C du C not playing ball.

[alan potts]

I use C du C with Eqdir and in the past it has been pretty good at putting stars in screen, my field of view is a decent size about 1.5x 1.0 degree. Even when I sync it in with a few targets once it cross the meridian it tells me it is a long way out, moving the FOV marks by a fair distance.

Now first I thought Polar align, which once was bad but now according to many checks (10plus) with PHD2 Polar Drift is better than 2 minutes error, good enough for decent guiding even down at below 20 degrees from the horizon.

Last night after a scpe change I checked it again the same way with PHD2, and this time the FOV is 2x1.3 or so, as a reducer is fitted, PA was said to be 1arc minute after a 6 minute run about 2 degrees from the Pole, slewing to Saturn it could even get close, maybe 5 degrees out, in any case I was unable to find it, got angry and packed up, not enjoying astronomy the last 2 days.

Any ideas of the problem.

Alan

[Adreneline]

Hi Alan,

I may well be way off the mark here (excuse the pun) but I have had very similar if not identical problems in the past which drove me nuts. Careful and methodical polar alignment using SharpCap, drift alignment and just a plain old eyeball approach failed to solve the problem.

One session I decided to make sure my imaging scope (ED80) was actually pointing in exactly the same direction as my polar scope and my guide scope (SW 9x50 sitting in tube rings on the top of the ED80), taking the polar scope as the reference. I positioned polaris smack in the middle of the polar scope and checked the guide scope and imaging scope only to discover that the imaging scope was no where near aligned to the polar scope - polaris was no where in sight.

To cut a long story short my NEQ6 saddle was twisting the vixen bar as I tightened it up; the twist was sufficient to throw the scope out of alignment. A new (GeOptik) saddle later and now all three are perfectly aligned and all is well. Slewing to a target always results in it being in view, albeit not necessarily smack in the middle but at least visible for the last manual nudge so that I can sync with CdC.

I then progressed to a parallel setup with both imaging scope/lens and guide scope mounted in tube rings. I now nearly always check that everything is aligned before I start - it might add five minutes to the setup process but in the long run it saves me time.

I hope this is not a red herring but it certainly solved my problem at the time.

Adrian

[almcl]

+1 for Adrian's comments!

If the main scope is not pointing exactly at the NCP on switch on, the first goto will likely be off.  

If you have a finder scope it may be worth seeing how close to the pole it is pointing before switching on power to the mount.

I have a diagram of how Polaris should appear in my 9 x 50 RACI (below).  If you have a similar finder, it may help?

If, after a successful couple of alignments, slewing to the other side of the meridian produces a large error, then cone error may be an issue, but that's probably a topic for another day?

[bottletopburly]

Platesolving is your answer , I know it’s been spoken about before Alan it’s worth the leg work in the end 👍

[steppenwolf]

It is of course very important to know that not just the mount but the telescope too is pointing at the NCP at start up but I have to say that plate-solving does indeed resolve any issue like this. Even though I have a fixed observatory, a very accurate mount and my telescope attachment to the mount is spot on, I still do a plate-solve at the start of each session so that I know that the mount/telescope will slew accurately from the very beginning.

[Laurin Dave]

Hi Alan

Are you putting EQMOD alignment points both sides of the Meridian?  Does it work well one side and not the other, if so then maybe you have a bit of cone error (scope not orthogonal to the mount axis). 

 

Dave

[alan potts]

30 minutes ago, Laurin Dave said:

Hi Alan

Are you putting EQMOD alignment points both sides of the Meridian?  Does it work well one side and not the other, if so then maybe you have a bit of cone error (scope not orthogonal to the mount axis). 

 

Dave

Dave,

I only really image on the rising side and them allow it carry on for about 30 mins max across the meridian, so I have no points that side I did about 3-4 months back but this problem seems to have raised its ugly head only in the last couple of weeks.

Alan. 

[alan potts]

1 hour ago, steppenwolf said:

It is of course very important to know that not just the mount but the telescope too is pointing at the NCP at start up but I have to say that plate-solving does indeed resolve any issue like this. Even though I have a fixed observatory, a very accurate mount and my telescope attachment to the mount is spot on, I still do a plate-solve at the start of each session so that I know that the mount/telescope will slew accurately from the very beginning.

I may get round to Plate-solving when I get off Janet and John books, so difficult for me, this new 071 is a nightmare, just do not understand a single thing, largely software based issues, how the hell do you know if it's working. Begining to wish I had bought a better CEM 120 mount.

Alan.

 

[alan potts]

2 hours ago, bottletopburly said:

Platesolving is your answer , I know it’s been spoken about before Alan it’s worth the leg work in the end 👍

All in good time, I'm still in junior school at this lark. 1st year too.

Alan

[alan potts]

3 hours ago, almcl said:

+1 for Adrian's comments!

If the main scope is not pointing exactly at the NCP on switch on, the first goto will likely be off.  

If you have a finder scope it may be worth seeing how close to the pole it is pointing before switching on power to the mount.

