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Why does my target keep moving?

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#1 hdoraisamy

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Posted 21 September 2020 - 06:12 AM

I was trying to image Jupiter and Saturn for the first time last night. The weather was clear - no wind. I'm located in south east Pennsylvania.

 

Here's my equipment:

Celestron Nextstar 8SE

ZWO ASI120MC camera directly attached to the scope (no diagonal)

I am using the default mount that comes with the 8SE

The ZWO is connected to my Windows laptop running Sharpcap 3.2

 

I didn't really bother doing a 2-star or a 3-star alignment since Jupiter is an easy target, so I manually panned my scope and focused till the planet appeared in my laptop

However the moment it appeared, it seemed to diagonally move across my line of sight and disappeared within 1-2 seconds. I had to pan again to get it to appear and the same thing happened immediately.

This happened with Saturn as well. I could see the rings and then bam - it moves across and disappears :(

 

I just could not keep the target steady in 1 location which was extremely frustrating. I am not touching the scope and it is on solid concrete ground.

 

Why would this happen? I would like to try again tonight.

 

Thanks



#2 AtmosFearIC

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Posted 21 September 2020 - 06:16 AM

You have to do a star alignment otherwise your mount won’t know how it’s meant to be tracking :)
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#3 BobT

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Posted 21 September 2020 - 06:21 AM

I am not familiar with your equipment but it sounds to me like your drive is not engaged.  I'm sure some NextStar user will chime in with specific advise.

 

BobT


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#4 neaptide

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Posted 21 September 2020 - 06:52 AM

Make sure tracking is on. I've had issues with my 8SE where the tracking turned itself off for some reason. 


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#5 hdoraisamy

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Posted 21 September 2020 - 07:01 AM

Here's the video that shows how fast the target moves (normal speed): https://youtu.be/6NmvYv2Mkws

 

I am using the Alt-Azh mount that comes with the telescope. 

 

I would have expected the target to remain stationary for at least a few seconds before being displaced due to the earth's rotation, or am I mistaken? Could it be that the screws holding the ZWO camera to the scope are not fully tight?

 

Thanks so much - My first time imaging with a scope



#6 zeddie

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Posted 21 September 2020 - 07:06 AM

You absolutely have to do an alignment for your scope to track. When you set your tripod and mount up, you will put it in some orientation with respect to north, south, east, and west. For example, once you set it up, you could pick it up and rotate it clockwise or counter-clockwise some random amount. Your mount doesn't know which way it is pointing, and therefor does not know which way to go to follow objects unless it is aligned. And I would suppose that the earth's rotation would be enough to make your image move without tracking on.


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#7 spacemunkee

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Posted 21 September 2020 - 07:09 AM

Things move fast, don't they! :)

You need to at least do a 2 star alignment or do a solar system alignment on planet.

But I would opt for 2 star for better accuracy, or make sure that mount is VERY level.
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#8 sg6

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Posted 21 September 2020 - 07:36 AM

You need to align, then the scope/mount/software is able to make some determination on movement required. So no alignment means no tracking or drive.

 

There may be a reduced alignment option in the menu - on a Meade you can get down to 1 star alignment and I am sure I have read of in effect a 0 star alignment. The 0 option means the scope blindly believes you have levelled everything perfectly, aligned North perfectly, and all data is 100% perfect.

 

Not sure about the 8SE and with that narrow field you are a lot safer toi just align it. Should only take 2 or 3 minutes.

 

Scope needs to have some idea as if due East the movement is vertically up, if due West then vertically down. The scope needs to know.


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#9 3snows

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Posted 21 September 2020 - 07:56 AM

With the SE mount you need to do an alignment.  If you're only interested in Jupiter it's easy.  Once you have it centered do a solar system align to Jupiter.  It should keep it in the field of view for a while.  The chip on that camera is small and with the high magnification you will see some movement, but the image should stay on the chip long enough to get a capture.  Mine typically will stay on chip for 5-10 minutes before I need to make a slight adjustment.


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#10 kathyastro

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Posted 21 September 2020 - 08:06 AM

The SE mount can't track until it is aligned.  You have to do an alignment, or you will be forced to track manually.  You don't need to use the goto feature if you don't want, but you must align it.


