Greg the PMX specs suggest 90lbs (or 40.90 kg) as the payload but make no distinction between visual and imaging payloads - which some mount manufacturers do specify. If you use 2/3 rds as imaging capacity that would take you down to 27kg, or 31kg at 3/4 capacity. So are the PMX numbers always listed as the imaging capacity?
Are you looking to reduce that load or your happy with it as is? What makes the dew shield so heavy, is it metal and an accessory to the OTA? I'd think you could get rid of at least 2kg on the front by going to a foam type dew shield. I use a piece of black marine carpet as my dew shield and it probably weighs less than 0.5kg for sure. Weight reduction is good for most scopes if it pushs you away from mount imaging limits.
Greg the PMX specs suggest 90lbs (or 40.90 kg) as the payload but make no distinction between visual and imaging payloads - which some mount manufacturers do specify. If you use 2/3 rds as imaging capacity that would take you down to 27kg, or 31kg at 3/4 capacity. So are the PMX numbers always listed as the imaging capacity?
Are you looking to reduce that load or your happy with it as is? What makes the dew shield so heavy, is it metal and an accessory to the OTA? I'd think you could get rid of at least 2kg on the front by going to a foam type dew shield. I use a piece of black marine carpet as my dew shield and it probably weighs less than 0.5kg for sure. Weight reduction is good for most scopes if it pushs you away from mount imaging limits.
I just realised there were 2 other heavy parts, a 16 inch dovetail plate and a inch Losmandy one. So that makes it over 42.3kgs.
The PMX is doing pretty but this explains why I am having everything to be perfect and there is no leeway. So I think that 40kg figure is the absolute max and that I am overloaded. I get round stars when everything is perfect.
I plan to upgrade the mount as you mention 2/3rd capacity is probably a good approach. The Honders is a very solid scope which is great for F3.8 but its heavy.
Anyone interested in a perfect PMX that is freshly regreased and a perfect PEMPRo PEC curved entered into it? I've had it about 3 years and it got the replacement worm which is around 1 to 1.4 arc second after PEC.
The best guiding I have ever achieved was with this mount with an AP140 and FLI Proline and MMOAG STi guiding. Also with a TEC180 both fairly large and heavy scopes and imaging trains but not as heavy as the Honders. Plus all the software - TPoint, Camera add on, Sky X Pro serious, Precision PE (I prefer Pempro though and the PEMPRO curve is already loaded into the mount).
An update if you've been following this. It is interesting to chronicle the sort of process you go through with new gear even if its high end.
I now have sorted the PMX mount and its giving round stars. I have checked 5 and 10 minute exposures and there is no reason to believe it won't do 30 minutes now.
I took some advice from here and looked for weight savings. I took the counterweight shaft extension off as it wasn't being used. That was quite heavy so I estimate about 2.5kgs or so. I took the thermal blankets off (only about .4kgs). I think I'll put them back on as I noticed some slight dew on the corrector lens this morning despite the dewheater.
I removed the top Losmany dovetail on put on the top of the rings. It wasn't actually adding rigidity like I thought and that must be another 1.5 kgs or so.
I tightened the cam pin and replaced the little socket screw with a better one and I tightened the worm pressure screws 1/4 turn. I don't think this did anything but thought I would tweak it a tad.
Mainly I got a proper T-Point model and sorted through the current error in the Polar Alignment report Sky X Build 8906. It reverses the instructions for the ME adjustment (Altitude adjustment). So its better to use the advanced polar alignment adjustment. This time also I slewed to a much lower northern star and the report gave it 99.1% ideal rating.
I did several T-point runs of about 30 points then a 300 point model of which 58 failed so it was 242 points.
I used 2 x 2 binning and very short exposures to centre the bright star for maximum accuracy.
Polar alignment now seems spot on.
I used .5 min and 2 maximum move for autoguiding settings, direct guide.
3 seconds subexposures with an SBIG STi (just bought a 2nd one for the Planewave, great little guiders) on a MMOAG and second delay to let the mount settle between corrections. I was getting a spurious PE until I used second delay. So not sure what that was but its gone.
Mount is very slightly balanced towards the ground so there is slight pressure on the belts.
Next is cable tidy up. I have replaced one power cable to the RHA back fan with a lead to the PMX power outlet. I've ordered some 12 volt splitter cables so power can come from the PMX to all accessories and not a lead with a splitter cable feeding everything.
The result is very good tracking and round stars and the super sharpness of the scope is allowed to shine.
