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I use a Telrad spotter on my Orion 6 inch Newtonian reflector telescope. I am considering adding a Sky Watcher ED100 APO 4 inch refractor to my viewing tools and am wondering how well a Tetrad unit would function on this telescope.  Does anyone have experience using a Telrad with a SW ED100 or with another 4 inch telescope?  

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In my opinion, a Telrad works because it works; it doesn't depend on the scope. Is there any particular reason why you think it might not work?

I use a Telrad with my SW ED120. It works the business. :happy11:

I attach it in a specific way so as to always be able to remove it easily. This is wholly unnecessary, you can attach it any way you like, it will be great.

tmp_10521-DSC_01622111060705.JPG

Block of wood, painted black (thank you, Jagger), serves as base; Telrad riser is screwed onto base. Dovetail clamp screwed to side of block of wood. Dovetail clamp clamps (as it would) to bit of dovetail forward of clamp which holds scope on mount. Recently, I have used an extra tube ring to attach a dedicated short dovetail bar for this purpose.

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Alternatively, you could go for a Rigel, which works by the exact same principle as a Telrad, but has a much smaller form factor and fits more easily on smaller scopes:

tmp_27450-DSC_01811492304360.JPG

Here you see my Rigel - with anti-dew band - attached to the TV85 using the same block-of-wood construction. You can also just bolt the base on somewhere convenient:

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DSC_0193.JPG

:happy11:

So if you're worried about a Telrad fitting on the tube, I would advise you to go for a Rigel. Both great finders.

Edited by iPeace
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Also the Rigel is much lighter than a Telrad, it won't upset balancing your scope to much,

you don't need the extra battery pack because the coin batteries last a very long time, that

is if you remember to switch it off when you are not using it. 

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I use the Rigel Quickfinder on my 12" dob but it would do well on a much smaller scope too. The Telrad is great of course but it can look a little ungainly on a small diameter tube. The Rigel is a little more resistant to dewing than the standard (unmodified) Telrad as well.

You get 2 bases with the Rigel unit, radiussed for larger and smaller tubes.

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I use a Telrad on my 100ED and it's fine. You won't need another Tetrad,  just the base.

I agree that the Tetrad is prone to dew but it is easily wiped. And the batteries do last for ever even if, like me, you always forget to switch it off! I've not tried a Rigel but I did have another red dot finder some time ago and I was always buying batteries for it. The fact that the Tetrad does not use the button type is a big advantage I think. 

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2 minutes ago, kerrylewis said:

I use a Telrad on my 100ED and it's fine. You won't need another Tetrad,  just the base.

I agree that the Tetrad is prone to dew but it is easily wiped. And the batteries do last for ever even if, like me, you always forget to switch it off! I've not tried a Rigel but I did have another red dot finder some time ago and I was always buying batteries for it. The fact that the Tetrad does not use the button type is a big advantage I think. 

It is indeed nice that the Telrad takes standard penlight batteries. And I like its extra red circle over the Rigel's two, but this is hardly a deal-breaker. There are dew heaters available for both the Telrad and the Rigel, if, like me, you must have one. My Rigel has taken just as long to drain its coin-sized battery (still using the first one), so that's good. The coin-sized batteries are traditionally not as easy to find as the standard penlights, but recently I seem to be spotting large blister-packs of them everywhere - perhaps becoming more ubiquitous?

:happy11:

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The batteries for the Rigel are the CR2032's. Available widely I've found and quite inexpensive but they last for ages anyway. My Telrad took a PP3 battery (2 terminals at the top end) rather than penlight batteries.

 

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12 minutes ago, mikeDnight said:

?Telrad on a beautiful ED refractor? ?

It could turn your elegant ED into an EEK! D.???

I think telrads are great finders, but they are as ugly as sin and designed to make Dobs look good! :icon_jokercolor:

My 100ED is an 'old gold' one that I've had for years and is rather careworn (like me) so the Telrad enhances it! Anyway it's dark and there's only me to see it! But if I had a Tak like you......

Edited by kerrylewis
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It really depends how you use the rdf. Unless it's a very familiar object I just use mine for initial placement near a bright naked eye star and then star hop with the raci

On this basis I find a telrad works on my big dobs and a baader skysurfer 3 on my fracs.

I am with Mike on fracs and telrads.

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I have a Telrad with AAs that corroded in it.  I haven't been able to get it working again even with a new battery holder soldered in.  That happened in well under 10 years.  My Rigel QF still has the same button cell going strong after 12 years and no corrosion evident.

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1 hour ago, John said:

Taks don't need finders ....... you just whisper gently to them what you would like to observe and they find their own way there :icon_biggrin:

Nice John! Now I want one even more. What use is a pension pot? :happy11:

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For me, the great thing about sharing dumb ideas with you is that it helps me reflect on them and improve.

So say you have a frac and a Telrad and you don't mind your frac looking a bit daft because it has to earn its keep and you'd like to attach the Telrad only not permanently and you suspect that repeatedly using the metal screws in the plastic base of the Telrad will eventually ruin it. In addition, you don't like the idea of a wooden block because that's just naff.

Got that picture? Good.

Forget about the base of the Telrad. Just use the riser. Attach a small dovetail to the bottom (which is conveniently flat) with some double sided sticky tape.

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Then attach a dovetail clamp to the scope with a tube ring.

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Now you can just clamp the Telrad on when you need it, and it will be up where you don't have to crouch in whatever is down by the feet of your tripod in order to actually use it.

Still ugly, but less so without a wooden block and lighter, too. You can always take it off for publicity photos.

That last sentence sounds horribly wrong. Yes, that's my coat, thank you.

:rolleyes2:

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4 hours ago, iPeace said:

elrad riser is screwed onto base. Dovetail clamp screwed to side of block of wood. Dovetail clamp clamps (as it would) to bit of dovetail forward of clamp which holds scope on mount.

"Screwed on to a block of wood"...

said the man who claims he doesn't know one end of a screwdriver from another !!!

or did you commission someone to turn said screwdriver ??

?

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Just now, Racey said:

"Screwed on to a block of wood"...

said the man who claims he doesn't know one end of a screwdriver from another !!!

or did you commission someone to turn said screwdriver ??

?

I don't remember explicitly making that literal claim, but I understand why you got that impression.

:happy11:

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4 hours ago, kerrylewis said:

My 100ED is an 'old gold' one that I've had for years and is rather careworn (like me) so the Telrad enhances it! Anyway it's dark and there's only me to see it! But if I had a Tak like you......

Youd need two telrads to make a Tak look good! Actually, my Tak isn't much bigger than a telrad!

Actually I don't dislike telrads. I even had one on my 6" achromat about 17years ago and thought it was wonderful.  

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7 hours ago, Moonshane said:

I don't think that it's fair to blame a product because it was ruined by failed batteries.

It is if it uses a power source susceptible to corrosion and there's insufficient shielding between the power source and the electronics to prevent damage due to caustic gasses from the power source.  They could have chosen button cells like Rigel, but they didn't.

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Everything Is a compromise somewhere.  Button battery life in a Rigel is about 250 hours. With aas (rigel do sell an option which to Install you have to chip away some of the casing) it's about 2700 hours. I must admit I have never heard of another issue like yours with a Telrad which in my view has a generally better build quality and fixing system. Each to their own :happy11:

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