eyepiece for Argo Navis alignment

[programmer]

Hi AN users.. was just wondering if people use illuminated reticle eyepieces for doing star aligns, or just regular eyepieces (med-hi power I'm guessing). I guess this is also mainly a question for non-driven scope users, as driven scopes must be a breeze to align.

[asterisk]

Whatever gives you that idea? I have used an illuminated reticle (12mm) but now use an Orion Starshoot Autoguider from Bintel with PHD Guiding and Startarg (http://www.andysshotglass.com/StarTarg.html).

Still as frustrating, but I am no longer crouched over the reticle for 30 minutes or longer.

[programmer]

I thought that being motorised, at least the star you're aligning on will stay put, unlike me having to nudge my dob to get the thing near the centre of the EP.

[asterisk]

Ah! A confusion of terms. Alignment = orienting an equatorial mount so that movement in RA matches the rotation of the earth. This requires that the axis in RA is as close as parallel to the earth's axis as possible - little mount axis and bloody big earth axis - very fiddly exercise! Drift alignment is a combination of simple instructions and black magic.

Once aligned, then the gear movement must match the earth's rotation - usually, the more expensive the mount, the better the match.

Given all the above, then, yes, you are right!

[Rodstar]

Programmer, all of the AN users that I have ever discussed this with just use an ordinary EP, usually in the medium to medium-high magnification range. Placing the object in the centre of the FOV to align is a bit of a guesstimate, but it is pretty accurate, certainly sufficiently so to obtain an outstanding result in terms of go-to pointing accuracy.

[astroron]

I do my two star alignment with a 9mm Plossl, then most of my observing is done with a 13mm Nagler, gets the object in the field of view nearly all the time.
Ron

[programmer]

Thanks everyone. Geoff, yes I meant an "Align Star" procedure according to Argo terminology not an equatorial mount alignment.. I thought there must have been some terminology mixup. Sorry about that :)

[Sentinel]

I use a Lumicon 25mm Crosshair Eyepiece

[Jeff]

Hi Tino,

I use an Orion 12.5mm Plossl illuminated reticle (about $90 from memory), and would not be without it. It makes things much easier when for dialing the Argo Navis in for the scope using SETUP MNT ERRORS.

After an hour or so sampling stars with the reticle, my RMS error for ArgNav pointing was down from around 15 arc-min to around 2 arc-min. Personally, I would have trouble doing this without a reticle.

Now makes it very easy to find small faint fuzzies (galaxies, planetary nebs, asteroids, etc) despite my rudimentary star hopping skills and light polutes skies. My main problem now is that it's getting so god damm cold outside, but it's warm inside and the wife beckons!!!

Happy hunting

[Tannehill]

Get things sorted with the Argo?

I use a 9mm reticle EP. But in a pinch your highest mag EP will work well enough. When using the Argo to dial objects in, I used my lower power EP (20-31 range), except when crusing for small planetaries, which often need more power to identify against background stars. Then I'd use a 13 or even higher power.

Regards

Scott

[programmer]

Thanks Paul and Jeff.


Great, because I just bought a 2nd hand 12mm reticle EP for $65. :) Sounds like an impressive accuracy too.


Yep, sounds like similar conditions and needs to mine.


:whistle: say no more

[programmer]

Hi Scott.

I haven't even written this up in an email for Gary K yet :D (Gary, I hope you don't mind me posting this here, will be supplementing this info for you in an email shortly) but.. I received his interim mounting solution and have tried it out on two sessions so far.

Basically the two tangent arms were modified to allow 'floating' of the arms to allow for dob base slack/play. With the Alt arm, there is so much lateral movement that I *still* need the braces on each side of the mount to cage in the OTA, but at least I don't need to reduce it to zero now.

With the Az tangent arm, I'm not sure if it's improved things. It's supposedly designed to allow for radial and vertical movement of the dob mount base, but with the grub screw holding the encoder shaft in place, I'm not sure about the vertical part :shrug: I was actually pretty happy with the original Az setup, so might resort to that again tonight (my pointing seems to be not as good as before, and I'm blaming the Az setup at the moment).

Having said that, I've been using a 12.5mm EP when finding objects, and it's either there or not far out, and nearly always in a 17mm (68deg FOV) EP, so maybe it's not that bad considering I haven't created a pointing model yet.

STILL haven't done a daytime test, and not sure when I'll be able to. It's just not that easy unfortunately.

Thanks for listening :)

[Tannehill]

That's okay, actually, for that type of mount. Having stuff almost always in a 17mm EP is about average, I'd say.

ON the Az, vertical (up and down) is what you need to permit to prevent binding. You want to try to avoid having any radial (spin, that's what I call radial) movement, as that will register on the encoder. The grub screw prevents the entire encoder bearing (the part buried in the coupler) from moving with the chasis when you spin the rocker.

On the ALT, even when I had that 5-7mm of lateral trunnion shift, the tangent arm should not drift up (or down) as you do that zenith-to-horizon maneuver with the OTA. If the tangent arm does drift, your 'floating' support pin/peg/fence isn't at the correct right-angle to the tangent arm.

Bah, I'm sure Gary K was all over this.

Suffice to say it'll work, and work great, once you get the kinks sorted. But it's worth reiterating that one shouldn't expect objects to be in the dead center of a 7mm EP with this set-up, the scope's tolerances being what they are. The ARgo is more that up to the task, but glueboard and plastic on the scope - mixed with a loose screw here and some changing humidity and temperature - are where it'll become evident.

Regards

Scott