I feel I have an OK knowledge of normal telescopes, reflectors, refractors, focal lengths and light gathering ability and I would be able to buy a good factory made telescope with this knowledge.
I was looking for information on this lens though. It is from a set of 100mm binoculars(navy binoculars the guy told us, ???). My father has made a telescope out of it, he's a boilermaker, and with boilermakers usually oxy cutting a nut off instead of undoing them, you can imagine the telescope is fairly crude, made out of steel and is heavy.
Now, the lens. 100mm, which in a normal refractor telescope would be quite good for amateur astronomy, but as this lens has a very short focal length of 370mm it stumps me.
What type of telescope has a 100mm f/3.7 lens? as I understand it, the lower the f ratio, the lower you can magnify the focal point and it has a larger field of view?
What should I be looking at with this telescope?
This might be an interesting project..
Views of Milky Way should be fantastic through this lens! Provided it is an achromatic doublet at least, of course. Have you any pictures of it ?
You said your father made a telescope out of it.. how does it perform?
With additional Barlow, you can increase the focal length to anything more appropriate for higher magnifications, if quality of your objective lens is sufficiently good.
most bino lens are of a short focal length..hence the f3.7 - a long bino lens can be as short as f5, otherwise the bino would be far too long to hold/inconvenient.
Usually false color is not such a problem because binos are used at such low magnification cf. telescopes, so it is less noticeable
this telescope should be used like a bino, sweep views of the sky, and pick out the large dso's
Would make a great rich field scope ie: low power views but I think you will be disappointed if you try a higher power eyepiece. Achros with a Focal length of F/5 and shorter will have quiet alot of CA (that blueish/purple halo) around any bright object with high contrast. A 100mm achro lens with a focal lenght of F/8-12 would give quiet nice views.
Only pictures I can take are with a mobile phone. Not very clear but here it what it looks like at the moment.
As you can probably see it does not have a focuser on it at the moment. Also with the eyepiece on the current plain it is now does not make for very comfortable viewing. I need to put a diagonal prism and a focuser on it.
Where the lens sit, that whole assembly twists to move the main objective lens closer for terrestrial viewing, and twist it the other way to get the lens to infinte.
The thing sits on a solid chunk of brass that is the same diameter as the base but 2 and a half inches thick and about 15kg.
Looks very solidly built..
Well, simply take a peek through it and you will know if it is worth any additional trouble.
I think it might be worth it.
The diagonal prism (or mirror) will have to be quite huge for F3.7
