Finderscope crosshair replacement

[Ric]

Hi all, a quick question.

Are the crosshairs in a Meade 8x50 finderscope able to be replaced?

I set up last night and began my alignment, the first star was fine and I slewed to the second star, looked in the finderscope and found in that the vertical crosshair had snapped.:doh:

I've never heard of this happening and this is the first time it has happened to me in three scopes and 32 years of astronomy. I've researched on the net but haven't found any info as yet and I don't really want to start pulling things apart if it is a non servicable part.

Cheers all

[Karlsson]

Hi Ric,

There was a thread by Erick last year addressing this issue:

http://www.iceinspace.com.au/forum/showthread.php?t=20812

[erick]

Ric, I used the finest copper wire I could pull out of some multistrand cable - just pulled across and superglued at the edge, excess trimmed off when glue dry.. But the copper is really too thick - stars vanish behind a wire so it isn't that easy to use. Also the copper could oxidise and grow "hairs"? But mine hasn't as yet.

Human hair is the better option. Others have done that with success.

Whether you get get at the crosshairs in your Meade finderscope, I don't know. They were easy to get at in the GSO finderscope.

Good luck
Eric

[Ric]

Thanks Karlsson, I'll have a read of that thread.:thumbsup:

Thanks for the advice Eric, I'll have to use my wifes hair though. I dont have any long enough or enough for that matter.:rofl:

Cheers

[Ian Robinson]

When I was a kid I had a wee accident with my telescope and the cross hairs were wrecked .... I plucked a hair from my head , cut it to length and used my long nosed tweezers and some airfix glue to put it in place .... worked a treat .... they're still there .

[Ric]

Thanks Ian, I have a couple of our cat's whiskers as well. They look like they might work effectively as well except they are white, I dont know if that will make any difference.

Cheers

[Ian Robinson]

Careful of these claws of death .... cats take a dim view to having their whiskers interferred with ....

[Ric]

I just wait for them to fall out naturally Ian, far safer.:lol:

Our cat is a 9kg Manx and rumbles with him result in blood transfusions for me.:scared3:

Cheers

[bojan]

Use spider web. This is right stuff, used for exactly that purpose in the past.

http://www.surveyhistory.org/cross-hairs1.htm
http://en.wikipedia.org/wiki/Reticle
http://www.practicalmachinist.com/vb/archive/index.php/t-126349.html

I was using the glass core from the optical cable, not easy to find these days because they are now made of plastic.
The good thing about it is that due to refraction, it behaves as double strand.

[Ric]

A very interesting idea and article Bojan.

Thanks for the link.

[Roger Davis]

I would suggest that you take the opportunity to make a double crosshair. Put the retaining ring/ferrule onto a piece of timber and then 4 drawing pins into a cross shape surrounding the ring. A fine gauge copper wire that you can strip from an old electronic choke can be wrapped around the drawing pins and over the ring to form a double cross hair with a square in the middle. Four dabs of epoxy, allow to set over night then trim with a sharp Stanley knife. Beats the heck out of using hydrofluoric acid on glass.

[erick]

Thanks Roger - the "tricks of the trade" - I'll file that away for my next rebuild. :thanks:

[Ric]

Thanks as well for the tip Roger, I like the idea of the double crosshairs to form a square in the middle. Definitely better for alignment.

Cheers

[Roger Davis]

The trick is to do it in one continuous motion without duplicating a length! Try to weave the centre crossovers for strength.

[Dennis G]

Hi Roger
I'm interested, but as my GS finder scope is new I'm reluctant to pull it down without first knowing more about your double cross hairs to form a square. How about showing or describing how and where these hairs are situated in the scope.

Dennis G

[erick]

Dennis, do you mean a GSO finderscope? If so, this thread may help:-

http://www.iceinspace.com.au/forum/showthread.php?t=20812

as embarrassing as it is to bring up my stupidity again!

Eric :ashamed:

[madtuna]

if you want a circle in the middle like in a Telrad use a pubic hair :D

[Ric]

:rofl::rofl:

[Roger Davis]

I have taken some pictures of the procdure of removal and fitting of new double crosshairs on a standard reticle base.
Remove the reticle ring.
Take off the old crosshairs with a pair of tweezers.
With a flat sided needle file across the old recesses, file into the ring to the original depth. This will allow the wire to sit to either side under tension and give the correct spacing for the central square.
Hammer in four small brads or four thumb tacks into a piece of timber.
Wind the wire crosshair around the brads to form the crossover pattern as shown in the picture, keeping a reasonable tension on the wire.
Push the wires down the nails to ensure that the reticle is held in place.
Put some dabs of epoxy onto the ring and wire and allow to set for 24 hours.
Trim with a SHARP blade.
Put back into finderscope.

[Ian Robinson]

A bit of very light nylon fishing line (4 or 6 pound breaking strain) might do the job too (if you get the clear (invisible) variety you might get the double hair effect .

[Ian Robinson]

:eek:

[Ric]

Thanks for the images Roger, that really puts it all into perspective.

Doesn't look too difficult at all. Just on the lookout for some very fine wire at the moment.

Cheers

[Ric]

My finderscope is all fixed now, I ended up using one of my wifes hairs which ended up being the same thickness as what Meade uses and it looks perfect.

At first it was a bit tricky focussing in with the old dodgy eyeballs but I got there.

A big thanks to everyone for their thoughts and ideas, it was all greatly appreciated. :thumbsup:

I also decided not to go for the telrad style as suggested by Madtuna. :rofl:

Cheers