GREAT!!!! Protrack Results (after a poor start)

[PRejto]

So, I've got a top mount (MEII) permanently set up. A TEC180 (so no mirrors flopping about, etc), and a 394 point T-Point model indicating that I'm within .1 tic from the refracted pole in both MA and ME. PEC is on and when last measured was sub arc-sec.

Yet, my Protrack results look crummy.

I see strange little stars growing in the general direction of RA in 5 min Protrack images. 15 sec control images do not show any distortion, nor do guided 5 min images. Why the little "budding stars" rather than just a general streak or egg shape? (X=RA)

I remember reading a post I think by Marcus saying that he needed to modify the RA tracking rate. Might this be the issue?

Any ideas greatly appreciated (while I waste time waiting for my ST-I to be returned).

Peter

[Bassnut]

I know this has been covered before, but have you tried protrack without PEC?. I get better results with PEC off.

[Paul Haese]

The tracking rate should not be the problem. Why are you doing unguided (I know your guider is away), surely guided is going to be producing better results despite whether the mount is top of the line.

If the stars are good guided then perhaps guided it should stay Peter.

I am not running protrack on my PMX as I run PEC. Although on my PME I use Protrack but not PEC. Each mount gets differing results but I still guide no matter what.

[PRejto]

Actually I didn't know that so thanks for letting me know. I will try with PEC off!

Peter

[PRejto]

Well Paul you are right. I'm doing this because I don't have a guide camera and thought I'd give it a try. Others do succeed, but I guess not me (so far!!). Tonight I'm trying to remeasure PEC just to be assured that it's working.

Peter

[SpaceNoob]

By any chance have you binned the 8300 sensor?

Looks like blooming due to the horizontal shift register. I am only asking this because I have seen this on bright stars when binning 2x2 with my own sensor.

This is an example quite close to what I experienced:

http://www.pbase.com/wjshaheen/image/134819312/original

http://m2.i.pbase.com/g4/02/508502/2/134819312.UDJWqM9M.jpg

[PRejto]

Chris,

Great! This looks identical to what I'm experiencing. One mystery solved. Many thanks!

Peter

[Octane]

I was thinking the same thing when I saw the thumbnails, it looked like blooming.

I didn't say anything because I didn't realise blooming can be horizontal, too. In my camera, it's always a teardrop shape north-to-south. :)

Mystery solved!

H

[PRejto]

Partly, anyway...

I checked PEC last night and it is .8 arc-sec peak to peak. Seeing was pretty poor so I think this is a good result.

However, blooming or not I sure see a lot of drift mostly in RA looking at the 16 min guiding graph I did to measure PE. This was 1x1 binned with a Trius at .95 arc-sec though the TEC140, camera north up with Protrack on. Looks like the drift is ca 4 pix over 10 min or so. Some drift in declination but looks to be a lot less.

Peter

[PRejto]

Finally, success!

I redid the model and now have a 480 point model that is essentially the same as the previous model but contains additional data points further to the north and south. This has changed the altitude recommendation of T-Point from a previous within .1 tic of refracted pole to 1.1 tics from refracted pole. I didn't move the mount but assume that T-Point just uses that difference to adjust how it moves/points with Protrack. The result now is about as good as I can imagine. Why the earlier model does not capture the altitude is not clear. The one anomaly is the 5 min TEC140 image showing a larger aspect change than any of the other images. Perhaps this means the TEC140 is moving relative the TEC180. But, the following 7 min image is very good.

Peter

[frolinmod]

Nice. Maybe you should change the title of this thread from "poor protrack results" to "envious protrack results." :P

[Octane]

That's amazing.

I look forward to the day when I get one of these babies!

Your unguided 7 minute exposure looks like one of my guided ones!

H

[PRejto]

Yes, I will. Done!!

Peter

[PRejto]

Patrick Wallace analyzed my models (on the Software Bisque forum) an came to the conclusion that either model should work equally well. That wasn't my experience but perhaps I was too hasty in giving up on the smaller model. The apparent change in the ME term comparing the 2 models is due to additional terms (HXSH and HDCH) being added to the model. These terms are quite similar to the ME term. His analysis also shows that I have about 4 arc-sec of hysteresis somewhere in the system (telescope + mount) but still achieve 7 arc-sec pointing accuracy.

Peter

[gregbradley]

Interesting side by side of the 180 and 140. I note the 180 stars are noticeably tighter. Because of the fluorite or the higher resolution capability of the larger aperture?

Greg.

[PRejto]

Greg,

I personally think it's the Trius and not the TEC140. Like you I think there is something suspect about the Sony chip on these APOs. Stars just look more blobby and no matter how much I work on the focus I get the same result. A pity because otherwise this camera rocks! And this is why I'm using it for colour data and not luminance!

Peter