

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


Explore Scientific 152mm f6.5 achromat
Aeries D-ERF
Quark Chromosphere f27 native, (f14 when focal reduced)
Mallincam .5x focal reducer (large format)
12nm Filter
ZWO174 (IMX249 chip 5um)
Huge Sense of Adventure Viewing Creation
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marktownley
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Re: Determining Scale of the Earth

Post by marktownley »

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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Re: Determining Scale of the Earth

Post by GreatAttractor »

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 scopes (90 mm, 200 mm), Lunt LS50THa, ATM SSM, ATM Newt 300/1500 mm, PGR Chameleon 3 mono (ICX445)
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Re: Determining Scale of the Earth

Post by Starry Jack »

Thank you gentlemen.

Jack


Explore Scientific 152mm f6.5 achromat
Aeries D-ERF
Quark Chromosphere f27 native, (f14 when focal reduced)
Mallincam .5x focal reducer (large format)
12nm Filter
ZWO174 (IMX249 chip 5um)
Huge Sense of Adventure Viewing Creation
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nickatnight
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Re: Determining Scale of the Earth

Post by nickatnight »

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


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Re: Determining Scale of the Earth

Post by Starry Jack »

My ignorance is here to serve you! ;)


Explore Scientific 152mm f6.5 achromat
Aeries D-ERF
Quark Chromosphere f27 native, (f14 when focal reduced)
Mallincam .5x focal reducer (large format)
12nm Filter
ZWO174 (IMX249 chip 5um)
Huge Sense of Adventure Viewing Creation
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