Aligning Goto Scopes - cross hair eyepiece

[Commanderfish]

Hi all,

For those with Goto mounts like my VX, for doing star alignments is some kind of cross hair eyepiece a must? I've seen the illuminated kind, is that recommended?

Cheers

Fish

[jambouk]

It's not a must, but depending on the focal length of your scope, it can help the goto accuracy.

If you have a shorter focal length, like under 1000mm, you have a reasonably wide field of view, so even if the goto is off a bit, the target is likely to be in the field of view. If your focal length is >2000mm then the field of view is much narrower and if the goto is off the target may be outside of your field of view.

But there are many other things which impact on how good your goto accuracy is.

I've always found if it is putch black, i'm never really sure where the centre of the field of view is, so i've used a reticle eye piece for a couple of years and live it, but others have never bothered and not encountered problems.

But it's not essential.

James

[Commanderfish]

My new scope is FL 2350mm so I think I'm going to need something! I'll do a bit more googling, perhaps the illuminated kind is not necessary until I start imaging?

[JG777]

As James mentions it is not a must but I have found it really does help. The combination of an illuminated RACI and an illuminated EP has given me really good alignments. It is nothing flash just a cheapie Seben EP buts it whole purpose in life is for alignments only, you certainly would not use it for normal observing.

One other way of getting the star central is to completely defocus it and make it into a large doughnut, that helps centralise things in the eyepiece.

[Vox45]

As James mentions it is not a must but I have found it really does help. The combination of an illuminated RACI and an illuminated EP has given me really good alignments. It is nothing flash just a cheapie Seben EP buts it whole purpose in life is for alignments only, you certainly would not use it for normal observing.

One other way of getting the star central is to completely defocus it and make it into a large doughnut, that helps centralise things in the eyepiece.

+1 I bought a Seben, works very well ... I don't see the need to pay more imho

[Commanderfish]

Funnily enough I just found the Seben whilst you guys were posting; I think I'll go for it, gets great reviews and cheap too.

Is there any benefit in an illuminated reticle finder scope? Presumably they only help in aligning the finder scope.

[JG777]

Well yes there is an advantage because you can see the crosshairs more easily, but plenty of people manage without illuminated finder scopes so it might just depend on your eyes and how dark the sky is. So a black cross hair may be harder to see if it is a darker sky. Personally on the big scope I like the cross hairs lit up. I have even added a very good quality RDF as an addition to the RACI and I have never really liked RDFs but every thing that can help the evening go smoothly should be considered. You really do need your finder aligned very well with your scope.

On my grab and go I use a non illuminated RACI and this works just as well but then there is no alignment to do.

[YKSE]

I've never felt the need of using an illuminated eyepiece, the Mark III zoom is all I need after initial alignment, with defocused stars as others have mentioned. Before I got the zoom, a MV 24mm, and HR 9mm is what I needed for allignning C8 on EQ3-2.

[MarkJ44]

Hi, I am relatively new and have read about defocussing etc, but from my own short expereince i purchased a 12.5mm illuminated reticle EP and found it improved my alignments accuracy heaps.

Cheers

[sheldondave]

Hi

I have found that using a reticle eyepiece (illuminated, 12.5mm Skywatcher) has really helped me to align my scope very well indeed. Once you have good alignment, you will not need it again till the next time you setup. I have also found that an illuminated reticle in my finder scope is useful not only when doing the initial alignment, but also when doing a GoTo at higher magnifications, when the object of interest may not be in the field of view.

Dave.