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Question about alt/az mount with wedge

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#1 kevinbreen

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Posted 10 July 2018 - 02:09 PM

Later on I’m going to try out my new Celestron HD PRO wedge for the first time from my location 52 degrees north.
Am I right in thinking that once I get polar alignment roughly okay (the wedge angle at 52 degrees and the RA axis pointing at north), then a solar system align on Jupiter should track Jupiter roughly ok, no worse than the alt/az solar system Align I’ve been employing up to now?
I know that there is a more precise way of doing it using stars but I just want to test the proof of concept this evening. Brief comments most welcome thank you

#2 WarmWeatherGuy

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Posted 10 July 2018 - 03:38 PM

When in equatorial mode the mount only tracks in one axis. The RA (AZ) motor runs but the Dec (EL) motor does not run. If your polar alignment is off then Jupiter will drift north or south in the eyepiece. After a while it will be out of the field of view. If you then do a "goto Jupiter" it will then use both motors and put Jupiter back in the eyepiece. Then the Dec/EL motor will again stop running while tracking. For that reason it will be worse than using solar system align with az/el. Even if you align with stars the things will drift out of the field of view if not polar aligned.

 

I had problems when using my 5SE with its built-in wedge. Every time I tried to do a goto to something with negative declination it would say that was outside of the slew limits. Do I want to continue? Just say yes. I also have the problem with my Evo when using a wedge.

 

Another thing that might freak you out is if you try to do a goto and you expect it to slew left and it slews right and goes all the way around such that your scope is pointing at the ground for most of the time. This is due to that #$@% cordwrap feature. You can turn off cordwrap but the setting does not persist when powered off.


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#3 xiando

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Posted 10 July 2018 - 03:39 PM

The better your polar alignment the better, but yes, Celestron's "EQ mode", disposes of the ALT commands so that motion is somewhat fluid in AZ when tracking.

 

Note that when I said "the better your polar alignment"...I meant make sure to accurately polar align. Once in EQ mode, ALT isn't 'there' (actively engaged in tracking)  to keep things in your FOV, so you'll have to periodically account for any drift. by using your HC to guide the target back to center position.


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#4 Cajundaddy

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Posted 10 July 2018 - 04:00 PM

Piling on...

As others have said, the more precise your polar alignment, the more precise your SE will track in EQ mode.  It can be done and you can get good results, but it may take practice to get good at polar alignment with this mount.



#5 RedLionNJ

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Posted 10 July 2018 - 04:48 PM

Also be real careful - I know you said "wedge angle at 52 degrees" - but depending on where you're measuring from,  this might actually be 90 - 52 = 38 degrees. The wedge is *probably* marked intuitively, bu tjust to make sure, check the scope (at least the finder) has Polaris in the FOV when pointed at the pole.

 

If you have one of those finders with a polar reticle in it, a very good (good enough for reasonable tracking) polar alignment is pretty easy to achieve by making sure Polaris is close to the correct position between the rings and stays within them as you move the scope in RA.

 

If your purpose is planetary imaging, you know you can use FireCapture to autoguide as you image, right? This guarantees you keep the target well within the ROI on the sensor.


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#6 phileefan

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Posted 10 July 2018 - 05:16 PM

Kevin,

 

I always used the EQ AutoAlign function on the CPC1100 then the autoguide function in FireCapture. 



#7 yock1960

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Posted 10 July 2018 - 05:42 PM

 

If your purpose is planetary imaging, you know you can use FireCapture to autoguide as you image, right? This guarantees you keep the target well within the ROI on the sensor.

Someday, I need to try this! I need it less after getting a Polemaster, but my foot has bumped a leg several times now, enough that it's off a bit again and it's too light now with Jupiter and I don't even think of it after getting out of bed for Saturn/Mars!

 

Steve


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#8 kevinbreen

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Posted 10 July 2018 - 07:05 PM

Thanks all of you for your feedback. I’ve just come in after a few frustrating hours perplexed and frustrated with tracking in basic solar system Align with a CPC 1100 without a wedge (something I’ve been successful countless times with my 8SE on its stock mount). There are things I need to figure out with the CPC itself never mind complicating things using a wedge also.

So, I’m thinking I need to proceed without a wedge for the moment and sort out the holy grail (for me) of tracking reliably without having to man the hand-controller up/down/left/right arrows to keep the flippin planet in the ROI. Yes, I use the cut out feature in F.C. which allows a small ROI to be had, but still I have to steer it towards the centre of the chip on a continual basis. This is a real (and probably unavoidable ) PITA.

All I want currently is to do planetary - I’ll get to DSOs later. I’m not concerned with field rotation, not until I try serious animations anyway - as if that’s gonna be possible here anyway, this is Ireland after all.
So....without a wedge then, with alt/az tracking enabled am I right in thinking that the F.C. autoguiding function will correct for any sloppiness inherent in an otherwise much-maligned S.S.Align? Is it that simple?
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#9 roelb

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Posted 10 July 2018 - 07:32 PM

I have tried FC autoguiding with the Evolution mount but FC gives an error. In SharpCap this is a experimental feature but worked although so now and then some manual HC corrections were needed.

