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LX 90 GoTo Seems a Bit Off?

Meade
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#1 Blackbelt76

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Posted 20 October 2019 - 08:17 PM

Hello all,

 

I'm not new to astronomy or telescopes.

I AM however *new* to GoTo computerized mounts.

 

Am wondering if I'm missing something in the alignment procedure

or is this lack of pointing accuracy inherent with this mount and drive? (i.e) Worm gear errors over time & slew distance?)

 

The GoTo is missing targets by approx 3-4 degrees declination primarily; though I have noticed some RA misses too

depending where I am slewing to.

 

My first hint that the mount was missing targets is when it failed to center Jupiter & Saturn this evening.

My first guess was perhaps the planet database was corrupt; but then tried bright stars etc with same issue.

 

Currently using the mount in alt/az.

 

My alignment procedure with this 8" LX90 is as follows:

 

1) Level tripod head.

2) Use Polaris as "True North" Lock RA

3) Level OTA. Lock Dec. (Using bubble level in eyepiece holder) **The declination circle indicates +3 degrees when bubble is centered** Hmmm? Dec Circle off or bubble level problem?

4) Turn on AudioStar; select True North alignment. GPS signal is ok.

5) Scope slews to first alignment star. It is off by 3-5 degrees. I center the star and press" Enter"

6) Scope slews to second alignment star. It is off by 3-5 degrees. I center the star and press" Enter"

7) Audio-Star shows "Alignment Successful"

 

Interestingly, when I slewed to the Ring Neb which is close to zenith at my location, it was well centered.

This ^^^ would make me believe it is a RA calibration error, but objects lower in DEC would be off in DEC as well.

 

I DID train the scope today w/o issue.

 

Any advice would be greatly appreciated.

 

I'd hate to have to go back to setting circles as in my younger days with telescopes. smile.gif

 

 



#2 Nobile2HD

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Posted 22 October 2019 - 12:57 PM

Hello there,

 

I too have an LX90 and find the gotos are generally very good. However the planets are not so great and are often at the extreme edge of my 30mm ES82 or just outside the FOV. From what i understand Meade use a fairly basic calculation which can result in this. If you take the J2000 coords and  enter them manually into the scope the planets will be located in the FOV; that's what I've found anyway. Certainly Saturn and Jupiter are low in the sky at the moment which probably exaggerates the problem.

In terms of the alignment procedure, I pretty much do what you do, level the tripod head etc, but I do not use true north; I always use select compass north with the Meade, so basically level the tube with a spirit level then point it north and go from there.

I am also quite particular about the alignment stars, I always use a 2 star alignment and always ensure the the stars are not hugging the horizon or at zenith and also not too close together or at opposite ends of the sky! This certainly seems to improve the accuracy of the goto. Therefore I hardly ever go with the Meades auto star selection for Alignment as it will often select a star such as Vega which is often too high at this time of year.

If you have a particular section of sky you wish to observe for the evening then a good tip is to choose alignment stars in that area of sky; gotos will then perform very well in that area, seems obvious I guess, but maybe something else to consider.



#3 Blackbelt76

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Posted 22 October 2019 - 06:38 PM

Hello there,

 

I too have an LX90 and find the gotos are generally very good. However the planets are not so great and are often at the extreme edge of my 30mm ES82 or just outside the FOV. From what i understand Meade use a fairly basic calculation which can result in this. If you take the J2000 coords and  enter them manually into the scope the planets will be located in the FOV; that's what I've found anyway. Certainly Saturn and Jupiter are low in the sky at the moment which probably exaggerates the problem.

In terms of the alignment procedure, I pretty much do what you do, level the tripod head etc, but I do not use true north; I always use select compass north with the Meade, so basically level the tube with a spirit level then point it north and go from there.

I am also quite particular about the alignment stars, I always use a 2 star alignment and always ensure the the stars are not hugging the horizon or at zenith and also not too close together or at opposite ends of the sky! This certainly seems to improve the accuracy of the goto. Therefore I hardly ever go with the Meades auto star selection for Alignment as it will often select a star such as Vega which is often too high at this time of year.

