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Rumbold2010

Polar alignment with a CPC and Wedge

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Hi all,

Much to my consternation, I'm finding dechipering the instructions on polar alignment of my CPC somewhat confusing. The guide that accompanied my scope suggests the scope should be positioned with the OTA parallel to the forks to align. What is not clear is, once polar alignment has been achieved, what are the next steps? Do I return the scope to it's normal position with the Alt index arrows lined up? Do I then do a further star alignment? Every time I read something, it serves only to confuse me further! One bit of good news, due to the snow, it's likely I have at least a couple of days to try and get my head round it. If there are any regular users of my setup that could offer up a step by step list of their approach to this, I'd be eternally grateful. I'm seriously considering trading the whole thing in!!

Thanks in advance guys :-)

Andrew

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Hi Andrew,

I have a CPC 800 and a wedge, and have managed to cobble together some step by step instructions from various sources. Still not sure if what I am doing is correct, but I'd be happy to share my experiences with you. 

I realise that your post is quite old now, and you may have actually traded your scope in, or you may have deciphered a method of your own, so if you could just let me know before I type up my really long set up procedure! 

Rae

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Hi Mark, 

Happy to share my experiences using the wedge with you. As mentioned previously, I'm not convinced I'm doing things exactly right, but I will go through my set up and alignment method, and would be extremely happy to compare notes with you regarding this.  It is a bit of a faff, and the steps are numerous. I don't think I can be that brief, so the instructions are going to seem really long, but after the third or fourth time of doing this, I had it down to just 20 mins. The instructions are very long, so rather than type them out here, I've attached a document where you can view them, and possibly even print them out for you to use next time you set up. 

I'm really not sure that I'm doing everything correctly, so please don't take my word as gospel! This is just what I have been doing and its been semi-successful. I say that because the first time I did it, the errors were: 

Azm: -00o 04' 10''

Alt: -00o 00' 02"

These errors are explained in more detail in the final step of the alignment procedure, but this is within the error limits it says to aim for. And given that North has been difficult for me to pinpoint exactly each time (again, this is explained in the first step of the procedure), it makes sense that the azimuth has the largest error. After doing this the first time, I was fairly convinced that I had it sussed! However, the errors the second time I did it were: 

Azm: -00o 09' 04"

Alt: -00o 05' 11"

Still within the error limits, and again, azimuth is further out than altitude, but they are larger errors. There is no denying it.  The third time I did it, the errors were: 

Azm: -00o 17' 48"

Alt: -00o 06' 46"

This time, the azimuth was over the recommended error limits. I didn't record the exact errors the next couple of times I did it, but they were definitely close to the errors in the third attempt. So it seems that I'm getting worse at it - not better! The last time I tried was in April, and I give up trying to observe during the summer. Waiting for the next clear night - now that its darker quicker - to try again. 

I still think that buying an inclinometer and digital compass may help me to be more accurate in the first couple of steps. 

Anyway, let me know what you think. And if you do anything differently. Maybe by collaborating, we can actually come up with a foolproof method for this! I'm surprised that given the popularity of these scopes, there aren't more detailed instructions out there. 

Polar Alignment Method CPC800.docx

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Useful guide thanks for taking the time to produce it and of course sharing it :)

I use to use  12mm illuminated reticule EP when aligning..

Another alternative is to de-focus so that you get larger diameter out of focus "donut" as I find it much easier to see if this is central than the just a pinpoint star... although there is possibility of some "mirror shift"...

Peter...

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Hi Mark, 

Happy to share my experiences using the wedge with you. As mentioned previously, I'm not convinced I'm doing things exactly right, but I will go through my set up and alignment method, and would be extremely happy to compare notes with you regarding this.  It is a bit of a faff, and the steps are numerous. I don't think I can be that brief, so the instructions are going to seem really long, but after the third or fourth time of doing this, I had it down to just 20 mins. The instructions are very long, so rather than type them out here, I've attached a document where you can view them, and possibly even print them out for you to use next time you set up. 

