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Equipment Discussions >> Mounts

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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: rmollise]
      #5972206 - 07/15/13 01:06 PM

It seems I'm thinking like an engineer ... a retired one!

Joke aside, I agree with you Rod. We are lucky to have a guy like you around here to help us. Thx!

I would really have wanted to be able to expose unguided for 3-4 minutes with a mount like AZ-EQ6 which costs triple than a CG5GT but it seems I'm dreaming.

I don't understand why EQ6/CGEM are so heavy and what material are they made of.


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Falcon-
Post Laureate
*****

Reged: 09/11/09

Loc: Gambier Island, BC, Canada
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Moromete]
      #5972215 - 07/15/13 01:09 PM

Quote:

I don't understand why EQ6/CGEM are so heavy and what material are they made of.



It is not a matter of materials, it is a matter of physical size. The EQ6 and CGEM are simply physically larger then the CG5.


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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: johnpd]
      #5972278 - 07/15/13 01:37 PM

Quote:

Moromete,

You have me thoroughly confused. How do you determine the accuracy of a Skywatcher mount when doing a test with a CG-5? Yes the AZ-EQ6 is heavier than the CG-5 but not prohibitively so. I had a CGE which I thought was going to give me a hernia. If you are interested in a lighter mount that should handle your C-11, you might want to consider the iOptron iEQ45. There is a AZ/EQ version of that also. Weightwise it is between the CG-5 and AZ-EQ6 and cheaper than the AZ-EQ6. Is there anyone near you that has an AZ-EQ6 or an EQ6 that you can do a test on?

JohnD




John, let me explain. I thought that since Synta owns Celestron and Skywatcher than the actual mathematical calculations done by the Synscan software must be identical to those done by Celestron Nexstar, the actual difference residing in the number of functions ported to Synscan. That's why I thought that 3 star alignment is computed/done the same with both CG5-Gt and AZ-EQ6. Am I wrong?

Regarding the IEQ45 I have looked at it carefully but it seems it's not good with a heavy scope like C11 especially because of the spring loaded worm gears which introduce significant shakiness both at high power viewing and with photography. If IOPTRON gets rid of the springs than it would be a nice mount with a heavy scope. The weight of the IEQ45 would be OK for me considering I can't permanently mount it. Another problem with IEQ45 I think is the software which I suppose is more rudimentary than Synscan. Than it's the noise when slewing at full speed which is similar to CG5-GT coffee grinder. Judging by pictures I'm not impressed with build quality of IEQ45. Lastly, in my country there is no service for IOPTRON products and IEQ45 costs a little more than an AZ-EQ6. Besides these there are mny things to like at IEQ45, especially the weight and the hand controller LCD during winter.


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cn register 5
scholastic sledgehammer


Reged: 12/26/12

Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Moromete]
      #5972367 - 07/15/13 02:06 PM

The Synta and Celestron hand controllers and software pre-date the merger so are essentially separate. They also appear to work in different ways, using different hardware architecture and motors.

But they are probably both based on Toshimo Taki's matrix method of aligning scopes, as is everyone else's.

They both do the same job - coordinate transforms - so will be similar.

But the detail of how they do it will be different and as far as I know there is little detailed interaction, they seem to have separate developers working independently.

Chris


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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: cn register 5]
      #5994159 - 07/28/13 05:17 AM Attachment (19 downloads)

Last night the weather was good and I decided to test seriously the ASPA function of my CG5-GT mount (pier mounted), which carries a C11, and I also pushed the LodestarC ccd to the limit.

To cut a long story short I'll say I was VERY IMPRESSED with Celestron ASPA because I reached repeatedly exposures of 300s UNGUIDED during the same night with a CG5-GT!

Now I'm convinced that with Celestron ASPA I'll never feel the need to bother with drift alignment and guiding can be avoided with almost perfect polar alignment. On the other hand, maybe I have an exceptional CG5-GT and I didn't know that. It's interesting that I haven't noticed any periodic error in my shots during the whole sesion which I can't explain myself why.

To be able to reach several exposures of 300s unguided with the CG5-GT, I aligned the mount on 2+1 stars (without any callibration stars) with LodestarC ccd mounted on C11, reducedat F/2.6. During alignment I used SharpCap with LodestarC and I activated SharpCap's red reticle function and put all 3 alignment stars in the middle of the reticle. After finishing the initial alignment, I started doing ASPA on star Altair which was near the meridian in South. Againg, during ASPA I centered Altair in middle of the red reticle of SharpCap. That was all!

After finishing Celestron ASPA there was no need for a re-alignment, unlike Skywatcher mounts! Thanks Uncle Rod for pointing this out. In the past I didn't used ASPA because I had to cycle power and redo the initial alignment of the mount which was a PITA for me and too much time consuming when observing sesions are short. So again Skywatcher/Orion hand controller lags behind the Celestron one because with Skywatcher/Orion your have to redo the initial mount alignment after finishing ASPA which is a PITA for me.
I would like to see in Skywatcher firmware 3.36 for AZ-EQ6 an ASPA like Celestron one which doesn't require a re-alignment.

