GM1000HPS - Unboxing

[perfrej]

One more thing... The prospect a model on a second night after a tripod move is slim. If you manage to get the mount perectly level again you can align the whole model on a single star. If, however, one tripod leg is 1mm more into the ground than the last session you will be off by seceral arcseconds...

Better is to just run a 25-point model from scratch every time you set up. It is automatic and takes 10-15 minutes of your time. Time that you wouldn't use for imaging anyway if you run it in twilight.

[perfrej]

Gah! I was too quick... Daytime use... Need to think about that.

/p

[pbsastro]

I have been thinking, regarding keeping alignment between sessions (where the mount is stored away and setup again), the main difference between HPS mount and regular mount (like AP) is that the HPS can be moved while off, while the AP must keep the clutches locked all the time, so that it still knows where it is pointing relative to itself. The HPS always know where it is pointing relative to itself. Let’s call it Relative RA,DEC

A mount alignment has two bi-dimensional variables (besides time and location): ALT,AZ and Relative RA,DEC. If we have both right we get the correct pointing. But if we don’t have one but have an object to point to we can get the other.

So, if we lose ALT,AZ by storing and setup, but we keep Relative RA,DEC, we can get ALT,AZ back if we point to an object (sun or other star) and center it using alt-az adjustment.

Am I thinking correctly?

Pedro

[pbsastro]

What i said last post would give me absolute correct alignment, as precise as I can do with alt-az adjusters. All I need is a sky object to point to, but we almost always have one, day or night. So precision is only limited by mechanical finess of alt-az ajusters. Right?

Pedro

[perfrej]

Correct but for the fact that a not perfectly leveled tripod will shift the adjustment axis and thus introduce error in the model shift.

[pbsastro]

My idea is that we don’t even need to level the tripod or any mount axis at all. No sprit levels.

All we need is that last time mount was used (and stored) it was correctly polar aligned and computer aligned.

Imagine a mount perfectly polar aligned and perfect computer aligned, working at night time. Now imagine move that mount (with scope mounted) from one tripod to another nearby, with different leveling and orientation.

After setting the mount in second tripod, all you need is to center one object in the eyepiece using the mount alt-az adjusters. The mount computer will never know it is working in a different tripod, for it is all the same, and for the user also, because the mount has now the exact same polar alignment as it had in the other tripod. And the computer alignment is the same as well, naturally, as we never told the mount anything.

And that would work also for night time. To polar align correctly we only need to point at one star or planet, and center it with alt-az adjusters.

If this is the case, the big advantage of the HPS is that we can unlock and move axis when storing which is advisable

I fear I may be missing something. It is seeming too simple and too easy...

Pedro

[perfrej]

Correct but for the fact that a not perfectly leveled tripod will shift the adjustment axis and thus introduce error in the model shift.

[pbsastro]

Ah, right! My mistake was that the mount setup has not only two vars that define where the scope is pointing, but also a rotational one around that axis (the scope pointing axis). It was really too easy...

Thanks for the help, Per!

[perfrej]

My previous answer was in response ¤129. A for your last post, you need to reconsider.

Suppose you level the tripod, align the mount and build a model. Then you take the mount down and put it back up the next day or night. This time the tripod is tilted 5° to the NE. You do your re-alignment procedure and all is fine for that point in the sky. All other points, however, are offset by the angle so the pointing model is nil and void. So, there are actually three parameters involved:

1. The relative angular positios of the axis

2. The Alt/Az angles of the mount itself

3. The plane that the Alt/Az angles are relative to.

For your re-alignment procedure to work you need two of them set and then you can obtain the third from a star.

Next comes the problem of setting the two fixed ones... As I said, the sky object is easy. The plane of the mount is not. In fact, when we are talking about precision mounts like the 10Micon ones we have to consider the errors very carefully. A scope that builds a great model with a Losmandy dovetail bar will most likely build a cruddy one with a Vixen bar. The reason is random flexure.

Let's point the scope, with a perfectly aligned mount, at a star at 15° elevation straight South. Build a pointing model and experience dead center stars on every slew and 20 minute unguided subs at a meter focal length! Great! But what happens when one of the legs of the tripod sinks 2mm into the ground? Let's say it is 50cm from the mount centerpoint.

