Illuminated Eyepieces

[Horus]

Could someone explain what this eye piece is used for. Ive seen a few for sale and can't quite get my head around their use?

Thanks Rich

[Johnboy]

Hi Rich,

Generally they have a cross hair reticule inside which is illuminated, which helps if you use a scope that needs to be aligned with a star. You can align the star directly onto the cross hair. This helps with Goto scopes.

Hope this helps.

John

[Horus]

Thanks John , are they worth the money though ?

[brantuk]

Illuminate reticles can also be use for polar alignment, measuring stuff, and guiding when taking LE photos

If you have use for one then it's worth it - how much is the one you're looking at?

[michael.h.f.wilkinson]

I used to use my 12.5 Kelner illuminated reticle EP for maunal guiding (yes I am that old). I also have a wide-angle one (22mm 70deg apparent field of view) which I use in my finder.

[Mike_F]

Thanks John , are they worth the money though ?

I think so, but I have a few uses for mine. I use it to:

- Ensure the finder is properly collimated with the main OTA it's mounted on.

- Help with accurate OTA alignment during the mount's GOTO alignment procedure.

- Help with Polar alignment, thanks to the "all star" polar alignment feature my CGEM mount has. (Once GOTO aligned, it then slews away from a star by a certain amount - your polar alignment error amount - then asks you to re-centre the star in the EP using the alt/az adjustments on the mount. Bingo - you're polar aligned.)

The one example I'd say isn't worth the money (or an money at all for that matter) is the Meade 12mm illuminated reticule EP. The one I purchased was complete junk, and I've heard others say the same about it.

Your mileage may vary - depending on the uses you might have for the item.

HTH.

Mike.

[JamesM]

The Celestron Microguide 12.5mm orthoscopic reticle eyepiece as an example can be used for measuring the gap/angle between double stars and can be used to measure size of moon craters etc. Great eyepiece but certainly not the cheapest type!

James

[Ben Ritchie]

I find it a useful tool to have in the eyepiece case - don't use mine much, and mostly for doing the three-star alignment for the mount, but find myself glad to have it when I do. They're fairly cheap to pick up used.

An even cheaper option for alignment is to use a non-illuminated one, or even a screw-in reticule. They work perfectly well with a slightly-defocussed star, especially as mount alignment stars are generally 1st or 2nd magnitude anyway.

[dmahon]

I find them excellent for getting a very accurate GOTO alignment with my scope when using it for visual observing. Roughly centre it in a widefield eyepiece then pop in the one with the crosshairs and get the star bang in the middle.

I bought a Skywatcher one which has been perfect.

[Merlin66]

I have a few illuminated cross-wire and squared graticle eyepieces left over from the "good ol' days" of visual guiding OM-1 cameras and hypered film.

They are obviously excellent for drift alignment and can be useful for checking position angle/ distances of double stars.

The use of DSLR/ CCD cameras nowadays makes it much easier to measure stuff on the PC screen than at the eyepiece, but if you're still doing visual observing it can help in getting the background stars in the correct positions as well as a quick check on planetary details and their relative positions.

Handy to have in the box.

[Horus]

Thanks guys.............i,m looking into buying a good used one.