Polar Alignment Issue? Help!

[mbalkham]

So first chance to get the scope going in anger since it arrive (4 months behind me) in NZ. Thought everything had gone pretty well until this morning when I zoom in on one of the lights (see attached). Note to self to check the 100% crop before setting the whole night's imaging off! All the frames are similar

I'm grappling with a few new things at the moment (not least a change in hemisphere but also new windows 10 pad which often refuses to speak to the scope and/or the guide cam) so scratching my brains a bit about what I did wrong. Any help would be appreciated.

Process so far: 

1. Rough alignment of tripod/mount using a compass, set-up and balance scope, wait for darkness.
2. Use alingmaster to do a 2 star alignment and adjust Az & Alt as required and all looked pretty good after initially struggling to find the stars I was looking for!
3. Repeat a couple more times on other pairs of stars (needing very minor adjustments so thought all was well)
4. Slew to the target (ETA Carina in this case) using C2C. Focus on a bright star using a bahtinov mask.
5. Set PHD2 running. I've ignored a warning in PHD saying that it can't keep up with RA adjustment (next mistake!)
6. Rattle of lights only 30s exposures ISO 3200 (noting I needed to recentre after about 30mins another warning sign missed!)
7. Pack up whilst shooting darks & bias

So I am wondering is this just poor polar alignment? Or have I not told all the bits of software (EQMOD, Alignmaster, APT, C2C) my correct location? Or is this something else?

Thanks in advance.

Another go tonight hopefully (clear skies please!)

 

[mbalkham]

Here's a processed (perhaps over processed!) complete image (reduced file size) will try again tonight if the clouds hold off!

[Mav359]

Three things from me...

"Use alingmaster to do a 2 star alignment and adjust Az & Alt as required and all looked pretty good after initially struggling to find the stars I was looking for!"

If you are using Alignmaster (I do its great) then the tripod MUST be perfectly level regardless of what mount, how good, GEM.... Its something to do with how the software works (others cleverer than me will explain)

"Set PHD2 running. I've ignored a warning in PHD saying that it can't keep up with RA adjustment (next mistake!) "

Early days in I made the mistake of trying to polar align using the polarscope long after the sun sets and picked the wrong star in the polarscope, as a result now i always do it at first dark to ensure i'm on polaris, if i ever miss that window i take the polarscope out and centre polaris then put the polarscope back and fine tune.  If PHD is complaining it can't keep up it could be as simple as that.

I'd bet its the first though, if you were so far out Alignmaster would give you an error saying something like the margin of error is too great or words to that effect. Its a pain but i'd tear it all down and start from scratch.

Lastly make sure that every piece of software you are using has exactley the same GPS co-ordinates, ive have seen and read about bits of software fighting one another.

 

 

[Pompey Monkey]

This might sound a bit daft, but have you set the direction of RA to reverse? Is it possible that you mount is tracking the wrong way and PHD is do in its best to correct for this? What's you max RA guide correction rate?

Apologies for stating the bleedin' obvious, but sometimes it's worth it!

[mbalkham]

Pretty sure tripod is level (on a concrete plinth around the house). I'll double check once I set it up again. I've not even tried the polar scope being down south (but perhaps I should!). Like I said the 2 star alignment looked good and I was fairly happy that it was looking good.

Def not a stupid question on the RA direction. I can't even find one! Looking at ASCOM Setup I'd assumed that setting Lat to 'S' in the location would do it as I couldn't see another setting. Same in Alignmaster which has Lat set to 'S'. In terms of PHD2 I can't find any settings relating to where the scope is. Does it work this out from the calibration?

Max duration RA 2000 and (Dec 2000) in PHD2 (default I think). I know I shouldn't be getting significant movement over a 30s exposure (certainly didn't in the UK).

 

 

[mbalkham]

Just measured the fall (using the mobile) and it retcons there's a 1.5 degree fall on the concrete (not sure how accurate the measurement is). Not sure that would be measurable on the tripod bubble? Say front legs are ~1m apart 1.5degrees would be ~25mm so maybe that is it!.  How critical is this likely to be?

[Pompey Monkey]

I would think that east-west levelling was the important one, after all you adjust the north south with the altitude bolts.

I guess ASCOM makes the RA direction call based on your lattitude.

BTW my first post from the train! 

[mbalkham]

Nice one, you on the mobile app? I've sometimes struggled with that!