I have a diagram of how Polaris should appear in my 9 x 50 RACI (below).  If you have a similar finder, it may help?

If, after a successful couple of alignments, slewing to the other side of the meridian produces a large error, then cone error may be an issue, but that's probably a topic for another day?

I have the guide camera which is lined spot on the the main scope, and I have just placed a 9x50 SW finder on the 70mmED, this I have yet to align, but that id fairly simple. Trouble is I don't know how the two imaging scopes are in relation to one another, something to look at that I didn't think of, then thats no surprise.

Alan

[alan potts]

3 hours ago, Adreneline said:

Hi Alan,

I may well be way off the mark here (excuse the pun) but I have had very similar if not identical problems in the past which drove me nuts. Careful and methodical polar alignment using SharpCap, drift alignment and just a plain old eyeball approach failed to solve the problem.

One session I decided to make sure my imaging scope (ED80) was actually pointing in exactly the same direction as my polar scope and my guide scope (SW 9x50 sitting in tube rings on the top of the ED80), taking the polar scope as the reference. I positioned polaris smack in the middle of the polar scope and checked the guide scope and imaging scope only to discover that the imaging scope was no where near aligned to the polar scope - polaris was no where in sight.

To cut a long story short my NEQ6 saddle was twisting the vixen bar as I tightened it up; the twist was sufficient to throw the scope out of alignment. A new (GeOptik) saddle later and now all three are perfectly aligned and all is well. Slewing to a target always results in it being in view, albeit not necessarily smack in the middle but at least visible for the last manual nudge so that I can sync with CdC.

I then progressed to a parallel setup with both imaging scope/lens and guide scope mounted in tube rings. I now nearly always check that everything is aligned before I start - it might add five minutes to the setup process but in the long run it saves me time.

I hope this is not a red herring but it certainly solved my problem at the time.

Adrian

Food for thought there, I have only really had this issue for a short while, a month tops, I will look at it tonight as looking outside it will be clear, as the hasn't been a cloud in the sky for weeks. I will also be able to line up the finder I put on the other day.

Alan

[Adreneline]

11 minutes ago, alan potts said:

hasn't been a cloud in the sky for weeks

!!!!! - are you on the moon?  

Hope you get it sorted.

I don't disagree that plate solving will sort it - I've tried that too and it works - but I felt it ought to work without recourse to that method.

Good luck!

Adrian

[alan potts]

2 minutes ago, Adreneline said:

!!!!! - are you on the moon?  

Hope you get it sorted.

I don't disagree that plate solving will sort it - I've tried that too and it works - but I felt it ought to work without recourse to that method.

Good luck!

Adrian

I agree with you. A little while back when I was fighting PA and trying to understand how to get it better, I got PA down into 3-4 arc mins area and all of a sudden there is was, say jupiter on first slew. in-frame but not centre. Now when I do it is it miles out in some cases maybe 5-6 degrees or more as when I start I can see Jupiter easily. Once I have synced to it then it will point OK. But the distance between map position and actual scope postion on the EQmod little chart is  a fair old gap

[alan potts]

Well I had a look at if the scope was pointing at Polaris and it was indeed a good way off, which was quickly put right. Even though I was able to centre the pole star east to west I was still a little off mark north to south which must indicate either PA isn't spot on or the telescope is not sitting parallel to the the polar axis, I tend to feel the latter is correct but in my view it was close enough.

Even doing this it slewed close to Saturn but still not in view of a 1.5x10 degree field of view, after moving the scope and sync setting on Saturn and another star a few times it behaved. But even though I synced to an object it still slew a good way off after to a star that was only 4-5 dergees away, something is not right here for sure. After messing around and instead used the Dialogue Setting in EQmod, then it set itself on on objects with good accuracy, even on a slew to M15 which was a fair way from where the scope pointed.

Another point for site friends helping me here, even when pointing is good after sync or other set-up methods and point s are saved, it it back to square one the next night. It doesn't remember anything even though sync points are loaded on Un-park. I do though have a feeling I had another box ticked in this EQ mod section beforehand when things were good.

Bit of a stinker this one I feel.

Alan

 

[stash_old]

A long shot but have you checked that EQMOD/CDC/etc are all using the same EPOCH - if one is using J2000 and another JNOW it does some funny things and PS helps but will not cure the problem nor will EQMOD alignment points. 

Just a thought 🙂

Plus have you ticked the "Save on Park" for alignment points else yours data will by 0 on startup.

 

Edited August 27, 2019 by stash_old

[alan potts]

4 hours ago, stash_old said:

A long shot but have you checked that EQMOD/CDC/etc are all using the same EPOCH - if one is using J2000 and another JNOW it does some funny things and PS helps but will not cure the problem nor will EQMOD alignment points. 

Just a thought 🙂

Plus have you ticked the "Save on Park" for alignment points else yours data will by 0 on startup.