If you have a particular section of sky you wish to observe for the evening then a good tip is to choose alignment stars in that area of sky; gotos will then perform very well in that area, seems obvious I guess, but maybe something else to consider.

Appreciate the input very much. You bolstered what I was going to do as soon as the skies clear.

I was planning on choosing my own alignment stars for the reason you mention.

..and yes, this time of year, one of the stars chosen by AutoStar was Vega.

I will use two stars, East & West and close to the celestial equator; I have a hunch this is the problem.

 

A Meade tech was kind enough to email me a basic diagnostic which I will also try; perhaps others will find it useful.

 

The missed objects were only a few degrees, but when the objects are not visible to to the naked eye; well, that kinda' kills the whole idea behind GoTo.

I will also be trying out the "High Precision" option..wonder if you have used it?

 

Below is the Mead Tech's diagnostic checkout..

Thanks Again...

From Meade:

Since this telescope was already replaced under warranty it does seem very unlikely to be a second scope (with similar if not identical?) issues. It could very well be something in the setup technique we just are not spotting in your description but everything you mention reads 100% correct to us.

 

The dec circle is movable and can be adjusted but has no direct connection to the computer and so only eyeball leveling is important. Any slight out of level condition will be compensated for during alignment and not impact pointing accuracy.

 

Let’s have you try what we call a “ping pong test” which may prove enlightening. Once you complete a successful alignment you can pull the alignment star #1 back up in the database, hit ENTER and then GOTO to slew back to it. It should hit that star right back on dead center assuming it was there originally for the alignment. You will then pull star #2 back up and repeat back and forth between those two stars a few times. You can understand why we refer to this as the ping pong test. We are looking for those stars to be consistently back in the middle of the eyepiece, and this is a really good test for the health of the motors and encoders as well as the gear train.

 

If the ping pong test passes we essentially know the motors and encoders are OK. If pointing accuracy elsewhere in the sky is still off we would then want to double check that the alignment stars themselves are correct, the named stars called for. If the test fails we know where the issue lies and it would be time to look at bringing the scope back in to have it checked out. If it points at everything except the Moon and/or planets that would indicate an issue with the time or date since those objects move and nothing else does relative to the stars.

 

The final possibility is that the scope points at those two stars and they are the correct stars and pointing at targets close to and/or between the two stars is fine but pointing at anything progressively further from those stars gets progressively worse. This can be indicative of an issue with the optical/mechanical alignment of the scope which again we would need to check out at the factory.

 


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#4 Nobile2HD

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Posted 23 October 2019 - 03:12 AM

Hi,

 

Meade's suggestion makes sense and although I have not tried it I know that objects close to the alignment stars will always be very close if not dead centered in the FOV.

In terms of High Precision, yes I have used it and it works very well, in fact I was using it last night to seek out comet C/2018 N2. It simply selects a close bright star first, you centre it in the FOV, press enter and the scope does a short slew to the object which will now be centered as well. When you are seeking out faint objects that requires AV it really does help as the object will be centered and saves you from searching around the FOV to find it. To note, you do need to remember you have it switched on as well, last night I went to view M15 and for a second could not understand why there was just a bright star in the EP and not the cluster!

Further to this, I rarely do astrophotography but when I do I always use the HP feature as it allows you to perform a fine focus on a bright star before centering on the object you want to photograph thereby minimising the effect of mirror movement; it also helps frame the object on the cameras viewer which is very helpful if the object is faint and you cant see it!


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#5 Blackbelt76

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Posted 23 October 2019 - 06:40 AM

Hi,

 

Meade's suggestion makes sense and although I have not tried it I know that objects close to the alignment stars will always be very close if not dead centered in the FOV.

In terms of High Precision, yes I have used it and it works very well, in fact I was using it last night to seek out comet C/2018 N2. It simply selects a close bright star first, you centre it in the FOV, press enter and the scope does a short slew to the object which will now be centered as well. When you are seeking out faint objects that requires AV it really does help as the object will be centered and saves you from searching around the FOV to find it. To note, you do need to remember you have it switched on as well, last night I went to view M15 and for a second could not understand why there was just a bright star in the EP and not the cluster!