I'm really not sure that I'm doing everything correctly, so please don't take my word as gospel! This is just what I have been doing and its been semi-successful. I say that because the first time I did it, the errors were: 

Azm: -00o 04' 10''

Alt: -00o 00' 02"

These errors are explained in more detail in the final step of the alignment procedure, but this is within the error limits it says to aim for. And given that North has been difficult for me to pinpoint exactly each time (again, this is explained in the first step of the procedure), it makes sense that the azimuth has the largest error. After doing this the first time, I was fairly convinced that I had it sussed! However, the errors the second time I did it were: 

Azm: -00o 09' 04"

Alt: -00o 05' 11"

Still within the error limits, and again, azimuth is further out than altitude, but they are larger errors. There is no denying it.  The third time I did it, the errors were: 

Azm: -00o 17' 48"

Alt: -00o 06' 46"

This time, the azimuth was over the recommended error limits. I didn't record the exact errors the next couple of times I did it, but they were definitely close to the errors in the third attempt. So it seems that I'm getting worse at it - not better! The last time I tried was in April, and I give up trying to observe during the summer. Waiting for the next clear night - now that its darker quicker - to try again. 

I still think that buying an inclinometer and digital compass may help me to be more accurate in the first couple of steps. 

Anyway, let me know what you think. And if you do anything differently. Maybe by collaborating, we can actually come up with a foolproof method for this! I'm surprised that given the popularity of these scopes, there aren't more detailed instructions out there. 

your point 5 in the document - it is OK, - you are only doing a rough polar align at this point.

I've only got a Nexstar 11 GPS - an earlier version of the CPC, but my handset has a 'wedge align' feature - does yours?

So in my case -

a) steps 1 -5 for rough polar align

B) switch on scope and do 2 star align

c) 'wedge align' - this points the scope at where Polaris should be - if you can't see it in finder/scope - use the MOUNT adjustments (as you did in steps 1-5) to move the scope so that Polaris is centred in the eyepiece (the scope has taken care of  the fact that Polaris has a slight offset from true north).

d) tighten down the mount again

e) turn off scope, turn on scope and do another 2 star align.

Repeat c,d, and e if necessary for greater accuracy

and then if you want to - do a drift align for the most accurate alignment

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I don't have the wedge align option. I spent a while having major problems trying to align because I couldn't find it on the handset. It was only reading stuff on another forum that I found out about the all-star polar alignment, which I was led to believe is the newer way to do it. I may be wrong though.

With regards to point 5, you say this is ok... Which bit? The bit where I'm trying to centre Poaris, or the bit where I said I wanted to try and position Polaris slightly off-centre using an app to show me its location?

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Hi Mark, 

Happy to share my experiences using the wedge with you. As mentioned previously, I'm not convinced I'm doing things exactly right, but I will go through my set up and alignment method, and would be extremely happy to compare notes with you regarding this.  It is a bit of a faff, and the steps are numerous. I don't think I can be that brief, so the instructions are going to seem really long, but after the third or fourth time of doing this, I had it down to just 20 mins. The instructions are very long, so rather than type them out here, I've attached a document where you can view them, and possibly even print them out for you to use next time you set up. 

I'm really not sure that I'm doing everything correctly, so please don't take my word as gospel! This is just what I have been doing and its been semi-successful. I say that because the first time I did it, the errors were: 

Azm: -00o 04' 10''

Alt: -00o 00' 02"

These errors are explained in more detail in the final step of the alignment procedure, but this is within the error limits it says to aim for. And given that North has been difficult for me to pinpoint exactly each time (again, this is explained in the first step of the procedure), it makes sense that the azimuth has the largest error. After doing this the first time, I was fairly convinced that I had it sussed! However, the errors the second time I did it were: 

Azm: -00o 09' 04"

Alt: -00o 05' 11"

Still within the error limits, and again, azimuth is further out than altitude, but they are larger errors. There is no denying it.  The third time I did it, the errors were: 

Azm: -00o 17' 48"

Alt: -00o 06' 46"

This time, the azimuth was over the recommended error limits. I didn't record the exact errors the next couple of times I did it, but they were definitely close to the errors in the third attempt. So it seems that I'm getting worse at it - not better! The last time I tried was in April, and I give up trying to observe during the summer. Waiting for the next clear night - now that its darker quicker - to try again. 

I still think that buying an inclinometer and digital compass may help me to be more accurate in the first couple of steps. 

Anyway, let me know what you think. And if you do anything differently. Maybe by collaborating, we can actually come up with a foolproof method for this! I'm surprised that given the popularity of these scopes, there aren't more detailed instructions out there. 

Hi Rae,

Thank you for your detailed response and sincere apologies for taking so long to reply, I've been sorting through "my content" and came across it. 

I now have an EQ mount so use my triplet frac on that mount and my CPC925 for visual only in AZ mode so I've sold my wedge. Sounds like you're staring to master the process and I wish you well.

Regards,

Mark

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I use the all star polar align in the hand control which usually gets me to within 5 arc minutes. Then it's best to do a drift align either with phd2 or manually with a cross hair if you require a better alignment 

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