14 replies to this topic

[asaint]

Hartmann

[Tom L]

Excellent article. I assume the final image where all 3 circles become one means the object is in focus? Just clarifying.

[ArizonaScott]

That would be correct Tom.

[Undermidnight]

I plan to make another one using triangles. That way, you get some diffraction spikes when in focus.

Jason

[ArizonaScott]

I'd be interested to hear how well it works Jason. I thought the use of a cross stitch hoop was a great idea. Years ago I made one for my ETX90 using a plastic lid from a small coffee can. Just happened to be the perfect size, and looked & performed well when covered in black felt.

[erik]

before i got my curved spider, i made a multiple aperture mask. but i went a different route. i ordered an extra dust cover and cut 4 holes in it. orion only charged me $5 for the cover, and it only took me a half hour to cut out the holes. worked very well too. just thought i'd bring that idea up as another option for making a mask....

[Undermidnight]

All good ideas guys! I could have gone the route of getting another dust cover, but while I was in Wal-mart, I was walking by the sewing isle with my wife and I saw the cross stitch hoop. Then I asked the lady at the counter what type of material would work. She had the perfect idea and I went with it..

Worked out pretty well!!!

I want to make a light box for flat fielding soon. Maybe use the hoop for the part to fits on the scope!!

Thanks for the comments guys...

Jason

[Awesomelenny]

Hi,
I just made my Hartmann mask last night. I used exactly those items that you had here from a craft shop that I went to. The only thing though was the glue. I went to Sears Hardware store and in the glue section, I came across GORILLA GLUE. I recall reading about that glue somewhere regarding its strength. Although this little bottle of goo was like $8.49, gosh it is incredible how strong it is! Hopefully I will try the mask out tonight!

[Dennis]

Great article and good timing. I am about to try some prime focus imaging! Thanks.

[Awesomelenny]

I tried it tonight using a 12mm eyepiece. It is really neat how this works. This ought to really do the trick when I will be doing some imaging! Great instructions!

[jack savard]

question

1.-is this work whit refractor or only on nwt

2.-and how big do we have to punch the hole
for a 85 mm objective
3 at what distance from center

4 who is Hartmann somebody can explain give more details

5 Ps I just find this on google it look a good practice to make one of the hole triangular go to see this http://cometman.com/Mask.html

6 this site show in the second image a new or better way to do maybe some try this succesfully http://www.amtsgym-s...as/ccdfocus.htm
7 last add I ope at this site from they used and other different mask but the interprting of result is VERY VERY interesting maybe we can do somthing like this whitout they sofware do you thing it is possible
http://www.sbig.com/...ls/hartmann.htm

[jack savard]

id it hartmann mask or Christoph Scheiner in 1619

this site said something different

http://www.astropix....I0817/I0817.HTM

also
it look if you put tree triangular the spyke help you to find the center focus
try it you see

[Undermidnight]

Glad the article helped out guys... I have purchased the parts to make another one using triangles this time.. I will try that glue you referred to at Sears..

Jason

[jack savard]

DO YOU MAKE YOUR TRIANGLE ONE

CAN WE SEE SOEM PHOTO OR RESULT

[JohnOwens]

OK, I'm a bit late here, but...
I found something handy at WalMart's craft area too. They have a circle cutter (also labelled for scrapbookers) that cuts circles in diameters of any whole number of mm from 25 to 150 (about 1" to 6"). It won't help cutting out the big circles for your big scopes, but it's handled everything I've needed for my little 4" and its finder (I've been getting carried away making bits out of posterboard lately, it's so cheap; I expect I'll be cranking out a black posterboard observatory dome soon). Let me go check the exact name of the device... ah, yes, the "Circle Scissor". It has similar issues of not cutting all the way through thicker materials, and it can be difficult to get it to stay in one place and not jump out of line, but overall quite useful. I might post a picture soonish, since I took a few for a "how to make a cheap light shield" article I'm working on.
OK, I see there's an easy way to add a picture here, so I'll do that. (First time posting here.)

Added: Just happened to be there again today, and checked the price on the "Circle Scissor". It's about $15. A bit much for such an otherwise-cheap project, but can be reused endlessly, of course.

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