 

Well it is very kid of you to come up with something different but I am sorry to say I don't have the first idea what you mean (Epoch, J20000 etc), any chance of being a bit more simple for me.   I have ticked Save on Park again, it had become unticked. The trouble is I have not been able to re-align with the new camera and not really being very sure of where I am. I have the Canon back on for tonight to do just that, a few weeks ago  all was well then the wheels came off.

Alan

[stash_old]

5 hours ago, alan potts said:

Well it is very kid of you to come up with something different but I am sorry to say I don't have the first idea what you mean (Epoch, J20000 etc), any chance of being a bit more simple for me.   I have ticked Save on Park again, it had become unticked. The trouble is I have not been able to re-align with the new camera and not really being very sure of where I am. I have the Canon back on for tonight to do just that, a few weeks ago  all was well then the wheels came off.

Alan

Epoch - used to calculate the coordinates (RA/DEC) in space of an object or point using a reference point based on date/time. So Epoch J2000  - J = Julian like the Julian Date, 2000 refers to the Jan 2000 at 12.00am. This is then used in a calculation with now date/time to produce RA/DEC coordinates of an object. There are others JNOW for example.

Anyway if one piece of software uses a given coordinate it needs to know what the base (Epoch) is else if it uses that info and assumes another Epoch then values produced are different. 

So as I understand it if CDC uses J2000 and EQMOD / APT uses JNOW  outcomes will be different IF they do calculations on the RA/DEC passed from CDC. In the set up on all three there is a tick box to set up which Epoch they are using - they should be the samebe it JNOW or J2000 (APT will convert see below )

Same goes for your location (LAT/LONG) altitute above sea level and PC Date/Time must be spot on.

If something needs changing as its wrong I am sure someone will point it out 🙂

I did say a long shot 🙂

 

[Stub Mandrel]

I never have problems with my HEQ5, but after a meridian flip all bets are off and a realign would be needed. In practice I can't image far enough past south to be worth flipping.

Is your problem after a 'flip' or when crossing the meridian with flipping suppressed?

[alan potts]

6 hours ago, stash_old said:

Epoch - used to calculate the coordinates (RA/DEC) in space of an object or point using a reference point based on date/time. So Epoch J2000  - J = Julian like the Julian Date, 2000 refers to the Jan 2000 at 12.00am. This is then used in a calculation with now date/time to produce RA/DEC coordinates of an object. There are others JNOW for example.

Anyway if one piece of software uses a given coordinate it needs to know what the base (Epoch) is else if it uses that info and assumes another Epoch then values produced are different. 

So as I understand it if CDC uses J2000 and EQMOD / APT uses JNOW  outcomes will be different IF they do calculations on the RA/DEC passed from CDC. In the set up on all three there is a tick box to set up which Epoch they are using - they should be the samebe it JNOW or J2000 (APT will convert see below )

Same goes for your location (LAT/LONG) altitute above sea level and PC Date/Time must be spot on.

If something needs changing as its wrong I am sure someone will point it out 🙂

I did say a long shot 🙂

 

Well I don't recall ever seeing these screen but I best bring the laptop in and sit an try and at least check this, I am sure I don't remember changing anything like this, but that will not mean I haven't. I started a thread last night about scope alignment with the PA, it seems some way out. I am stripping the scopes off today and going back to basics as this seems a sensible thing to do. All problems seem to have come from trying a duel rig, even though I am sure I set it up as good as the equipment would allow. None of it was cheap and cheerful gear and all seemed solid and well made.

Many thanks for taking the time to do this for me,

Alan.

[stash_old]

One other factor that caused me a lot of problems was - balance of the OTA's. If you get this wrong , i did, Cdc or Apt, will try and go to the correct coordinates (assuming everything with Lat/Long,Date/Time and Epoch is ok) but will do the following (well it did with me 🙂 )

1. Slew either short or long of the correct place.

2. Slew to the correct place but then "move", after "settling", away from the object desired.

3. In some positions it would not slew anywhere near and refuse to slew to the correct point.

After rebalancing this removed 99% of these problems (nothing is perfect in Astro LOL ).

Good luck with your "return to basics" it would seem the best route if that was all working before the change to a dual rig.

 

[alan potts]

2 hours ago, stash_old said:

One other factor that caused me a lot of problems was - balance of the OTA's. If you get this wrong , i did, Cdc or Apt, will try and go to the correct coordinates (assuming everything with Lat/Long,Date/Time and Epoch is ok) but will do the following (well it did with me 🙂 )

1. Slew either short or long of the correct place.

2. Slew to the correct place but then "move", after "settling", away from the object desired.

3. In some positions it would not slew anywhere near and refuse to slew to the correct point.

After rebalancing this removed 99% of these problems (nothing is perfect in Astro LOL ).

Good luck with your "return to basics" it would seem the best route if that was all working before the change to a dual rig.

 

It is balanced a tiny bit rising side heavy, this I am told helps guiding as the AZ EQ 6 works better like this, results sugeest this is correct based on what I see.

It doesn't do any of the things you suggest, wide of the correct place in a lets see how much we can annoy Alan mode.

Alan