So, we have a new tilt of your mount, amounting to atan(2/500), which comes out to 0.229° or 13.75 arc-minutes. Thus, a single point re-align of the mount axis will fail since only one of the three is set. If you then twist your object into the center of the CCD you have adjusted two axis that are not on the same plane as they were the day before. It cannot work.

When you want to track objects reliably (unguided) you have to have a model that represents the sky accurately from the vantage point of the two axis on which the mount can move, Ra and Dec. That model depends not only on the polar alignment; in fact, it will compensate for the polar mis-alignment. Now, if you have an NEQ6 and want to get good polar lignment you do not have to worry about the plane that the mount is on. That mount will not, however, track unguided for an hour (which my GM2000HPS does) with round stars.

The one thing you will love about the GM-series is the encoder. It NEVER looses track of the angular positions of the axis.

/per

[perfrej]

Haha! You beat me to it

[pbsastro]

Haha! You beat me to it

Yes, by one minute, but only because you were patient enough to write a very detailed explanation. Thanks!

But your previous comment was important to confirm my error and help me figure it out.

So summarizing, If I get perfect tripod leveling, ALT should be dead on, no adjustment needed. Then, I can resume previous operation by using only AZ adjuster to center object.

Now to get perfect tripod leveling, I need two things:

1. A precision spirit level permanently fixed to the tripod. There are some vials that I can attach to the tripod.

2. A tripod with precision leveling adjustment. Rob Miller tripods are one example that provide this.

I think I got it right now. Thanks again.

Pedro

[perfrej]

No worries

I still think you should consider the numbers in my calculations, though... It is a challange, for sure!

/per

[pbsastro]

Back to the 1000HPS itself, I have a doubt about the weight because some places state 18 Kg, but the pdf on 10micron website states:

"The main body of the mount, without the counterweight shaft, has a weight of only 19.5 kg – 43 lbs."

I guess the diference is because the head comes with an adapter plate that includes AZ adjustment pivot. And can come with a specific tripod/pier adapter plate.

Per, the pictures you show on page 1 of this thread show all three sections in the base. The picture you show in page 3 shows only one section. i think you put it in a scale when you took that page 3 photo.

My doubt: the 18 Kg include the pivot plate (2 sections) and 19.5 Kg include the tripod adapter plate (3 sections),

or the 18 Kg does not include pivot plate (1 section), and 19.5 Kg include pivot plate but not tripod adapter plate (2 sections)?

Also you mentioned you drilled three holes in the tripod to attach the tripod adapter plate. If you had to drill the holes, why not drill the holes for the pivot plate instead, you would have one plate less, right?

Thanks,

Pedro

[pbsastro]

No worries

I still think you should consider the numbers in my calculations, though... It is a challange, for sure!

/per

Per, Are you talking about the case where the tripod leg sinks 2mm?

Even if we have a perfect 25 model, it will become invalid if the tripod leg sinks 2mm. In fact, with the tripod leveling, I can get the model back to validity, without making it all over again.

I think (not 100% sure) that a precision leveling tripod can get us a precision to 0.2mm, so about 1.4 arc-minutes. I am not sure if that is enough, but it should be because I don't think we can get much better stability from a tripod, either from very slight leg sinking or by leg bending when scopes moves (weight move).

What do you think?

Pedro

[perfrej]

The base plate "adapter" weighs close to nothing. It is a thin aluminium plate. I probably weighed it without the plate, but a rough estimate tells me that it weighs less than 300g. Putting the mount directly on the tripod base plate (which is sized for the GM2000) would leave the mount with no sliding support, and leave the stability to the three M6 friction knobs. The holes for the friction knobs (in the mount) obviously are not holes, but rather arcs. Not an option - you need the plate.

10Micron's tripod is the most stable one I have come across. In fact, I think it is better than my super stable pier I cannot make if budge and the legs are extremely stable. As for angular precision when leveling, I have just found out that a precision machinist sprit level can be had with a 2mm/m precision (~7'). It will, however, send you back €350.

I am quite sure that you will do well with that setup, allthough I do not think that your model will be good enough for unguided operation. That, however, is easily solved by running a model before any night-time adventures. 15 minutes of your time just before astronimical darkness.

