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A new 22" dob is being born


Pablito
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Hi,

Some time ago I started with new project - 22" F/3,75 dob. I have optics from my trusted maker. The rest is in my hands :)

Almost all work with plywood is done. Side bearings are partially prepared (two 12mm layers). Have to admit that octagonal style requires much more work than standard cube...

Next step: mirror cel. I have laser cut parts for 27 points cell. Tomorrow I will weld the frame for it :)

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Learn something new every day, I thought a coma corrector would have been a must for such a fast focal ratio.

Impressive build you have going on Pablito, will be watching your progress.

Rick

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I only say what I saw. I was observing at two StarParties through "twin mirror" in a scope I made last year to my friend. He has Ethos eps, coma is visible but do not hit eyeballs ;)

Lot of people was looking through it and no one complained on coma. More other nice things were visible ;) Best M13 I've ever seen...

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With very good eyepieces, coma corrector is not needed ;)

Good eyepieces get rid of astigmatism--they can't do anything about coma. At f/3.75 you'll have horrible mushy views at low and medium powers without a coma corrector. I tried using my f/4 at low power without a corrector once; that's not an experiment I'll repeat :Envy: ... Perhaps at the star party when you were viewing without a corrector you were at medium to high power? Then you see substantially less coma.

Nice looking build, BTW!

Edited by umadog
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  • 2 months later...

Pablito - I've followed this build of yours with much interest and it looks to be even more impressive than your other scope posted on the forum! Your woodworking skills are a tough act to emulate.

Do you have any more updates on progress?

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Thank you :)

Yes I have a progress and I am goint to finish it in a week. I had some brake in making but I got back to it two weeks ago. I am finishing secondary cage today - painting spider and flocking it inside. Plywwod is painted and looks awesome ;)

Will post some pics soon.

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Ok, have pics :)

Unfortunately I dont't have all the poles ends so I can't fiinish the dob. Still don't know how it happened... I have them somewhere but found only two... Will have new set in the end of the week ;)

What's left to do? Attach pole ends, balance the scope, fix side bearings, but first of all - some lathe work with knurled bolts. Have to take some thread off to fit my design. Will show it when it's done.

On one photo I shown linear bearing (inside primary box). I have string edge support for the primary and it will be fixed to linear bearings, During collimation primary will change it's position as well as the string. It will reduce astigmatism to minimum.

Take a look ;)

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