#10 Spacedout again

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Posted 12 July 2018 - 12:23 AM

I found the wedge to be a pita on my cpc 1100 too due to lack of practice and experience. My last couple of nights out I did a semi sloppy alt/az two star align, then locked on Jupiter or Saturn and used the sync function. Both planets stayed fairly centered on my laptop for imaging.

#11 RedLionNJ

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Posted 12 July 2018 - 08:52 AM

So....without a wedge then, with alt/az tracking enabled am I right in thinking that the F.C. autoguiding function will correct for any sloppiness inherent in an otherwise much-maligned S.S.Align? Is it that simple?

Yes, it will. There are options (reversed or not-reversed) you can set for the corrections in alt and az, as well as the size of the 'nudges' and the frequency of checking for 'need to nudge' (and also tolerance in pixels).

 

If the Celestron mount is anything like the Meades, you should be able to hook up the camera directly to the ST4 port on the mount, make sure the driver is installed and configured in FC and away you go.

 

First time, it will need some experimentation with the settings, but once it's approximately right, it will be good forever. Once the planet strays more than some number of pixels from its previous position, FC will request the mount 'nudge' slightly in the appropriate direction to re-center (or at least get back within the threshold).

 

I used to use this all the time on my Meade mount. 



#12 kevinbreen

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Posted 12 July 2018 - 10:04 AM

Yes, it will. There are options (reversed or not-reversed) you can set for the corrections in alt and az, as well as the size of the 'nudges' and the frequency of checking for 'need to nudge' (and also tolerance in pixels).

If the Celestron mount is anything like the Meades, you should be able to hook up the camera directly to the ST4 port on the mount, make sure the driver is installed and configured in FC and away you go.

First time, it will need some experimentation with the settings, but once it's approximately right, it will be good forever. Once the planet strays more than some number of pixels from its previous position, FC will request the mount 'nudge' slightly in the appropriate direction to re-center (or at least get back within the threshold).

I used to use this all the time on my Meade mount.


That’s great news, Grant. I take it this will also work when I’m using a wedge and have a fairly good polar alignment set up?

#13 xiando

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Posted 12 July 2018 - 11:10 AM

That’s great news, Grant. I take it this will also work when I’m using a wedge and have a fairly good polar alignment set up?

When tracking in alt-az mode, the mount (or many mounts anyway) adjust ALT, then AZ (or visa versa) not ALT&AZ simultaneously... it's a district, periodic correction movement in one direction followed by the other. This leaves those who are imaging using an alt-az mount with the task of checking each sub in the dataset to ensure it's not carrying a visual record of that correction, and then disincluding any such subs from the stacking set to avoid messy final output...

 

when an applicable alt-az mount is put into equatorial mode, (like various Celestron alt-az mounts) the mount only tracks (unguided) in AZ

 

So if you're imaging with an alt-az mount in EQ tracking mode, using a wedge, and running unguided, you really need to be accurate with polar alignment.


Edited by xiando, 12 July 2018 - 11:10 AM.

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#14 kevinbreen

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Posted 12 July 2018 - 11:48 AM

When tracking in alt-az mode, the mount (or many mounts anyway) adjust ALT, then AZ (or visa versa) not ALT&AZ simultaneously... it's a district, periodic correction movement in one direction followed by the other. This leaves those who are imaging using an alt-az mount with the task of checking each sub in the dataset to ensure it's not carrying a visual record of that correction, and then disincluding any such subs from the stacking set to avoid messy final output...

when an applicable alt-az mount is put into equatorial mode, (like various Celestron alt-az mounts) the mount only tracks (unguided) in AZ

So if you're imaging with an alt-az mount in EQ tracking mode, using a wedge, and running unguided, you really need to be accurate with polar alignment.


Thanks. If alt/az tracking was employed on a wedge which was set up for EQ tracking, would this be asking for trouble, or do you think auto guide could handle it and still keep the planet in the ROI? Or would the entire mount explode under the strain?

#15 RedLionNJ

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Posted 12 July 2018 - 02:41 PM

FC autoguide will handle it just fine. I used this on a Meade wedge for many years - I can think of no reason why the same wouldn't apply for a Celestron mount.  Corrections in dec will hopefully be few and far between (and generally in one direction for extended periods, depending on how your PA is off and on which side of the meridian you're imaging.

 

As I said, I would be VERY surprised if the Celestron mount doesn't accept what I would consider to be 'regular' autoguiding corrections when in polar mode on a wedge.

 

There's no substitute for trying it.

 

As Xiando says, you will doubtless "lose" some frames due to motion causing blurring. AutoStakkert will weed those ones out as poorer quality.



#16 xiando

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Posted 12 July 2018 - 03:00 PM

 

Thanks. If alt/az tracking was employed on a wedge which was set up for EQ tracking, would this be asking for trouble, or do you think auto guide could handle it and still keep the planet in the ROI? Or would the entire mount explode under the strain?

 

The mount won't explode.

