AstroPhysics Riccardi Honders Astrograph 305mm F3.8 arrives!

[PRejto (Peter)]

Hi Greg,

I think it is a mistake to expect that T-Point and PEMpro drift alignment are going to "agree" very much on where to place your PA! There has been endless and heated discussion about this on the SB forum. If I have digested the discussion properly T-Point is making a mathematical construct of all the pointing combined with flexure issues of every setup and offers various PA recommendations based on what one desires to do. But, PEMpro offers great PA at just one sky location. (Dec=0, etc) So, it seems all PA Is a compromise. Patrick W. has said (perhaps reluctantly) that using drift alignment is good enough as long as one also uses T-Point to model the sky so that Protrack can do its thing. But, so is T-Point PA!! Of course, if you moved the polar axis when you ran PEMpro drift you've got to recalibrate into your large model to get it to work again! The recommendation is to recalibrate as a "portable mount." The other possible reason your new T-Point model didn't work so well is that maybe your polar axis moves, especially MA, might have not been as accurate as you thought. There has been much discussion about that as well and now are methods to move using fiducial stars to confirm accurate adjustments. So, you re calibrated after you made moves of PA?

Peter

[gregbradley]

Originally Posted by SpaceNoob

Hi Greg,

I had a similar issue recently, somehow my PEC got all wacky and threw out my subs. I used the wizard in theskyX to refine my polar alignment and now it sais my error is 0" and 0" to the refracted pole. New PEC run via pempro showed no drift from polar misalignment, the new PEC resulted in +/- 0.2" corrected. I now have perfect tracking again. I'm assuming the constant nights of -6 here have probably contributed to whatever suddenly threw off the usual perfect performance I get from my mount. 30minute guide logs are a flat line and I had a few subs with 1.3" FWHM at 2.5m focal length.

Originally Posted by PRejto

Hi Greg,

I think it is a mistake to expect that T-Point and PEMpro drift alignment are going to "agree" very much on where to place your PA! There has been endless and heated discussion about this on the SB forum. If I have digested the discussion properly T-Point is making a mathematical construct of all the pointing combined with flexure issues of every setup and offers various PA recommendations based on what one desires to do. But, PEMpro offers great PA at just one sky location. (Dec=0, etc) So, it seems all PA Is a compromise. Patrick W. has said (perhaps reluctantly) that using drift alignment is good enough as long as one also uses T-Point to model the sky so that Protrack can do its thing. But, so is T-Point PA!! Of course, if you moved the polar axis when you ran PEMpro drift you've got to recalibrate into your large model to get it to work again! The recommendation is to recalibrate as a "portable mount." The other possible reason your new T-Point model didn't work so well is that maybe your polar axis moves, especially MA, might have not been as accurate as you thought. There has been much discussion about that as well and now are methods to move using fiducial stars to confirm accurate adjustments. So, you re calibrated after you made moves of PA?

Peter

What are fiducial stars? Fixed stars?

I did use the accurate polar alignment once and it did work reasonably well.

I was getting round stars and then I noticed my mount needed more setup - the bolt on tripod legs bolts were not all tight and the mount plate needed a shorter bolt etc. Plus after that it needed to be relevelled.

I did more last night. I used T-Point again and got it close but not round stars. I did another 105 point model and got the report saying to do a very large lowering of the altitude. It wasn't right. I wonder if this tripod pier has some flex in it still. Not all bolts are as tight as they could be.

Yes I redo a full model once I change PA adjustments in PA.

I did the Pempro drift again. That got me reasonably round stars. Not good enough long term but good enough for one night.

The thing I like about Pempro is that drift is actually measuring the thing you want to eradicate directly rather than indirectly with Pempro. I have had great results with Pempro before though. As a contractor I always want the actual measurement over the planned or ought to be measurement. It saves a lot of errors from off assumptions.

Greg.

[PRejto (Peter)]

Yes, but not to be pedantic. PEMpro drift alignment gives a great result for just that one area of the sky. Image in a completely different area and you may find that drift is much worse. Of course, a good model + PEMpro is going to correct that through Protrack. At least that is my take after reading endless discussions on the subject (of which I tend to agree with Patrick a bit more than Ray G)

Peter

PS My understanding of a "fiducial star" is just a star at a position in space such that if you mechanically move the mount to centre on it will in one step account for calculated errors in ME and MA.

[gregbradley]

Thanks Peter. Makes sense on the definition. Fiducial mean fixed.

I did another 200 point model tonight. I implemented the accurate polar alignment actions. I realised when I did it before I first had done the ajustments from the Polar Alignment report first then the accurate polar alignment adjustments plus I was not careful enough about centring the star in the image.

