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Equipment Discussions >> Mounts

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Tonk
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Reged: 08/19/04

Loc: Leeds, UK, 54N
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6112671 - 10/02/13 09:18 AM

Quote:

P.P.S. You'll probably have more flexure on your setup than the polar alignment figures you've indicated.





Not a lot of flexture at all - I have a very solid connection to my TV85 - its a small scope


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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6112702 - 10/02/13 09:36 AM

Quote:

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.




Tonk,
Didn't mean to be disrespectful, we just seem to have a different way of expressing our thoughts. Clear skies and many good moments with your new mount.

P.S. you'd be surprised how much flexure all systems have if measured


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Tonk
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Reged: 08/19/04

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Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6112703 - 10/02/13 09:36 AM

Quote:

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...





Spending time to get a good PA with the GM-8 is very doable but does take around 2 hours to set up to the level required. PEC training is vital as is carefully off balancing the scope to stop "floating" between worm faces. Its bloody hard to do but I've spent 10 years practicing. When it comes off it works - however its not reproduacble without extreme effort. Another night it might only be be 2-3 minutes unguided. Best setups have reached 6 minutes when above 40 alt.

I'll happily dig out some RAW images + ones for the GM1000HPS (I shoot DSLR) but meantime here is an mosaic image of 8 hours accumulated with 6 minute unguided subs with my GM-8 taken back in 2007. It was an APOD too

http://www.cloudynights.com/photopost/showphoto.php?photo=14659&size=big&...

So after 10 years doing it the extreme hard way - I got a new mount ...


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orion69
scholastic sledgehammer


Reged: 05/09/10

Loc: Croatia
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6112732 - 10/02/13 09:50 AM

Tonk, PA of course matters, but even if you have perfect PA with low end mount quality unguided imaging isn't really repeatable except with very short subs (usually <1 min).

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Tonk
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Reged: 08/19/04

Loc: Leeds, UK, 54N
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: orion69]
      #6112741 - 10/02/13 09:55 AM

Have you used a GM-8 with the Gemini controller ? - it isn't low end at all. But then its not hi-end either by a long shot. Yes I agree it is not repeatable and that was always the issue for me but it is doable and I've done it many many times over the last 10 years. To date I've never guided!

Also my resolution on the Canon 450D camera sensor is only 2.25 arc seconds per pixel - so I'm not shooting high quality images either. I thought I'd made that clear earlier


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jjongmans
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Reged: 02/11/12

Loc: The Netherlands
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6112753 - 10/02/13 10:00 AM

All depends on image scale whether or not unguided imaging is doable... Short focal lengths (<1000mm) and big pixelsize are more forgiving..

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Per Frejvall
sage


Reged: 09/28/12

Loc: Saltsjöbaden, Sweden
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: jjongmans]
      #6113026 - 10/02/13 12:17 PM

I really have to support Tonk's claim that it is simple. In fact, most mounts are simple to get operational if you know the caveats and have both practice and manual reading to lean on.

The procedure for a 10Micron mount is to roughly align to north using polaris, a compass or the chimney you know is about north. After that you need three stars or "model points". These can be input via the hand controller or, if you operate by means of a PC, via any software that can sync an ASCOM mount. One such software would be my model maker, another CdC.

After a three-point alignment has been completed the hand controller will tell you how much to rotate the Az and Lat knobs, and, of course, the polar alignment error. You then proceed to adjust them.

Clear the model and run another one, this time maybe with a few more points. Most times you can leave it as is after this, but feel free to adjust again if the error is still not to your liking.

At this point you will have a reasonably god tracking model for 10 minutes exposures at around a meter of focal length. The first light moment with my GM2000HPS produced pinpoint stars with around 10 model points and two adjustments of the knobs. Unguided.

Now, one more thing to think of is the stability of the pier or tripod. The tripod I use when I use a tripod is the 10Micron Centaur. Very sturdy, and the distance between one foot and the perpendicular line between the other two is about 80cm with the legs in their unextended position. Suppose it sinks one millimeter on one side... Back to school:

tan(v) = 1 / 800
v = atan(0.00125) = 0.0716 degrees = 4.3 arc minutes

This should give an indication as to the "power of the error". A very small error can throw things off considerably.