Further to this, I rarely do astrophotography but when I do I always use the HP feature as it allows you to perform a fine focus on a bright star before centering on the object you want to photograph thereby minimising the effect of mirror movement; it also helps frame the object on the cameras viewer which is very helpful if the object is faint and you cant see it!

Thanks again...

 

Appreciate hearing you've tried HP pointing. I haven't done it yet but will. Seems like a great feature when seeking out difficult visual objects.

I was out this morning at 4am with great success. I guess there is a small learning curve in GoTo. :)

50% moon this morning and sky glow to my east were not optimal for seeing, but the GoTo worked great.

 

Based on my observations this morning, it seems wide excursions of 50-60 degrees or more in AZ or ALT will induce some inaccuracy in pointing but usually within my FOV with a 40mm EP. Best guess is a little gear tooth slop.

 

FWIW; I noticed better pointing accuracy when I used True North (Polaris) vs Magnetic North.

 

Appreciate your input and I'm thrilled I don't have a encoder issue.

My first scope did have some serious issues with alignment which I sent back.

Doubtful Meade will tell me what they found; though I suspect either a encoder issue or HBX database errors, mechanical or EPROM.



#6 decep

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Posted 23 October 2019 - 09:40 AM

Is the LX90 new or used?  And... How is your balance?


Edited by decep, 23 October 2019 - 09:42 AM.


#7 Blackbelt76

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Posted 23 October 2019 - 11:29 AM

Is the LX90 new or used?  And... How is your balance?

Balance is perfect; scope is new and problem has been solved..

 

Thanks



#8 Jeff Lee

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Posted 23 October 2019 - 11:35 AM

Does your controller have the "high precision" setting? If so (after using a two star  alignment with stars you choose), you should find you get good goto's. My experience is with an LXD75.



#9 Piet Le Roux

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Posted 23 October 2019 - 11:54 AM

Hello all,

 

I'm not new to astronomy or telescopes.

I AM however *new* to GoTo computerized mounts.

 

Am wondering if I'm missing something in the alignment procedure

or is this lack of pointing accuracy inherent with this mount and drive? (i.e) Worm gear errors over time & slew distance?)

 

The GoTo is missing targets by approx 3-4 degrees declination primarily; though I have noticed some RA misses too

depending where I am slewing to.

 

My first hint that the mount was missing targets is when it failed to center Jupiter & Saturn this evening.

My first guess was perhaps the planet database was corrupt; but then tried bright stars etc with same issue.

 

Currently using the mount in alt/az.

 

My alignment procedure with this 8" LX90 is as follows:

 

1) Level tripod head.

2) Use Polaris as "True North" Lock RA

3) Level OTA. Lock Dec. (Using bubble level in eyepiece holder) **The declination circle indicates +3 degrees when bubble is centered** Hmmm? Dec Circle off or bubble level problem?

4) Turn on AudioStar; select True North alignment. GPS signal is ok.

5) Scope slews to first alignment star. It is off by 3-5 degrees. I center the star and press" Enter"

6) Scope slews to second alignment star. It is off by 3-5 degrees. I center the star and press" Enter"

7) Audio-Star shows "Alignment Successful"

 

Interestingly, when I slewed to the Ring Neb which is close to zenith at my location, it was well centered.

This ^^^ would make me believe it is a RA calibration error, but objects lower in DEC would be off in DEC as well.

 

I DID train the scope today w/o issue.

 

Any advice would be greatly appreciated.

 

I'd hate to have to go back to setting circles as in my younger days with telescopes. smile.gif

I have been using a 8" LX90ACF for more than a year and I can get it to be very accurate. Looking at your setup list I would like to make a few suggestions :

Don't trust the built-in bubble-level on your tripod : they are seldom accurate and remember when you place the scope on top of the mount your are still going to tension the mount and it would not be the same as with the tripod by itself.

Don't use the bubble in the compass eyepiece : its a useless piece of kit. 

