The box is huge (4.5' x 1.5' x 1.5') that is comes in and the unit is double boxed with plenty of styro foam packing. I have done a visual check and everything is sound. The scope comes with two dove tails and rings, 1x 2" extension, 2x 1" extension, battery holder and cable for the cooling fans, varies bolts to hold the dove tails and rings together and a 3" focusor.
The focusor is huge and will most likely easily handle the QSI. Perhaps even much large format cameras too. There is no movement when the focusor is locked off, even when applying a fair bit of force. Very solid and looks dependable (tests will prove one way or the other though). It will eventually get replaced but only for automatic focusing reasons. the whole focusor runs very smoothly and certainly is a massive improvement from the previous version.
I took a look out over the valley with it. The scope is slightly out of collimation and will require some careful work to get it right. Even slightly out of collimation I could see leaves on trees at 4 km away. With collimation it should come up quite nicely. Obejects viewed snapped into focus and appeared quite sharp.
I am not overly keen on the metal tube though. It has a seam and this is likely to move a bit. I will watch to ensure that focus and collimation do not shift with changing temperatures in the test. I suspect though that if ever they make carbon fibre tubes this is one thing I will replace or I will look at making it a truss tube myself with carbon fibre tubes.
This scope could not be carried on a G11. That mount is too small for this scope. Something a little beefier is required. The tube is quite large and would present considerable lever action in wind. Certainly the new EQ8 should handle it, so too NJP, EM400, Titan, PME, PMX, Mountain Instruments, ASA and any of the other quality mounts.
Sorry Paul i was going on the rated capacity of the G11 which is 60lbs(25kgs) and the GSO spec's shows it weighing in at around 22kgs, so a bit off, now if it had a CF tube might be a different matter
Sorry Paul i was going on the rated capacity of the G11 which is 60lbs(25kgs) and the GSO spec's shows it weighing in at around 22kgs, so a bit off, now if it had a CF tube might be a different matter
Maybe if it had a carbon tube it might be able to take the weight, but it just means that it will be at the border line. Any wind and the idea is shot.
Its probably going to need 2 hours or more to stabilise temperature wise.
I find my CDK17 takes about 2 hours to get the mirror temp within .5C of ambient.
If the temp difference is more than about .5C you will find focus is softer.
If it is 3C different it will be quite soft. So keep that in mind. With these types of scopes it is best to turn the fans on early to get the temps equalised as early as possible.
Delivery of the scope this AM.
This scope could not be carried on a G11. That mount is too small for this scope.
Just some images of the packing included
Paul
Interested in this comment. I thought that the GII could carry the scope especially if in an observatory and shielded from wind etc.
I realize it's better to have a mount with greater carrying capacity but at 22 kg I thought it was within the capacity of the GII particularly some of the loads I have seen the less capable EQ6 carrying quite successfully.
Allan.
Thanks Greg for the tip. I would hazzard a guess and suggest that this particular issue is more extreme during the the summer months. Would that be correct? Day time temps at my observatory during winter are pretty stable as we are close to the ocean. Night time the temperature usually drops around 5 degrees at most so cooling should happen pretty quickly but I reckon cooling for an hour would be best. I gather you have dew control in place?
Allan, I don't know. This thing is pretty big. It is 860mm long and 370 mm wide. That makes for a pretty large sail in the wind. Even a slight breeze will create havoc for guiding with the G11. Added to that; 22kg combined with finder scope, camera and cables and you are nearly at the 25kg payload of the G11. It might be ok in an observatory and mounted on a G11 but it would be a punt to try it. Mind you as you say there are plenty of examples of large scopes being on top of lesser mounts.
For me it seems the temp difference is a little more in winter but not much. It often is about 3+C difference so far in the cold months and about 2-3C in summer for me.
As far as mounts go. If anyone thinks a G11 will handle a huge wind sail like that they are dreaming. No way. Anything over 5kmh will wreck the guiding. I am talking from experience with my 12.5 inch RCOS and Tak NJP. Under calm conditions it did OK even though it was really too heavy for the NJP but anything over 5kmh was no good. Sometimes I got away with putting a heavy tall tray on the roof in front of the tube to create a wind break. But that was when the wind was only about 10kmh and even then it did not work well.
