Alignment, polar and star

[fortytwo]

Hello all,

 

 

So like many amateurs I am trying to master the art of alignment. I have had reasonable success the first time after following Astrobabys guide that I got from this site.

However I do have one or two questions arising from that.

 

 

Below is an extract from the excellent guide.

 

Setting the date and time
We now need to set a date and time for a known transit of Polaris. For the sake of this tutorial and ease of visibility on the accompanying pictures we are going to set a transit time of 23:00 on October 10th.
To set date and time simply turn the Date Circle ( Fig 7 ) until the date you require is in line with the time you require for transit. The date circle is divided into months and days with markers for every 2 and 10 days.

 

 

 

You can see in Fig 7 the Date Circle being turned to its setting for the transit time of 23:00 on October 10th - i.e. the time shown on the RA Index
( 23:00 ) lines up with the Date shown on the Date Circle ( i.e. 10th of the 10th ) in Fig 8.
The RA Index has two sets of numbers. The upper numbers are for the Northern Hemisphere the lower numbers are for the Southern Hemisphere.
How do you know what time and date to use as a transit ?
To find out what time and date Polaris is in transit you will need either a star catalogue/almanac OR a quick way is to use a program called PolarFinder. You can get this free on-line from

 

 

Using PolarFinder you can find a time for transits at your location and simply set up the polar scope circles on your mount for your own time and date. Remember to compensate for Summer Time or Daylight Saving Time and use GMT only if your in the UK.

 

 

My question is….she keeps saying we will use this date for convenience, or use a known transit time for your location….so do I just find any transit date/time or should I use the one from the date I wish to observe, and do it every time?

Presumably if I move to another location I should re-do it? For example in the summer we spend time about 80 miles south of our normal home position.

 

My second query relates to 3 star alignment, or star identification in general.

I guess I am looking for tips and tricks more than technical advice here.

When I did my first three star alignment, the first challenge was knowing which stars to use.

Not being familiar with star names yet, I was able to identify a couple to use, but they weren’t necessarily stars that would stand out when viewed through the scope, and as we know a scope reveals many more stars than the naked eye, so I struggled to know if I was aligning with the correct star!!!!

Can anyone recommend good stars for alignment in the Northern Hemisphere from a suburban area where the first 15 degrees of elevation are generally unusable?

Sorry for the long post and I hope I have explained myself adequately.

 

 

Many thanks in advance,

Jeff.

[PeterCPC]

Hi Jeff

I would really help if you told everyone what equipment you are using. There are differing methods of alignment for different mounts.

Peter

[ronin]

Cannot give any insight to the first might be that the explanation is technically correct but manages to confuse the idea. People polar align be setting polaris at the appropriate position on a reticle circle. Whether or not this is technically referred to as a transit time I have no idea but I doubt there is a transit of anything involved as in Mercury Transit.

The second: At this time you have Arcturus as a single bright star (orange/red) in the West, getting low now. Vertically up and a bit South East you have Deneb and Vega, Altair is there but seems more "hidden". Caph at one the end of Casseiopia is commonly used. Another may be the one at the end of the handle of the plough, Alkaid, but that will be sort of half close to Arcturus. At this time they are the bright ones. Not that many that  are obvious and single. Generally advised to avoid Polaris if possible, reason is that when angles are concerned Polaris may be defined as close to zero, close to rotational axis of the earth. In software and maths zeros are best avoided, expecially if there is a division concerned.

 

[Davey-T]

Astrobabys guide it probably too comprehensive so confusing for the beginner (sure she won't mind the gender change  )

Star aligning is a very good way to make you recognise stars starting with the brightest ones, I think you can set Stellarium (if you haven't already downloaded it you should ) to just show the brightest stars and if you really want you can replicate your home horizon.

You need a finder scope properly aligned to your main scope.

Dave

[fortytwo]

46 minutes ago, Davey-T said:

Astrobabys guide it probably too comprehensive so confusing for the beginner (sure she won't mind the gender change  )

Star aligning is a very good way to make you recognise stars starting with the brightest ones, I think you can set Stellarium (if you haven't already downloaded it you should ) to just show the brightest stars and if you really want you can replicate your home horizon.

You need a finder scope properly aligned to your main scope.

Dave

Apologies to Astrobaby, duely changed

To be fair I have found her guide the most understandable up until now, and I have looked at alot!!!!

Its just that last time I tried, although the scope slewed to the area it was always a bit out with the desired object just outside the FOV, and I am not sure if that was from the Polar aligning, or incorrect star alignment.

 

1 hour ago, PeterCPC said:

Hi Jeff

I would really help if you told everyone what equipment you are using. There are differing methods of alignment for different mounts.

Peter

Yes of course it would, wouldn't it. I will add it to my signature.

My apologies.

 

@Ronin, thankyou for the star suggestions, I will look for these tonight, clouds permitting obviously.

[fortytwo]

I can't yet add a signature so for the record I currently have:

Skywatcher 200 refllector

Skywatcher 130 refractor

HEQ5 Pro

EQ5

and about 3/8 cloud cover lol

[Davey-T]

Polar alignment  and star alignment are two different things.

PA aims the RA axis in the general direction of Polaris at a given time and it's location can be found from one of the many apps and Stellarium, this helps the mount keep tracking the stars depending on the main limitation which are the mount mechanics.

Star aligning tells the mount where your targets are, after a few iterations it should know where to look again taking into account mechanical limitations, HEQ5 should give good results.

Dave

[SilverAstro]

On 23/07/2016 at 13:00, fortytwo said:

Can anyone recommend good stars for alignment in the Northern Hemisphere from a suburban area where the first 15 degrees of elevation are generally unusable?

There is a pdf chart showing the SynScan alignment stars in their constellations here http://www.jimscosmos.com/wp-content/plugins/stars/docs/synscan-finder-stars.pdf 

[SilverAstro]

"Transit" =  "Culmination" ?