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DSLR star alignment

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#1 JB103

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Posted 25 May 2019 - 12:13 AM

Hello guys and gals 

wondering if someone can help me out ? 

I've got the polar alignment done ,telescope with DSLR attached and  balanced, but how does everyone do star alignment with the camera attached (without the use of a computer ) ?

I'm using live view but its so hard to see the stars , I live in a borttle 6 but with a lot lights and the camera I'm using is a Canon rebel T1i.

any hints or advice would be greatly appreciated.



#2 scadvice

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Posted 25 May 2019 - 12:53 AM

Because I have to setup and take down every time I actually have three scopes on my setup to make it easy. The main scope, a guide scope and a finder scope. I use the finder to do my star alignment check with crosshairs. I check that the main scope and the finder scope are aligned to each other early before it's dark.

 

A good finder scope is worth the cost to make things easy on yourself. 

 

Here is an example of one. 

 

https://www.highpoin...der-scope-93781


Edited by scadvice, 25 May 2019 - 12:54 AM.

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#3 mmalik

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Posted 25 May 2019 - 04:49 AM

...how does everyone do star alignment with the camera attached (without the use of a computer ) ?

Star alignment with what? You may not be asking the question correctly...

 

 

If you need to align your main scope with the finder or other scope, you'll need to zoom in (magnify by pressing + button on the camera) on a bright star and center it and make sure the same bright star is center in finder/other scope. Note: You'll use the same zoom function to fine focus your camera.

 

 

If you are talking about aligning the mount then zoom-in (camera LCD) on a bright start near/around the target object and align on that star. Once mount is aligned to a significant star, you can next go to the actual target and it will be dead center on the camera sensor. Aligning on a star far from the intended target can misplace the target on the camera sensor. Hope this helps. Regards


Edited by mmalik, 25 May 2019 - 07:05 AM.

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#4 t_image

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Posted 25 May 2019 - 11:06 AM

Hello guys and gals 

wondering if someone can help me out ? 

I've got the polar alignment done ,telescope with DSLR attached and  balanced, but how does everyone do star alignment with the camera attached (without the use of a computer ) ?

I'm using live view but its so hard to see the stars , I live in a borttle 6 but with a lot lights and the camera I'm using is a Canon rebel T1i.

any hints or advice would be greatly appreciated.

Just another example of the requirements triangle of

                 time/effort
money                              quality result

in AP, where you cannot have all three (often not two). You must lose at least one or two to have the other....

So your camera/gear situation will demand a little more time/effort from you than others experience.

The optics in front of your camera also can make things difficult. (you didn't offer details on such).

With f/1.4 or f/2.8 aperture lenses, it is much easier to quickly detect stars....

 

I imagine you aren't aware to know how to describe it better, but "its so hard to see the stars" can mean different things.

  • Do you mean pointing at various directions makes it difficult to access the back of the camera?
  • Do you mean the camera sensitivity+optics make it difficult for the camera to register any stars in live view?
  • Do you mean the camera LCD display is so small and far away from where you are standing it is hard to see the little pixel size points of light?

Also have you played around with your camera just hand-held under the stars and are familiar with all the options that could make the situation better? ie: some cameras have better display in video mode...Using the highest ISO setting to see the stars is helpful. There's no requirement that you have to use the same settings when you start taking images...I have though seen somewhat experienced AP'ers struggle with such because they had somehang-up with using high gain that is just silly. Also focus magnifier option as mentioned above is helpful....

 

If your camera is at least able to see the alignment stars, but seeing is still troubled, you might consider what others without PC connections do:

purchase a portable external monitor to connect via HDMI to camera...

For ~$100 a nice 5-8" display can be had that with a cable to camera can be held in your lap while while you are sitting down and hand controlling the direction of the mount, no contortions to see the small LCD on camera to know where the camera is pointed....

Note for most Canon cameras they've crippled video features so you don't have the option of turning off all the display items on the screen, in order to have a 'clean' "live view" of just the scene output to monitor.

