Have you thought of using a stainless steel round head nut and bolt pushed through a balck piece of fabric. Only problem is you have to have a sunny day and a bit of distance.
Looks like a reasonably easy gadget to make. Should be possible to build one inside a DSE 2xAA switched battery pack using a bright white LED and a pinhole in Alfoil. I've built a rough and ready prototype: looks good but it's a bit late to test it on a scope tonight. More later.
I've built two prototypes today. They look good. Yet to test, but if they work, you're welcome to one of them. Cost would be about $20 inc postage. But it needs to work
It's a basic star. Nice and compact (size of a TicTac box) but no brightness control, just an on/off switch. The source size is about 0.1mm. Uses 2x AA batteries and a white 5000mcd high brightness LED. Will report back on how/if it wortks.
Tested with a 60mm Unitron refractor tonight. It shows classical diffraction patterns (inside/at/outsude focus) when viewed in the dark at a distance of 48 feet (indoors). I don't have an SCT, and my 12" LB Newtonian is not easy to get into position to test indoors - will work that one out tomorrow.
So far so good, though I don't think it's bright enough to use in during the day.
Dimensions 7cm x 3cm x 2cm
See the two prototypes, below.
DN
(perhaps this thread should be moved to the DIY forum?)
Last edited by dcnicholls; 22-12-2006 at 11:35 PM.
What would it take for the unit to be effective during the day too?
What I've just done. I increased the pinhole size to 0.6mm (the smallest drill bit I had). The pinhole is now made of thin stainless steel, and the hole is perfectly round (as viewed in a 10x magnifier). I couldn't make the previous smaller pinholes consistently round.
The result is a vastly brighter "star", readily visible away from direct sunlight (outside) at 30 metres (I didn't try further but will tomorrow).
Artificial stars serve two purposes. One is to allow a "star test" as described in Harold Suiter's book. The second is collimation. You don't need such a small (or, alternatively, distant) pinhole for collimation. So the gadget as it now stands should be fine for collimation during the day.
For star testing, the apparent angular size determines what size telescope you can use it on. The current pinhole appears as 1 arcsecond at a distance of 124 metres. So star testing is probably not possible (I think) in daytime for a large telescope.
DN
Last edited by dcnicholls; 23-12-2006 at 09:59 PM.
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