Thanks Paul that looks great so when the scope is mounted the focuser pints down in home position ?
cheers Pete
Yep, that alleviates trying to balance the scope through different parts of the sky.
Quote:
Originally Posted by DaveNZ
Thanks, I just popped out to the observatory and had a look.
I have some Bobs nobs and springs but I think I'll just use the GSO set in the mean time.
I'm rather impressed with the conical mirror. I wasn't expecting that. This means a simplified cell design. You would think GSO would advertise this as a point of difference.
Yeah Jim is not great at getting the word out. Luckily he has the likes of me on his side.
I have not bothered with Bob's knobs yet on any GSO scope. I have them on my C14 but not on the GSO gear. The secondary adjustment screws look a little flimsy to me but I'll see how they go before I go changing things.
thanks again Paul I will do that with mine so just undo the 2 bolts on either side of the truss bracket that are screwed into the fist secondary plate and rotate then screw it back together again
cheers Pete
thanks again Paul I will do that with mine so just undo the 2 bolts on either side of the truss bracket that are screwed into the fist secondary plate and rotate then screw it back together again
cheers Pete
Yeah all 8 bolts on all the trusses first then rotate. I figure that is what you meant.
hi Paul
well I did as you have done with the front secondary cell support and wow what a difference it made with balancing works like a charm while I had the front cell off I changed the aluminium sleeves I installed for bracing for carbon fibre
thanks again Paul for mentioning that about swinging the cell around
cheers Pete
I installed the Moonlite focusor with an Altair adapter and have the motor hooked up to a Robofocus control unit. The motor works well with the Robofocus software and manual controls.
Both cameras feed into a MHP which will directly connect to the FitPC. MHP and FitPC will ride on the same D bar. I need to tidy up the wiring a bit more yet.
I have also installed a dew heater on the secondary. I tested that tonight too and that works well. It gets quite warm on full power with the MHP contols, so I till try it on 3/4 first and that should be enough to eliminate dew. I will probably do something about the red insulation tape, I just need to work on eliminating the sideways movement of the cabling.
After some collimation I took an image of a water tower 5 km away from our home across the valley whilst the scope was sitting on a bench. The resolution is pretty reasonable I think, of course star testing and imaging will confirm my thoughts on the matter. See photo.
Hello Paul,
I think it's a remarkable image at 5km. The handrail around the top of the tower is 50mm in diameter (2 arc seconds) which gives a sense of scale. As a test of resolution the guy wires, which are many times smaller probably 6 or 8mm in diameter(0.25 - 0.33 arc seconds) are well resolved and give or take the accuracy of the 5km, are right up there with (slightly better than) the manufacturer specified resolution and probably right at the diffraction limit.
The scope seems to be holding focus quite well with small temperature shifts.
I have done a few 5min test exposures and all is well.
I havent tested how well the scope holds collimation with the weight of my QSI683 camera when I do a meridian flip. It is fine with just with a 2" laser collimator.
Commissioning commenced over the weekend. Scope and camera are installed with FitPC riding on the scopes back. Moonlite focuser is driven by the Robofocus controller I had.
I had to run cables reverse through the mount to communicate with the weather station and the roof controller. For those interested I ran a Ethernet cable through the mount down onto a Ethernet over power module and that communicates directly with the router.
The Mount Hub Pro powers the computer, camera, dew heaters and focuser. In other words everything on the scope.
So far all appears to work. Now for V curves and some collimation testing. Pictures tell the story.
Cable management needs a little fine tuning but this is ok for now. Nice to have a large scope that does not have a balance issue.
Very nice installation Paul. For what its worth, Kendrick Astro used to supply thin copper tape with their RC secondary heaters. The copper tape was thin but wide (thus equivalent cross sectional area to wires) and adhesive on one side so it would stick to the secondary vanes. Worked very well for me on my small RC, with no noticable thickening of a secondary diffraction spike. Blackened with a marker pen you could hardly see it. I guess they changed away from it for a reason.
RS-online here in Australia carries a range of adhesive copper tape:
Very nice installation Paul. For what its worth, Kendrick Astro used to supply thin copper tape with their RC secondary heaters. The copper tape was thin but wide (thus equivalent cross sectional area to wires) and adhesive on one side so it would stick to the secondary vanes. Worked very well for me on my small RC, with no noticable thickening of a secondary diffraction spike. Blackened with a marker pen you could hardly see it. I guess they changed away from it for a reason.
RS-online here in Australia carries a range of adhesive copper tape:
Kendrick still supply the copper strips. At this stage I am seeing how effective the heater is before installing the copper strips. The tape I used is the same as that I used on my RC and it was not evident in the diffraction spikes on the images that I had a heater cable installed. It's something I'll consider if the spikes look odd though.
After sorting a minor astigmatic issue with the secondary; commissioning has resumed. Sync into existing pointing model, V curves and guiding sorted (guide camera needed to be lowered to gain focus).
I have decided that the MPCC is probably not going to cut the mustard long term for me. I think the stars look a little soft in the centre of the image, but detail seems reasonable.
I have found that collimating the scope is certainly finicky and I am currently waiting on the GPU CC and a couple of adapters to alleviate any slack I have in the compression ring which is currently holding the camera in place. Using cats eye collimation gear shows good collimation without the camera in place but once the camera is on board the collimation seems to change. Now that could be the secondary cage not providing enough support or it could be the compression ring on the focuser draw tube. For now I'll go with the later. There appears to be a little movement upon tightening the compression ring. Slews across the sky seem to maintain a consistent collimation.
An f4 is really quick at gathering photons and I can see the attraction. The image attached shows the lagoon with 4 minute subs at 28 minutes integration. No flats applied as I need to get collimation sorted first and then I'll do flats. If you look hard you can see the warts near the bottom of the image. Overall though my OCD is happy with the current results.
I'd seen some comparisons between coma correctors a little while back and the MPCC faired better than the GSO one. It not as good as the Paracorr Type II or the other one you're looking at.
hi there Paul
that image looks pretty darn good I think if you are having any issues with collimation it will be the top secondary cage being not braced enough since my mod on my 10" version I have diminished 99% of the flexure in the front cage and when I point the scope in any direction in the sky it seems to hold collimation very well I have also added compression springs under the secondary mirror adjustment screws which make it a lot more precise in adjustment
cheers Pete
I am now approaching final completion of commissioning.
Everything is now screw threaded into position and I have installed shims to adjust for tilt.
I am using the GPU coma corrector which gives superior star sizes and detail sharpness over the Baader. However, the GPU is very sensitive to tilt.
I had to also pay particular attention to the focuser being aligned with the optical centre of the scope. It was slightly out and that combine with tilt made it difficult to find the exact problem.
There is still some slight slop coming from the focuser via the draw tube. It needs some final tweaking to prevent slop from one side of the meridian to the other. Gravity can be a pain in the you know what.
You'll find a few images of the corners of last nights run in the moon light. So ignore the gradients. Flats need adjustment too since my fiddling with collimation.
One more lot of frames taken about 85 degrees up and with slight better corner stars.
It looks to me that my bottom left stars are now slightly over corrected rather than being under corrected before.
I also used CCD Inspector which would help show which way it was out as well.
CCD Inspector is good but if I got a good result from manually correcting tilt I would find it was senior to what CCD Inspector would say as occasionally it would not give the same answer twice on the same image. But if you know how your camera is oriented with regards to the images then it does give an idea as to which way the camera needs to be packed out. Its another tool. It can also be helpful to use it to know when to stop!
I figure that is what you meant.
