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Equipment Discussions >> Mounts

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psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: GIR]
      #6111469 - 10/01/13 03:55 PM

The ultimate astro-couch potato!

Gotta love it!!!

I'm keeping track of this thread (and others like it), for next spring when I spring for a new mount. My needs are weighted slightly differently than others (because I'm an idiot, so I need things really idiot-proof. I'm not an idiot when I have time to learn things, but I generally only get once or twice a month to get out under the stars, so the learning curve is sloooooooow, hence the idiocy), but I'm looking at the 10 Micron, the ASA and the PMX. Speed of polar alignment will be important for me, as well. (AP's are great, but there are a few reasons I probably won't go with them, though if I did, it'd be the Mach 1.)

Very cool stuff....

Paul


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famax
member


Reged: 07/01/07

Re: ASA DDM60 Pro vs. GM1000HPS new [Re: psandelle]
      #6111821 - 10/01/13 07:32 PM

If polar speed is your main goal, you should consider a mount with polar scope.
So the mach one should fit.


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psandelle
professor emeritus


Reged: 06/18/08

Loc: Los Angeles
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: famax]
      #6111862 - 10/01/13 07:55 PM

Yeah, but you have to get the AP polarscopes perfect first before you can use them. I also like the extra accuracy of some of these modelling routines to do it.

To show how idiotic I am, I like the fact the PMX has "tics" on the alt/az adjustments to make it easier to get it correct.

Paul


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: orion69]
      #6111980 - 10/01/13 09:11 PM

Quote:

If I understood correctly ASA DDM60 or DDM85 is able to do 30min unguided imaging with my FL (<= 1000mm) and GM1000HPS or GM2000HPS can't (I believe it says so in manual).





If you are going to say this, then you need cite the location in the manual. I am certainly not aware of such a limitation, nor would I expect it to be in the manual (and have not found it in either the GM1000HPS or GM2000HPS manuals).


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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: EFT]
      #6112029 - 10/01/13 09:39 PM

Quote:

Quote:

If I understood correctly ASA DDM60 or DDM85 is able to do 30min unguided imaging with my FL (<= 1000mm) and GM1000HPS or GM2000HPS can't (I believe it says so in manual).





If you are going to say this, then you need cite the location in the manual. I am certainly not aware of such a limitation, nor would I expect it to be in the manual (and have not found it in either the GM1000HPS or GM2000HPS manuals).




Sorry you are right, at the time I wrote that I couldn't find the text.

Here is it now, from GM1000HPS manual:

"5.6 Notes on autoguiding
When properly aligned, and using the dual axis tracking option, the GM1000HPS
mount is able to track stars with extreme accuracy. Usually autoguiding is not
required, and may easily be counter-productive if the seeing is worse that about 1
arcsecond FWHM; in that case, guiding corrections will likely “correct” what are
really movements of the guide star image due to the atmosphere.
With very long exposure times (tens of minutes) tracking errors could show
nevertheless. In this case you will need autoguiding.
In order to minimise the
possible errors introduced by the guiding corrections, you will need to use a very
low “aggressiveness” setting in your autoguiding software, and/or very low
autoguide speed (down to 0.1x) and integration times up to several seconds.
If your alignment is not very good, you may use higher autoguider speeds and
faster integration times in order to track objects, but accuracy will suffer
accordingly.
Note that if you need to autoguide on the declination axis, you may obtain a
slightly better result if you disable the dual axis tracking option, so that the
declination corrections will be always in the same direction."

Edited by orion69 (10/01/13 10:19 PM)


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EFT
Vendor - Deep Space Products
*****

Reged: 05/07/07

Loc: Phoenix, AZ
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: orion69]
      #6112144 - 10/01/13 10:35 PM

Thanks for finding that. I do think that it says something different though. That is, that no system is perfect and guiding may be necessary at times and depending on the equipment, etc. The 10Micron mounts are very good at unguided imaging, but, like any mount, are not meant exclusively for unguided imaging. There are times when very high magnifications on very deep objects at very long exposures may benefit from guiding, but as pointed out, guiding may actually be counter productive. Not having hands-on experience with the ASA, I can't say what the limitations of the direct drive systems are, but they are certainly different than a hybrid belt/worm system. Beyond the absolute encoder systems, it's a little difficult to make direct comparisons since the tech is so different.

The truly amazing thing about both of these mounts is their ability to measure and correct for problems other than simply tracking precision. Being able to model orthogonality issues and the like truly makes the equipment up in this range amazing. I do think that direct drives are really cool tech.


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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: psandelle]
      #6112356 - 10/02/13 01:15 AM

I'm starting to sound like an ASA commercial but they do have a fantastic polar alignment routine...

Turn on the laser, check which side of Polaris north pole is located at that time (about 1 degree), and point the laser beam roughly to the north pole.
Open Sequence and choose 3 star polar alignment routine. Sequence will automatically choose you 3 targets, take pictures and plate solve them. After that you'll pick a bright start from south side of Meridian (about the same altitude you're located) slew there and place the start in the middle of the crosshair with the Autoslew key pad ...and push a button.

