PHD2's Polar Drift Alignment routine

[almcl]

Does anyone use PHD2's Polar Drift Align?

Since moving to an OAG, I can no longer use Sharpcap's excellent PA routine and, lacking an east or west horizon, can't make drift alignment work. 

So, apart from using the polar scope (which admittedly often gives errors of less than 5') the only thing available is the PHD PDA tool.  But there's a problem.  The field of view is miniscule (909 mm focal length onto an ASI 120 mini - seldom more than one star available) and the target circle is seldom visible on the screen once things have stabilised and moving the star even a short distance in the indicated direction almost always results in a *bigger* error being reported at the next iteration.  

Anyone who has got PDA to work care to offer their thoughts or any tips?

I have contacted the author of the routine and carefully followed his (very quickly and friendly provided) advice, but so far haven't resolved the problem. 

[Laurin Dave]

Maybe a bit left field but do you still have a guidescope ?    I use an OAG but keep my 60mm guidescope piggybacked and just unscrew the ASI120 from the OAG and put it on the guidescope…   do PA in Sharpcap then screw it back on the OAG.

No experience (yet) of drift aligning

Dave

[almcl]

I do still have the guidescope, Dave, but one of the reasons for shifting to an OAG  was to loose the almost 5 Kg of extra weight that the guidescope (an ST80) generated.  I am quite keen to keep that reduction if possible, but it's certainly something to consider.

As well, focusing the guide camera after removal and replacement takes forever at the moment, although a cunning trick in Cartes Du Ciel involving reposition the OAG field of view has simplified that a little.

[Laurin Dave]

more off the wall suggestions... Any way you could take the ST80 off after PA? I.e. Is it clamped on a rail...  maybe a lighter  guide scope just for PA?  On the OAG focus once sorted and locked I'd have thought you could take the camera off and on without affecting its focus.    Another suggestion would be Drift alignment with Backyard EOS although I'd have thought this would take longer than using Sharpcap.. but be more accurate

hope this is some help

Dave

[michael8554]

Instead of using PHD2's excellent Drjft Alignment with your guidecam and oag, instead use your 700D and the DARV Polar Alignment method:

https://ideiki.com/astro/usersguide/darv.htm

Not used it myself but I hear it gives good results.

Michael 

[Star101]

Removed as no use if  poor visible East/West horizon.

 

 

[Thalestris24]

The OP can't drift align as he can't see either E or W. I'd recommend getting a qhy mini guidescope and second guide cam. the qhy mini is small and very light.

Louise

[bottletopburly]

+1 qhy mini guide scope very small and light ditch oag , works with sharpcap PA .

[wornish]

+1 for what bottletopburly said.   

I use a skywatcher 9 x 50 Right Angled finder scope with a C Mount adapter and a Toupcam to do my polar alignment and guiding.  I sold my ST80.

 

[michael8554]

7 hours ago, Thalestris24 said:

The OP can't drift align as he can't see either E or W. I'd recommend getting a qhy mini guidescope and second guide cam. the qhy mini is small and very light.

Ooops! Misread he couldn't see NCP, my bad !

But he says "horizon" - anywhere a good distance away from South and above the terrestrial horizon would be better than nothing ?

Michael 

Michael 

[RayD]

I think at 909mm f/l you're not in the region of needing to use OAG, so of course you could just fit an external guid scope/cam.  However, you may find OAG better suits you, which I do with my TAK, in which case you could use a Polemaster which could be particularly useful if you have to set up each time given how quick it is.

Just another thing for consideration.

[Thalestris24]

9 hours ago, Thalestris24 said:

The OP can't drift align as he can't see either E or W. I'd recommend getting a qhy mini guidescope and second guide cam. the qhy mini is small and very light.

Louise

I wasn't necessarily meaning to ditch the oag, just a way to do polar drift align. However, I know one person on here who uses a mini guidescope to guide an sct!

[almcl]

Thanks all for the thoughts and suggestions.  

I do have a spare finder scope which I did use with a QHY 5Liim for a while but moved on to an ST80 and then to the OAG in pursuit of more accurate guiding.  This has largely been successful and PHD2 now often reports average total oscillation down around the 0.5" mark, but this does seem to be dependent on a good PA - hence my quest for something better than the results from just the polar scope.

When it was on the rig the ST80 was secured by rings to an aluminium bar on top of the SW200P rings. Getting it out of the rings in the dark would be simple enough, not so sure about getting the guide camera back into the OAG and getting the correct focus - even with the Baader click lock...

Must admit a second guide cam is a distinct possibility (I could fit it to my EQ5/Canon 200mm EF 2.8 lens rig - which does use a finder scope to guide) but was hoping to avoid the expense...

My 'Horizon' looked something like this a couple of years ago (trees have grown more since this image and for street light reasons the mount is usually set up further in, making the western view worse). Green line is meridian, blue is the celestial equator and red are the cardinal points.

Agreed an OAG isn't a strict necessity, but it has certainly produced better guiding and, bearing in mind I'm imaging at 0.89", this is quite desirable. A polemaster would certainly be a consideration, but the expense question rears its head (again!) and having read the on-line instructions for it, I was a bit daunted, hence my hope that someone on SGL was using the PHD2 Polar Drift Align successfully and could tell how they did it?
 

[Thalestris24]

Hi you might be able to pick up a gpcam v1 cheap second hand (I have one but no plans to sell it  ) or RVO do a qhy5ii for £139 which seems quite a good price. I see Altair Astro also do a mini guide scope for £125. I have the qhy one though both seem rather expensive for what they are. Such is astro life...

Louise

[almcl]

30 minutes ago, Thalestris24 said:

...both seem rather expensive for what they are. Such is astro life...

Ain't that the truth, Louise ?  ?

I don't think I'll risk another QHY 5L - it was the  large USB connector port which broke on my first one - so possibly look for a full sized ASI 120 (the mini is good and compact and has a the much smaller and easier USB port but is almost £30 more.   Not sure how PHD2 will cope with two identical cameras...

[Thalestris24]

I think you can have multiple cameras of the same type but only one connected to phd2 at a time. Dunno how you might have managed to break a full size usb connector, lol. The one at RVO is the older qhy5ii not a qhy5l-ii, though not a lot of difference mechanically - just different sensors I think. I've no doubt the newer GPCAMs are better in some respects, but a bit more expensive, of course.

Louise

[almcl]

2 minutes ago, Thalestris24 said:

Dunno how you might have managed to break a full size usb connector, lol. 

 

The supplied cable was massive, heavy and inflexible.  The only thing supporting the camera's usb socket was a couple (or so) of pretty indifferently soldered connections to the internal printed circuit board.  Over time cable flex broke these free and the camera refused to connect. 

[Thalestris24]

I never use 'supplied' usb cables! They are always too short and never the best quality! I get Lindy or Ex-pro,  Hi Speed Shielded usb 2.0 cables. I don't have any usb 3.0 devices - yet  

ps any socket can succumb to wrenching. I did that to my SA mini usb socket when I tripped over the cable in the dark! I managed to replace and repair the socket, fortunately.

Louise