/per

[perfrej]

OK, so I have released a new version of the ASCOM driver and a new version of the Model Maker. I decided to look at satellite tracking now that astronomical darkness at my latitude is soon gone altogether. I downloaded a TLE file with all satellites in orbit and tested. Fantastic! You select the satellite in the hand controller and select the passes it will make. Press enter an on it goes, tracking with visible motion and meridian flipping on demand.

Never tried that before! Maybe I should shoot the ISS... Only problem I just tracked it for a full pass and it goes straight through my house wall

/per

[pbsastro]

The base plate "adapter" weighs close to nothing. It is a thin aluminium plate. I probably weighed it without the plate, but a rough estimate tells me that it weighs less than 300g. Putting the mount directly on the tripod base plate (which is sized for the GM2000) would leave the mount with no sliding support, and leave the stability to the three M6 friction knobs. The holes for the friction knobs (in the mount) obviously are not holes, but rather arcs. Not an option - you need the plate.

10Micron's tripod is the most stable one I have come across. In fact, I think it is better than my super stable pier I cannot make if budge and the legs are extremely stable. As for angular precision when leveling, I have just found out that a precision machinist sprit level can be had with a 2mm/m precision (~7'). It will, however, send you back €350.

I am quite sure that you will do well with that setup, allthough I do not think that your model will be good enough for unguided operation. That, however, is easily solved by running a model before any night-time adventures. 15 minutes of your time just before astronimical darkness.

/per

Thanks for your reply, Per, and sorry for the late reply, I was out for a few days.

Regarding the adapter plate, I am still confused. In your setup pic we see 3 sections. The first section from top is part of the mount and has the arc-shaped holes. The second one has the az-adjust pivot. The third one is just a tripod adapter right? My question was regarding this third (bottom most) section, couldn't you screw the second plate directly to your tripod, since you drilled the holes yourself. i thought the third plate was only for people who cannot or do not want to drill their tripod plates.

So you weighted 18Kg with probably the first plate only, and the second one is about 0.3Kg.

Do you have a clue where the 19.5Kg (without counterweight bar) mentioned in 10micron specs comes from? Maybe with all three plates?

Sorry about being picky, but weight is very important to me as I have to setup the mount every time I use it. I wanted to understand the exact weight before making the order.

Regarding the spirit level, You mention 7 arc-min precision, but I found typical precision levels have 10 arc-sec precision (0.05mm/m), and can go to 4 arc-sec.

I have one bought about 12 years ago, which it seems to me it is 10 arc-sec, it says "0.05 x mm 1000".

I don't remember the cost, but was for sure way less than €350.

What precision do you think would be required for 20 min unguided exposure at 1 meter focal length?

Thanks for all the help,

Pedro

[Velvet]

Thanks for your reply, Per, and sorry for the late reply, I was out for a few days.

Regarding the adapter plate, I am still confused. In your setup pic we see 3 sections. The first section from top is part of the mount and has the arc-shaped holes. The second one has the az-adjust pivot. The third one is just a tripod adapter right? My question was regarding this third (bottom most) section, couldn't you screw the second plate directly to your tripod, since you drilled the holes yourself. i thought the third plate was only for people who cannot or do not want to drill their tripod plates.

So you weighted 18Kg with probably the first plate only, and the second one is about 0.3Kg.

Do you have a clue where the 19.5Kg (without counterweight bar) mentioned in 10micron specs comes from? Maybe with all three plates?

Sorry about being picky, but weight is very important to me as I have to setup the mount every time I use it. I wanted to understand the exact weight before making the order.

Regarding the spirit level, You mention 7 arc-min precision, but I found typical precision levels have 10 arc-sec precision (0.05mm/m), and can go to 4 arc-sec.

I have one bought about 12 years ago, which it seems to me it is 10 arc-sec, it says "0.05 x mm 1000".

I don't remember the cost, but was for sure way less than €350.

What precision do you think would be required for 20 min unguided exposure at 1 meter focal length?

Thanks for all the help,

Pedro

Hi there

I have the 10 micron tripod and the GM1000. I am female and I weigh about 65kgs in total. All i can say is that i lift the GM mount onto the tripod by myself. I am not a weight lifter by any means and it is heavy, but i manage

it quite well. My rig is used as a portable one as I dont have a home obsy. I transport it to dark sites and use it as is at home on the tripod. Hope this helps you.