A new FLI 7 position filter wheel for 50mm square filters arrived. Much better the way it attaches to the Proline. 2 bolts go through the Proline to lock it in place to the filter wheel. Plus it sits dead flush with the camera. There is no way it can tilt. Its a tad heavier (600grams) but its all 7 filters (so sick of changing narrowband filters) and a good system for mounting the filters. The face has a deeper well so the adapters make thread does not have to be so short. All in all a nice unit.
Tonight will show but I am optimistic that any tilt issues are history.
The imaging train from the filter wheel back feels sturdier and more rigid.
A new FLI 7 position filter wheel for 50mm square filters arrived. Much better the way it attaches to the Proline. 2 bolts go through the Proline to lock it in place to the filter wheel. Plus it sits dead flush with the camera. There is no way it can tilt. Its a tad heavier (600grams) but its all 7 filters (so sick of changing narrowband filters) and a good system for mounting the filters. The face has a deeper well so the adapters make thread does not have to be so short. All in all a nice unit.
Tonight will show but I am optimistic that any tilt issues are history.
The imaging train from the filter wheel back feels sturdier and more rigid.
Greg.
I think that's what come with mine last week. Bolts directly onto the PL16803, no flex observed. I had to adjust the Pyxis 3" rotator's delay settings to boost the torque a bit.
I think that's what come with mine last week. Bolts directly onto the PL16803, no flex observed. I had to adjust the Pyxis 3" rotator's delay settings to boost the torque a bit.
Yes that's the one, FLI CFE 5/7. A nicely made unit. It seems to vignette a bit less as well. I think the opening is a bit wider than the CFW4/5.
The bolt on is a big improvement. Expensive for a filter wheel though eh?
A blip compared to the camera and 50mm LRGB/Ha/SII/OIII Astrodon's.... Our $$ certainly isn't where it was.....
True.
One thing I noticed today after using it for the first time last night. Generally speaking, with an image train like this that has several dovetail connectors with grub screws that lock it in place, I think its better to put it together on a bench then mount it on the scope rather than add things whilst part is on the scope. It opens the door to tilt. I think these dovetails will lock in slightly out of whack.
I think also its good practice to tighten the grub screws to slightly tight first one, then diagonally opposite to slightly tight then the next 2 then snug up to final tightness in the same way.
I am wondering if a little bit of Teflon grease on these dovetail fittings is not a good idea so they can slide into the final lock position and not grab in some slightly skew position.
I think that's what come with mine last week. Bolts directly onto the PL16803, no flex observed. I had to adjust the Pyxis 3" rotator's delay settings to boost the torque a bit.
Ooooh squeeeel that looks bwudiful, look out imaging world here comes Chris ..hmmm? have to come over sometime and drink beer..I mean check out your gear (I always get the word gear and beer mixed up for some reason )
One thing I noticed today after using it for the first time last night. Generally speaking, with an image train like this that has several dovetail connectors with grub screws that lock it in place, I think its better to put it together on a bench then mount it on the scope rather than add things whilst part is on the scope. It opens the door to tilt. I think these dovetails will lock in slightly out of whack.
I think also its good practice to tighten the grub screws to slightly tight first one, then diagonally opposite to slightly tight then the next 2 then snug up to final tightness in the same way.
I am wondering if a little bit of Teflon grease on these dovetail fittings is not a good idea so they can slide into the final lock position and not grab in some slightly skew position.
Greg.
Yeah, I put everything I could together on a bench, I even took off my focuser. The whole train effectively. I got my partner to help me bolt it on to the back of the CDK. She's a tradies daughter, comes in handy when things need fixing or telescope gear needs to be setup with assistance
I usually apply pressure against the two connecting components and lightly screw in the bolts until they bite a little. Then tighten them a bit each until they're all tight and nothing tilts out. With a rotator in the mix, everything needs to be perfect.
Yeah, I put everything I could together on a bench, I even took off my focuser. The whole train effectively. I got my partner to help me bolt it on to the back of the CDK. She's a tradies daughter, comes in handy when things need fixing or telescope gear needs to be setup with assistance
I usually apply pressure against the two connecting components and lightly screw in the bolts until they bite a little. Then tighten them a bit each until they're all tight and nothing tilts out. With a rotator in the mix, everything needs to be perfect.
Good approach Chris.
I am wondering though if a bit of Teflon grease smear would also help them seat well. I would be worried though it could make stuff slip but I a smear would prevent the aluminium dovetails from grabbing before they are well seated.
