star alignment using high power

[tripleped]

Don't know how  I missed  this  before, but  I recently read somewhere on  SGL and on Skywatcher's  website  that  using  high power  when centering  a star  for  goto alignment gives better  results. Tried this out  last  night and now  I can see firsthand  how well that works.  I chose  Jupiter  and  Altair  for alignment. Started  with low power on Jupiter, approximately centered,  then switched  to  7 mm EP (170 X,  22 arcmin FOV in my scope)  and  centered. Repeated procedure  on Altair to complete the alignment.  Then, keeping  the  7 mm EP in,  slewed  to Saturn, and there it was, within  the narrow FOV.  As others have  said its much easier  to be more precise  when centering  a star  when the FOV is narrower, and  the result  is better alignment. 

 

[lenscap]

39 minutes ago, tripleped said:

As others have  said its much easier  to be more precise  when centering  a star  when the FOV is narrower, and  the result  is better alignment. 

Yes, and it is even more precise if you de-focus the target to produce a large circular blob nearly as big as the fov. Then there will be no doubt when it is centered.

[tripleped]

yes, thanks for the reminder.  I will  do that  as  well next time.

[Neil H]

Hi I use a 12mm cross hair eyepiece for alignment the star will be a sharp point of light between the cross hairs

[Astro_Dad]

On 06/10/2021 at 19:24, Neil H said:

Hi I use a 12mm cross hair eyepiece for alignment the star will be a sharp point of light between the cross hairs

I’ve just started trying one of these illuminated reticule eyepieces - I’ve found it takes a lot of practice on f/12 ish (pretty high mag) but works well at f/5. I’m sure will become easier and perhaps it’s harder using phone to control movement vs physical controller. 
 

@lenscap good tip there, will try that when using the cross hair. 

Edited October 27, 2021 by Astro_Dad

[oscar_camilleri]

To add to this, recently I purchased a wifi dongle for my mount. And was impressed how much better the alignment and goto functionality was when control from my ipad. Everything was smack in the middle of my eyepiece. Usually its either towards the edge or i have to hunt around a little.

[mikemarotta]

On 06/10/2021 at 10:31, lenscap said:

Yes, and it is even more precise if you de-focus the target to produce a large circular blob nearly as big as the fov. Then there will be no doubt when it is centered.

I hadn'tthought of that. Of course. Thanks for the lesson.

Best Regards,

Mike M.

[bomberbaz]

+1 for a crosshair eyepiece, although I use a slightly longer 20mm eyepiece with a slightly wider FOV but in an F1700 scope that is still x85 with the crosshair. 

That is with pushto also, not goto but still the same idea.

[wookie1965]

I use a zoom saves swapping eyepieces 24-8 mm

[ScouseSpaceCadet]

36 minutes ago, wookie1965 said:

I use a zoom saves swapping eyepieces 24-8 mm

I may have found a use for the OVL zoom I never use... I've been using a 24mm 65° then swapping to a 12mm 60°. I assumed the zoom fov at 24mm wasn't wide enough to acquire the target?

[wookie1965]

Usually just out I use my telrad first get it close look through the 24mm centre it then just work down to the 8mm. 

[ScouseSpaceCadet]

14 minutes ago, wookie1965 said:

Usually just out I use my telrad first get it close look through the 24mm centre it then just work down to the 8mm. 

I'll give it a try next time out. If there ever is a next time. Bloody weather!

[Zermelo]

It will depend on the scope's focal length as well. Centering with a 12mm reticle in my F12 Mak will be more precise than in my F5 Newt.

But also, I expect that the accuracy and consistency of the mount's mechanisms (and probably other factors too) set a limit on the value of deploying extra magnification during the alignment phase. In not sure that adding a barlow when setting up my Mak is going to improve the results with my £300 mount.