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Ideas for a homeade solar finder?

JB80

By JB80
in DIY Astronomer

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JB80

JB80

Posted
Posted

Pretty much what the title says, without one I am wasting a lot of time trying to find the sun and was wondering set up others use.

I am thinking maybe a little pinhole type thing would do the trick, maybe out of those triangle things you get in pizzas to hold them together. Drill a hole in one and use the second as a backing plate.

Would this work?

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JamesF

JamesF

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I honestly have no idea what the triangle things in pizzas are, but I believe two discs mounted about 100mm apart, the rear one with a centre-spot and the front with a small hole in the centre should work fine. The difficulty is aligning it, I guess. Mounting them on an old RDF mount would probably help.

Alternatively, there's this which is rather nice:

http://platypusart.com/wetherell/sculpture_georgian.html

James

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JamesF

JamesF

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Oh, I see. They're to stop the top of the box collapsing into your pizza. I guess that's mostly for delivery? I think we'd get laughed at if we tried to get a delivery pizza here. Mostly we make the dough in the breadmaker and make our own.

Anyhow, I reckon a couple of those would work fine. Arranged as for the brass one I linked to. Painting the front one black perhaps helps a bit with contrast, but I've no idea. Perhaps it was just done for aesthetic reasons. Having it adjustable still seems like a good idea to me, but I've never tried using one. I use the "is the shadow of the telescope as small as I can make it?" method :)

Another option might be to find a dressmaking pin with a large head (you can get them with large round plastic blobs on the head, I think?) and stick that into the face of one of the pizza supports at right angles. The pin would then act as a gnomon and you just need to move the scope until the pin is under its own shadow. Does that even make sense?

James

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JB80

JB80

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I always thought they were to hold it together in case of being knocked whilst being delivered. Oh well, either way that's just something I have around and seems like it's usable.

That will be the set up I will try, I've knocked a hole in one and it seems like it will work as long as once it's place it doesn't move, not sure how to make it adjustable but I'll look into it. So unless I cave in and buy one first it looks like that will be what I'll go for unless a easier system pops up.

The gnomon idea sounds sensible enough, at least I think it makes sense. I might have to try that too and see how it goes, I know we have pins somewhere around the house.

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sologuitarist61

sologuitarist61

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I had this problem with my refractors then one day I didn't put the Herschel wedge on - looked the the shadow of the scope until it was as small as possible and lo and behold, a nice big blob of sunlight suddenly drowned out the shadow - put the Herschel wedge back in and the sun was perfectly in the middle. Now do this every time and it is so much quicker. Won't work if you use solar film of course as no sunlight will show, but with the wedge .. perfect!

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Merlin66

Merlin66

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A length of 18mm diameter thin wall tubing, about 120mm....

A strip of gaffa tape over one end centrally pierced with a needle

A strip of masking tape over the otther end, mark the centre with a pencil cross

Mount on tube with a laser bracket, or similar

Works 100%

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JB80

JB80

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That's what I was trying to remember.

I knew I had sen yours but couldn't remember, I was picturing a backing plate for some reason.

I think I may have that sort of thing at hand and I do have a small junk finder scope holder I can use and it beats gluing plastic to a bracket.

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JB80

JB80

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This is what I have gone for in the end, I got given an old tasco 50mm and was struggling to find a use for it but I took the finder off and then apart and just added tape to the ends.

post-8383-0-48988400-1343897486_thumb.jp

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ollypenrice

ollypenrice

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The pinhole and screen idea is what I use as well. However, don't make rods for your own back by putting fancy centre circles or targets on the screen and then trying to align the lot so that the circles are aligned.

Leave the screen unmarked. Put the whole thing on the scope, find the sun once using the traditional scope's shadow method, centre the sun in the EP and then mark the screen where the sun's point of light appears.

Does it matter if it isn't in the middle of the screen? Not to me. I just want the dot on the screen to tell me that the sun will be in the EP, which it will be. I prefer a translucent screen so I can see it from behind, which is where I will be sitting when I want to see the sun in the EP. My version uses a de-lensed, de-eyepieced, SW finder tube with black EP cover and pinhole on the front and EP translucent plastic 1.25 inch cover on the back. The old finder tube had the good grace to be 1.25 inches, simplifying matters - for once!

Olly

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JB80

JB80

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Leave the screen unmarked. Put the whole thing on the scope, find the sun once using the traditional scope's shadow method, centre the sun in the EP and then mark the screen where the sun's point of light appears.

Does it matter if it isn't in the middle of the screen? Not to me. I just want the dot on the screen to tell me that the sun will be in the EP, which it will be. I prefer a translucent screen so I can see it from behind,

This is what I have done, like you said it doesn't matter a great deal just as long as it works.

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JB80

JB80

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Today was the first day I got to use the finder and it works a charm, I was on the sun in under 10 seconds.

Brilliant. :D

Still I can't get the eq2 to track, the sun is always going slightly down and left in the eyepiece. So much so I don't even want to try putting the camera on.

Does anybody know a good vid or tutourial for aligning a eq2 in daylight?

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JamesF

JamesF

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Still I can't get the eq2 to track, the sun is always going slightly down and left in the eyepiece

That sounds like it might be a mount alignment problem. How confident are you of that?

James

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JB80

JB80

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Not very, it's kind of hard to really pin point my latitude on it, not impossible though I suppose.

Plus I'm using old marks I did to find North using the true noon shadow and I'm not overly confident in them either.

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JamesF

JamesF

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When themos made his EQ1-based widefield imaging platform, I think he was using some sort of plate-solving system with images from the camera to get the EQ1 properly aligned. Might be worth having a look at that?

James

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JB80

JB80

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Thanks James, I'll have a look through those links and hopefully can sort something out.

My other option is to do a proper polar scope align with the eq3-2 at night and use that.

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