 

If your issue is camera/optics sensitivity, then you still have the option of taking a longer exposure at the highest ISO to see if you can detect some stars and then slightly move mount control until aligned....

 

Note with EQ mount, polar alignment determines tracking accuracy,

star alignment determines GOTO pointing accuracy.

You can use a finderscope or larger FOV/smaller focal length optics to center the stars, it may just mean the pointing won't be spot-on with your main optics+camera.

 

You may be at the limit of your tools' usefulness. It might be either time/effort or spend a little $$ for less time/effort on star alignment.....


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#5 JB103

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Posted 25 May 2019 - 08:27 PM

Just another example of the requirements triangle of

                 time/effort
money                              quality result

in AP, where you cannot have all three (often not two). You must lose at least one or two to have the other....

So your camera/gear situation will demand a little more time/effort from you than others experience.

The optics in front of your camera also can make things difficult. (you didn't offer details on such).

With f/1.4 or f/2.8 aperture lenses, it is much easier to quickly detect stars....

 

I imagine you aren't aware to know how to describe it better, but "its so hard to see the stars" can mean different things.

  • Do you mean pointing at various directions makes it difficult to access the back of the camera?
  • Do you mean the camera sensitivity+optics make it difficult for the camera to register any stars in live view?
  • Do you mean the camera LCD display is so small and far away from where you are standing it is hard to see the little pixel size points of light?

Also have you played around with your camera just hand-held under the stars and are familiar with all the options that could make the situation better? ie: some cameras have better display in video mode...Using the highest ISO setting to see the stars is helpful. There's no requirement that you have to use the same settings when you start taking images...I have though seen somewhat experienced AP'ers struggle with such because they had somehang-up with using high gain that is just silly. Also focus magnifier option as mentioned above is helpful....

 

If your camera is at least able to see the alignment stars, but seeing is still troubled, you might consider what others without PC connections do:

purchase a portable external monitor to connect via HDMI to camera...

For ~$100 a nice 5-8" display can be had that with a cable to camera can be held in your lap while while you are sitting down and hand controlling the direction of the mount, no contortions to see the small LCD on camera to know where the camera is pointed....

Note for most Canon cameras they've crippled video features so you don't have the option of turning off all the display items on the screen, in order to have a 'clean' "live view" of just the scene output to monitor.

 

If your issue is camera/optics sensitivity, then you still have the option of taking a longer exposure at the highest ISO to see if you can detect some stars and then slightly move mount control until aligned....

 

Note with EQ mount, polar alignment determines tracking accuracy,

star alignment determines GOTO pointing accuracy.

You can use a finderscope or larger FOV/smaller focal length optics to center the stars, it may just mean the pointing won't be spot-on with your main optics+camera.

 

You may be at the limit of your tools' usefulness. It might be either time/effort or spend a little $$ for less time/effort on star alignment.....

so I'm using my VixenSD81S (f7.7)connected to my camera with reducer kit , I will take your advice and pick up a small external monitor and also a better finder scope ( it came with a red dot finder ) 



#6 JB103

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Posted 25 May 2019 - 08:28 PM

Because I have to setup and take down every time I actually have three scopes on my setup to make it easy. The main scope, a guide scope and a finder scope. I use the finder to do my star alignment check with crosshairs. I check that the main scope and the finder scope are aligned to each other early before it's dark.

 

A good finder scope is worth the cost to make things easy on yourself. 

 

Here is an example of one. 

 

https://www.highpoin...der-scope-93781

I think a new finder scope would be very helpful, thanks 



#7 PhilipPeake

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Posted 25 May 2019 - 08:42 PM

Live view doesn't really work well for me, unless there are enough bright stars in the area to act as guides, and even then it can be difficult.

 

I tried using the viewfinder - no better (and a stiff neck!).

 

What worked for me was 30 second exposures and hoping to see my target on the resulting image, but even that is a bit hit and miss.