This way I proved myself that it's actually possible to take 300s exposures with a heavy C11 on a cheap CG5-GT mount WITHOUT GUIDING!

I have to point out that all 300s shots were done in the NW part of the sky and I hadn't enough time to take some 300s shots in E or S.

Lastly, I reached the maximum exposure limit of the LodestarC software which is 300s.

To reach F/2.6 with C11 I stacked a 2" x0.5 GSO reducer over the AlanGee telecompressor.

Below is a single exposure of 300s of M81 taken with LodestarC + C11 (F/2.6), without guiding, dark frame or flats.


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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Moromete]
      #5994160 - 07/28/13 05:18 AM Attachment (30 downloads)

M101, single exposure of 300s, unguided, no flats or darks.

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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Moromete]
      #5994161 - 07/28/13 05:19 AM Attachment (24 downloads)

M63, single exposure of 300s, unguided, no flats or darks.

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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Moromete]
      #5994163 - 07/28/13 05:20 AM Attachment (20 downloads)

M51, single exposure of 240s, unguided, no flats or darks.

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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Moromete]
      #5994500 - 07/28/13 10:51 AM Attachment (15 downloads)

M51, single exposure of 240s, unguided, 1 dark frame substracted, no flats.

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Mike X.
scholastic sledgehammer


Reged: 06/28/10

Loc: Greece-Athens and Rome-Italy
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Moromete]
      #5997812 - 07/30/13 04:33 AM

Hello gents, Just a small update as this weekend I managed to use th azeq6 under a dark sky for some immaging.
I found the pointing accuracy excellent.better than my cg5 actually.
I aligned with the c6 reduced ad 945mm and a qhy5m attached to it.
After a 3 star alignment the mount would bring averything near the field of view of the tiny sensor of the qhy5m which means it was dead center for my Ed 80 and the qhy8l.

I used also the skywatcher "ASPA" routine.I found no difference in precision than the celestron ASPA.
This is a ghidepraph at 500mm


upload gambar

This is the result at F:945mm ( guided at 500mm)
From a city sky ( I was about of focus too )

Hope it helps.
Ps. Oh...and on this photo I just used the polar scope.


On this one..( which is a work in oroject) I used the polar alignment routine.
I photograpghed at 500mm and guided with the c6


All in all this mount and the neq6 are in a totally different league than the cg5 photographically and in terms of payload.
In terms of accuracy I wouldn't be occupied at all.

I hope I've been of help.


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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Mike X.]
      #5997909 - 07/30/13 07:36 AM

You are very helpful Mike. Thank you for posting such valuable information about AZ-EQ6 mount!



1) After doing ASPA with AZ-EQ6 did you to re-align the mount (with Celestron you have to) ?

2) Since I managed to take a few 300s shots totaly unguided with my CG5-GT (after doing ASPA once) with C11(F/2.6)+LodestarC in NW part of the sky, just out of curosity, can you try to expose for 300s unguided with AZ-EQ6 in NW and C6 at F10 and a DSLR and post the results to see if there are trailed stars or not?


Chose any DSO you want in NW. I doesn't metter the quality of the image in this case but if star trailing exists and how bad it is.


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neptun2
scholastic sledgehammer


Reged: 03/04/07

Loc: Bulgaria
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Moromete]
      #5998116 - 07/30/13 10:16 AM

I can share my experience with the HEQ5 Pro mount that i have. I am happy with the goto accuracy and also the polar align routine in the latest firmwares. You need to make another 3-star alignment after the polar align routine to be sure that your gotos will be accurate but this is not something which takes so much time. Also i always use the stars suggested by synscan for the goto alignment without problem. In the recent versions of synscan the software knows which stars are best for the alignment and suggests them correctly. In the very older versions you needed to be careful what to select but this not a problem anymore.

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Mike X.
scholastic sledgehammer


Reged: 06/28/10

Loc: Greece-Athens and Rome-Italy
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: neptun2]
      #5998140 - 07/30/13 10:28 AM

I do as neptun does, after the ASPA i re aling with 3 stars.
But it's a very quick process.
It is true that since the mount is polar alinged the initial gotos are way better than before.

I can try with the C6 ad f/10 but i doubt the mount will show similar results with the guided photos.
Actually i rarelly use teh C6 at /10 since the exposure times rise for about 3 times than at f/6.3 while the resolution i get reduced with the CCD/dslr is more than enough even for smaller objects.
if i remember well at f/10 i used it only in 2 targets, M13 once (and i dropped it as at f/6.3 was more than ok) and blue snowball where even at f/10 is tiny.

I haven't measured the PE but i get the impression that for the AZEQ6 has a smoother curve than the one i was getting with the CG5..so even unguided should perform better probably.

