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Do you need to realign a mount each session?

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7 replies to this topic

#1 JackGanssle

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Posted 27 September 2021 - 01:58 PM

If one were to get a good 3 star alignment and then park the scope in the home position and turn the scope/mount off, do you need to do another 3 star alignment if you power up the next night?

 

I'm running an EQ6R. The obvious answer is "just try it out!". Alas, I can't observe until winter as we live in the woods and the leaves obstruct the sky.

 

Thanks!



#2 robbieg147

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Posted 27 September 2021 - 02:02 PM

I think it would depend if you were on a tripod or a pier? On a tripod I would realign every time myself as over a period of time tripods will creep, on a pier I would say you are ok?


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#3 rgsalinger

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Posted 27 September 2021 - 02:11 PM

If all that you are doing is visual and the system  is on a very solid platform - ashpalt, concrete or (what I use) pavers sunk into the lawn, then no. If you are imaging you may want to check that the polar alignment is correct. Also, make sure that that all the necessary settings - time, location, etc are retained by the hand controller or by the mount driver (if using a computer).

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#4 ram812

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Posted 27 September 2021 - 02:39 PM

Hello! I don't share your mount, but can say for sure (Like those above) re-checking your alignment if not solidly positioned won't hurt a bit and is pretty much necessary if imaging. I put mine on "Hibrinate", then the next day "Wake up" the mount, punch up "Last alignment", then slew the mount to the first star of my previous alignment where I can see if anything has moved overnight. Simple from there if it has, as all that's necessary is to hit "Realign", re-center the star and then go hit the other 5 for the nights' updated alignment! If you don't have a pier or the tri-pod is on a lawn with just little pavers under the tripod tips I'd just count on it needing at least a check. Good luck!

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#5 Seiten

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Posted 27 September 2021 - 02:59 PM

I see you posted a camera in your signature, so Im assuming you have some interest in photography stuff way out there.

 

Polar alignment:  I check mine at the start of every session.  Its key for me to minimize star trails and lessen guiding in DEC.  Mine is on a tripod sitting on concrete and its protected from most outside influence, but it still will shift polar alignment from night to night ever so slightly.

 

Star Alignment:  This is going to be sensitive to the above.  If the polar/RA axis alignment shifts, it will shift your star alignment as well.  The advanced photographers dont worry too much about star alignment because they are using plate solving to zero in on the subject and dont have a need to have a precise initial goto on a new target.  I however, sometimes like to gaze all around the sky and having a good star alignment model makes things alot easier.  Actually, I use a script within APT to run  a series of plate solve/sync's to 4 different ALT/AZ locations in my viewable sky.  These plate solve/sync'c update the alignment model in EQMOD and it eases all gotos for the night.  Its similar to what the Starsense Alignment device does but just with your main imaging train rather than a separate camera.  My APT script takes less than 5 minutes and I have a good model for the night.



#6 Raginar

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Posted 27 September 2021 - 03:06 PM

If one were to get a good 3 star alignment and then park the scope in the home position and turn the scope/mount off, do you need to do another 3 star alignment if you power up the next night?

 

I'm running an EQ6R. The obvious answer is "just try it out!". Alas, I can't observe until winter as we live in the woods and the leaves obstruct the sky.

 

Thanks!

Assuming you can 'sleep' your mount somehow, you don't need to recreate it.  If you're imaging and you've polar aligned, I never even bothered.  Plate solving will get you to your target and any mount without active encoders requiring a model for tracking doesn't need it.



#7 DuncanM

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Posted 27 September 2021 - 03:13 PM

If one were to get a good 3 star alignment and then park the scope in the home position and turn the scope/mount off, do you need to do another 3 star alignment if you power up the next night?

 

I'm running an EQ6R. The obvious answer is "just try it out!". Alas, I can't observe until winter as we live in the woods and the leaves obstruct the sky.

 

Thanks!

 

IIRC, the EQ6-R has a mode to reuse the previous alignment upon powerup.

 

However, if you're doing astrophotography, you can skip the star alignment process (but not polar alignment) and use platesolving to find your targets.

 

Basically, your control software will match the star pattern in the camera image against a database, using the mount's reported estimated position, as a starting point, and in a few seconds it will determine the actual location to arc second accuracy, so that the next goto should centre the target accurately.

 

You can experiment with this using the free Demo of Astroart 8:

http://www.msb-astro...com/down_en.htm

 

just lookup plate solving in the help file.



#8 SkipW

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Posted 28 September 2021 - 06:15 PM

Does the EQ6-R have an equivalent to Celestron NexStar's 'Hibernate' function?

 

With that system, you point the mount to any convenient position (electronically - don't release the clutches and move by hand), hibernate, and power down. On the next power-up it will ask if you want to resume or re-align. If you resume, confirm the time (reset as needed), and it picks up right where it left off. If you didn't bump or move anything in the interim, and the time is consistent between sessions (i.e. both exactly right, or both off by the same amount) the pointing accuracy is about as good as it was before hibernating. I've left telescopes set up on tripods at the Okie-Tex Star Party for the better part of a week, and they're great for looking at planets during the day and don't need realignment each evening.

 

Even if it doesn't have an official 'Hibernate' or equivalent, if it has a way to re-use the previous alignment, just selecting that, checking the time and setting if needed, should bring you back up as long as nothing has been moved between shut down and re-start.




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