Heq5 Pro PEC training

[johnnyt123]

Hello once again

I have been looking at PEC training my Heq5 Pro.
I cam across this website:

http://www.togastro.com/ozzzy/pec.html

It details how to do it. Just want to ask if you can have the corrections made through an autoguider through the ST4 port and not have to do it manually for 20 odd min...

regards
John..

[Amaranthus]

If you want to use PEC, it's best not to do it with ST4, as they'll be fighting (i.e. the ST4 will ignore any PEC-based corrections). Better option is variable-speed PEC via EQMOD, where the sidereal speed is first modified by PEC and then pulse guiding is used to make the additional corrections.

[Garbz]

Manually PEC training sounds archaic.

From what I understand PEC + autoguiding via ST-4 is a bad idea, as Barry mentioned above. The mount will receive a PEC correction from EQMOD and an autoguide correction from the ST-4, which one does it follow, and if it follows both at once, will it overshoot?


Oh and if you pulseguide via EQMOD you can actually automatically train the PEC mid imaging session. Just start imaging like you normally do, go into the PEC tab in EQMOD and hit the record button. When it finishes capturing the number of cycles needed and starts applying PEC correction you should instantly see your number of PHD corrections decimate (assuming good polar alignment), and providing you properly park your scope before shutting down it will retain the PEC curve.

If you fail to park your scope or the power to the mount goes out I think you need to re-train, though I'm not quite sure on this.

[Amaranthus]

The only catch with training whilst imaging is if you are dithering (and you really should be). Each dither mucks up the PEC, so I don't unfortunately use this feature.

Chris is right about parking - EQMOD saves the worm position that way.

[Garbz]

Well as we mentioned about parking if you're careful you only need to train once. I'm sure you can go one imaging session without dithering, heck if you train over 4 cycles you really only need to go 40min without dithering on the HEQ5 right?

Maybe I'm biased because I don't dither (no software capable of it). But in my experience hot pixels are easily picked up in image pre-processing and are much more easily fixed than eggy stars :)

[Amaranthus]

Dithering is essential for Drizzling, which I do a lot of with my under sampled gear

[johnnyt123]

Dithering and Drizzling...two terms i have heard of before but not quiet ever came around to understanding them......

Can anyone please enlighten me...:)

[Garbz]

Dithering is slewing slightly between frames so that as you're recording a hot pixel or other sensor related noise does not stay fixed in the one spot. The idea being that as soon as you stack the resulting image the hot pixel disappears (assuming you didn't remove it through pre-processing).

Drizzling is also slewing slightly between frames but for a different purpose. It's an image processing technique that works if your optics are better than your sensor (i.e. your image is undersampled). A good example is taking a photo of something that is less than 1 pixel wide on your sensor. If your optics can resolve it then the object will appear as a bias on one pixel. Slew slightly then it will appear as a small bias on another pixel. When drizzling the missing data between the pixels is inferred and you end up with a larger picture with a higher resolution than your camera alone was capable of. But as said you only get extra detail if your camera is the weak point in the system. If your optics are the weak part all drizzling gets you is big files and longer processing times on the computer.

You can dither without drizzling, but you can't drizzle without also dithering.