I noticed I had one corner with distorted stars the other night and I was shimming out the camera to correct. It was difficult. So yesterday I took them off and reseated them on the bench and last night it appears to be round stars in all corners so something was off a tad.
Also I found the MMOAG eyepiece holder tends to hit against the CFW so I had to grind off a section so that it clears it. I think it might have been pushing the CFW out a little bit causing the distortion. Does your MMOAG hit your CFW 5/7? We have essentially the same setup here with the exception you have a rotator. Otherwise its exactly the same. Great minds eh?
Greg.
Last edited by gregbradley; 15-07-2015 at 12:18 PM.
I am wondering though if a bit of Teflon grease smear would also help them seat well. I would be worried though it could make stuff slip but I a smear would prevent the aluminium dovetails from grabbing before they are well seated.
I noticed I had one corner with distorted stars the other night and I was shimming out the camera to correct. It was difficult. So yesterday I took them off and reseated them on the bench and last night it appears to be round stars in all corners so something was off a tad.
Also I found the MMOAG eyepiece holder tends to hit against the CFW so
I had to grind off a section so that it clears it.
Greg.
Ok, my MMOAG only impacts with the CFW at certain angles, rotating it to 0 degrees (relative to the shortest edge of the CFW) with say +/- 5 or so degrees, there is no impact. Mine is a Monster-MOAG, not sure if you're using a Mega-MOAG or an older version. This one is a few weeks old, so would be a recent run I guess. It's very slim but sturdy, and no visible vignetting issues outside of the spec of what I'm expecting to see on the CDK itself.
I'm using the Monster MOAG as well and it hasn't changed since it came out although I notice Astrodon now have a 2 or 4 port version for guide cameras in different orientations. Not sure what for. Perhaps you could run 2 autoguiders at once or just for more guide stars?
Mine was just clipping the CFW almost imperceptibly and I only noticed it because I was hunting for what was pushing one corner of the camera.
MMOAG is a great accessory and has served me well for several years.
Another chapter is unfolding with this scope. I bought Raki's AP1600GTO to mount the Honders as the PMX as good and smooth as it is was at or bit past its capacity. Following the principle of overmounting your scope I thought it was appropriate. I could have gotten another PME but wanted to try AP as anything AP I have had has always performed the best of anything.
Also a lot of RHA owners use AP1600's I found out.
I am in the process of modifying my pier (almost finished) to hold it and also to upgrade the bolts to larger sizes so its really rigid. I may end up going permanent pier rather than this fairly solid but portable pier I have from Mountain Instruments.
The AP1600 can handle 100kgs of load. It also field upgradable to super accurate encoders which gives less than .2 arc sec tracking and eliminate PE.
I may end up getting those at some point in the future when the Aussie dollar recovers (what - say 2020???).
I drove to Melbourne and Lakes Entrance to deliver my trusty PMX to Erik and pick up the AP1600 from Raki. Over 3000kms later it is at home.
So it will be 2 separate systems, the CDK on a PME and the RHA on an AP1600 both able to run at the same time with 2 different computers so I can get maximum imaging time done and probably do several combined images. PL16803 on the CDK and something smaller on the RHA perhaps an 8300 camera. That gives a similar FOV to each other and matches the pixel to focal lengths well.
By the way if anyone wants to buy an AP RHA there is one up for auction on Astromart. I think this is the 2nd one I have seen for sale since AP started making them 3 or 4 years ago, so its rare.
Also Rolands personal AP175 refractor. You can bet that is a beauty.
Exciting times for you Greg.
How about mounting the RHA on the PME and the CDK on the AP 1600 as this would suit the carrying capacities of the mounts better?
Exciting times for you Greg.
How about mounting the RHA on the PME and the CDK on the AP 1600 as this would suit the carrying capacities of the mounts better?
Josh
Yes it is Josh. I mainly want to make sure I am getting the full sharpness the AP optics have to offer.
I think carrying capacities are similar. The PME 2 capacity is 105kgs but I suspect SB exaggerate their carrying capacity a tad.
I like the idea of like with like (AP with AP) besides the PME handles the CDK17 easily.
Greg, you are like a dog with a bone! Once an idea gets planted you certainly see it through quickly. I'm sure that AP mount will be great! I wonder if you will miss the ability to just home to get going?
Home position is definitely useful. You can do home with the encoders or if you get a home sensor fitted. But from users accounts once its setup its not really an issue.
that looks bwudiful, look out imaging world here comes Chris 
..hmmm? have to come over sometime and drink beer..I mean check out your gear (I always get the word gear and beer mixed up for some reason 
)
