SharpCap polar align vs phd drift align

[assouptro]

Hi 

I have recently moved my mount, I took it on a camping holiday and as a result I had to re-polar align it once it was back on my home built pillar. 

I had read about SharpCaps polar alignment routine and I figured it would be a well spent tenner.

I downloaded sharpcap 3.1 and set up a 50mm finder with my Qhyii m camera.

I totally wasted my first clear night.

I struggled with the sharpcap routine simply as a result of the length of time it took for the image from my qhyii m to refresh on screen! I set the exposure to 15s but it took sometimes up to 2 min for an image to appear on screen no matter what I did with exposure time, gain, usb settings etc! This made the whole process unbearable but I preserved.

Once I had what was close to “excellent” sharpcap alignment, I realised the latitude and longitude settings in sharpcap were on default. I didn’t know how much of a difference this would make so I reluctantly had another go at the polar alignment routine.

It was frustrating. On the YouTube videos it all looked so simple but I have to admit I find sharpcap difficult to comprehend.

So on to the second night. 

I started imagining, I am only using a ts65mm apo with a 420mm focal length and when I had eyeballed the alignment on my camping trip I was getting pretty good guiding with phd and prior to moving the mount I was imaging with a 12” Meade with an oag at around 200mm fl and getting less than 1 second guiding corrections.

My guiding now was erratic at best and when I looked at the result of my first 20min sub I could see movement and eggy stars! Grrrr!

So I started my usual routine using Phd drift alignment. This takes time too and by the time I was satisfied, not happy, just satisfied I only had enough time to take 2 x 20mm subs before the dawn. 

Day 3. Yes, we had 3 nights of clear skies without a moon! This is a rare thing here in the northwest and I had spent the first 2 tinkering.

I decided, after more research, to try Sharpcap again, but this time downloading version 3.2 and using my faster laptop, the one I use for processing, and a shorter usb lead. 

I could now refresh the image at any rate I desired! I managed the sharpcap routine in 10min! My results were less than 10seconds on both axis!

As it wasn’t completely dark yet I followed this up with a drift alignment with phd. I made a couple of very small adjustments to get the dec lines horizontal (or as near as damn it) 

The experience has put me off moving my mount again!

So after all that, if your still reading, my question is, which is more accurate, Sharpcap polar or Phd drift?

Cheers

Bryan  

 

 

[spillage]

I always struggled with the PHD drift routine and never felt I was 100% happy with my efforts. I do not have sharpcap as I picked up the qhy polemaster for a bargain price. This I am sure works in the same way as sharpcap and takes me 5 mins and seems to have noticeably improved my tracking.  I guess for speed and ease I would use sharpcap and when I had the time run a really long drift in PHD.

[cjdawson]

I don't know which is the more accurate of the two routines, as I've not tried the PHD version.   The videos that I've watched on it make it look like a very long winded process compared to the SharpCap routine.

I personally use a fast I5 laptop to run my imaging, so haven't noticed any of the slow problems that you've spoken about.

All I can do here really is relate my experience of SharpCaps routine and say that I've not had any problems with it going slow, or any of the issues that you mention.

The results of having aligned using SharpCap for me is that once my PHD2 guiding has settled down, I get a nice looking sign wave of corrections due to the periodic error in my mount.

Before I started using SharpCaps alignment routine, I never got that sign wave shape, and I had loads of issues getting 1/2 decent images.

[assouptro]

1 hour ago, cjdawson said:

I don't know which is the more accurate of the two routines, as I've not tried the PHD version.   The videos that I've watched on it make it look like a very long winded process compared to the SharpCap routine.

I personally use a fast I5 laptop to run my imaging, so haven't noticed any of the slow problems that you've spoken about.

All I can do here really is relate my experience of SharpCaps routine and say that I've not had any problems with it going slow, or any of the issues that you mention.

The results of having aligned using SharpCap for me is that once my PHD2 guiding has settled down, I get a nice looking sign wave of corrections due to the periodic error in my mount.

Before I started using SharpCaps alignment routine, I never got that sign wave shape, and I had loads of issues getting 1/2 decent images.

Thanks for the reply.

Yeah, the laptop was probably the problem, it’s an older windows 7 machine it it does have 6Gig of RAM? I’m not sure what the processor is but it’s a dual processor.

I tend to use that for guiding and image acquisition as I leave it outside at night and wouldn’t cry too much if it got damaged or stolen. 

I then keep an eye on it remotely with chrome Remote Desktop which I can do from my other laptop or even my phone from anywhere! It’s great being out with the family or friends knowing I can check in, change targets, or sub times etc from my phone! 

 I hope someone can tell me which is the more accurate, it would be good to know? 

Cheers 

Bryan 

[assouptro]

2 hours ago, spillage said:

I always struggled with the PHD drift routine and never felt I was 100% happy with my efforts. I do not have sharpcap as I picked up the qhy polemaster for a bargain price. This I am sure works in the same way as sharpcap and takes me 5 mins and seems to have noticeably improved my tracking.  I guess for speed and ease I would use sharpcap and when I had the time run a really long drift in PHD.

Thanks for the reply.

I think that’s sound advice, and pretty much what I was thinking, I think a drift alignment has to be an actual test of the movement of the mount with relation to the rotation of the earth and should be more accurate, but I’m hoping someone can chip in with some facts to support that theory?

cheers

Bryan 

[Tomatobro]

I have to set up my mount every time and use Sharpcap to PA.  The Alt adjustment bolts are very tight to use when the mount is fully loaded so I made up a 60mm finder scope and ZWO mono camera in the clamp and just use this to get the PA somewhere near. With little weight on the Alt bolts they are much easier to adjust.  I then pull this scope and fit my imaging gear and then make a final PA adjustment again using Sharpcap on the tracking scope.. Sounds a bit long winded but in practice takes no time at all especially as I can usually do the PA long before it gets fully dark. 3 second exposures allow Sharpcap to do its stuff.  I think the location data is so that Sharpcap can allow for atmospheric diffraction.

I see PHD making adjustments in both directions so I figure the PA cannot be that far out

Edited July 4, 2019 by Tomatobro
more info

[michael8554]

Just as a general tip, don't spend ages getting PA down to zero. PHD2 will guide out PA of 5 arcmins.

In fact if you have Dec Backlash, a gentle Dec drift in one direction and Dec balanced the same way means Dec never needs to reverse direction and PHD2 will easily guide out the drift. 

You can quickly check PA by running PHD2 Guide Assistant for a couple of minutes until the PA figure in that window settles. 

5 arc mins of PA  error is a very small amount to measure, so I'm not surprised that the various softwares come up with different figures in their results. 

PHD2 Drift Align can be a PITA and time consuming, particularly the time spent at the outset working out which way to move the star in the circle, and having to wait 30 secs for the drift to settle each time you remeasure. 

But if you quickly get close with PHD2 Static Polar Align (SPA), or SharpCap, or Polemaster, then verify with PHD2 Guide Assistant, that should be good enough. 

For absolute accuracy use a Drift Alignment, and the Dec line above, below, or on the line in PHD2 Drift Alignment has to be a very accurate visual clue. 

But like I said, you don't need to be hugely accurate. 

Michael