Carrey mask with wires

[sabin_fota]

I managed to build an Carrey mask with wires for my 90mm refractor.

I use aluminium sheet and wire from fishing line.

http://sevenastronomy.blogspot.ro/2012/09/masca-carrey-cu-fire.html

[daz]

Looks interesting....

[nmoushon]

Have you tested it out yet?

[sabin_fota]

tonight

[Gina]

I'm thinking of making a focussing mask for my wide-field lenses but probably a Y.

[sabin_fota]

I posted the results

[sabin_fota]

Tests, 30", ISO 800:

1. Bahtinov

2.Hartman improuved

3. Carrey

Conclusions:

1.Despite of results of Hartman and Bahtinov masks, the focus is not achieved according to the Carrey mask.

2.The Carrey mask is more precise than the other two.

[Gina]

Some excellent images you have there - very nice indeed

[nmoushon]

Thats really interesting results. Do you mind sharing where you got the information to make this?

[sabin_fota]

Thats really interesting results. Do you mind sharing where you got the information to make this?

http://www.astronomy.ro/forum/viewtopic.php?t=9573&postdays=0&postorder=asc&start=0

from romanian astronomers forum

[lukebl]

Very interesting results. Seems like Carey masks have been around for a while but somewhat eclipsed by Bahtinov: http://www.btinterne...y/careymask.htm. I wonder why, as they do seem more accurate than Bahtinovs?

[nmoushon]

Thanks for the info Sabin. But for those of us that can only read enlglish here's a site in english that tells you DIY steps to make your own. Though I like how you did yours with the strings Sabin. Nicely done. Looks good too.

http://www.btinternet.com/~gfcarey/careymask.htm

[jimao22]

Hi,

Actually, the issue was developed by me on the Romanian astronomy forum and for those (a lot I suppose) who don't speak Romanian, I will explain what me and Sabin did.

I found, sailing on the internet, about someone who did make a Bahtinov mask from wires.

My problem was to achieve focus when using narrow-band filters, because of small quantity of light passing through these filters. Because of that, I spent a lot of time to focus with my classic Bahtinov mask, whith poor results most of the time.

So I sow this wired mask as an opportunity to increase the light quantity and shortening the focusing time.

Using a 2D CAD program, I made a template from a sticky film. This film I used to drill the holes in the right places into the aluminium plate. The picture bellow are clear, I hope.

First is the Bahtinov plan and second the Carey mask plan I did make.

I made two because I waned to see the difference between - which is much better.

[jimao22]

So, these are the film templates:

Bahtinov template

Carrey template

[jimao22]

The film on the aluminium, as template for drilling and cutting:

[jimao22]

The frame for Carrey

The frame for Carrey with central profile cut:

[jimao22]

Carrey mask almost done (painted):

And wired...

[jimao22]

The same story with Bahtinov - just the final picture here:

[jimao22]

Now is coming the interesting part !

I made the tests for the wired masks. The most important goal for me was to test the gain in luminosity against the classic Bahtinov mask I already had.

To do this, I tested aiming a star 2.2 magnitude (not very bright), having in mind that not always you have around your region of interest a very bright star to focus on it.

So, meet Alphecca (Corona Borealis).

First picture - Alphecca on clear filter, 1 second exposure, bin 2x2:

[jimao22]

The following picture is same star, using the classic Bahtinov mask, clear filter, 1 sec, bin 2x2:

[jimao22]

And this is again Alphecca, but on the new mask. The difference is obvious! Same exposure time, same binning, same filter.

[jimao22]

Now, the heavy artillery: narrow-band filters.

H-alpha 7nm filter is a very restrictive filter. Very few light is passing by. First picture is an exposure of 10 seconds through the classic Bahtinov mask with this filter.

The second picture is the same but the wired mask... Amazing, isn't it?

[jimao22]

Sorry - the second picture from above is the classic Bahtinov 30 sec

Now is the amazing part - wired Bahtinov 10 seconds:

[jimao22]

The last test was mad with the most restrictive filter SII. The picture are (1) 30 seconds classic Bahtinov bin 2x2 against (2) 10 seconds wired Bahtinov bin 2x2:

[jimao22]

...and take a look at Alphecca trough the same filter, wired Bahtinov, 30 seconds. Is incredible...