Polar aligning an EQ8 on a pier

[glowingturnip]

Hi,

My sons' school will soon be taking delivery of their new observatory equipment, so I'm looking forward to lots of fiddling about as we set it up.

The mount is an EQ8 on a permanently mounted pier (in an obsy on the roof).

Obviously we'll be wanting to get an accurate-as-possible polar align on it, so I'll be looking to drift-align it, rather than the usual squint through the polar-scope that I do with my own equipment.

I'm planning to use the drift-align feature in PHD2 to do this (we have a ZWO ASI120 planetary/guidecam coming too), but I was wondering if people have a preferred way to do it instead of PHD ?  I think the EQ8 even has its own align feature, though I'd have to read the manual for that.

We'll have an SCT and a frac side-by-side on a saddle bar on the mount, so any tips on getting those aligned together appreciated too. 

I think I can set a permanent PEC in the EQ8 as well.  I presume I just do that by guiding it with PHD for a few minutes.

Fun times ahead... 

[orion69]

PA procedure in PHD2 is good, I used it last few times and it works very well. For me it is preferred way of drift alignment because I don't have to take my camera off.

PEC could be useful if you'll be using longer exposures with guiding camera (>4 sec), around 2 sec not needed.

[ollypenrice]

You will probably not find it at all easy to get the two instruments parallel. This is harder than it looks. By far the best device is the Cassady T GAD

These are out of production and very expensive, though they work. I tried a Maxguider HD from ADM to carry one of a pair of Tak FSQ 106 refractors and it was woefully inadequate in terms of stiffness for imaging but it might have been OK for visual. There are tube rings but modern refractors are often too short to be well held in these things. I'm not a fan.

For most purposes, though, precise alignment won't be necessary. I'd be inclined always to do the star alignment in the SCT so that it will be the cone error of that one which is fed into the sky model. The target will probably be there in the field of the refractor using a widefield EP anyway.

Olly

[glowingturnip]

thanks Olly.

Yeah, it's not really going to be a DSO imaging rig,  we're only 5 miles from central London so the LP is shocking, so DSO's are going to be pretty much out of scope - it'd just be me or some of the advanced after-school clubbers who might attempt it occasionally, bung a guidecam in the frac and see if we can get anything decent with a DSLR from the SCT (probably not).  Planetary and lunar on the other hand could be lots of fun with the ZWO and much more accessible for the kids.

So as you say, if we can get the field of view of the refractor (an ED80) enveloping the fov of the SCT (10") then we're good enough - idea is that we could have a video feed to a laptop of the wide view for boys to look at who are waiting their turn at the eyepiece of the SCT.  Good tip re aligning using the SCT, thanks.

[Earl]

If your going to be using an SCT id not look at DSLR or CCD id go video onto a screen others can look at, probably a better way togo it as many people can all see results instantly.

Your PA will not need to be as critical for this either

[glowingturnip]

totally agree.  The kit will be 'DSLR-capable', the school have plenty of them anyway, but as an educational thing, I don't think any kids are going to want to sit quietly waiting for a guided scope to capture 3hrs plus of data, and then do darks frames etc etc, so that's just a nice-to-have.  No plans of getting a CCD for it at all.

Planetary cam stuff on the other hand I reckon would be really cool for them - press record on the laptop, take home a couple of minutes of video on a memory stick, download registax, and off you go.

I refuse to have that much of a mount and not have it accurately polar-aligned though  ;-)