Personally..at these focal lenghts and ratios (f/6+)..i wouldn't bother to go unuiged for more than 1 or 2 minues.


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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Mike X.]
      #5999520 - 07/31/13 04:38 AM

Thx Mike and Neptune for explanations.

So you have to re-align the AZ-EQ6 after ASPA. Now that's just plain stupid from Skywatcher because Celestron solved this problem years before and the fix must be very easy. Because of the re-alignment I quited using ASPA with CG5-GT (until Uncle Rod said there's no need to re-align now) because re-alignment took too much time during my short sesions and I found it annoying too.

Mike, if possible try a long exposure of any DSO you want (e.g. M51 or M81) or a star of 300s UNGUIDED with AZ-EQ6+C6(at 1500mm)+DSLR in NW part of the sky to see how it compares to my unguided exposures of 300s with CG5-GT. I'm just curios to see if there will be any star trailing with AZ-EQ6 in this case (after doing ASPA). It doesn't matter how pretty is the final image.

I intend to use the AZ-EQ6 with C11(reduced to F/6)+DSLR => 1650mm (close to your C6 at F10).


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Mike X.
scholastic sledgehammer


Reged: 06/28/10

Loc: Greece-Athens and Rome-Italy
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Moromete]
      #5999687 - 07/31/13 08:53 AM

I will gladly try it but I doubt there will be no trailing even with drift alignment at such focal length.

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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Mike X.]
      #5999716 - 07/31/13 09:20 AM

Like you, I couldn't believe my eyes when I saw the 3 images (M81,M101,M63) I posted and detected no star trailing after 300s without guiding but just doing ASPA with CG5GT after a 3 stars alignment (I used the first stars suggested by the HC).

Like I said before all 300s unguided images were taken in the NW part of the sky.

Maybe it was a very lucky night for me, I don't know.


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Mike X.
scholastic sledgehammer


Reged: 06/28/10

Loc: Greece-Athens and Rome-Italy
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Moromete]
      #5999742 - 07/31/13 09:41 AM

When i mean trailing ,I don't mean drift but tracking error because of the periodic error.
Now I know that the cg5 has a really high but guidable periodic error.
It has a periodism of approximately 600". 597" if I'm not mistaken ,so it is impossible to get a photo without being influenced by it...even at 300 sec.
Of course much depends from the what someone expects from a photo.
Round stars for me can be oval for others and viceversa.

for sure my cg5 had a pretty high PE...and the longest I did at 1500mm with round stars unguided was 50-60 seconds.
Here is an example of blue snowball


It should be somewhere in the middle

For sure the azeq6 has one less gear for the trasmission of motion..that should leave only the worm gear PE in theory which is good...in theory.
I will do the test ASAP and post the results.
I will do more actually..il will use the integrated alignment routine when I do the test so you can have a direct confrontation with he cg5 but as I said before I don't have high expectations for unguided shooting .

Edited by Mike X. (07/31/13 09:44 AM)


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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Mike X.]
      #5999983 - 07/31/13 12:27 PM

Mike, I agree with everything you said (including periodic error) and it's logical to not believe that's possible a 300s exposure without any guiding (especially with CG5GT) but posted 3 images to show it. I can't explain myself this performance and maybe I was very lucky.

An advice: use Altair as one of the first 2 aligment stars with AZ-EQ6 and than do ASPA again on Altair, than realign mount using the same 3 stars in the same order. After finishing this do the long unguided exposure at NW sky.
At least that's what I did when I exposed for a 300s unguided single frame (except realignment, which is not mandatory for Celestron mounts).


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Mike X.
scholastic sledgehammer


Reged: 06/28/10

Loc: Greece-Athens and Rome-Italy
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy new [Re: Moromete]
      #6000410 - 07/31/13 06:36 PM

Moromete, i believe you about the 300s seconds.Please do not take me wrong.Afterall you have posted them they are there and i see them.;)
From my point of view are very nice but the tracking error is evident.(please forgive my critique).
Being said that i must say those are amongst the best 300" unguided subs i have ever seen for a CG5.
When i plan to do subs with a longer focal leght and i let the mount on it's place for a few days generally i do a drift alingment.I find it usefull personally to have as less corrections in DEC as possible.

I will try your suggestions though with the SW ASPA routine.
So far i find it very good...but i hardly remember the stars i used.
For sure during the 3 stars alingment i use bright stars, Vega almost allways, Arcturus too some times.


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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Celestron Nexstar vs Skywatcher Synscan GOTO pointing accuracy [Re: Mike X.]
      #6001094 - 08/01/13 07:33 AM

Mike, I actualy welcome constructive critique because it helps me learn from my mistakes. For example, I dislike the obvious coma and I think my images are not sharp and I wonder why.


The lack of sharpness is due to coma, lack of guiding or low resolution of LodestarC?

How/Where do you spot tracking errors in my images?


Please be critique and help me improve my technique.


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