The most important thing to make your goto accurate is to level the OTA in all directions : The only way to do this accurately is to mount a level on the OTA facing the length of the tube and centred on  the pivot point. You then start by turning the OTA to be parallel with two of the tripod legs and adjusting one of these two legs until the OTA stays level when you turn it 180 degrees between the two legs. You then turn the OTA to point to the third leg and adjust that leg until it stays level when  it is rotated 180 degrees. Check the first two legs again  and then if it stays level  for the full 360 degrees. Don't loosen the Dec knob after you have done this just point the scope more or less to true north and Lock the Az knob. True north is not critical because any error will be rectified when you sync with the first star, after the second you ready to go.   

  X-T100 005s.jpg      


Edited by Piet Le Roux, 23 October 2019 - 03:34 PM.

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#10 Blackbelt76

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Posted 23 October 2019 - 03:52 PM

I have been using a 8" LX90ACF for more than a year and I can get it to be very accurate. Looking at your setup list I would like to make a few suggestions :

Don't trust the built-in bubble-level on your tripod : they are seldom accurate and remember when you place the scope on top of the mount your are still going to tension the mount and it would not be the same as with the tripod by itself.

Don't use the bubble in the compass eyepiece : its a useless piece of kit. 

The most important thing to make your goto accurate is to level the OTA in all directions : The only way to do this accurately is to mount a level on the OTA facing the length of the tube and centred on  the pivot point. You then start by turning the OTA to be parallel with two of the tripod legs and adjusting one of these two legs until the OTA stays level when you turn it 180 degrees between the two legs. You then turn the OTA to point to the third leg and adjust that leg until it stays level when  it is rotated 180 degrees. Check the first two legs again  and then if it stays level  for the full 360 degrees. Don't loosen the Dec knob after you have done this just point the scope more or less to true north and Lock the Az knob. True north is not critical because any error will be rectified when you sync with the first star, after the second you ready to go.           

Thanks for the input.

 

Yep; I discovered the first day I had the LX 90 NOT to trust the built in tripod bubble.

As said, not new to scopes or astronomy; just new to GoTo. smile.gif

 

Seemed a little silly to me for Meade to attempt to automate placing a bubble level in a tripod head.

 

I DID use the spirit level across the OTA but did not rotate RA 360 degrees as you suggest.

Seems like a good idea & thanks for the tip; it makes perfect sense to do so.

 

True north is not critical because any error will be rectified when you sync with the first star, after the second you ready to go.

 

Curious about this ^^^?

 

I understand the GPS will determine my position on earth and then slew (X) amount to the first star based on it's internal RA/DEC database coordinates converted to ALT/AZ coordinates.

I would have assumed getting (north) as close as possible would reduce pointing error to the first star? RA drive?..and thereby further reduce any undershoot/overshoot to the 2nd star?

 

Perhaps I'm not understanding "how" the GoTo HBX is instructing the ALT/AZ motors.

Certainly something to look into and experiment with by intentionally setting "Home" maybe 10-20 degrees east or west of north and see what happens.

 

I am enjoying the LX immensely and am amazed for alt/az that it can visually track at sidereal rate w/o any perceptible "stair stepping."

 

Will probably get back into AP next spring with a wedge.

I cut my teeth back in the day using a GEM, so never had a alt/az and certainly never had a GoTo.

Back then we had to understand how to locate objects with star maps, understand RA/Dec and insure we polar aligned the daylights out of our GEM for AP, especially considering my exposure times were sometimes more than 1 hr. No digital imaging back then, film/cold camera's and gas hypered...Certainly no stacking software either! How barbaric huh? LOL

 

Looking forward to auto-guiding with computer and software..and I fully understood when I purchased the LX 90 that the LX 200 would probably be better suited

to AP; but I think I can polar align properly smile.gif and deal with PEC by hand, and hopefully greatly reduce any DEC corrections which I can do myself manually if need be.

 

Again, thanks for the setup tip on rotating the scope 360 and check level throughout.

