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Newbie & Handmade refractor problem

casemonster

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casemonster

casemonster

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HI All,

I knew it wouldn't be too long before I had to join an astronomy forum and felt that the time is right as I have now hit a wall with by most recent car boot purchase!!!

I have completed 47 orbits of the sun and at my 15th orbit I had a fairly in depth, but brief two year love affair with the sky. Like most kids of that age I had a pair of 8x30 bins and the obligatory Tasco scope. As you can imagine, with such a pile of brown smelly stuff for a telescope, my interest wained, and alchohol, girls and motorcycles soon took over.

Once you get to know your constellations, it never really leaves you and although I could still never name them all, I would from time to time watching the sky with the 8x30 bins.

Time has moved on from my first glimpses at the sky and my interet was rekindled, after watching Prof. Cox's "wonders of the universe" and marvelling at the images from that rather fantastic piece of equipment, the Hubble space telescope. The science has come on in leaps and bounds and we know so much more than we did when I had a face full of Zits.

I still have my 8X30's and bought a pair of 12x50's a few years back which have opened up the sky for me again, if a little wobbly to hand hold.

At a car boot last summer, I stumbled across what I thought was an absolute bargin. It was what appears to be a homemade refractor of some age. It has no markings on it as to it's make and it has the look of being made possibly in the 40's or the 50's with a five foot wooden tripon mount.The scope is about five-foot long and has an objective lens of 105mm. It came with the following: an H20 and a k12, an astromical right angle converter for these (T).

However, It doesn't work........I.e. it doesn't focus. All you get is a blob of light that won't focus within its range, ...

Does any one have a step by step ideas or tests that I can carry out. I have tried to do a bit of research on refractors and it appears the objective lens appears to be the two lens apochromatic type, as they are both taped together.

Before anyone says it, I would love to go out and buy a 10" mirror, but I would like to point out that funds are very limited and I was hoping to get this thing working as stepping stone for a while.

Any help you could give would be appreciated.

Kind regards

Chris

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Peter Drew

Peter Drew

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Hello Chris. First impression is that a component may be missing from the optical train, you could try focusing on something close as well as distant as that would give a wider range to try and get an image. A picture, if possible, would be a great help.

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faulksy

faulksy

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hi chris and welcome to sgl. been there with bikes and girls great time.any way dont know much about refractors but does the focuser work i.e. does the draw tube move back and forth.also have you tried a differen e.p. (eyepiece) incase its some thing simple like that if yes to the above have you tried moving the e.p. forther out of the focuser to see if image gets better or worse. also what focal length e.p.s are you using.the h20 and k12 are these e.p. s

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casemonster

casemonster

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Thanks Faulksy & Peter,

Ok, I have tried changing the eyepieces, and have also taken out the angle finder bit ( not sure what that is called) and the draw tube works fine.

Oddly enough I have just tried to focus on a nearby object, around 300 yards away, by placing the object in my line of sight, as seen through the objective lens without any eyepieces in and then moving the eyepiece outside of the tube and I was around 7 or eight inches (estimated) away from the tube at full extraction before I got an image focused, though not very clear.

I have taken some photo's which I will down load in a short while. Before I do, Peter, did you mean a photo of what I am seeing through the lens or of the compenent parts of the telescope?

Many thanks

Chris

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Capricorn

Capricorn

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The two eyepieces are not good, I would suggest that you invest in a cheat 32mm plossl, I say 32 as it is possibly the most useful for getting the scope working. Not selected for observing, but until you can see through the scope the observing comes later.

The diameter is reasonable, 105 = 4", length sounds like f/12 ish. It will be an achromat, but they tend to be at that design. Tal make 4" f/10's that are held in high regard.

The problem you say is you cannot get a sharp image.

This is most likely that the eyepiece is at the wrong place for the image formed by the objective lens. Catch is too far back or too far in. If you get the 32mm then try that as it is longer and will produce an image easier the the others. Also if the image you can get is getting better as you wind out then you can lift the plossl out a bit more to see if a sharp image is possible further back.