But tonight I did it very precisely and one axis was perfect the other was still off. With Protrack tracking adjustments activated it helped but still you could see it was fighting drift. So I did a quick Pempro polar alignment wizard and indeed the Azimuth was perfect but the altitude was a it off. A couple of quick adjustments and it was spot on and now very round stars (not perfect but then its poorish seeing) with protrack on.

I am seeing some spikes though. I hope that is the seeing and not some dirt or fraying belts in the mount. But round stars I am happy so both tools were helpful here.

Plus it pays to carefully read the instructions! (accurate polar alignment instructions).

Time will tell if that drift is corrected generally or only for one patch of the sky but to be honest I have never noticed any mount to guide well in one patch and not another. Usually better when the scope is pointed near the zenith.

Greg.

[SpaceNoob (Chris)]

Originally Posted by gregbradley

Thanks Peter. Makes sense on the definition. Fiducial mean fixed.

I did another 200 point model tonight. I implemented the accurate polar alignment actions. I realised when I did it before I first had done the ajustments from the Polar Alignment report first then the accurate polar alignment adjustments plus I was not careful enough about centring the star in the image.

But tonight I did it very precisely and one axis was perfect the other was still off. With Protrack tracking adjustments activated it helped but still you could see it was fighting drift. So I did a quick Pempro polar alignment wizard and indeed the Azimuth was perfect but the altitude was a it off. A couple of quick adjustments and it was spot on and now very round stars (not perfect but then its poorish seeing) with protrack on.

I am seeing some spikes though. I hope that is the seeing and not some dirt or fraying belts in the mount. But round stars I am happy so both tools were helpful here.

Plus it pays to carefully read the instructions! (accurate polar alignment instructions).

Time will tell if that drift is corrected generally or only for one patch of the sky but to be honest I have never noticed any mount to guide well in one patch and not another. Usually better when the scope is pointed near the zenith.

Greg.

Spend 30 minutes clearing your PEC, collecting, applying, and verifying a new one with PEMPro... I did this recently after my PME and PMX performance suddenly degraded when we had 2 weeks of -6 and below. I am assuming you're re-greasing routinely as is advised too?

[gregbradley]

Hi Chris,

Yes the PMX often sounds like it needs extra grease. I haven't yet though. Its not that old really and lightly used. But yes I have the grease. Is there a video or tutorial on how to grease it?

My place does not go below about 4C and the last time I used it I got round stars at my dark site.

I did some more T-Point and autoguiding massaging last night and am getting round stars now. They could be a bit better but they are acceptable.

I'll do another large T-point run and perhaps a fresh PEC. Can't hurt.
I find Pempro a very nice piece of software. Very bug free and easy to use. Hat's off to Ray Gralak for making such a reliable piece of software. That's a standout.

I'm also thinking of replacing the belts as a lot changed their belts over to the newer grey ones from the original black ones.

The dew heater works well. The optics have been dew free in the morning now since I installed it.

I am familiar with dew heaters. It seems fairly warm like an electric blanket. I have it turned down to a really low level and have the strap under the thermal blanket. It has a sensor but its warm all the time. Is that normal?

I am noticing that this scope does show up bad guiding more than others. I think that's because its F.8 and a star off centre even for only a short time records a fairly bright spot so errors show up in the image more. Of course the plus side is the stars when done well really look good.

Greg.

[SpaceNoob (Chris)]

Originally Posted by gregbradley

Hi Chris,

Yes the PMX often sounds like it needs extra grease. I haven't yet though. Its not that old really and lightly used. But yes I have the grease. Is there a video or tutorial on how to grease it?

My place does not go below about 4C and the last time I used it I got round stars at my dark site.

I did some more T-Point and autoguiding massaging last night and am getting round stars now. They could be a bit better but they are acceptable.

I'll do another large T-point run and perhaps a fresh PEC. Can't hurt.
I find Pempro a very nice piece of software. Very bug free and easy to use. Hat's off to Ray Gralak for making such a reliable piece of software. That's a standout.

I'm also thinking of replacing the belts as a lot changed their belts over to the newer grey ones from the original black ones.

The dew heater works well. The optics have been dew free in the morning now since I installed it.

I am familiar with dew heaters. It seems fairly warm like an electric blanket. I have it turned down to a really low level and have the strap under the thermal blanket. It has a sensor but its warm all the time. Is that normal?

I am noticing that this scope does show up bad guiding more than others. I think that's because its F.8 and a star off centre even for only a short time records a fairly bright spot so errors show up in the image more. Of course the plus side is the stars when done well really look good.

Greg.

Hi Greg,

There is a link for the PMEII/MX/MX+:
https://youtu.be/qe11z6sQzz4

For the PME:
https://youtu.be/yl2mqN0py08

I would perform this every 12months for low use, or 6months for high use. Then follow up with a new PEC run. I do 6monthly just because of the variance in conditions here.

