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New Focusing Aid

George

By George
in Imaging - Discussion

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Psychobilly

Psychobilly

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William Optic Megrez 72 With 0.8X FF ( II or III would be ok ) This is the 3rd order - easy to Cut by hand version...

http://www.btinternet.com/~psmithuk/Focus_Masks/WO_Meg72/PS_WO_Meg72FFIII_TO.pdf

I made one out of 240 gsm photo paper and gave it a quick coat of black spray...

Works a treat if the firstlight images are anything to go by.

Billy...

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Psychobilly

Psychobilly

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Anything that anybody wants (mask wise) i'll do...

Just let me know inthis thread the OD of the fornt of the OTA , the OD of the central obstruction and the focal length you want the mask to work at takign into acount any barlows of focal reducers taht you use.. and I'll knock them up...

The weather forecast is brill for tonight and tomorrow so i'm probably going to have PsychoBillys Nebula Frenzy IV and Possibly A Cluster Crescendo as well... so it might be a day or two before i can do it...

Billy...

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peteri

peteri

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Looks like I should have posted the question I posed in the DIY section here! Anyway, at the risk of repeating my self, here it is:

I recently made a Bahtinov focusing mask using stiff black card and it works extremely well. However, I have seen posts on some astronomy discussion forums where people have talked about going to extraordinary lengths to make these masks out of metal in order to avoid flexure. I am left wondering just how important slight flexure is in these masks? After all, the light from a star is a planar wavefront and the mask will cast the same shadow whether it's perfectly flat or has some very slight curvature (as in the case of my card mask).

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Psychobilly

Psychobilly

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I have replied in both as well...

i have both laser cut steel ones accurate to stupid tolerances ones i have cut out of foam board and emergency ones that i have made out of paper they all work.. the edge definitin is so much beter inthe first order metal ones but eben a curly paper one stuck to the front of the dews shield gives reasonable results just harder to see the exact focus point...

I have been using a paper one for all my Megrez 72 images that i have taken as i still havent had the metal ones made yet.

Billy...

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Ferox

Ferox

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Hi Billy,

Having tried the 3rd order mask for the 127mm Mak, FL 1500mm central obstruction 38mm could you please post the 1st order one. The concentric rings for the OD were fine as I put it in an emboidery frame which fits on the scope.

Thanks

Andy.

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Psychobilly

Psychobilly

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Hi Billy,

Having tried the 3rd order mask for the 127mm Mak, FL 1500mm central obstruction 38mm could you please post the 1st order one. The concentric rings for the OD were fine as I put it in an emboidery frame which fits on the scope.

Thanks

Andy.

There you go Andy try this one...

http://www.btinternet.com/~psmithuk/Focus_Masks/127MAK/PS_127MAK_FO.pdf

Billy...

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glennbech

glennbech

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Hi Billy; I finally measured up the Megrez 90; 11.7mm OD. The focal length of the scope is 621mm and the Aperture 90mm. I usually use it with a 0.8 reducer taking the focal lenth down to 497.8mm.

Could you be so kind to create a mask template for the megrez?

Did anyone request a mask for a Skywatcher Explorer 200? How do i measure the size of the central obstruction if that is neccesary?

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Psychobilly

Psychobilly

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Hi Billy; I finally measured up the Megrez 90; 11.7mm OD. The focal length of the scope is 621mm and the Aperture 90mm. I usually use it with a 0.8 reducer taking the focal lenth down to 497.8mm.

Could you be so kind to create a mask template for the megrez?

Did anyone request a mask for a Skywatcher Explorer 200? How do i measure the size of the central obstruction if that is neccesary?

think you might have posted the OD wrong...

correct it and i'll do the mask straight away...

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Psychobilly

Psychobilly

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No Probs...

Just to refresh people minds....

I need the OD of the point taht you want to mount the mask... the OD of central obstruction and the focal lenght that you want the mask to work at including any barlows or focal reducers in the "calculation".

For shorter focal lenght refractors I can usually get a spacing that works Native and with a 0.8X FR/Flattener...

posted masks are third order as they are easier for people to cut... Really need access to an A3 printer for the 14" Rob .

Watch this space for first order ones... if I can get things sorted out :D

Billy...

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  • 2 weeks later...
Kai

Kai

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Hi Billy

I have one of the new William Optics Flt98's (F6.3) being delivered tommorow , any chance of ......... :hello2:

When you get it post the measurement here and I'll do you a template...

No on second thoughts send it to me for a few weeks and i'll try it out for yah... :D

Billy...

Come to the Spring Star Party and you are welcome to use it :p

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