Well I'll check next time I'm out (looks like the clouds rolling in might mean that's not tonight!)

[kens]

Another bleeding obvious thought: when you aligned your mount with a compass you did point it South (not north) and account for Magnetic Declination which in NZ is quite a lot (20+ degrees) and in the right direction (true north is west of mag north)

[mbalkham]

Magnetic Declination could be it! Just checked outside and looks like I'm well off south! Clouds might be clearing so maybe time for another go!

[Pompey Monkey]

1 hour ago, mbalkham said:

Nice one, you on the mobile app? I've sometimes struggled with that!

Well I'll check next time I'm out (looks like the clouds rolling in might mean that's not tonight!)

The mobile web page seems a lot more user friendly after the forum upgrade  Good luck with the magnetic declination correction!

[ollypenrice]

Could you not try a DARV alignment to get you something like right to start with? http://www.cloudynights.com/page/articles/cat/articles/darv-drift-alignment-by-robert-vice-r2760 I'm always suspicious of software packages for things like alignment. They're all very marvellous when they work but they have no common sense. The DARV method is just classical drift made more easy to read. Above all it cannot lie or make a mistake or have the wrong box ticked or... etc etc. It is a direct measurement with no third party involved. Once your out and back trails are more or less overlapping you cannot be far out. At this point you could try Alignmaster but first I'd want to know I was close enough for it to work consistently.

Olly

[mbalkham]

Thanks Olly. I tried it last night and struggled! Not sure why still too sleep deprived to make sense of it all. All I know for sure is I spent 4hrs and failed to get a single image, also broke the game pad and maybe the usb slot on the pad! Grrrrr!

[kookoo_gr]

For your issue it could be bad polar alignment or flexure at your setup and you need to spend time and be patient, also don't put your anger(?) at your equipment (your broken game pad). you need to be thorough in order to locate and eliminate/reduce the cause of your problem, unfortunately this will take time. Here are some advises and how i do things when i setup my equipment for imaging.

Make sure that all the software works with your equipment during daytime inside your house, you don't want to search for drivers, or a fresh download for a software that doesn't work in the middle of the night in the field, alternatively you can have your software at a backup flash drive with you along with any electronic documentation and images for quick help if everything goes south. Finally make sure that each software that uses coordinates has the correct coordinates and altitude of your imaging location. If phd uses any coordinates it uses them via eqmod.

Setup phd2 for your guiding system, i suggest you watch the video and read the documentation carefully, it will save you a lot of trouble when guiding

As for the hardware part, i make sure that my tripod is level to the ground. The bubble level of the eq6 is good enough for the job.

in order to remove the polar alignment issue, master the drift alignment method as proposed by olly. In my early days of imaging i learned it and my PA was spot on, even though the last year i use alignmaster when i first started using it i confirmed my PA with a drift alignment and it was perfect. This method will also remove any errors by bad alignment from the mount's polar scope (make sure the polar scope is aligned, http://www.astro-baby.com/HEQ5/HEQ5-1.htm you can see how to align the polar scope). As to how i polar align my mount my workflow is the following. Level the tripod and make sure it points roughly at north with a compass (south in your case) load my gear at the mount, balance it and once the light is dim enough to see polaris i use the polar alignment procedure of eqmod to polar align the mount. Then i use alignmaster/drift align for fine tuning my polar alignment. I mentioned that the eqmod software has a method for polar alignment. It is a fast way for quick polar alignment using the mount's polar scope, i won't go into details about the procedure since the eqmod documentation describes it thoroughly and i suggest you read it carefully.
 

Other causes of your bad guiding could be bad balance at your equipment, see this video for proper balance of a scope

 

Another cause is cables dragging at your equipment, practice cable management to avoid these issues (lately i am trying for a final solution at my cable management problem)

now that i covered the basic obvious things that might cause this issue you need to tackle flexure, it is caused by various parts of your equipment that are not tight enough. Make sure that every piece of equipment is tightly placed, the guide scope is tightly screwed at your imaging scope, the focusers of both scopes are locked when they are focused

Also it is a good thing to know at your screen which direction is which,  i used the direction keys form eqmod and moved the image eg. east for 3 seconds and saw where a star moved and placed a sticker at my screen noting east and did the same thing for north south, in my case at my screen north is left, south is right, east is down and west is up, that way if something goes wrong when guiding i know at which axis to look, also it makes framing an image much easier.

I hope these will help you solve your problem