Edited by kathyastro, 21 September 2020 - 08:07 AM.

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#11 Jethro7

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Posted 21 September 2020 - 08:26 AM

Hello,

You have to do those alignments. Your mount needs to know where it is at. It has been years sence I played with one of those Nexstar  mounts. If I remember correctly you cant manually manipulate the scope after the star align.you will lose the alignment if you dont use the HC or computer. After alignment you need to switch from Celestial to Solar System.There is a different tracking mode between Celestial and Solar System. The mount is still in Celestial tracking mode after the Star align. You need to tap in Solar System Objects or tap on Jupiter,  on the computer so the mount now understands it is tracking a planet not a star. 

 

HAPPY SKIES TO YOU AND KEEP LOOKING UP Jethro

 

P.S. I just remembered a few things about the Nexstar Mount. You need to make sure the mount is level and I had better luck with tracking if I oriented the mount  pointing compass North.  Anything to help it do the job. The Nexstar mount was designed for entry level visual, you might look into keeping the scope and getting a GEM mount. I took my Nexstar mount apart to try and get the horrible backlash out of the Azimuth but by design I could not eliminate enough to do any good. The backlash in the Azimuth does not mater a whole lot for visual but imaging it is everything. So I sold the Nexstar mount. 


Edited by Jethro7, 21 September 2020 - 08:55 AM.

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#12 hdoraisamy

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Posted 21 September 2020 - 10:27 AM

Thank you all! I learn something new everyday :) I was under the impression that the 2-star alignment was only required to use the Nexstar's Go-to feature. But reading everyone's responses, it is clear that this is required in order to align.

I will try again tonight and see if I can get it to work. Clear skies everyone :)


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#13 spacemunkee

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Posted 21 September 2020 - 10:49 AM

2 star align...

 

Planet button, Jupiter, GO-TO! There it is! grin.gif lol.gif



#14 hdoraisamy

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Posted 21 September 2020 - 11:51 AM

2 star align...

 

Planet button, Jupiter, GO-TO! There it is! grin.gif lol.gif

Probably a dumb question, but I'll ask. Can I use either Jupiter or Saturn for one of the 2-stars to align? They're easily visible and identifiable. Or does it have to be a star?



#15 Peter in Reno

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Posted 21 September 2020 - 11:58 AM

It's generally not recommended to use planets as part of star alignments probably because planets changes positions constantly and stars don't. But after you are done with star alignments, make sure to set the tracking rate to solar instead of sidereal if you want to observe or take pictures of planets. For moon, set the tracking rate to Lunar.

 

Peter


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#16 descott12

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Posted 21 September 2020 - 12:04 PM

So here is a wrinkle to all this. My AZ-EQ5 mount does not need to be aligned in any way for tracking to be turned on and work well. So the alignment itself is not needed. That is in EQ mode. Not sure about Alt-Az.

 

In the case of the SE and Evolution mounts, you cannot physically start tracking until an alignment is done. Is that because they are Alt-Az and a star model is needed for some reason?

Shouldn't any mount be able to start sidereal-rate tracking regardless of where it is pointed?



#17 kathyastro

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Posted 21 September 2020 - 01:28 PM

So here is a wrinkle to all this. My AZ-EQ5 mount does not need to be aligned in any way for tracking to be turned on and work well. So the alignment itself is not needed. That is in EQ mode. Not sure about Alt-Az.

 

In the case of the SE and Evolution mounts, you cannot physically start tracking until an alignment is done. Is that because they are Alt-Az and a star model is needed for some reason?

Shouldn't any mount be able to start sidereal-rate tracking regardless of where it is pointed?

An EQ mount can track well as long as it is polar aligned.  That is because the  polar alignment tells it what direction the stars move.

 

An alt-az mount (or an alt-az / EQ mount in alt-az mode) has no idea what direction the stars move until you tell it which way it is pointing.  That is why you need to do an alignment.


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#18 Jethro7

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Posted 21 September 2020 - 02:19 PM

Probably a dumb question, but I'll ask. Can I use either Jupiter or Saturn for one of the 2-stars to align? They're easily visible and identifiable. Or does it have to be a star?