 

ps: The level placed on the OTA assumes the OTA has no distortions along it's axis; yes?


Edited by Blackbelt76, 23 October 2019 - 03:54 PM.


#11 OzAndrewJ

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Posted 23 October 2019 - 04:07 PM

Gday Blackbelt

 

Perhaps I'm not understanding "how" the GoTo HBX is instructing the ALT/AZ motors.

Basically, when you set the mount North and Level, that isnt what you are doing wink.gif

What you are really doing is pointing the OTA to a point where Alt = Az = 0

( hence why you must point Nth even in the Sth hemi )

On starting to do an align, the mount does an internal synch for that position and then does a dead reckoning slew to the first star ( assuming a perfectly vertical Az axle ).

Any error on the first star is normally due to errors in accuracy of level/north setup.

You then centre the first star and when you hit OK, it does a new synch and then slews to the second star, again assuming a perfectly vertical Az axle .

Any errors this time are "assumed" to be associated with level errors in the base and a suitable ( but crude ) model is built to cover for it.

Thats all there is to it.

Andrew Johansen Melbourne Australia


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#12 Blackbelt76

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Posted 24 October 2019 - 05:02 AM

IYou then start by turning the OTA to be parallel with two of the tripod legs and adjusting one of these two legs until the OTA stays level when you turn it 180 degrees between the two legs. You then turn the OTA to point to the third leg and adjust that leg until it stays level when  it is rotated 180 degrees. Check the first two legs again  and then if it stays level  for the full 360 degrees. Don't loosen the Dec knob after you have done this just point the scope more or less to true north and Lock the Az knob. True north is not critical because any error will be rectified when you sync with the first star, after the second you ready to go.   

 

Tried this last night...seems awkward and not too easy considering the weight of the scope is now on the tripod.

Difficult but not impossible.



#13 Piet Le Roux

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Posted 24 October 2019 - 12:08 PM

It becomes easier with practice...the side of the level on which the bubble is, is the side that must drop to get the bubble in the middle, grab the bottom section of the leg just below the leg lock lever, this way you can control the amount it drops when you loosen the lock. More important : did the exercise yield any results?  I did not mention this but you must first get the error to be the same on both sides of the 180 degree swing of the OTA by loosening the Dec knob and adjusting the position of the OTA, then you start adjusting the legs. 


Edited by Piet Le Roux, 24 October 2019 - 12:16 PM.


#14 Blackbelt76

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Posted 24 October 2019 - 01:58 PM

It becomes easier with practice...the side of the level on which the bubble is, is the side that must drop to get the bubble in the middle, grab the bottom section of the leg just below the leg lock lever, this way you can control the amount it drops when you loosen the lock. More important : did the exercise yield any results?  I did not mention this but you must first get the error to be the same on both sides of the 180 degree swing of the OTA by loosening the Dec knob and adjusting the position of the OTA, then you start adjusting the legs. 

Yes, I saw some improvement.

Interestingly, my setup procedure seems to yield a pretty good level as I rotate thru 360.

Agreed on tensioning the scope to tripod; may cause some movement, but I generally don't crank down on it that hard, just snug.

 

Although some have said close to North is good enough, I'm not finding that in my case. (magnetic vs Pole star)

If I align north using Polaris and select 2 stars at least 50 degrees apart and close to the celestial equator, I get very good results.

Last night the Audiostar wanted to choose Vega & Altair.

 

Lastly, when it slews to the first guide star, it does NOT appear in the scope EP, but I do see it in my 9x50.

 

Luckily for me, it has not turned too cold here yet as I would not want to practice this in 20 degree weather; would rather just be observing.

 

Thanks again.


Edited by Blackbelt76, 24 October 2019 - 02:00 PM.


#15 Airlid

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Posted 24 October 2019 - 06:44 PM

Blackbelt:
I have had my LX90 for almost 2 years now and I have tried quite a few different solutions to enable guiding and have been unsuccessful. I would be very interested to see what solution you come up with when you do it.
As far as set up alignment goes my scope is on a wedge and I use a polar camera to align the Alt axis of the scope to the North celestial pole. Good luck in your endeavors.

