TheSky sky map.

[Tandum]

How accurate is the sky map in TheSky? I've noticed lately that my plate solved images are slightly off with the thesky. I'm looking at ngc-6164 and plate solving in maxim. Aligning to the sky puts the object high and right so I figured I'd solve and align to the central star, HD 148937. It is also off. I put some cross hairs on the maxim image, centered the star, plate solved and synced and this is the image from the sky.

What's wrong here? Simply errors in location co-ordinates?

[Barrykgerdes]

Are you trying to overlay a computer generated simulation with a photograph? How much is the change is it within the tolerance of the display? Are both pics at the same epoch?

There could be many reasons for the discrepancy

Barry

[Tandum]

It's just a tight fit to get all of this object into the field of view and I want accuracy. I see J2000 when syncing between maxim and thesky, is that the epoch? I don't see epoch anywhere in help for thesky.

I think it's a co-ordinate issue, the sky says Alt is 59 while the temma driver says 53 degrees. The temma driver does not allow decimals of seconds in the location. That could be it.

[Barrykgerdes]

Hi Robin

59 degrees verses 53 degrees is a mammoth error something drastic is wrong. Have you identified the correct stars? That seems to be the most likely problem. Has the CCD image been correctly scaled.

J2000 should be the confirmed epoch of the star coords. However most of the planetarium programs display as Jnow. which is the coords of the object at the selected date after the annual movement is factored in. However discrepencies will generally be only fractions of an arc second.

I have done a manual form of plate solving when preparing images for inclusion inclusion in Stellarium and it requires quite a lot of work to get the coords of the corners to overlay the texture accurately and then find the exact centre.

I actually picked up one or two older images that looked good in low density star fields but when more stars were added the original plate solve had identified the wrong stars.

Barry

[Dennis]

Hi Robin

I have found that the Tak EM200 on screen “Cross Hairs” are not accurate with all my astronomy applications; The Sky, Starry Night Pro and SkyTools. The difference between the “real position/target” and the “cross hairs” is generally off by a few arc seconds.

I think that this has something to do the how and what the EM200 encoders report as the RA and DEC positions – they are less accurate than the planetarium apps can report on hence I always find a small discrepancy and the cross hairs tend to jitter too.

I recall being surprised at this when I first used my EM200 several years ago, but a search of the Tak Yahoo Group indicated that this was normal and it has not bothered me since then for how I set up and the type of work that I do with the mount.

Cheers

Dennis

[Tandum]

Definitely the right star Barry, I'll need some clear sky to check anything more.

I've seen it jitter as well Dennis. I would have thought a platesolve and a sync would have put the mount on target though. I do have both maxim and thesky connected to the mount via poth. I'll have a play when it clears up.

I can still slew from 6188 in the south east to m27 in the north west, including a flip, and have m27 come up close to center on the sensor so it's not all bad :)

[edit]
My bad, I had 157 instead of 153 entered for E in the tak driver :P