 

Although once-upon-a-time (prior to purchasing an eq mount) I fully intended to try guiding my alt-az mount, and since I still have the hardware and plans for my EQ conversion (adding a wedge to a nexstar 130SLT isn't as simple as just adding a wedge) , I plan to when I have time for "fiddling", I've never tracked an alt-az in eq mode, so I can't answer other than to say again that accurate polar alignment is desirable even when guiding, and especially when operating unguided (for either alt-az in EQ mode OR a regular EQ mount.)

 

So yeah theoretically you can guide it, and when guiding could account for DEC(effective) error, but like I said, I haven't guided using one yet so can't say with absolute certainty either way. Conceptually? Sure. Empirically...?

 

Again, you'll still need to polar align with a reasonable degree of accuracy, even for visual with guiding.. For instance, you couldn't be ten degrees off and expect any decent guiding.


Edited by xiando, 12 July 2018 - 03:01 PM.


#17 kevinbreen

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Posted 12 July 2018 - 04:15 PM

FC autoguide will handle it just fine. I used this on a Meade wedge for many years - I can think of no reason why the same wouldn't apply for a Celestron mount. Corrections in dec will hopefully be few and far between (and generally in one direction for extended periods, depending on how your PA is off and on which side of the meridian you're imaging.

As I said, I would be VERY surprised if the Celestron mount doesn't accept what I would consider to be 'regular' autoguiding corrections when in polar mode on a wedge.

There's no substitute for trying it.

As Xiando says, you will doubtless "lose" some frames due to motion causing blurring. AutoStakkert will weed those ones out as poorer quality.


Sounds great. BTW how do you enable those chimes in fire capture that indicate when the planet is in the field of view?

#18 kevinbreen

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Posted 12 July 2018 - 05:06 PM

Update (for anyone interested).
My CPC 1100 (WAS experiencing systematic drift to the bottom of the ROI and to the right of the ROI. I enable FC’s autoguiding and *it seems to be doing the business* (clouds just rolled in but no rain is forecast), however there is still a mild slow drift to the bottom of the ROI.
Question for experienced Celestron-mount autoguiding users/sages - would you mind sharing your Firecapture autoguiding parameters?
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#19 RedLionNJ

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Posted 13 July 2018 - 11:37 AM

You should be able to eliminate the mild, slow drift in dec/altitude by increasing the dec correction in FC. As long as the target stays entirely within the cut-out, a mild, slow drift is a non-factor when it comes to alignment and stacking.

 

I'm not familiar with the warning beeps in FC - the only noise features I have enabled are histogram ("bird chirps") and start/end exposure.

 

Also be very careful when referring to ROI/cut-out, etc.   When using the "cut-out" feature, it will automatically follow the planet within the ROI. This makes focusing easier, as well as making life easier later for AS!3.



#20 kevinbreen

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Posted 13 July 2018 - 11:52 AM

You should be able to eliminate the mild, slow drift in dec/altitude by increasing the dec correction in FC. As long as the target stays entirely within the cut-out, a mild, slow drift is a non-factor when it comes to alignment and stacking.

I'm not familiar with the warning beeps in FC - the only noise features I have enabled are histogram ("bird chirps") and start/end exposure.

Also be very careful when referring to ROI/cut-out, etc. When using the "cut-out" feature, it will automatically follow the planet within the ROI. This makes focusing easier, as well as making life easier later for AS!3.

Thanks Grant

I enabled “Do a short beep when starting/stopping capture” under Settings:General.
Maybe I misread a discussion about a month ago in which Ferret was employing the same method as I was when getting the planet in the ROI - I said I used binning and jacked up the exposure and gain so that when fixing the dodgy red dot finder on the planet it was easy to see in the corner of my eye if the planet was on-screen by the unmistakable flash of brightness on-screen. I thought I read that you said you enabled bird chirps which serve to notify you that the histogram jumped with the arrival of the planet in the ROI. Maybe I dreamt it!

#21 RedLionNJ

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Posted 13 July 2018 - 12:49 PM

Thanks Grant

I enabled “Do a short beep when starting/stopping capture” under Settings:General.
Maybe I misread a discussion about a month ago in which Ferret was employing the same method as I was when getting the planet in the ROI - I said I used binning and jacked up the exposure and gain so that when fixing the dodgy red dot finder on the planet it was easy to see in the corner of my eye if the planet was on-screen by the unmistakable flash of brightness on-screen. I thought I read that you said you enabled bird chirps which serve to notify you that the histogram jumped with the arrival of the planet in the ROI. Maybe I dreamt it!

Nope - that's a correct interpretation of bird chirps. You can set the "volume" (really frequency) such that there's a dull buzz when there's nothing visible on the preview, then when something comes into view (even by a little bit) the volume and frequency both increase quite a bit. Can actually be a bit piercing as I use the same PC speakers for imaging music, too - so they're decent-sized JBLs with their own power supply.


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#22 kevinbreen

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Posted 13 July 2018 - 01:15 PM

Great, thanks! I've both versions 2.5 and 2.6, but I can't for the life of me find where to find such a thing, where is it?




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