Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_imaging_challenge_banner_dslr_mirrorlesss_winners.thumb.jpg.9deb4a8db27e7485a7bb99d98667c94e.jpg

Simon Dunsmore

Aligning polar scope with main scope

Recommended Posts

Hi All, 

Well we've had some lovely clear nights of late here in Kent and I've been out enjoying the stars. 

Please forgive me if this is a silly question. I've been using my EQ5 goto mount for some time and although it works, I can never really get it that accurate and spend some time slewing around with a wide angle EP to find the target. Last night I had a sudden thought of something I may be doing wrong and wanted to check with you wise folks. 

When setting up, should the main scope be aligned with the polar scope? By this I mean when polaris is centered in the polar scope, should it be in the cross hairs of the EP. If so, how do I do that? 

As always, thanks for your help. 

Cheers 

Simon 

Share this post


Link to post
Share on other sites
2 hours ago, Simon Dunsmore said:

Hi All, 

Well we've had some lovely clear nights of late here in Kent and I've been out enjoying the stars. 

Please forgive me if this is a silly question. I've been using my EQ5 goto mount for some time and although it works, I can never really get it that accurate and spend some time slewing around with a wide angle EP to find the target. Last night I had a sudden thought of something I may be doing wrong and wanted to check with you wise folks. 

When setting up, should the main scope be aligned with the polar scope? By this I mean when polaris is centered in the polar scope, should it be in the cross hairs of the EP. If so, how do I do that? 

As always, thanks for your help. 

Cheers 

Simon 

The mount should be aligned with the north celestial pole, this is done by using Polaris as a guide. Polaris shouldn't be centred in the cross hairs, use the information provided in the handset or an app such as Synscaninit to find the correct position for Polaris on the graduated ring in the pole finder. The mount should also be pointing at the NCP.

Share this post


Link to post
Share on other sites

Hi, 

Thanks for your help. I usually polar align the mount and then do a three star alignment. So it looks like I just need to be a little more accurate 

Share this post


Link to post
Share on other sites

I've never looked back since starting to use Polemaster - brilliant bit of software  - easy to use, just follow the directions on screen.

 

Annie

Share this post


Link to post
Share on other sites

Thanks Annie, I'll check it out. On another note.  Does anyone think that using an eyepiece with illuminated cross hairs adds noticeably to the accuracy of a goto mount? 

Share this post


Link to post
Share on other sites

An eyepiece with illuminated crosshairs will improve the accuracy of your one, two or three star alignment as you will get the alignment star more centered so yes, indirectly it will add to the accuracy of your GoTo. I always use one for alignment and alignment of my finderscope which I do during star alignment 

Share this post


Link to post
Share on other sites

Annie can you post a link to polemaster please  all I can find is a camera system at £278

Share this post


Link to post
Share on other sites

https://www.qhyccd.com/index.php?m=content&c=index&a=show&catid=136&id=32

It is a camera, it fits on the front of your polarscope, and attaches to your laptop via a cable.  Following a software routine, it helps you to do very accurate PA.  It's probably more relevant for imagers.  I have one and it is very good and saves having to kneel down and crane your neck at awkward angles trying to adjust bolts at the same time.  I bought mine after I fractured my knee and kneeling wasn't an option at the time.

It's not cheap but it is brilliant.

Carole 

Share this post


Link to post
Share on other sites

Ok thanks I think it may have to wait a bit . I have not told the bank manager that the new telescope is coming in at well on its way to £1400 with mods and upgrades lol 

Edited by Neil H
  • Sad 1

Share this post


Link to post
Share on other sites

If you have a guide scope and camera then SharpCap has a polar alignment routine that works in a very similar way to a Polemaster but a SharpCap licence is only £10. 
 

It works very well - very quick and very accurate. 

  • Like 2

Share this post


Link to post
Share on other sites

Yep +1 for sharpCap quick & easy

The best tenner you will ever spend

Edited by Frank the Troll

Share this post


Link to post
Share on other sites

Hi Folks, 

Thanks for your messages. Can I just clarify, if my polar alignment is more accurate does this mean that finding guide stars and ultimately objects will be more accurate? 

Thanks for your help 

Simon 

Share this post


Link to post
Share on other sites

So I still need camera , I will look at this once I sort everything else out 

  • Like 1

Share this post


Link to post
Share on other sites

For visual only you should get close enough using just the polar scope. I’ve attached a screen shot of the app I use and you can see where Polaris should line up. 
 

Note the app corrects the image so you don’t have to do any mental gymnastics trying to work out any image flips you need to do. 
 

This done and the alignment starts should be there or thereabouts and then the Goto reasonably accurate. 
 

A camera / guide scope combo is incredibly accurate but I doubt fit what you’re looking to achieve it’ll make a huge difference. 

A500CDBA-B495-4C40-8DF9-08D16949AC38.png

Share this post


Link to post
Share on other sites
On 19/01/2020 at 08:17, Simon Dunsmore said:

When setting up, should the main scope be aligned with the polar scope?

As an imager I don't really know what the correct answer is to your question but I know what works for me.

My imaging scope is a camera lens that sits in a large tube ring. At the beginning of each imaging session I centre Polaris on the cross hairs of the polarscope and then I centre the imaging scope cross hairs on Polaris so I know the imaging scope is aligned with the polarscope.

