Good artificial star needed-pls advise

[uhb1966]

Hi All!

Does anybody know where to get a good artificial star at a decent price?

Spending 100$ on a simple white LED with a potentiometer seems a bit strange to me 😕 

EDIT: just found this one at FLO-looks decent: https://www.firstlightoptics.com/other-collimation-tools/hubble-optics-5-star-artificial-star.html 

Does anyone have some experience with this one?

Best, U.

 

Edited December 12, 2020 by uhb1966
found@flo

[Tomatobro]

I have one. Needs to be as far away as you can get it >15m

[paul mc c]

I recently collimated my 127 mak,which was way off after receiving it,i used an led flashlight with the front covered in foil with a tiny pin hole in it and was able to get perfect collimation.

[banjaxed]

20 minutes ago, paul mc c said:

I recently collimated my 127 mak,which was way off after receiving it,i used an led flashlight with the front covered in foil with a tiny pin hole in it and was able to get perfect collimation.

I did exactly the same with excellent results.

[paul mc c]

Just now, banjaxed said:

I did exactly the same with excellent results.

Yip.....and i used it during broad daylight.

[banjaxed]

Just now, paul mc c said:

Yip.....and i used it during broad daylight.

Me too 👍

[steppenwolf]

Quote

EDIT: just found this one at FLO-looks decent: https://www.firstlightoptics.com/other-collimation-tools/hubble-optics-5-star-artificial-star.html 

Does anyone have some experience with this one?

I too have this one and it does work very well indeed but you need to place it as far away as possible for the best results.

For daytime use, you could also try a chrome plated steel ball when the sun is out - this can be remarkably good!

[Louis D]

I've used a black nickel plated ball bearing at one end my darkened house lit by a tactical LED flashlight (torch) next to the scope at the other of the house.  That produced a very fine specular highlight.  The black nickel plating reduced other reflections a bit by being darker than chrome plating, but has little effect on direct, specular reflections.  It makes it easier to see the shape of the reflection when analyzing aberrations or collimation.

[ollypenrice]

40 minutes ago, Louis D said:

I've used a black nickel plated ball bearing at one end my darkened house lit by a tactical LED flashlight (torch) next to the scope at the other of the house.  That produced a very fine specular highlight.  The black nickel plating reduced other reflections a bit by being darker than chrome plating, but has little effect on direct, specular reflections.  It makes it easier to see the shape of the reflection when analyzing aberrations or collimation.

I agree. The balbearing is still used by optical professionals. Simple and very effective.

Olly

[vlaiv]

Problem with ball bearing is that one does not know actual diameter of reflection - which makes it hard to calculate needed distance for resolving and spherical aberration.

I thought of DIY-ing it, and in fact it is not hard at all to do it.

You need a piece / strand of optical cable (you can even purchase one partially made for data centers), strong LED - small drill - like really small - 1mm or less and some electronics / battery holder to power the LED.

Small hole is drilled in acrylic LED housing from the front and you insert clipped strand of optical cable in it and use clear epoxy or superglue to cement it in place. Rest is easy.

Once I calculated bill of materials and time spent doing it - price of getting ready made one suddenly did not seem so steep (for someone already having drill and drill bit for modelling and other things like casing and 1/4 thread insert or at least 3D printer to print housing - it would probably be worth DIY-ing it).

I ended up getting this one:

https://www.teleskop-express.de/shop/product_info.php/info/p10781_TS-Optics-artificial-Star-for-Telescope-Tests-and-Collimation.html

 

 

[Merlin66]

Vlaiv,

Suiter gives details of the glitter spot sizing in his "Star Testing Astronomical Telescopes", Appendix F, p 337.

 

[vlaiv]

29 minutes ago, Merlin66 said:

Vlaiv,

Suiter gives details of the glitter spot sizing in his "Star Testing Astronomical Telescopes", Appendix F, p 337.

 

I'm not sure it can be that simply approximated.

It will depend on how shiny / smooth material is and angle of incident light. In computer science / graphics, there are different models for specular highlights. More info can be had here:

https://en.wikipedia.org/wiki/Specular_highlight

 

[Jamgood]

I use my mobile phone torch on my Samsung. Wrap foil around the phone, tiny pin hole, done. Works a treat. 👍

[Merlin66]

Vlaiv,

First approximation.... 1/300 the diam of the ball when using the sun.

I use the Hubble artificial star torch. I also made an adaptor for the Hubble pinhole plate to fit the old Foucault tester. I can now "play" with various lamps -Neon, Flouro, etc to check the spectrum.

 

[Paz]

I've got one of those 5 star things which works fine,  but I have only used it for collimation, not for testing anything else.