Edited by Airlid, 24 October 2019 - 08:04 PM.


#16 Blackbelt76

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Posted 24 October 2019 - 09:22 PM

Blackbelt:
I have had my LX90 for almost 2 years now and I have tried quite a few different solutions to enable guiding and have been unsuccessful. I would be very interested to see what solution you come up with when you do it.
As far as set up alignment goes my scope is on a wedge and I use a polar camera to align the Alt axis of the scope to the North celestial pole. Good luck in your endeavors.

Not sure if I understand your post in relation to my issue.

 

“Guiding” is not a problem. The LX90, once a object is centered in the EP, tracks quite satisfactorily.

The issue is the initial 2 star alignment concerning accuracy when using subsequent GoTo commands.

My efforts with the aid of some here are slowly paying off.

 

It would seem to get the LX90 to align properly, a few strict setup procedures need to be followed.

 

Level Tripod

Level OTA

Good north setup

Essential Training of the drive periodically

Calibration of drive motors when needed depending on DC input voltages.

 

appreciate your post.



#17 Piet Le Roux

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Posted 26 October 2019 - 09:29 AM

Yes, I saw some improvement.

Interestingly, my setup procedure seems to yield a pretty good level as I rotate thru 360.

Agreed on tensioning the scope to tripod; may cause some movement, but I generally don't crank down on it that hard, just snug.

 

Although some have said close to North is good enough, I'm not finding that in my case. (magnetic vs Pole star)

If I align north using Polaris and select 2 stars at least 50 degrees apart and close to the celestial equator, I get very good results.

Last night the Audiostar wanted to choose Vega & Altair.

 

Lastly, when it slews to the first guide star, it does NOT appear in the scope EP, but I do see it in my 9x50.

 

Luckily for me, it has not turned too cold here yet as I would not want to practice this in 20 degree weather; would rather just be observing.

 

Thanks again.

Yes one more thing: stay away from magnetic North input. The magnetic North declination in the Audiostar data base is very out dated and you would be off by a few degrees depending on where in the world you are. There are a few smart phone apps that would give the magnetic declination for your location and can use your phone's build in compass to show true North.  If your first star can be found in the finder scope you doing well. At home I am well acquainted to were north is and can setup without a compass and be in a 27mm Panoptic every time, at other sites I use a compass or Google Earth.    


Edited by Piet Le Roux, 27 October 2019 - 01:05 AM.

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#18 Piet Le Roux

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Posted 26 October 2019 - 09:43 AM

Blackbelt:
I have had my LX90 for almost 2 years now and I have tried quite a few different solutions to enable guiding and have been unsuccessful. I would be very interested to see what solution you come up with when you do it.
As far as set up alignment goes my scope is on a wedge and I use a polar camera to align the Alt axis of the scope to the North celestial pole. Good luck in your endeavors.

I Have all the kit for guiding : wedge, guide scope and CCD camera but have not gotten that far. I have just decided on a camera to start with and received that last week. Its a Fujifilm X-T100 and I am waiting for an Fuji X to 48mm adaptor that should be here next week. I have a GSO 0.5 focal reducer that I must first get to work. My plan is to first become comfortable with the camera setup by taking some lunar and sun shots and then some short exposure deep sky , then polar aliment, PEC training and then guiding with PHD. I think to get good tracking for AP one should tic all the boxes. I hope when I get to guiding you can give us some advise!    


Edited by Piet Le Roux, 26 October 2019 - 09:44 AM.


#19 Blackbelt76

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Posted 26 October 2019 - 02:19 PM

Blackbelt:
I have had my LX90 for almost 2 years now and I have tried quite a few different solutions to enable guiding and have been unsuccessful. I would be very interested to see what solution you come up with when you do it.
As far as set up alignment goes my scope is on a wedge and I use a polar camera to align the Alt axis of the scope to the North celestial pole. Good luck in your endeavors.

 

Airlid, for me, I classify "guiding" in 3 formats.

