SynScan Position Reporting

[spacedyemeerkat]

My SynScan unit is reporting a slight difference in location to astronomy programs compared with what I am seeing through the eyepiece.

The yellow target in the attached picture shows where the SynScan unit thinks it's looking; the telescope itself, on the other hand, was completely centred in M37, slightly up and left of the target in the picture. It's only a small difference, and might be perfectly normal, but my slight OCD doesn't like it

So, is this normal?

[Tribal-Wolf]

You may have to reset the handset and start over

[spacedyemeerkat]

It's aligned a couple of times every night it's used - unless you mean a factory reset?

[brantuk]

Use the PAE feature (pointing accuracy enhancement) - you aren't far off according to your picture. A better initial star alignment will improve things (do this in one quarter of the sky). The more you use the pae the more accurate the scope gets over the course of a session.

In particular use the pae when you move to a different area of sky - you'll find it helps a lot.

[spacedyemeerkat]

I am not sure it's the alignment since the object is always centred in the finderscope and eyepiece.

It feels like the SynScan is literally misreporting what I am actually seeing to the software (eg TheSkyX, Stellarium). Am I right in thinking that alignment wouldn't affect this given the fact it's centred as above?

[brantuk]

Oh I may have misunderstood what you're asking. If the scope has gone to where you told it and the object is in the eyepiece and finder, then it must be aligned ok.

The problem may be in the config of the software. Did your pc update the time last night? And if this hapened before bst, is the time on the handset taken from the pc or another clock? That's my first gut feel.

Also - what eyepiece are you using to do the alignment - if it's low power then there is considerable room for error.

[spacedyemeerkat]

I am using a 10mm eyepiece for alignment. The time was taken from my iPod on one occasion and a different PC on another occasion. Perhaps I'll give it a try from the laptop tonight although that again points towards alignment which means I wouldn't be seeing correctly through the eyepiece in the first place anyway, doesn't it?

It's just really odd that the object is in perfect view and yet SynScan reports that it's ever so slightly off to the PC programs.

Incidentally, I left my telescope tracking Mars for about an hour last night and it was still perfectly centred when I returned - even though TheSkyX was reporting it as slightly off.

I am puzzlicated

[brantuk]

Lol - yes a 10mm should make it accurate enough

Keep me posted when you've tried again

[Merlin66]

Could it be your using different Epoch years in the programs? ie Current epoch v's Y2000???

[chrisshillito]

Could it be your using different Epoch years in the programs? ie Current epoch v's Y2000???

Sounds a reasonable explanation to me. I don't think you can change the epoch the synscan uses but the planetarium may well have an option somewhere that turns precession on/off.

Chris.

[Merlin66]

Chris,

You can certainly change the Epoch in Cartes du Ciel...don't know about others.

[spacedyemeerkat]

Thanks for all the responses, folks. Really grateful!

I've located an option in TheSkyX which is accompanied by the following text:

"Because equatorial coordinate systems are based upon the orientation of Earth’s axis, their accuracy

diminishes over time due to, among other factors, precession. For that reason, many publications

reference equatorial coordinates at a specific point in time known as an equinox. If you are using

RA/Dec coordinates, it is important to choose the correct equinox (either 2000.0 or 1950.0). The

1950.0 equinox setting can be useful, as many older publications list equatorial coordinates

according to the 1950.0 equinox."

It's currently set to "current" with an option for 2000 or 1950 so I'll give those a try tonight.

Incidentally, now I've got ASCOM drivers installed with EQMOD, I can control my 200 with both Stellarium and TheSkyX which enables me to use the sync command (not available on SynScan). This sorted out the problem last night but it'd still be good to get the basic function sorted.

I'll let you know how it goes.

Thanks again!