Hello, 

NO!!! it has to be two or three bright stars at least 35° above the Horizon and with good  separation. Polaris A Star. Is usually not recommended to Align on. I do believe on Celestron mounts when centering your alignment star in the eyepiece you need to slew the star up and to the right last, so you may have to overshoot it a bit to do this move. I am not sure why, it was the only mount that I had to do it that way but it makes things work.

 

HAPPY SKIES AND KEEP LOOKING UP Jethro


Edited by Jethro7, 21 September 2020 - 02:24 PM.

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#19 spacemunkee

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Posted 21 September 2020 - 02:41 PM

Probably a dumb question, but I'll ask. Can I use either Jupiter or Saturn for one of the 2-stars to align? They're easily visible and identifiable. Or does it have to be a star?


Not dumb, but there's always a few stars that are easily identifiable that should stand out as a good bit brighter than any around it. Once that's done, select Jupiter in the solar system menu, and off it goes!
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#20 3snows

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Posted 21 September 2020 - 04:02 PM

Probably a dumb question, but I'll ask. Can I use either Jupiter or Saturn for one of the 2-stars to align? They're easily visible and identifiable. Or does it have to be a star?

Not a dumb question and the answer is yes, although it's called a "Solar System" align, not 1 or 2 star align.  You can align on the planets if you use the "Solar System" align as your alignment procedure.  If you're only viewing planets it works well.  In fact I once used this option when viewing the sun once and it was extremely accurate all night as well.

 

The write up is here: https://www.cloudyni...-mount/?hl=+8se


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#21 hdoraisamy

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Posted 21 September 2020 - 04:20 PM

Not a dumb question and the answer is yes, although it's called a "Solar System" align, not 1 or 2 star align.  You can align on the planets if you use the "Solar System" align as your alignment procedure.  If you're only viewing planets it works well.  In fact I once used this option when viewing the sun once and it was extremely accurate all night as well.

 

The write up is here: https://www.cloudyni...-mount/?hl=+8se

This is cool! Thank you :)



#22 Michael Harris

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Posted 21 September 2020 - 08:58 PM

I have done this with the same scope and camera (Evolution mount version but same otherwise). With the small chip camera at prime focus it is amazing how fast things move. The alignment is where you start but sometimes even finding the planets can be a challenge. Keep climbing that learning curve, it can be frustrating but the images are worth it.


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#23 hdoraisamy

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Posted 23 September 2020 - 04:55 AM

So I tried to perform a solar system alignment with Jupiter. The steps I followed were to:

1. Enter the basic settings in the hand controller

2. manually pan/tilt until jupiter is center in the eyepiece

3. i then carefully swap the eyepiece for the ZWO camera and connect to sharp cap

 

This is where things fail. The screen is all black even though i could see jupiter through the eye piece a few seconds back. I try playing with the focus, but no luck. I tried adjusting the gain and exposure - still no luck.

I thought i finally saw a blob, but it moved fast before i could get to focus it further and align it.

 

This is very frustrating :(

 

As an alternative, I would like to image using my DSLR directly connected to my scope through an adapter. I have a Canon EOS Rebel T6. I am very comfortable shooting the milky way and some of the DSOs with my DSLR.

 

If I were to connect my DSLR directly to my scope, what should my settings look like? Bulb mode? What should my exposure and aperture be? Lastly, can i still take multiple images with my intervalometer and stack them with autostakkert?

 

Thanks



#24 3snows

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Posted 23 September 2020 - 06:56 AM

Did you align to Jupiter?  It's not enough to just center it.  You need to use the menu option in the Hand Controller to actually align to it.  It's under "Align / Solar System Align / Select Object".  Or something like that.



#25 spacemunkee

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Posted 23 September 2020 - 07:16 AM

So you didn't complete alignment procedure with the eyepiece in? Need to do that.
Even with a lower power eyepiece you should be able to eyeball it to center of field of view and confirm alignment.

Be close enough for visual or quick planetary captures. I routinely eyeball center with a 32mm eyepiece for 2 star alignment to do visual, and it's good enough.

And then the focus difference between eyepiece and camera may be a lot. May even involve extension tubes.

Best of luck next time.


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