 

What I now use is a red-dot sight, this one:

 

https://www.amazon.c...0?ie=UTF8&psc=1

 

Together with a hot-shoe mount, this one:

 

https://www.amazon.c...0?ie=UTF8&psc=1

 

Then just put the dot where you want it in the sky, 30 or 60 second exposure (or two) and final tweaking.

Works tolerably well. Not as good as a goto mount, but better than the alternatives (in my opinion).

 

The biggest problem is that the hot-shoe mount is far from a tight fit, so you have to at least check alignment each time you mount it. I apply fairly gentle pressure to push it forward while tightening. That usually is enough to get it back in the same position, then (in daylight) put the dot on something (a tree top in my case), and use live view or the viewfinder to verify that whatever you used is in the center of the image.

 

Using this, my target is almost always on the image for my test exposure (somewhere...) with my 300mm lens.


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#8 LJ000

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Posted 26 May 2019 - 02:33 AM

If you have a red dot finder, that will be sufficient to get you in the ball park. Just make sure the telescope and finder are aligned before hand.
On the DSLR live view use a sub-sec shutter speed and a low iso like 800 (I have an 8” astrograph so you may need to higher these numbers if you have a smaller aperture scope) and even without taking an exposure you should be able to see a bright star like Capella/vega/dubhe etc. in your live view. Simply zoom in and centre it and move to the next star.
I live in a bottle 8 which is heavily light polluted and I can easily see stars to align with most of the time no problem.
Make sure your in focus too as you won’t see any stars at all.

I no longer have a finder as it was replaced by my guide camera/scope so have to align my stars by looking down the body of the telescope to get within the general area of the target star. After some movement I can see it in my live view and go from there. This is without any finder at all.
Failing that, you could always star align using a low mag eyepiece (25mm) if it helps you then simply switch to the DSLR and afterwards.

Hope this helps


Edited by LJ000, 26 May 2019 - 02:35 AM.

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#9 eric gillin

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Posted 01 June 2019 - 12:24 AM

are you talking about doing a goto mount star alignment


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#10 JB103

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Posted 01 June 2019 - 07:19 PM

are you talking about doing a goto mount star alignment

exactly, but for some strange reason I cannot get stars to show up on my camera during live view mode 



#11 rdricks2000

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Posted 01 June 2019 - 07:38 PM

If the ISO is cranked up and you are not seeing any stars it may be focus. There is a pretty small window of focus you need to hit for them to show. It’s not uncommon for me to rock focus back and forth for a while to get them visible. 


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#12 JB103

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Posted 01 June 2019 - 08:05 PM

If the ISO is cranked up and you are not seeing any stars it may be focus. There is a pretty small window of focus you need to hit for them to show. It’s not uncommon for me to rock focus back and forth for a while to get them visible. 

ok thank you I will try again this Wednesday , its been rain and clouds since I posted this. 

.



#13 eric gillin

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Posted 01 June 2019 - 09:20 PM

first like the other guy said focus could be a problem. focus on a distant daytime object and you should be close for the stars, at least close to see a fussy star. or use the moon. I have my focus locked and never move it. I use live view for star alightment then go to work taking pictures.  second problem could be starting you goto alightment from home position. if your mount is not starting to move from a good home position when it starts going to your first star it could be pretty far off, believe me way, way, way, off. watch a pretty good video on youtube from the channel called astronomy shed, the video is called ( complete mount and scope setup part one. third thing I would say use only bright stars , do not expect high iso to bring out every faint star, every camera and scope is different of course. but know you limit. finally do not expect your alightment to go so good all the time. most of the time my first star shows up in the screen no problem, but sometimes who knows what goes wrong. good luck .


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#14 Michael Covington

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Posted 01 June 2019 - 11:05 PM

I always use the DSLR in live view mode and simply put the star on the dot in the middle of the screen (Nikon) or the center of the grid (Canon, grid turned on).  That is surprisingly accurate.


Edited by Michael Covington, 01 June 2019 - 11:05 PM.

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