1) Visual

2) Short exp times <3mins

3) Long Exposure >3mins

The LX 90 does NOT have a dec correction if autoguiding unless one uses a converter.

The other issue "not a problem" is RA tracking and PEC. I've read the LX200 has more teeth in it's RA gear which would

provide for better/smoother tracking in astro photography.

The LX200 also has a guiding port, the LX90 does not.

 

If one sets up a very accurate Polar north alt with a wedge, Dec guiding will be minimal, if at all depending on a few factors, tube flex, come error, drive issues (pec)

 

As Piet Le Roux pointed, he has a wedge; which I too will get next year.

The wedge removes the common issue of field rotation.

 

For now, once I'm locked to a target, usually a planet or the moon, I have successfully captured images as long as I keep the exp times short enough; usually under 30 secs. For anything longer, a equatorial wedge will be necessary.

 

I shoot with a unmodified nikon D-300, EP projection and some prime focus.

 

I have tried quite a few different solutions to enable guiding and have been unsuccessful.

 

Are you talking about the clock drive tracking/following the object in the eyepiece once found or the initial alignment?

These ^^^ are two different topics.

 

Are you in alt/az mode or are you using a equatorial wedge? 

 

My issue was setting up the scope in a proper level position; which I think I have solved.

 

Auto guiding will be new to me; almost seems too easy for someone who came from the days of film, cold cameras and gas hypered film. wink.gif

Most of my guiding back then was over 1 hour. I didn't have access to stacking software etc...we didn't even have Photoshop then. I'm letting my age show. LOL I guided visually with a 80mm refractor, piggy backed to a 8 inch Newtonian. All guiding was manually done with a hand controller as I watched thru the 80mm refractor.

 

The good in all that is that I know how to accurately polar align a scope. wink.gif

 

Let me know if you need any help with your "guiding" issue, which I am still not sure what you mean by "guiding"?


Edited by Blackbelt76, 26 October 2019 - 02:21 PM.


#20 OzAndrewJ

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Posted 26 October 2019 - 03:51 PM

Gday Blackbelt

 

The LX 90 does NOT have a dec correction if autoguiding unless one uses a converter.

Dont understand

In polar, you can

a) pulseguide in both RA and DEC

b) use old fashioned guide by normal moves

c) buy an APM909/clone to get an ST4 input, but no matter what, it will guide both axes.

There were some versions of handbox firmware that came out where DEC pulses got sent to the RA card

but there is a patch for that.

Andrew Johansen Melbourne Australia



#21 Blackbelt76

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Posted 27 October 2019 - 04:18 AM

Gday Blackbelt

Dont understand

In polar, you can

a) pulseguide in both RA and DEC

b) use old fashioned guide by normal moves

c) buy an APM909/clone to get an ST4 input, but no matter what, it will guide both axes.

There were some versions of handbox firmware that came out where DEC pulses got sent to the RA card

but there is a patch for that.

Andrew Johansen Melbourne Australia

That's what I meant; w/o some sort of converter, there is no st4 input to the LX 90.

I didn't say it can not be moved in DEC.

 

b) is what I plan on doing; always did it this way.



#22 Blackbelt76

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Posted 27 October 2019 - 09:40 PM

Final report...

 

it seems the 2 star alignment gets the object just at the edge of my 9x50 finder, but not in the scope at my widest FOV using 50x.

 

High Precision pointing seems to be the way to go, at least for me.

 

 When I use HP pointing, it nails it every time...very happy with that.

The only downside is that it takes a tad longer while the Audiostar pulls a star from its database

close to the object of interest.

 

I would certainly be happier if the 2 star align did a better job centering the object.

Still noticing if I choose the 2 stars, it still misses by a few degrees.

Did a lot of leveling, base,scope..using polar north.

Maybe just a question of more setup practice.

 

Another poster here mentioned he uses High Precision Pointing often; I probably will as well.

 

Appreciate all the great advice and tips.