I then perform a polar alignment; I used to do this just using the polarscope and an iPhone app but I now use the PA routine built into the ASIair software to refine my 'visual' method. Following the PA I know the mount is aligned with the NCP and I have confidence my imaging scope is centre on the NCP as well.

When I slew to my first reference star, e.g. Capella, I can pretty well guarantee it is slap in the middle of the field of view but I plate slove using ASIair and then sync the mount using Sky Safari. I then slew to a second reference star and it is usually bang on target; if it is not a second plate solve and sync mount and I am good to go. I readily achieve 300s unguided images without star trails; having said that I typically only use 120s or maybe 180s exposures.

So, after all that, in my view it is advisable and desirable to align the main scope with the poalr scope.

Adrian

Share this post


Link to post
Share on other sites

Your polar scope needs to be calibrated, that is, aligned to the RA axis of the mount:

https://www.myastroscience.com/polarscopecalibration

You need to also account for cone error if you're expecting to see Polaris centered in the main scope and the polarscope at the same time.

Having Polaris centered in both isn't necessarily what you're looking for though. Just make sure that your polar scope is calibrated and you've corrected cone error as well as possible. Then go through whatever polar alignment routine you use.

If you're imaging and using a guider just use Sharpcap Polar Alignment. Just get Polaris in the FOV of your polarscope (you have to get a rough polar alignment to get Sharpcap to work) and then use Sharpcap from there. It's great.

  • Like 2
  • Thanks 1

Share this post


Link to post
Share on other sites
On 19/01/2020 at 08:17, Simon Dunsmore said:

When setting up, should the main scope be aligned with the polar scope?

Hi Simon, to answer your original question, only the mount needs to be aligned, not the scope.

  • Like 2
  • Thanks 1

Share this post


Link to post
Share on other sites

I have had my guide and main scope (400mm Lens) both aligned and not aligned. Not noticed any difference. As long as PA is good to begin with everything else should be good. I never used Star Alignment as takes forever and it is never near. What I do use is Plate Solving. For imaging I find this brilliant as once PA'ed I can get onto target within 2 minutes and start imaging. Well worth spending the time setting up within software (APT or SGP does it).

On a side note, as said above, Sharpcap is brilliant and cheap!

  • Thanks 1

Share this post


Link to post
Share on other sites

I have an AVX mount. ANd living on lat 56 degr north means the polarscope is useless unless I don't want to poke my eye out because of the long handle on the bolt (and how the bleep can they sell a mount like this??)

So I do this which is good enough for visual. 

I find out my lat and long position. This for entering locaton in handset.

I set my lat adjustment on the mount as exact as possible. Then I adjust with the azimuth knobs until I have polaris fairly close on the finder.

 

Then I do a two star alignment and add one or two calibration stars.

This is good enough for visual. If you just do visual, don't over complicate things with a polemaster. 

Just adjust with the knobs as close as possible and also enter your position with lat/long coordinates and exact time. 

 

This makes my mount slew to chosen targets and put them almost always fairly in the middle of the eyepiece.

 

I believe there should be a polar aligh routine in your mount, not sure about the menu location though. The avx has one that is said to be quite good.  The option might be visible only after a star alignment routine has been done. Check the manual.

Share this post


Link to post
Share on other sites
1 hour ago, Simon Dunsmore said:

Thanks Peter, 

I'll take a look and report back 

Good luck :)

Also, I forgot to mention: Before I start with adjusting the lat/az knobs, I sight in on Polaris over the mount saddle. Kind of like sighting with iron sights on an old rifle. Hope this makes sense?

Then I put the scope on and balance in RA/DEC etc. And then I proceed with the process described earlier. I use a 38mm (21x) eyepiece in the beginning when star aligning. And carefully align so that I have align star i center and same with calibration stars.

It is not 100% polar aligned but fairly close. The whole process takes some 5-10 mins if you have the routine. And when I slew to objects when done, they're almost in the center up to 100x mag eyepiece. Also good enough for 30 sec exposure time imaging.

 

So all I'm saying is: Don't fork out £300 on a polemaster just yet as I think you don't need it. You would also need to hook up computer with sharpcap etc making it not so spontaneous anymore. Instead get the location and time settings both on handcontrol and alt/az knobs as exact as possible. Check your lat/long coordinates f.ex in google maps.

 

10 mins and you're up and running. Always try to find ways to make it simple :) And, most important, have fun and enjoy :)

Share this post


Link to post
Share on other sites

Hi Peter, 

Thanks so much for taking the time to explain all of this, genuinely appreciate all the help. As you say,  I'm learning away from the polemaster, just need a few clear nights to work on the process. 

Will let you know how I get on. 

Thanks again 

Simon 

  • Like 1

Share this post


Link to post
Share on other sites

To ease neck pain by reducing the time spent grovelling beneath the polar scope, here's a simple trick; shine a laser pointer through the polar scope and see where it's pointing in the sky. The polar scope's optics will align the beam roughly with itself and that gets you close to Polaris before the final grovelling and contorting begin! The usual caveats apply regarding the adult use of lasers.

I don't find that the ultra-precise centering of alignment stars using a crosshair improves my GoTo significantly. Any gain is overwhelmed by the amount of image shift involved in refocusing. (This is with an SCT.)

Olly

Edited by ollypenrice
  • Like 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.