It'd be OK if you had high observatory walls and the mount sitting a bit low. But these long tubes stick out past the average observatory wall and into the wind stream by about 300mm depending on your situation.
Funnily enough my TEC180 is not particularly wind affected on the same mount. But then again the tube is only 200mm in diameter versus about 400mm.
So not the best type of scope for a windy area. A truss is quite an advantage in that situation or situate your observatory in such a way that common winds are blocked somehow.
Basically a large scope on a lesser mount will mean unreliable results. Sometimes it will be OK and other times not. Balance and polar alignment would have to be perfect. PEC would be a big plus as well. But wind shielding would be a deal breaker if its missing.
Perhaps a curved piece of metal that you can attach above your roof line (assuming a flat roof) that creates a wind tunnel may be workable.
Say something about 500mm tall and 500mm in a U shaped perhaps a cone style leaning slightly backwards.
I'd be interested to know how much the aluminium tube affects focus with changing temperatures. I suspect it will but perhaps not that badly.
Greg.
Quote:
Originally Posted by Paul Haese
Thanks Greg for the tip. I would hazzard a guess and suggest that this particular issue is more extreme during the the summer months. Would that be correct? Day time temps at my observatory during winter are pretty stable as we are close to the ocean. Night time the temperature usually drops around 5 degrees at most so cooling should happen pretty quickly but I reckon cooling for an hour would be best. I gather you have dew control in place?
Allan, I don't know. This thing is pretty big. It is 860mm long and 370 mm wide. That makes for a pretty large sail in the wind. Even a slight breeze will create havoc for guiding with the G11. Added to that; 22kg combined with finder scope, camera and cables and you are nearly at the 25kg payload of the G11. It might be ok in an observatory and mounted on a G11 but it would be a punt to try it. Mind you as you say there are plenty of examples of large scopes being on top of lesser mounts.
Looks like the consensus is that unless I upgrade the mount then I will have to settle for the 10" GSO RC. And I wonder if this will be as much of a 'step up' from my 10 " SCT to bother doing. I see that several users are doing a 12" SCT on a Losmandy mount without problems!
Have to go back to square one and rethink this.
Looks like the consensus is that unless I upgrade the mount then I will have to settle for the 10" GSO RC. And I wonder if this will be as much of a 'step up' from my 10 " SCT to bother doing. I see that several users are doing a 12" SCT on a Losmandy mount without problems!
Have to go back to square one and rethink this.
Might be ok if/when the carbon fibre tube model comes out though Allan?
I brought up the G11 question after reading BINTEL's description of the product:
OTA weight : 21kg (without rings or dovetails)
We recommend a German equatorial mount with a 60 pound (minimum) to 100 pound or greater payload capacity. Mounts include the Losmandy G11 (60 pound capacity) and Losmandy HGM Titan (100 pound capacity). Other suitable mounts are also available.
I brought up the G11 question after reading BINTEL's description of the product:
OTA weight : 21kg (without rings or dovetails)
We recommend a German equatorial mount with a 60 pound (minimum) to 100 pound or greater payload capacity. Mounts include the Losmandy G11 (60 pound capacity) and Losmandy HGM Titan (100 pound capacity). Other suitable mounts are also available.
Unfortunately that was the information that I was going on as well, Logan.
Maybe the CF tube is what I want as you say.
Allan, you can give it a try I suppose but be mindful of the wind factor. This is way longer than an SCT of similar size. It is actually a bit longer than the C14. That makes for a longer lever arm and hence the concern. It might be a good excuse to upgrade the mount.
Greg, I am curious about the aluminum tube expansion and contraction. Mind you some of the other firms are producing tubes in aluminum. deep sky instruments being one I can find, but only for 10" scopes. Time will tell though.
If my calcs are correct ? a 20C drop in temp over a 750mm aluminium section will change its length by less than half a micron ! (0.0003 mm)
If the contraction is uniform, it is barely going to show up and is probably well within the noise.
