Drift alignment with phd2

[gonzostar]

Hi

Last night was one of those frustrating nights!

Calibrated avx mount 2 star alignment, 4x calibration stars (adjusted mount). Repeated. Then did futher alignment (undo syn). Got alignment reading  on handset to 0 00 03" in RA 0 00 01" in dec

Connected to phd2 and star kept drifting off. PHD2 suggested its drift  Alignment as apparently getting 20 arc mins of error!

 But struggled with drift alignment. I an using the orion autoguider and uses a ST-4 cable.

Couple of questions

Is it easy to use phd2 drift alignment? as i did struggle the trnd lines would not settle in the center more so with RA

Why is there such a difference with reading from the handset and what phd2 tells me?

Cheers

Dean 

 

[Thalestris24]

13 minutes ago, gonzostar said:

Hi

Last night was one of those frustrating nights!

Calibrated avx mount 2 star alignment, 4x calibration stars (adjusted mount). Repeated. Then did futher alignment (undo syn). Got alignment reading  on handset to 0 00 03" in RA 0 00 01" in dec

Connected to phd2 and star kept drifting off. PHD2 suggested its drift  Alignment as apparently getting 20 arc mins of error!

 But struggled with drift alignment. I an using the orion autoguider and uses a ST-4 cable.

Couple of questions

Is it easy to use phd2 drift alignment? as i did struggle the trnd lines would not settle in the center more so with RA

Why is there such a difference with reading from the handset and what phd2 tells me?

Cheers

Dean 

 

Hi

You don't mention doing any actual Polar Alignment! This is separate from star/pointing alignment and involves manually adjusting the alt and az. See P29 of the manual  You can used PHD2 drift alignment, Polestar alignment or handset alignment but whichever method you use you need to manually adjust. 

Louise

[gonzostar]

I have just had a quick look at p.29 and seems to be the procedure i am following It was first couple of times i have used phd2 drift allignment. I guess its practice of course. Is it quite different with phd2 using st4 cable to drift align?

Have you tried polestar alignment?

I seem to manage quite well 2 mins light frames, but now want to increase duration of light frames. 

Dean

[alacant]

3 hours ago, gonzostar said:

trnd lines would not settle in the center more so with RA

Hi. Don't worry about the RA. Slew to a star just west of the meridian and near the equator. Hit Tools > Drift Align > Drift. Wait for at least a minute. Look at the DEC line -usually red-. Hit Adjust. Loosen the west azimuth bolt 1/4 turn. Tighten the east bolt to take up the slack. Hit Drift. Wait at least a minute. Which was has the DEC line moved? You now know that west of the meridian, tightening the east bolt moves the DEC line in that direction. Write it on the cheat sheet. Armed with that, you can now hit Drift as many times as is necessary to get that red line horizontal. Next, slew 90º either way in RA then down toward the horizon as far as you dare. Hit Altitude. Now repeat the process but this time adjust the altitude bolts.  HTH.

[gonzostar]

Thankyou very much for this very clear explanation, very clear indeed.

Do you have a suggestion when to say  this is fine in terms of polar alignment error or just as close as you can get for the dec lins to become horizontal

Now i have to wait for a clear night to try it out.  

Dean

[alacant]

Hi. It depends. What's your guide/imaging setup? With my 400/760 combination 1 to 2 seconds is fine. HTH

[gonzostar]

I have a orion star shoot autoguider  with its 50mm guide scope. This is connected via a st-4 cable to a celestron avx mount.  On the mount is a 8" SCT (with a 6.3 focal reducer

I have many pictures of DSO's unguided.Using 2 min lsubs

 I thought my polar alignment was fine. However PHD2 seems to disagree !

Dean

 

[alacant]

Ah, OK. If you had 2 minute exposures without trailing, your polar alignment must be good. I think your mount may have DEC backlash. Try guiding RA only; set the DEC guiding to none. That should improve the guiding. Or, instead of AUTO, try guiding DEC north or south only and make the mount east heavy -balance and move the counterweights say 1cm-. In any case, to get the gears meshed, make sure you nudge the mount north for about 30 seconds before hitting calibrate.

Is there any way you can get a direct connection to the mount? The main issue with st4 is that it must be re calibrated each time you change target. HTH.

[gonzostar]

Ok will give all the above ago next clear night whenever that will be. I will also try phd2 guiding assistant to help get rid of dec backlash. When you say nudge the mount north i presume this is the manual guide feature in phd2. Going east heavy does improve the amount of decent exposures that i could use. 

Cheers

Dean