Velvet

[pbsastro]

Hi there

I have the 10 micron tripod and the GM1000. I am female and I weigh about 65kgs in total. All i can say is that i lift the GM mount onto the tripod by myself. I am not a weight lifter by any means and it is heavy, but i manage

it quite well. My rig is used as a portable one as I dont have a home obsy. I transport it to dark sites and use it as is at home on the tripod. Hope this helps you.

Velvet

Hi Velvet,

Good to hear from you. I am near to join your club (1000 HPS).

I am able to setup alone my 33Kg fork mounted LX200. But it is not something I like to do often, and is not good for my skeleton.

I was hoping to have the mount (without counterweights) setup in the tripod for everyday travel to the balcony.19.5Kg from the mount and 10Kg from the tripod (special light one) it gets about 30Kg, which is near the unconfort zone.

BTW I read there is a new smaller 10Micron tripod designed for the 1000HPS, but I could not find anything about it, photos, weight or price. Anyone has any info on it? Per reports is regular Centaurus tripod is rock solid, but it should be at 25Kg. Even the carbon fiber version is too heavy for me at 16Kg, I don't want to go behind the 10Kg for the tripod, there are some rock solid solutions as the Berlebach Sky.

Thanks again for the input,

Pedro

[pbsastro]

Besides this one, do you know other forum about 10micron mounts?

For field use, what batteries and chargers do you use/recommend? deep-cycle right?

Pedro

[DanH]

As I said elsewhere, I build my own power station.

I use 2x22AH Panasonic gel batteries serially connected, and a 24->12VDC converter as 12VDC is necessary for some accessories (like the Moonlite DRO)., Both outputs are protected by fuse and independantly switchables. I have put a digital voltmeter connected to the 24V side to know how my batteries are doing.

Everything is placed in a water resistant box (of marine type) and weights 15.5KG

[Velvet]

Besides this one, do you know other forum about 10micron mounts?

For field use, what batteries and chargers do you use/recommend? deep-cycle right?

Pedro

I use 110 amphour 12v leisure deep discharge battery and use the baader specific converter for the GM1000 mount 12v to 24v. It is now available. You can use a 12v to 220v ac inverter, that works quite well too. Saves me carrying 2 x 12v batteries

Velvet

[pbsastro]

Thanks DanH and Velvet. I thought people were using real 24v batteries. But in fact internally they are made of two 12v batteries...

I used to use three 6v batteries in series for my LX200. So I can now use 2x12v or a 12 to 24v converter.

The 2x12v solution will offer more time: double amphour and avoids 12v to 24v conversion loss (there is always some).

If we do not want the double weight, we can probably use two smaller batteries in series.

I will check if I can find locally the same or similar batteries you use.

Thanks,

Pedro

[perfrej]

I would definitely recommend using 12V batteries ony and feeding the mount from a good 12-to-24 converter. Most of the stuff is 12V, only the mount needs 24. Also, on amphours... One 12V 20Ah battery is 20Ah. Two 12V 20Ah batteries in series is 24V but still 20Ah

As for bettery types and deep discharge, please remember that a lead-acid batery is discharged when the voltage is at 11.90V. So, anything below 11.9 volts and our battery is being destroyed. Gel batteries have better resistance to deep discharge damage, AGM (Advanced Glass Mat) ones are essentially immune to deep discharge. Besides, AGM can take 50% of the rated capacity in charge current, while liquid and gel only take about 25%. This is important if you, for instance, have a 20A charger connected to a 20Ah battery. The liquid battery will be able to use about 5A of your 20A as food while the AGM battery will be able to use 10A. End of battery lesson

My remote observatory in progress will use a Sonnenschein 40Ah gel with a continously running 240V charger that supplies 8A. The battery will act as stabilizer and feed the system for a few hours in case of power outage.

/per

[pbsastro]

Thanks Per, I was not aware of AGM type. I will definitively make sure I will buy AGM type, for both discharge immunity and half charge time.

Regarding the amphour, two 12V 20Ah batteries in series is 24V-20Ah, but one 12V 20Ah with a 12V-24V converter is 24V-10Ah. The converter is only a converter it cannot feed energy and energy is VxAh. In fact it will be less than 10Ah because the converter as any device cannot be perfect and will have loss.

Thanks,

Pedro