Telescope will now move away from the star exactly an amount you're misaligned from north pole. All you have to do is to turn the mount (altitude and azimuth knots) and move the star back into the middle of the crosshair ...and you're polar aligned.

You can repeat the Sequence procedure with more stars but the accuracy should be under 10 arcmin with one go.


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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: EFT]
      #6112390 - 10/02/13 02:00 AM

Quote:

That is, that no system is perfect and guiding may be necessary at times and depending on the equipment, etc.




This is very much true...

I've learned that if you want to do unguided imaging successfully your overall system has to be pretty solid. ASA software can measure all kinds of flexures and hysterisis and I was quite surprised to find out how much flexure my setup had, even I thought it'll be solid like a rock. But there will always be some sort of unwanted movement whatever you'll do.

Sequence can reduce quite a lot of negative effects created by flexure by modeling them out. Especially the MLPT (local pointing model) is very effective. However, even that can't make time flex disappear (temperature changes, relaxation effects, etc.)

I really don't know where the limit is but the longer the focal length is, the more difficult everything becomes. However, with my 600 mm FL I'm not even close to that limit.


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Tonk
Postmaster
*****

Reged: 08/19/04

Loc: Leeds, UK, 54N
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: GIR]
      #6112459 - 10/02/13 04:29 AM

Quote:

I'm starting to sound like an ASA commercial but they do have a fantastic polar alignment routine...




OK I'll do my practical experience bit for the 10u. So this is no different in method and outcome with the GM1000HPS but no laser is actually required. There is even Per's software to totally automate it bar the physical alt/az adjustments

Did you know even the the lowly Losmandy Gemini does this type of polar alignment as well (via model building)? And its also quick. The only downside here is the precision of the mount is lower so measuring final PA misalignment usually is in the +/- 2 arc minute range where as with the 10u and ASA mounts you expect < 0.25 arc minute to be acheived within 15 minutes.

Quote:

You can repeat the Sequence procedure with more stars but the accuracy should be under 10 arcmin with one go.




Did you mean 10 arc sec? The 10u is under 1 arc in one go and gets to 0.25 arc sec in two goes most of the time. Worst I've had in 2 iterations is 0.41 arc sec polar misalign - and even this is good for 10 minutes unguided @ FL 600mm not even using dual axis tracking



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Tonk
Postmaster
*****

Reged: 08/19/04

Loc: Leeds, UK, 54N
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6112462 - 10/02/13 04:34 AM

Quote:

However, with my 600 mm FL I'm not even close to that limit.




Too true - its my favourite FL and makes anything look good . At this FL I can get my Losmandy Gm-8 going unguided for 4 minutes (but here about 10% images are tossed)

Hence those unguided times of 10 minutes @ FL 2800mm quoted (way) above are remarkable in my mind


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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6112464 - 10/02/13 04:41 AM

Quote:

OK I'll do my practical experience bit for the 10u. So this is no different in method and outcome with the GM1000HPS but no laser is actually required. There is even Per's software to totally automate it bar the physical alt/az adjustments





OK, why don't you run us through the routine to see how it's done, instead of just saying there is no difference and Per has done something...


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Tonk
Postmaster
*****

Reged: 08/19/04

Loc: Leeds, UK, 54N
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6112468 - 10/02/13 04:45 AM

Quote:

Here is it now, from GM1000HPS manual:




That paragraph doesn't say the 10u cant go unguided for 30 mins (as that is entirely dependent on FL and other factors such as target altitude from horizon etc) . What it is correctly saying is you may have pushed a limit in which case you can autoguide and heres how to set up to autoguide this mount.

So this sentence ...
Quote:

With very long exposure times (tens of minutes) tracking errors could show nevertheless.




.. uses the word could - practically this limit is far more likely to be reached at 2800mm than 600mm depending how well set up and PA corrected etc the mount is. As always you can elect to autoguide your way out of a limit


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Tonk
Postmaster
*****

Reged: 08/19/04

Loc: Leeds, UK, 54N
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6112472 - 10/02/13 04:53 AM

Quote:

OK, why don't you run us through the routine to see how it's done, instead of just saying there is no difference and Per has done something...






Will do - its already on another thread in this forum .. but I have to rush now to uni .. or if you care to use the forum search - I wrote a full setup review back in August

Will put the link here when I get back tonight


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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6112482 - 10/02/13 05:19 AM

Quote:


Quote:

You can repeat the Sequence procedure with more stars but the accuracy should be under 10 arcmin with one go.




Did you mean 10 arc sec? The 10u is under 1 arc in one go and gets to 0.25 arc sec in two goes most of the time. Worst I've had in 2 iterations is 0.41 arc sec polar misalign - and even this is good for 10 minus undguided @ FL 600mm not even using dual axis tracking






Yes, I meant under 10 arcmin when using 3 stars and doing it quickly. How much under, depends how careful you are. Of course you can always use more stars or repeat the procedure and then we can talk about under 1 arcmin figures, which are excellent even for permanent setups.

