A homemade 4 position manual filter wheel

[kinetic]

Hi,

Here is my latest work in progress:

Converting the DSI Pro II monochrome camera to a more
practical filter system without spending too much money.

So far it's only a manual wheel but I have enough clearance
around the filter carousel to put a toothed belt, glued inside
out around it's circumference.
A small dc motor/reduction gearbox I have will mesh with this
nicely.

Total thickness from nosepiece endplate to T-thread the other
side is 22mm...but I could probably shave 3mm off of this and
get 19mm....comparable to the ATIK wheel.

Nosepiece is from the DSI, Baader IR is fitted in it's end.

regards,
Steve B.

[Terry B]

Very clever.
I wish I had the skill to do the same.:thumbsup:

[peter_4059]

Impressive Steve. The advantage of doing it this way is that the Meade filters fit in the wheel. I don't think the 19mm Atik wheel has enough clearance for the Meade filters to fit in it. I had to get a lower profile set of filters to fit the 19mm wheel I bought.

Peter

[leon]

Certainly is impressive, :eyepop: I always did want to get a lathe one day, :) nice work.

Leon :thumbsup:

[AlexN]

Awesome Steve... Looks very well done...

You going to get it anodized black for that sexy finish?

[kinetic]

Thanks guys for your comments...



Nope Alex, I quite like Royal Blue :)

Update: Filter wheel will stay manual for now, I couldn't find
anything that would reliably glue the rubber belt to the thin
platter edge.
So I knurled the edge in the lathe to add some thumb grip.
Some pics....all ready for testing :D

Steve

[AlexN]

Dude! Awesome!

Such a professional finish.

[Ric]

Excellent piece of work Steve, you are very talented.

I'll will be interested in seeing the results of your work imaging wise.

Cheers

[kinetic]

Hi,

A bit of an update on the filter wheel.....

Yesterday I finally got the courage up to do the 48mm chop
to the OTA of my 12"Newt to allow the filter wheel/ camera assortment
to reach focus.

Quite an easy job, saw the 12" F5 mirror up close for the first time :)

I spotted the terrible light leak that Alchemy talks about in his very
informative 'chop your Dob' article....got a photo of it here.
Some pics attached, I can reach focus! :thumbsup:
It was funny, until I actually did a test last night on Rigel, I was
a bit panicky....It's not like I can add 48mm back on the tube :help:

Ready to test on the sky now....

Steve

[AlexN]

Awesome steve!

Where is the light leak coming from? is that from the focuser? or leaking in thorugh the filter wheel?

If its coming through the filter wheel, Just wrap the setup in al foil when in use...

Alex.

[kinetic]

Yes Alex, it's coming from the badly fitting Crayford style focuser
on the GSO.
The base flange has a curvature to possible fit a 10 inch scope
ideally, and it looks like they try to get away with it fitting a 12inch.
Bottom line is that it has 4 points of contact with the OTA and that
lets light in.
Alchemy's article clued me up on it, however when I saw the leak for
myself I couldn't believe how bad it really was!
Why go to all the trouble of making such a lovely job, only to do silly stuff
like that... :)

Steve

[AlexN]

So whats the plan? find the point where the light is leaking in, and seal it up with something? Maybe of all dodgy ideas, melt some plastic over it... or silicone?? As a temporary fix, some duct tape :)

A cork or neoprene rubber gasket may be the go as a more permanent fix

[kinetic]

Hi Alex,

As we discussed in chat, I'll probably baffle the tube and fit a baffle close
to the leak.....and fill it with something as you say.
I can't see the point trying to file a curvature on the flange to suit
the OTA, not worth the effort....

Steve

[Michael Clark]

Hi Steve,

How about this idea. To fix the light leak, remove the focuser from the OTA, remove the mount from the focuser, clean the underside of the focuser mount, get some JB weld or similar aluminium 2part filler. Mix it up, Apply to area where light leaks in. Temporarily fit back into OTA so filler takes the shape of the tube (make sure you use release agent of some kind, gladwrap works well. Let dry, remove from OTA, trim off waste, repaint. Done!

I would probably try to do this on a dummy OTA. ie 2 segments of mdf cut to the required radius and covered with a section of tin or gal, or use an old cake tin or tupperware container, as long as it's the same dia as the OTA. The reason, you don't want the filler dripping onto your secondary or getting stuck on anything useful.

Cheers
Michael

[kinetic]

Michael,

what a brilliant idea!
Using the curvature anywhere immediately adjacent where the focuser
was should do ok.....
I have some Fullers liquid metal too!....
Thanks mate!

Steve

[Michael Clark]

Steve,

My pleasure. let us know how it works out.

Cheers
Michael

[astronut]

Steve,
Michael is another of those great people from M.A.S!!!:lol: very helpful.
Just as a side bar to your problem.
My 12" Lightbridge is coming up to 3 years old, the base plate on it fits flush with the curvature of the tube.
When I bought the Bintel (G.S.O) 10:1 focuser, the supplied base plate had the same problem as yours.
I've noticed this on ALL the G.S.O scopes.:screwy:
Now the Lightbridge series are all made by G.S.O. They must of made the base plate especially for the size of tube.

[kinetic]

Hi John, Michael,

I reckon the base plate is made for the OTA of a 10".
It is close, but not close enough.
I did the job today, just as Michael described....
I'll give the liquid metal a good 24hrs before I touch it.
Seems to have done the job perfectly......pics to come :)

For now, here is a filter wheel webpage I made today to describe
the whole project.
Please forgive my terrible web-page designing skills!
http://mywebsite.bigpond.com/astrosteve/filter_wheel.html

Steve

[kinetic]

Hi all,

At last a decent sky to test it on...
Here is a quick 50 Lum +50 each of RGB x10sec
of part of NGC 253.

Worked well, no re-composing the shot after
delicately spinning to the next filter.

I'm a happy chappy.:D

Also attached, 50x lum of Eta Carina from tonight.

regards
Steve B.

[AlexN]

Good Going Steve! :) Good to see it finally got time under the sky! :)

[Michael Clark]

Nice work with the imaging Steve,
Obviously the liquid aluminium worked Ok. Great work on the filter wheel to, you should go into production.

Cheers
Michael

[kinetic]

Thanks Mike,
Liquid Metal job went extremely well....I was probably a
bit too miserly with the amount, I had a few low spots.
It sanded down nicely though.
I put a fresh sheet of 400 wet and dry over the OTA
tube and gently rocked the focuser back and forward over it
until it bedded down.
In hindsight, I reckon I should have added heaps more, let it spill
out the sides as you press down.
In a few hours, pull it carefully off and cut any excess off with
a stanley blade while it's still reasonably soft.
And be careful none gets on the two Allen grub screws!

Thanks for the advice!

regards,
Steve B.

[Michael Clark]

Excellent!