#23 Piet Le Roux

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Posted 28 October 2019 - 12:02 AM

Let first look what "High Precision" does :

 

If High Precision is turned on, when looking for a faint celestial object (i.e.,

a nebula or galaxy), AudioStar first slews to a nearby bright star and displays “ENTER to
Sync”. Center the star in the eyepiece, then press ENTER. At that point the telescope has
a high precision alignment to that part of the sky and it then slews to the object that was
originally requested.

 

So it basically forces you to sync regularly. It is not going to make any difference with your 2 star initial sync. I never use it but I am in the habit of syncing manually on any object of which I am certain by pressing "enter" for 4 seconds and than again to confirm.This way your system stays accurate for the length of your viewing session. 

 

The only way your first star can be off by few degrees, if your scope is perfectly level, is if your north position were off by a few degrees. When choosing your north position it is very easy to be off by a degree or two but it does become better with practice but I would not worry about it because after the initial aliment all should be well.          


Edited by Piet Le Roux, 28 October 2019 - 12:14 AM.

  • Blackbelt76 likes this

#24 OzAndrewJ

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Posted 28 October 2019 - 12:17 AM

Gday Blackbelt

re

 

It is not going to make any difference with your 2 star initial sync.

Piet is correct. Synch merely adjusts the encoder datums to match the current target, it does not touch the base align model.

Hi precision will slew to a bright star on EVERY goto, which can get annoying.

If you are rubbernecking everywhere, then it is OK, but if you go to an area of sky and plan to stay there for a while, it is better to just find one target and synch on it manually, then just slew around.

Its the same as a HiPrec slew, but you only need to do the synch once.

Andrew Johansen Melbourne Australia



#25 Blackbelt76

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Posted 28 October 2019 - 05:59 AM

Let first look what "High Precision" does :

 

If High Precision is turned on, when looking for a faint celestial object (i.e.,

a nebula or galaxy), AudioStar first slews to a nearby bright star and displays “ENTER to
Sync”. Center the star in the eyepiece, then press ENTER. At that point the telescope has
a high precision alignment to that part of the sky and it then slews to the object that was
originally requested.

 

So it basically forces you to sync regularly. It is not going to make any difference with your 2 star initial sync. I never use it but I am in the habit of syncing manually on any object of which I am certain by pressing "enter" for 4 seconds and than again to confirm.This way your system stays accurate for the length of your viewing session. 

 

The only way your first star can be off by few degrees, if your scope is perfectly level, is if your north position were off by a few degrees. When choosing your north position it is very easy to be off by a degree or two but it does become better with practice but I would not worry about it because after the initial aliment all should be well.          

Interesting. I did not know holding the enter key after locked on for 4 secs will re-sync. Great tip!..especially if I plan on being in that area of the sky for a while.

Also interesting, my HBX does not say "Enter to Sync" although my instruction manual uses those words.

Mine reads "Slewing", then stops and displays a star name, then I hit "enter"again.

 

I don't believe my (TRUE) north is off as I am centering Polaris with a fairly high mag EP; certainly less than 1 degree FOV.

 

@ Andrew Johansen: Thank you for your information as well.

 

I'm beginning to think my expectations may have been too high with a GoTo scope.

..and yes, using HP pointing all the time can get annoying; not so much in a rubber necking regard; more like robbing a a little

observing time from me. smile.gif

 

It seems setting up the telescope should not be so finnicky if all one wants to do is some casual observing.

 

My hopes were (based on what I read prior to purchasing the LX 90), was a easy setup; easy alignment procedure and then

slew right to the alignment stars.

I know how to do precise polar alignment as I had to learn this years ago with a GEM; although I must confess, I thought

"roughing in" North (+- a degree or two) and basic leveling in alt/az would be all I needed to get objects centered...guess I was wrong. wink.gif

 

I know how to star hop, but was hoping the GoTo would eliminate much of that.

 

The "Press Enter for 4 secs" is not in the Meade manual; I'll find that VERY useful.

 

Last evening the sky was especially clear following several hours of heavy rain the day before.

Had a great time and find the scope to be great fun and a nice optical instrument.

One of these days the initial alignment will slew directly to the 1st alignment star and I'll probably faint. LOL

 

Thanks again to all.




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