If the contraction is not uniform due to points being constrained by brackets that have different thermal expansion rates (eg different lengths and geometry, dovetails, mounting fixtures or different materials) or the circular diameter of the tube affecting things then bending might occur and that may or may not affect things more so by way of collimation and tilt.
Does the primary/secondary distance change the focal length on these OTAs?
I would expect that anyone is who imaging across that temperature change will have probably changed filters and/or performed a refocus anyway !
Not that most focussers are reliably able to reposition within the 1/10 micron range anyway - there is more flex and backlash and minimum focus increments in the system to worry about that this.
So I doubt that simple thermal movement on its own is likely to be an issue.
Congrats Paul, looks like the goods for you.
Why not get started on a truss style tube, using C/F poles. It would be a good winter projects, and not impossible.
Either way I am tipping you will love this new scope.
Gary
No you've made an error there somewhere. Coefficient of expansion for 2mm aluminium works out to about .35mm for 20C. You must've missed a few decimal places there. But your point still stands.
On the CDK17 the digital readout goes to 3 decimal places for accuracy.
Usually a move of .020 (I think its in inches though = .025mm for every .001 inch) will cause focus to be noticeably improved or worsened at 2939mm focal length. So .375mm tube increase over 20C = around 100 units per 1C on my CDK17 focuser. That definitely shifts the focus quite a bit (100 units on the focuser that is).
So .375mm (as small as it is) is significant at long focal length and will definitely be noticeably out of focus for every 1C shift.
Don't forget these expansions are magnified by whatever focal length you are using and in the case of the 12 inch its pretty long.
Now we see why the top manufacturers go for the CF tube or the temp compensating cell (Tak BRC250 which has rods that match the expansion of the alum tube when they used Al. Now they are shifting back to CF).
Although there must be people on this site using an Al tubed 10inch RC that will know how much it shifts with temperatures in case this is overstated.
Greg.
Quote:
Originally Posted by rally
If my calcs are correct ? a 20C drop in temp over a 750mm aluminium section will change its length by less than half a micron ! (0.0003 mm)
If the contraction is uniform, it is barely going to show up and is probably well within the noise.
If the contraction is not uniform due to points being constrained by brackets that have different thermal expansion rates (eg different lengths and geometry, dovetails, mounting fixtures or different materials) or the circular diameter of the tube affecting things then bending might occur and that may or may not affect things more so by way of collimation and tilt.
Does the primary/secondary distance change the focal length on these OTAs?
I would expect that anyone is who imaging across that temperature change will have probably changed filters and/or performed a refocus anyway !
Not that most focussers are reliably able to reposition within the 1/10 micron range anyway - there is more flex and backlash and minimum focus increments in the system to worry about that this.
So I doubt that simple thermal movement on its own is likely to be an issue.
One thing to keep in mind folks between the Al and the CF tube is only maybe a few grams in weight. Expansion is no real difference because the primary cell and secondary spider are in fact connected by 2 big Al slabs as in the losmandy plates or at least they were in the 10" model.
I doubt there would be 1 Kg of difference between the CF and epoxy model and the Alumin tubed model.
The 10" was as big as you would want to go on a G11 particularly if you are going to use a guide scope of any size.
Good luck with it Paul. Look forward to seeing your results.
Thanks Doug. The 12" scope now has just two rings and the dove tails are bolted to them. Unfortunately there is not connection with the scope. So the tube is the only support to the mirrors at each end.
One thing to keep in mind folks between the Al and the CF tube is only maybe a few grams in weight. Expansion is no real difference because the primary cell and secondary spider are in fact connected by 2 big Al slabs as in the losmandy plates or at least they were in the 10" model.
I doubt there would be 1 Kg of difference between the CF and epoxy model and the Alumin tubed model.
Hmm, good point Doug. So the chief benefit is reduced flexure and focus change with temp presumeably. I wouldn't have expected that. Shame, but makes sense if you have heavy dovetails and mirror mountings I guess.