I'm sorry Tonk but I simply have hard time believing your stories how easy and accurate everything is with 10micron. We can always highlight the one time best estimates or tell only half of the story, but repeating things and doing them routinely is quite another matter.
There seems to be a lot of of people who can do unguided imaging with mediocre gear or hit polar alignments on the spot with one go ...if they'd just wanted to.

P.S. just read another thread were you said you've been using 15 stars and three iterations for polar alignment. So we're comparing apples and oranges here.
P.P.S. You'll probably have more flexure on your setup than the polar alignment figures you've indicated.


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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: GIR]
      #6112525 - 10/02/13 06:48 AM

Guys, just a comment or two about unguided imaging...

If you say that mount is capable of unguided imaging that should mean that it routinely produces long and "perfect" (in my case required 30 min) subs. Routinely means that maybe 1 of 50 is bad, not 50% or 20% or 10%, time when sky is clear is precious.

As far as GM1000HPS goes: in manual says that tracking error is +- 1" in 15 min. That means +- 2" for 30 min, and in my opinion this is too large error for mount to be used for 30 min unguided imaging.
Of course, I'm not saying that something is wrong with GM1000HPS, I'm just trying to figure if it would be useful for my needs. That goes for ASA too.

As for Losmandy Gm-8 being capable of 4 min unguided subs @ 600mm with "only" 10% tossed (which is already too much to be useful), I very much doubt that. Please show us few (not just one) unprocessed FITs of those unguided subs...


In my opinion if mount has absolute encoders it should be used for long time unguided imaging. If mount requires at some point (lets say 30 min and above) guiding, then much better solution would be (for me at least) to buy mount without encoders but with greater capacity (PMX?).

Edited by orion69 (10/02/13 06:50 AM)


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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: orion69]
      #6112545 - 10/02/13 07:10 AM

Quote:

In my opinion if mount has absolute encoders it should be used for long time unguided imaging. If mount requires at some point (lets say 30 min and above) guiding, then much better solution would be (for me at least) to buy mount without encoders but with greater capacity (PMX?).




Knez

As said before, it's not just what the mount can do technically but how well the whole setup is built. I know that ASA mounts can be very accurate and their modeling software is also top notch. Good modeling is actually a very important factor when doing unguided imaging with high res encoders. But it's not enough if there are e.g. flexure issues with the scope and camera.

So I can only tell you that with my setup taking 30 min exposures reliably (if needed) is no problem. However, my scopes are f/3 and f/2.8, so there is really no need for me to do extra long exposures.
What others are doing or what is possible to do, is something I don't want to speculate.


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famax
member


Reged: 07/01/07

Re: ASA DDM60 Pro vs. GM1000HPS new [Re: orion69]
      #6112555 - 10/02/13 07:20 AM

That's make sens orion.

Gir, Tonk isn't saying anything wrong, he just mistype
arc/sec and arc minutes somewhere.
By the way you are demandung proofs on 10µ and we were able to give you feedback, not only from us, but from other users.

You are not able to tell us the plus and minus of the asa.
So you are just here to bash 10µ ?

10 arc ' is huge for your polar alignement even for the first step.
After two steps, the 10µ , in the field is usually beetween 20" to 40 ".

It take 10 minutes to do so, after that you can add 12 minutes for your 20 point modelling, and you are ready to go.


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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: famax]
      #6112565 - 10/02/13 07:34 AM

Quote:

Gir, Tonk isn't saying anything wrong, he just mistype
arc/sec and arc minutes somewhere.
By the way you are demandung proofs on 10µ and we were able to give you feedback, not only from us, but from other users.

You are not able to tell us the plus and minus of the asa.
So you are just here to bash 10µ ?






I think this thread is going to a direction I have nothing to add anymore. As said before, all high end mounts (in right hands) are capable of producing beautiful astrophotos.

P.S. famax I wish you'd read my comments more carefully before jumping into so ridiculous conclusions


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jjongmans
super member


Reged: 02/11/12

Loc: The Netherlands
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: GIR]
      #6112595 - 10/02/13 08:09 AM

I was able to do 20 minutes unguided subs on the first clear night a had with my DDM60 at 1380mm.

1) Polaralign with the green laser.
2) Run 3-star pointingmodel (all automated with Sequence).
3) Fine tune polar alignment (once).
4) Create 25 to 50 point tracking model or declination model.
5) Point and shoot 20 min unguided at 1380 mm

Easy does it....


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Tonk
Postmaster
*****

Reged: 08/19/04

Loc: Leeds, UK, 54N
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: jjongmans]
      #6112660 - 10/02/13 09:11 AM

Quote:

I'm sorry Tonk but I simply have hard time believing your stories how easy and accurate everything is with 10micron.




I'm sorry you think this way. But I know exeactly what I have experienced - its an excellent mount that is nice and easy to use. There are certainly others who would back this up.

Maybe you should go and try one for yourself.


This link is my write up of my first night out + Per describes his automated model building tool in the following posts (its free to use)

http://www.cloudynights.com/ubbthreads/showflat.php?Cat=&Board=lxd55&...


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