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New Focusing Aid

George

By George
in Imaging - Discussion

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NiteGawper

NiteGawper

Posted
Posted

Also what type of company can cut the 'proper' versions?

I want to search locally, but dont even know what type of company to look for!

Cheers

Aza,

I just got a rough quote from an engineering firm in Swindon (Wilts) for the Tal2 third order Mask made with thier laser cutter. To get it done in 2mm Mild steel would be £70.00 + VAT !!!!!!!!!!

So, quick question for Psychobilly... The palce that made your prototypes, how much would they charge?? I know a few chaps on here have the Tal2 - could they make a "small" batch if the interest was there??

To get a one off made for £70.00+VAT would never get past the wife - there is only so much spending you can keep under the radar!!! LOL!!!

NG

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ngc2403

ngc2403

Posted
Posted

hello,

mmm just to point out that you can do this with card or cardboard like i have done for all of my scopes, cutting some shapes into the card that are pointed or radial lines of little holes works well too. i think that you are all alittle mad buying stainless steel masks for £80+ a pop

hope that you enjoy it ally

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NiteGawper

NiteGawper

Posted
Posted

Also what type of company can cut the 'proper' versions?

I want to search locally, but dont even know what type of company to look for!

Cheers

Aza,

I just got a rough quote from an engineering firm in Swindon (Wilts) for the Tal2 third order Mask made with thier laser cutter. To get it done in 2mm Mild steel would be £70.00 + VAT !!!!!!!!!!

So, quick question for Psychobilly... The palce that made your prototypes, how much would they charge?? I know a few chaps on here have the Tal2 - could they make a "small" batch if the interest was there??

To get a one off made for £70.00+VAT would never get past the wife - there is only so much spending you can keep under the radar!!! LOL!!!

NG

Sorry Psychobilly, I just read (properly) your posts above and my question about pricing seems a tad premature!! :oops: :oops: :oops:

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Psychobilly

Psychobilly

Posted
Posted

Hi NiteGawper...

One off costs for engineering firms always seem high but essentially the same amount of "skilled" work is needed to produce 1 as it is to produce thousands...

Typically a firm will look to charge £30 and hour plus for an operators time (more for a programmer) and then you have to add the material,consumablein (this case the gas) and teh machine costs - these laser and water jet cutters are expensive pieces of kit so the hourly rate on them is quite high.

The loading and setup time are the same if your making one or making a sheet full...

One part i used to have made - a small brass bush woth a coupel of m2 tapped holes at specific points and different depths used to cost us £5 eachmade by "hand" but once i found the right machine i used to get tehn for 30p each the machine would make 1200 and hour...without any "human" intervention. saved the firm a packet!!

I always share any drawings, ideas etc that I produce ... have given wedge and pier drawing out in the past

So for the time being I'm quite happy to keep knocking out whatever templates people want and you can make your own prototypes...

Mine have just been sprayed matt black and are in the top oven curing...just in case they get to see some starlight later...

Billy...

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George

George

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I printed the image supplied by Billy on some A4 at work today and laminated 3 times to make the sheet really stiff. Unfortunately this made it too stiff for cutting :laughing2: :laughing2: :laughing2:

Anyhow I printed another copy here at home and just cut out the paper stencil, I painted this with some matt black spray hoping the paint would stiffen the paper which it did to a degree. I then crudely just taped this to the ED80 OTA with some masking tape to test, this was not ideal as the tape pinched the mask and caused it to bow.

I had about 40 Min's of clear sky tonight so I did a quick test and here's one of the images:

focus-test.jpg

As you can see we have a result :hello1: this looks a pretty near perfect image despite the mask being bowed, and the FHM graph in DSLR Focus confirms this is at max levels.

I'm pretty pleased because this proves the Bahtinov mask is a great aid for fine focusing and it also proves that Billy's calculations and the images he has provided will work.

All I have to do now is make something a bit more substantial than this pretty floppy first effort :laughing2: :laughing2:

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Reggie

Reggie

Posted
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that looks slightly off focus tbh george, if you look closely the centre diffraction line is closer to the left side than it is the right, looking back at my images that billy posted I was also slightly off.

In my defence I was looking at the diff. spike on liveview on the cam from an awkward angle and only took those as a quick test as I was gagging to get imaging on M31 :( Still either way, I bet you spent very little time focusing, I know I didn't but the resulting image was very good for star shape (And I suspect you found your test shot for star shape to be very satisfactory) and they can be gotten tighter if we take a little more time.

Next time out I'm going to spend 20-30mins doing some focus test shots on 2-3 different subjects (or less with the speed these things seem to take focusing :D)

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George

George

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In my defence I was looking at the diff. spike on liveview on the cam from an awkward angle and only took those as a quick test as I was gagging to get imaging on M31 :( Still either way, I bet you spent very little time focusing,

It took a minute at the most, your right tho its not quite there this is where the leccy focuser would come in, the PC lcd when viewed from an angle can be deceptive. Still...this new mask is far superior to the hartmann :D .

I'll have another go at making a less floppy one this afternoon/evening.

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Psychobilly

Psychobilly

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Hi Steve, They are way better than a hartman in my opinion they give a very distinct and clear picture at critical focus (you center one diffraction spike between two angled ones) and also show you which way you need to adjust ( the center line sweepos across the "V" as you got through focus.

Billy...

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Reggie

Reggie

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Hi Steve, They are easier to use than a standard hartmann mask and they are more precise, the claim is that they are better than FWHM measurements of focus via software for hand focusing. They are also very quick to use, no longer than you would spend focusing for an eyepiece without a mask.

If you look through the mask way out of focus it acts like a squashed 3 point hartman, 3 'comb' shapes coming towards each other in an obtuse triangle, but the difference being instead of merging into one single image like a hartman does when you hit focus you get the spikes as in the images.

Get the centre spike dead centre between the crossed spikes and you have perfect focus. If you look at the top focus test image that billy posted you can just make out the obtuse triangle where I am close to focus, then in the 2nd its much closer to the centre but still a teensy bit off, more time spent would've given perfect focus.

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MartinB

MartinB

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These look brilliant. Not sure about being better than FWHM but a whole lot quicker!! Trouble is, I'm totally cack handed. So what is the advice to someone like me who struggles folding an envelope. Are you going to go ahead with a production run Billy. I will certainly be looking for one for my 8" F4 newt. Guess the template for the 8" skywatcher should be fine.

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