They're good mounts, but like anything moving, it needs a service to be running at optimum. If your polar alignment is bang on, which I suspect it is, its worth at least just checking your PEC is correct by checking it with Pempro. I do around 5 cycles, any seeing issues should process out anyway. Assuming its all good, you should have corrected PEC within an arc second. Mine is around +/- 0.2" and +/- 0.3" for the PME and PMX respectively, with PEC applied.

Here in Canberra I've found that I really need to maintain my PEC seasonally, my dome completely freezes up, ice everywhere. I started by chasing my tail thinking that my polar alignment had somehow slipped, so I used PEMPRO wizard to refine it.... end result was horrible and off significantly. I went back to TPOINT polar alignment, synch east near home, small calibration runs to the east to refine it to 0/0 using the wizard and my camera, then do a large 200-300 point run, but the tracking issue was still evident. I performed a new PE collection with Pempro, applied it, and boom... Mount is perfect again.

Hope you can isolate the issue soon and have everything running at optimum.

Cheers,

Chris.

[gregbradley]

Thanks for that Chris you have been most helpful.

Greg.

Originally Posted by SpaceNoob

Hi Greg,

There is a link for the PMEII/MX/MX+:
https://youtu.be/qe11z6sQzz4

For the PME:
https://youtu.be/yl2mqN0py08

I would perform this every 12months for low use, or 6months for high use. Then follow up with a new PEC run. I do 6monthly just because of the variance in conditions here.

They're good mounts, but like anything moving, it needs a service to be running at optimum. If your polar alignment is bang on, which I suspect it is, its worth at least just checking your PEC is correct by checking it with Pempro. I do around 5 cycles, any seeing issues should process out anyway. Assuming its all good, you should have corrected PEC within an arc second. Mine is around +/- 0.2" and +/- 0.3" for the PME and PMX respectively, with PEC applied.

Here in Canberra I've found that I really need to maintain my PEC seasonally, my dome completely freezes up, ice everywhere. I started by chasing my tail thinking that my polar alignment had somehow slipped, so I used PEMPRO wizard to refine it.... end result was horrible and off significantly. I went back to TPOINT polar alignment, synch east near home, small calibration runs to the east to refine it to 0/0 using the wizard and my camera, then do a large 200-300 point run, but the tracking issue was still evident. I performed a new PE collection with Pempro, applied it, and boom... Mount is perfect again.

Hope you can isolate the issue soon and have everything running at optimum.

Cheers,

Chris.

[gregbradley]

Just another little update.

I managed to get round stars last night from the PMX so it is capable of handling the RHA with care. The scope was slightly off balance and I rebalanced it plus I did a new PEC curve, tightened all the adapters and fittings and did a new 100point t-point model which basically said its good enough. The T-point model errors were quite low. I did one before the rebalance and tighten and got terrible t-point model errors.

So now the only tweak needed now seems to be getting the camera perfectly square which I did this morning. If there is even slight tilt it shows up in the corners quickly as elongated stars. Usually only one or two corners not all 4 or one side is sharp and the other a bit out of focus.

F3.8 is a hard taskmaster but worth it for the speed. But for sure once I've got it all perfect its gonna be a case of don't touch anything!

Its an interesting journey as there are now quite a few scopes that are F4 or faster on the market and the faster they are the fussier they will be to tune. So the speed comes with a demand for accuracy in all things around it. No free lunch here. Luckily this scope does not need collimation as that would be a challenge.

Greg.

[gregbradley]

I am close now. Almost perfectly round stars to all corners. There is still a slight amount of tilt. Its a matter of working out the spacers and making sure the Proline is seated flat against the filter wheel.

Gee the images look nice when its all aligned. Really nice.

Greg.

[gregbradley]

Did some imaging last night. Tried some more spacers - it got worse. Reverted, beautiful images.

For the sake of perfection a tiny shim has been added and I'll do a really large T-Point model tonight if its clear. Its now awfully close and the images are drool quality. This scope is magic when everything is setup for it.

I do notice I get slightly better tracking when the scope is on the West side. What's with that?

Greg.

[Joshua Bunn (Joshua)]

Originally Posted by gregbradley

I do notice I get slightly better tracking when the scope is on the West side. What's with that?

Greg.

It's magic when it's all going well, hey Greg.
Maybe your setup is counterweight heavy, the worm lifting the gear? Not that I think it's any difference on a Paramount...

Josh

[PRejto (Peter)]

More of a thought bubble than anything else, but assuming perfect balance weight wise on each side the only difference would be a considerably different moment due to the scope length from east side to west side. But, why that might matter is not at all clear to me except possibly to note that on one side the larger moment is being lifted, the other lowering. I wonder what you might see if you turned off declination guiding? Any difference from side to side when the only corrections are in RA?

