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Boatgypsy

By Boatgypsy
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Boatgypsy

Boatgypsy

Posted
Posted

Hello all,

I've joined here to see if I can improve my knowledge of things astronomical.

I live on a narrowboat so get to stay in some remote and dark parts of the country - perfect for stargazing.

I have a Tasco f900 as my first scope - recently acquired. It has sparked off my interest, so much so that I am looking at building my own 12" Newtonian.

My first question (of many) is....... what is the relationship, in terms of size, between the primary mirror and the secondary - is it a percentage size, or is it a matter of how much light you are prepared to sacrifice for definition?

Ian

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barkis

barkis

Posted
Posted

Hi. Ian. Welcome to the SGL forums.

It has to be a great life navigating the waterways of The UK.

a 12" Newtonian is a huge step up from a 60mm Refractor, and the views will astound you. As for the secondary mirrors size, a rough guide would be 25% of the Primary's diameter, therefore 3" minor axis diagonal in a 12" scope. Of course the focal ratio comes into play too.

The shorter the focal length, the larger the diagonal to prevent light loss, especially for imaging the sky. There are formulas to work it out when the time comes.

Enjoy your stay, and any questions you have, will get loads of responses.

Ron.:)

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glowjet

glowjet

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Hi Muddy,

A very warm welcome to SGL,nice to build your own scope, however, one of the first accessories you are going to want are dew heaters, living right on the river, great for dark nights, bad for moisture, enjoy the forum.

John.

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Boatgypsy

Boatgypsy

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Hi again all,

Thanks for all your replies and suggestions.

I should have said - for those who are interested - I'm on the Llangollen Canal near Whitchurch, Shropshire. It's a very unpopulated part of the country, hence the lack of light pollution.

I will be making my own mirrors for my home made scope, at least I will be grinding them. I've been trying to get hold of a second hand kiln to cast my own glass, but that is looking to be too a step too far at the moment. It seems from what I have read on here and elsewhere that grinding ones own mirrors is not that popular in England. I've read some very useful information on the Stellafane site in the US and I'm confident that I can produce a useable mirror.

The body for my scope will be an octagonal lightweight structure made from ash plywood, with bracings and trimmings in oak and polished brass, I'm hoping for a nice antique look combined with a useful instrument.

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Mark at Beaufort

Mark at Beaufort

Posted
Posted

Welcome to SGL Boatgypsy. I owned a 60 foot semi trad from 1996 until 2008 and cruised many of the canals. I always took my large binos and sometimes an SCT but unless you find the right location the LP could be a problem. I enjoyed the Llangollen Canal and often moored at Whitchurch just after the Whitchurch Arm and before the Viking hire boat centre. If I remember at the junction with the Montgomery (Frankton Junction) someone has a nice observatory and a very dark site.

Good luck with your project.

Mark

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