What I want to convey is that a model well built can be a model lost if the stability under the mount is not up to par. Still want to use three cement tiles (1'x1') under your tripod legs on the lawn? I thought not

Both ASA and 10Micron mounts do track in both Dec and Ra. This, combined with a modeled "sky", will reduce tracking errors to pure field rotation. Perhaps someone with experience in field rotation calculations can chime in and give us a rough figure on how much a field rotates with a polar error of, say, one minute (which is easily obtainable with 10u and most likely with an ASA as well) during a 10-minute exposure. It is not going to be much (I think) so it is apparently fairly useless to hunt down the last few arc-seconds of polar error (even though it is fun to do so, especially on a fixed pier).

Another two cents, eh?

I really enjoy the simplicity of the 10Micron products!

/per


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Tonk
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Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Per Frejvall]
      #6113152 - 10/02/13 01:23 PM

OK I have 10 years hard experience using Losmandy/Gemini - the GM1000HPS is virtually identical in set up, modeling and PA align procedures, so it was very easy for me to get used to this mount on my first night. Maybe we should factor that in .. but all the same its is a very easy setup for the experienced or novice user.

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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Per Frejvall]
      #6113197 - 10/02/13 01:48 PM

I guess there is a need to clarify something even this is getting quite odd.

First of all what I was telling about the ASA polar alignment routine, was a very quick way of having a good basic alignment (in couple of minutes). At the same time Tonk was using far more stars and iteration and wondering why his results are so much better. In another thread he said it took 40 minutes but can be done in less time if practised. So not a very fair comparison.

With all due respect Per what you are telling about 10Micron, ASA mounts can do easily and if you ask me quicker also. If you're using such a rough estimate of north pole there is no way to plate solve right away. However with the help of laser beam (ASA mounts have), you'll get the alignment so close to north pole that plate solve can be used immediately. All you have to do is let the Sequence perform an automated 3 star alignment. And if that's not good enough, you can do another round right away with e.g 10 stars. If done properly, that will put you to under 1 arcmins territory.

It's also a lot easier just to put the star back in the middle of the cross-hair than trying rotate AZ/Alt nobs according to hand control instructions ...at least for me.

I'm sure both 10Micron and ASA mounts are able to do very accurate polar alignments but I think when comparing things a bit more more unbiased attitude would help
Hope I can finally stop commenting this thread


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tomcody
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Reged: 07/06/08

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Re: ASA DDM60 Pro vs. GM1000HPS new [Re: GIR]
      #6113300 - 10/02/13 02:44 PM

Tonk & GIR,
I think you guys are both basically saying the same thing, that both mounts have good software, are accurate, and are good mounts to own. Both mounts require the same thing : learning the software that runs them! which as we all know is a little different for each mount made, although they all do about the same things.
After reading this very informative thread, for which I thank each of you for your great comments, I think it comes down for a new purchaser to decide which companies' mount is best for them and their needs. I have made my personal preferences know, but I would be happy to own either mount as judging from your comments (except for mechanical design) there are more similarities than differences.
Regards
Rex
P.S. Tonk, I have a new Losmandy GM-8 being shipped soon ( as I am purely visual now, this is all I need ) and am looking forward to equipping it with the new Losmandy DSC's which should be out soon.


Edited by tomcody (10/02/13 02:49 PM)


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Tonk
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Reged: 08/19/04

Loc: Leeds, UK, 54N
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: tomcody]
      #6113330 - 10/02/13 03:04 PM

Yeah - done too.

BTW I'm now down to 15 minutes to get target PA after 2 months of practice . Actually I wasn't wondering why my PA was better I was merely recounting the prodedure written in the manual and how I executed it. I'm sorry I didn't spot you were not using a multistar model - my bad.


Anyway the OP and anyone else interested in these mounts should have plenty to go on now. Right now I'm far more concerned that this dark of teh moon has produced no clears nights at all and the planned present for my wife is getting delayed a month


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CounterWeight
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Reged: 10/05/08

Loc: Palo alto, CA.
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: tomcody]
      #6113331 - 10/02/13 03:04 PM

Here is one question I wanted to ask those using the 10um and ASA.

I have high (we are talking ~35* / ~45* obstacles on E and W sides of my permanent pier. To North maybe 20* but have clear view of Polaris (all these I mean elevation) and South I have lowest - to neighbor rooftop across street.

So my sky is a rectangle N<->S. Will i still be able to benefit from the point / sky modeling if I am permanent mounted?

Thanks for your thoughts on this - this a great thread !