It may be the eyepieces, or you are not actually pointing at anything so no image to form. Easily done there is a lot of nothing up there.

Final option is the objective has moved and the image is no longer in the middle.

Can you actually see through the front lens? As in is it clear?

Eek!

as they are both taped together

Do you literally mean this ?

Do you mean there is tape around the lens but the lens are one cemented unit?

You need some big, distant, very hard to miss object during the day.

Aim the cope at that and play with the focuser and see if you get an image. If you do leave the focus at that point. Distant means a few miles. Big means hill, mountain not tree or church. You want too big to miss.

There are other options but it needs some simple equipment and a suitable place to try

Should be OK to get operating but not easy over several posts.

Where are you?

Is there a club in your area, usually some one understands optics at one.

If the lens are literally taped together and not cemented then I suggest you do not try yet to get it working. If the surfaces keep touching you will scratch them and the lens will be useless. If this is the situation then need pictures to suggest an option.

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casemonster

casemonster

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Wow,

I am really chuffed with all the info I am getting. I hadn't expected this much interest!!

Ok Capricorn,

Will invest in decent eyepieces as I go along but for the moment they will have to do. Not sure what a Plossl is?

The front lens is clear, not sure if cemented as I didn't want to remove the tape, in case it fell apart. Last time I tried it at night I used the Moon, today I tried a large tree 300 yards away.

I am in Essex. Not a member of a club.

You suggest that the lens is in the wrong way round. How do I tell which is the domed and which isn't? the lenses appears to be in two halves, which end points out? the thinner or the fatter lens.

Many thanks

Chris

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casemonster

casemonster

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Thanks for the info.

I have just taken a look at the weather tonight, seems to be a clear one when I just caught it on breakfast news. Will hope to see what swapping the objective lens around does... it doesnt seem to make much difference as a terestrial scope, so I am not that hopeful. I have had a look at the lens and can't work out which way the lens is, convex ot concave, so will try it both ways on a bright star/planet, 50/50 chance

BTW take a look at the picture of the lens out and look at the tape around the lens, it has the words ORO and the symbol \v/ written in pencil around the outside. Does the symbol mean anything? Also, it has some extra screws at the objective end, should these be out or in for a basic set up?

Sorry for all the questions, only I would love to get this scope going as bins are great but not that great!!!

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casemonster

casemonster

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OK, I'll start off with the lens as seen in the photo with fattest part at the front. Seriously the convex/concave side is so slight I cant tell! :)

What about the eyepieces.... should i use the 20mm or the 12mm to get it all started whilst I am mucking around with it. The scope came with 2 eyepieces and a handmade moon filter and they all look used so I am guessing it must have worked at some point. :(

Cheers

Chris

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casemonster

casemonster

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Thanks Cadwell 14,

What is a star diagonal?? GULP!!! I am a newbie....So not much of clue. I have bought ,what I thought ,would be a point and focus but seem to have stumbled upon something that needs a bit more experience.

BTW Cadwell...LINCS....Aha ...a fellow Biker??:)

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nightfisher

nightfisher

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Has this scope been tried using a star diagonal, loads of refractors wont focus without one.

same thought, have you tried it with a 90 degree star diagonal fitted in the focuser, might be all that it needs

regarding the lens orientation, the fat lens goes in to the scope first, so that the thin lens is at the very front

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casemonster

casemonster

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Aha..I now know what you mean by Star Diagonal...

Yes have tried it with this but still no joy terestially.

Will wait for tonight and will try lens in one way.. star diagonal in and out and then swap the lens round and try again. will try 20 & 12 mm lenses and pull eye piece lens out of diagonal and move it out of the focuser to see if I can get it focused by holding it.

After all that I will be clueless and will have to wait until I can afford something worthwhile.:)

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