Fully Threaded Filter Holders

[Merkhet]

I use  Vixen Lanthanum eyepieces. The old style with parallel bodies.   They have a filter thread size of roughly 29/30 mm. 

At the telescope end they are threaded the full length of the tube.

I want to be able to screw a filter holder right down inside the mounting tube so that I can fit a measuring reticle to one of my eyepieces.

Does any one know a make or supplier of filter holders that are threaded the full length of the outside of the holder, so they can screw right down inside the eyepiece?

A UK supplier or the name of  maker would be very welcome.

Many thanks.

[MarsG76]

I don't understand, you want to screw the filter all the way into the eyepiece tube... like only the actual filter glass?

The filter housing outside diameter is the same as the tube so with the actual filter housing I doubt it... at least I haven't heard on anyone needing to put a filter all the way into the EP.

[Merkhet]

That's correct     MarsG76  .

I want a filter holder that has no shoulder on it.      Threaded the full length of the filter holder on the outside. So it can go right down into the eye piece and almost touch the lens.

I have a few  graticules from microscope eyepieces.  i have dropped one into the telescope end of the Vixen eyepiece and it comes into focus perfectly.

The graticules are various diameters  and have a variety of scales on them.   One has a 360 degree protractor engraved on it, I put that one away in a safe place but cannot remember where at the moment.  One has a cross hair with micrometer scale on the horizontal and one has a grid of squares  of about  18 squares by 18 , handy for drawing the Sun onto pre printed charts and one has a stand alone 180 degree protractor.

I want to make an eyepiece similar to the Baader illuminated eyepiece  people use for measuring double stars separation and angular distances.

The illumination is easily sorted with a dimmable LED and a drill hole.

Instead of paying out about 160 UK pounds I have the makings to hand apart from the fully threaded filter holder.

If they are not made I shall do a work arond and make apush fit holder, as used in microscopes many years ago.

Cheers for asking.

 

[101nut]

Not a direct answer but if you had a couple of dirt cheap, second hand filters you could cut off the threads, cut a couple of small notches to take the tips of a pair of screwdrivers or a lens spanner and turn them into 1 ¼" clamping rings. Run one up the tube, insert your filter/graticule/pin then fix in place with the second threaded ring ... Bit delicate but should work.

AndyG

 

[Louis D]

50 minutes ago, Merkhet said:

I have a few  graticules from microscope eyepieces.  i have dropped one into the telescope end of the Vixen eyepiece and it comes into focus perfectly.

Curious that this works because Vixen Lanthanum eyepieces have an internal field stop between the lower negative section and the positive upper section.  Which focal length did you try this with?  Perhaps not all of them have an internal fieldstop.  Generally, all you have to do is place the reticle etched side against the fieldstop and it will be close to being in focus.  For negative/positive designs, though, you'd have to do some disasembly to get at the internal fieldstop.

[MarsG76]

Sounds like the one with the 360 degree protractor engraved on it is put away extreme safe place by the sound of it... he he

Sounds like a interesting project.... I haven't heard or a fully threaded eyepiece filter, but as stated above you could do a makeshift solution just to hold it in place... I am curious to how it will work out for you. 

Also see if a illuminated reticule EP might not be cheaper to import from say the USA than paying the UK price, that from what I can see are a fair bit higher than anything else... same number as in dollars but IN POUNDS!!! Have a look at BH Photo & Video or OPT Corp, I'm sure they ship to the UK and it might end up being around half the price delivered.

 

[Merkhet]

Louis D     You sure are on the ball with your brain power today.

It works fine with the 20 mm   but not the  7 mm eye piece.     I had only tried the 20 mm until you threw some light on the subject.

I held both up to a light and peered down them  with an eye glass.    the 7 mm is that small an aperture, I cannot see if there is a  stop in there.

The 20 mm when looked through from the the telescope side has a disc of light showing through of around 18 mm and no sign of a stop to my untrained eyes.

 

They were bought at the end of 2000 . 

In the Vixen catalogue of the day ....

code no. 3757       LV Series.       LV20mm.     AF 50 Degrees (W)      20 mm eye relief    142g.

code no. 3864           ''                LV7mm       AF 45 Degrees                       ''                148g.

"A high-grade optical glass Lanthanum Crown is used for their convex field lens. Fully mulyi-coated optics...."

 

I found the receipt for the 70 mm bought around the same time.

That was roughly  £110.00p    UK pounds.    A lot of money to me in those days.  I remember dithering about whether to get one or not.  Money well spent in the end.

 

I will get there by hook or by crook, but I wont be shelling out a wadge of money when I have the makings, tools and enthusiasm to adapt my gear accordingly.

 

MarsG76   I saw them many years ago as a commercially made item, it could possibly have been something to do with photography. I cannot remember where I saw  them.

 

Thanks for the input so far everyone.

 

[Louis D]

It sounds like you're trying to create your own version of the old Celestron Micro Guide eyepiece.  Here's a PDF on it's usage.  Sometimes they come up used for around $100 USD give or take $20 here in the states.  Baader sells a version of it today under their brand.  Here's a PDF for theirs.

You could start with a cheaper illuminated reticle eyepiece picked up used, remove the existing reticle, and replace it with yours.  I bought a perfectly usable Orion 20mm Illuminated Centering Telescope Eyepiece used off CN classifieds for $50 shipped a couple of years ago.  It just needed some resoldering on the illuminator to get it working again.  The optics were fine.

Measure the diameter of your target reticle.  You'll want an eyepiece with a field stop of about that same size to see the entire thing.  I'm guess yours are from the larger 30mm barrel eyepieces rather than the smaller 23mm barrel ones since they are nearly the correct size to fill a 1.25" barrel.

As far as obtaining a 1.25" filter retaining ring, I'd look for a cheap color filter that uses a retaining ring on the female threaded side to hold the actual filter glass in place.  That should be a standard sized 1.25" retaining ring.  Just remove it with a spanner wrench and try threading it into your eyepiece.

[Merkhet]

Louis D    might like to see  the two eyepieces I was talking about.

7 and 20 mm Vixen Lanthanum.  The views through the base of the lenses are 7 mm on the left and 20 mm on the right.

 

[Merkhet]

I took a hacksaw to a very cheap engineers vernier protractor and after a bit of lathe work on some scraps of aluminium and the addition of a microscope measuring eyepiece, I ended up with a micrometer eyepiece that has a vernier protractor for measuring angles.  I have seen a lot on the internet made with six inch plastic protractors.  They seemed a bit big for my liking.  The vernier protractor cost about 25 uk pounds on ebay and that compares well to some architects drawing, plastic protractors of around eighteen pounds!

I thought long and hard before cutting the thing up.   Worth it in the end.

I have had this about a month now but no cloud free nights to try it out yet.  Seems to work fine in the daylight though.

The reason I wanted to put a measuring graticule in my telescope lens was so that I could convert the device to take a proper astronomical eyepiece.

Some pictures of the microscope eyepiece version follow.

 

 

[Louis D]

Dang!  That's some nice machining to put it all together.  I can't even fathom what a major manufacturer would want for one of those if they ever made one.

I've had lots of clear nights this July because high pressure settles over Texas every year this month.  The problem is, the residual heat and humidity (90 degrees F at 11pm and 40% humidity) and mosquitoes make it absolutely miserable to observe.  I end up dripping sweat on my equipment and having to sponge off when I come inside.