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Tonk
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Reged: 08/19/04

Loc: Leeds, UK, 54N
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: CounterWeight]
      #6113340 - 10/02/13 03:11 PM

Quote:

P.S. Tonk, I have a new Losmandy GM-8 being shipped soon ( as I am purely visual now, this is all I need ) and am looking forward to equipping it with the new Losmandy DSC's which should be out soon.




Neat - you will enjoy it! BTW I still own the old DSC's - kept more for sentimental reasons though they can be used to act a (lower resoution) backup input for the Gemini for when you take clutches off to hand move the scope. My poor GM-8 hasn't been used for 2 months (you know why!)


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Tonk
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Reged: 08/19/04

Loc: Leeds, UK, 54N
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Tonk]
      #6113357 - 10/02/13 03:19 PM

Quote:

I have high (we are talking ~35* / ~45* obstacles on E and W sides of my permanent pier. To North maybe 20* but have clear view of Polaris (all these I mean elevation) and South I have lowest - to neighbor rooftop across street.

So my sky is a rectangle N<->S. Will i still be able to benefit from the point / sky modeling if I am permanent mounted?




Yeah this should be OK -

I too have east cut off about 35-40 degrees and west is a bit better at 25. Like you the open parts are north and south (I'm set up in a holiday trailer park in a narrow wooded valley - but its dark!). In some respects this stops you imaging in the rubbish low altitude clagg with all the refraction issues when tracking!


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GIR
super member


Reged: 01/02/10

Loc: Finland
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: CounterWeight]
      #6113359 - 10/02/13 03:22 PM

Quote:

Here is one question I wanted to ask those using the 10um and ASA.

I have high (we are talking ~35* / ~45* obstacles on E and W sides of my permanent pier. To North maybe 20* but have clear view of Polaris (all these I mean elevation) and South I have lowest - to neighbor rooftop across street.

So my sky is a rectangle N<->S. Will i still be able to benefit from the point / sky modeling if I am permanent mounted?

Thanks for your thoughts on this - this a great thread !




Hi Jim

As long as you have a view on targets you'd like to shoot, it's no problem. You can modify the pointing model horizon any way you want. So when making models the obstacles in the horizon are automatically taken into account.

Something like this...

Pointing model


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frolinmod
Carpal Tunnel


Reged: 08/06/10

Loc: Southern California
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: GIR]
      #6113388 - 10/02/13 03:34 PM

Quote:

You'll probably have more flexure on your setup than the polar alignment figures you've indicated.



Now there's a realist no doubt with some experience under his belt.


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Per Frejvall
sage


Reged: 09/28/12

Loc: Saltsjöbaden, Sweden
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: frolinmod]
      #6114512 - 10/03/13 02:49 AM

I second that he obstructions pose no problems with either mount. In fact, my balcony setup (where all my work is done) has a terrain mask that looks like in my screen dump of the model maker further up this thread. The grren part is the mask.

/per


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CounterWeight
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Reged: 10/05/08

Loc: Palo alto, CA.
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Per Frejvall]
      #6115042 - 10/03/13 12:17 PM

Very good to hear Thank you!

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Hilmi
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Reged: 03/07/10

Loc: Muscat, Sultanate of Oman
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: CounterWeight]
      #6124078 - 10/08/13 03:15 AM

Thank you all for all the wonderful feedback. I have taken a lot of time to ponder things and I have come to respect both mounts.

I have been swayed more towards the GM1000HPS for the following reasons:
-Complete package available including carry case, this saves a major amount of headache when making the purchase as you don't have to hunt down mount adapters, tripods and so on.

-I've had laptops fail on me before, the ability to run without one is like having a backup. If you get only 6 to 8 nights a year in truly dark sites, you don't want to get there only to find that you can't operate your mount because your laptop is dead.

The bad news is that it's going to take longer than I expected because it turns out that nursery fees these days are higher than what I would have paid to go to college to earn a degree back in 1996.


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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: ASA DDM60 Pro vs. GM1000HPS new [Re: Hilmi]
      #6124080 - 10/08/13 03:23 AM

Hilmi,

last weekend I nearly got worked over because my laptop ran out of battery. Even though I have a mount that doesn't need a laptop, the camera requires one!

so use a DSLR, you counter.. using a DSLR is an option only if you can go unguided (remember, no laptop..) which means you need a very good polar alignment. I don't know about the rest of you but I am totally dependent on the laptop for polar alignment (no view of Polaris where I am).


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