Peter

[gregbradley]

Originally Posted by PRejto

More of a thought bubble than anything else, but assuming perfect balance weight wise on each side the only difference would be a considerably different moment due to the scope length from east side to west side. But, why that might matter is not at all clear to me except possibly to note that on one side the larger moment is being lifted, the other lowering. I wonder what you might see if you turned off declination guiding? Any difference from side to side when the only corrections are in RA?

Peter

Ah yes that might explain it. With the OTA on the west with it pointing to the east the counterweights are being lifted (I have make it slightly imbalanced to the east to prevent oscillations) and when OTA is on the east and the counterweight is lowering and the imbalance is causing it to press down very slightly but in the opposite direction. Maybe slight backlash?? It was only a slight difference. Both gave round stars, but on OTA on the east looking west gave slightly rounder stars.

Greg.

Originally Posted by Joshua Bunn

It's magic when it's all going well, hey Greg.
Maybe your setup is counterweight heavy, the worm lifting the gear? Not that I think it's any difference on a Paramount...

Josh

It was a very slight difference Josh so its probably more to do with some slight flex in something or tiny backlash.

Greg.

[gregbradley]

Yet another workout tonight. I tried the .5 min and 2 maximum move in autoguiding per the CCDware min/max move calculator. I also did accurate polar alignment from the last T-Point model ( a very small adjustment to the mount). I also corrected a bit of flex between the camera and the filterwheel when the scope was pointing directly up. Bang round stars. Awesome.

A tiny bit off in one corner at a full 1x1 image of a 16803 camera (4 screens wide) is good enough. I think that will even disappear when I switch to a new filter wheel soon (the existing was slightly modified at one point by me and not 100% square now but normally its not noticeable).

The smallest flex causes corner stars to go off. Apparently also slight PA errors but mostly flex. So the camera has to be well seated and no flexing.

So now I leave it alone! Don't touch anything! I think I will even walk past it very slowly. Its enough to make you superstitious.

But boy when its all perfect the images it downloads are breathtaking. I've used lots of high end scopes and this one is the best.

Greg.

[Atmos (Colin)]

Glad to hear that you're finally getting closer to "officially" starting your imaging runs

[Joshua Bunn (Joshua)]

Good stuff Greg!

Originally Posted by gregbradley

I also corrected a bit of flex between the camera and the filterwheel when the scope was pointing directly up.

What did you do to correct the flexing?

Originally Posted by gregbradley

Apparently also slight PA errors but mostly flex.

How long are your integrations?

Josh

[gregbradley]

Originally Posted by Atmos

Glad to hear that you're finally getting closer to "officially" starting your imaging runs

I know! Hilarious really how much work goes into setting up a precision instrument.

[QUOTE=Joshua Bunn;1184244]Good stuff Greg!



What did you do to correct the flexing?

I put some 1.5mm blue plastic spacers (the type used in construction you get from Bunnings) at each of the 4 corners. Then I pushed the camera in hard whilst I locked off the filter wheel. There is still a tiny flex that I expect to handle fully when a new 7 position filter wheel arrives. But at this stage its not worth chasing as I think I will go backward. Its like contracting. Sometimes there is a point on a job if go beyond you start going backwards! Knowing when to stop is important sometimes.


How long are your integrations? At the moment 5 minutes but I think now longer should not be a problem. It came over cloudy as I was testing so next clear night I will test, 10, 15, 20 minutes. I might also do a "quick" 300 point T-Point model.

That new accurate polar alignment feature in T-Point is pretty cool The model said good enough but in the adjustment section it said to lower the axis by 1.3 tics. The accurate polar alignment though made me raise it about 2.5 tics. I then got even rounder stars. How about that.

I may play with the refine curve feature of Pempro but last time I managed to get the refined curve uploaded when I had just done the 2nd curve data with the PEC turned on but not the next day trying to load a saved curve. Pempro is a bit awkward sometimes. Its not clear how to load and save things and reload. It seems more oriented to playing back the curve in real time but that would mean turning on that program everytime you wanted to image. Unless I am misunderstanding it.

My current curve is 5th order and the RMS value dropped a fair bit. Last time I used just the linear curve and the refined curve was adding the 2 curves. I am getting better results with the new curve than the older refined curve.

Greg.

[Joshua Bunn (Joshua)]

Are you saying you are finding this setup more susceptible to polar alignment errors than your other scopes?
I would have though it to be hard to find PA drift errors in 5 min exposures and at 1.17m FL, considering how close to the pole you are.

One other thing Greg, are you seeing flexure in your image train or tilt?

Josh

[gregbradley]

Good point Josh. It was probably just the better guiding.
Its tilt and its not much now. I can see a tiny flex between the camera and the filter wheel. About to be remedied with a new filter wheel.

Guiding now and roundness of stars is very good.

Greg.