Daylight Saving Time

[Simon Dunsmore]

Hi People, 

Quick question. So last night I got out under the stars, beautiful clear night. Anyway, I used starcap to polar align, so far, so good. Next I did a three star alignment, it was here that things started going wrong. 

I noticed that I was a fair way off each alignment once the mount had pointed to where it thought they should be. Subsequent objets   were also some way off target. Once I got home it dawned on me that we are now in DST in the UK. On Synscan I had selected no rather than yes to the DST question. My question is, would this have made much of a difference to the accuracy of the mount finding the target? 

Sorry if its a silly question. BTW the mount is a Heq5 Pro. 

Thanks for your help 

Simon 

[Cornelius Varley]

A difference of 1 hour (DST v GMT}  equates to 15 degrees between the target and where the handset believes it to be based upon the handset settings.

[Simon Dunsmore]

36 minutes ago, Cornelius Varley said:

A difference of 1 hour (DST v GMT}  equates to 15 degrees between the target and where the handset believes it to be based upon the handset settings.

Thanks, so that would make a significant impact on accuracy. Thanks that helps to know. 

[jambouk]

It would only make a difference in the “accuracy” of the first star in the Three star alignment routine, where it would be 15 degrees off. Once you’d centred that star and clicked accept, the handset would then start to build the map of the sky above it and rotate it all by 15 degrees thinking that maybe the mount wasn’t level or whatever, so the second and third stars should have been closer. If the second and third stars were not closer to the suggested locations by the mount, then this isn’t due to the BST issue. The time, date, long and lay and altitude, are used to figure out what is in the sky above the mount, once your start to do a star alignment it then just relies on a fixed map of the stars in its memory and these bits of user-input data are no longer used, other than to help what is below the horizon. This is why putting the exact date, time, location, altitude is unimportant, especially if you know which are the alignment stars, and as long as you are not on a set up which you plan to park and come back to the next night.

James

[Mr Spock]

Not allowing for BST always throws alignment out. It's best to have the time and date correct. Oh, don't forget to put your day and month in that ridiculously backward format...  

[Simon Dunsmore]

2 hours ago, jambouk said:

It would only make a difference in the “accuracy” of the first star in the Three star alignment routine, where it would be 15 degrees off. Once you’d centred that star and clicked accept, the handset would then start to build the map of the sky above it and rotate it all by 15 degrees thinking that maybe the mount wasn’t level or whatever, so the second and third stars should have been closer. If the second and third stars were not closer to the suggested locations by the mount, then this isn’t due to the BST issue. The time, date, long and lay and altitude, are used to figure out what is in the sky above the mount, once your start to do a star alignment it then just relies on a fixed map of the stars in its memory and these bits of user-input data are no longer used, other than to help what is below the horizon. This is why putting the exact date, time, location, altitude is unimportant, especially if you know which are the alignment stars, and as long as you are not on a set up which you plan to park and come back to the next night.

James

Hi James, 

Thanks for your reply, makes sense, but leaves me a little puzzled as to why I just can't get this to work properly. As mentioned I levelled the mount, obtained a good polar alignment, used GPS to input coordinates, put in the date the right way round etc. Did a three star align. To check the accuracy I asked the mount to slew to the pliedes. I could see these just above the trees. The mount slewed in the right direction but was pointed below the horizon.  Tried everything I could think of. I read somewhere that it may help to do a one star alignment then park the mount, switch off and start again doing a three star alignment. 

Any suggestions would be much appreciated 

Thanks again and stay safe 

Simon 

Edited April 12, 2020 by Simon Dunsmore
Error

[jambouk]

Simon,

GOTO can sometimes just be odd.

What I would do, is set the mount up in day light (either inside the garage or outside where you were), and roughly get it polar aligned (literally point it north), mount the scope on its own and put the scope in the home position.

Boot it up, input the data for date etc and put the time in as you entered the time last night and enter the same time you were setting up last night. Then do a three star alignment using the same stars you used last night. Set you planetarium software to the yesterdays date and the time you set up and confirm the stars you have picked would have been in the areas of the sky the scope is now pointuing to, you have to use your imagination to think that star should be rouhgly due east, about 45 degrees above the horizon etc. If the first star is out, then make an adjustment to roughly get the scope to point where you think the star should be. Then accept and move on to the net two stars each time checking those stars are where you think they should be. Once the alignment is done, and hopefully reported as sucessful, go to the pleiades and see what it does now. If it slews to below the horizon again, there is something wrong, and I suspect it is user-related, rather than equipment related (it usually is). In that instance, I would take a photo of everything to you on the handset up share it here or email it me and i'll check what you are doing.

Also make sure the clutches are tight and that there is not a ton of backlash.

James

[Simon Dunsmore]

Hi James, 

Thanks so much for your help. Really appreciate it. I think I'll do as you suggest but I'll do it live tonight. Hopefully, as you say it's a user related issue. Of course it could be that I centered the eyepiece on the wrong star! I have installed an app on my phone to help ensure that I'm centering on the correct one. 

Thanks again 

Thanks 

[jambouk]

Simon,

If you are busy today, fair enough, but if you have a spare hour or so, I would strongly urge you to do it during daylight, as it is so much easier to fiddle with things, it is warmer, and there is no time pressure to get it up and working if the sky is clear. Most of these kind of things can be rectified in day light with a cup of tea and go and wander off and do something else then come back to it, reduces the stress levels. You don't need arcminute accuracy for this kind of testing, ball-park is sufficient.

Good luck and report back.

James

 

[Simon Dunsmore]

Hi James, 

Thanks. Unfortunately, I'm painting the fence today. Think I'll give it a shot tomorrow morning. Great advice. Will get back to you! 

Cheers 

Simon 

[Simon Dunsmore]

Hi All, 

Just thought I'd get back to you with an update. So, success!!! Went out again last night, did my basic polar alignment and then tweaked with starcap. This time, I entered yes to DST. Went for a two star alignment. First star was way off, but after confirming that I was actually on the correct target went for a second. Almost spot on. 

Then asked the mount to slew to the Beehive Cluster, spot on, as was every other target. First time I've actually got this working properly. 

Thank you all so much for your help 

Clear skys 

Simon 

[jambouk]

Great news. Well done.

[Jiggy 67]

FYI.. As far as I understand it, the 3rd star in the star alignment process has nothing to do with aligning your handset to the stars above, the purpose of the third star is to correct cone error which occurs when you cross the meridian 

[Carbon Brush]

My solution is to use GMT all year round on scope controls and the observatory computer.
So much easier than fiddling around with daylight saving.

Definite thumbs up for trying mount setting/alignment in daylight.
I may know someone who has a friend who couldn't get a CG5 to align at night.
March 3rd it worked. Next time out March 10th it didn't.
A daylight check March 11th, with tea and biscuits for diagnostics purposes, showed a mount March/October/November mix up!

These funny folks in other countries who don't know how to order year month and day. Or is that year/day/month? They cause a lot of bother.

HTH. David.