bamus

My new purchase - Skywatchwr Star Adventurer. Waiting now for clear skies to see what this little mount can do.

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The wedge and a new piggy back mount for xmas. The old piggy back wasnt ideal as it connected to the diagonal adding to much wait to the optical chain!

shame ive not had chance to get out with it all yet

hi Craig

are you intending to use celestron as guide scope? bit more focal length than mine 400mm

I have changed my funny small guide lens with proper guide scope - SW80/400. Lens was doing quite good job as a guider, but 135 focal length can not beat 400

Is it still possible to manualy guide the scope after the motors are installed? Say when the battery is dead... and no power near..

After fitting upgrade kit, manual handling is not possible any more.

Stan here are the setting I am using my scope is an f5 ratio so I have lowered the calibration pulse rate to 250. Still learning what they all do but hopefully a bit of tweaking should improve things tonight.

as you are guiding through finder, I would suggest to change minimum motion to 0.06

could you also post screenshot of phd screen. I would like to see how noise levels look line with noise reduction 3x3

QM have you seen this canon battery power supply?

Astronomiser - Automated Astronomy and AstroImaging Solutions

It's a must have in my opinion I only have one battery and like you say.. Doesn't last long in the freezing cold! Roll on payday

cheaper option here:

eBay - The UK's Online Marketplace

Oh well the snow makes the country side look lovely if nothing else. I was reading an article by the maker of PHD and he said webcams were not ideal for PHD he recommended the QHY5 cameras that might be my next investment later on once I have tested all this later.

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Don’t give up. I was able to get stars above 6 mag with Logitech 120. Perhaps 4000 series are more sensitive and you would get better results. Don’t forget to reduce noise by using median noise reduction in PHD settings.

http://stargazerslounge.com/imaging-discussion/125230-unmoded-webcam-guider.html#post1663012

wow! this is briliant! its much easier than I thought it would be. wish I have seen this kind of instructions before I have spent £300 on GOTO upgrade kit. Love X-mas light!

actually it was easier than I thought it will be. I have used B&Q brand lithium grease.

HI All

I think I’ve got it sorted J I took my mount completely apart, cleaned and greased all moving parts. Corrected all slacks between motors and mount. Put it back together (I thought I have used to much or too thick grease as axis were not moving as freely as they used to), have done proper PHD drift polar alignment, and have changed Dec algorithm Lowpass filter. Not sure what main reason for improvement, but peaks from DEC graph are gone and I can do 10 minutes exposures without any sight of stars trails. I so glad that it works now.

Graph in PECperp is not within +-1.5 arc sec in both axis. Without guiding my old EQ5 has got PE within +-18 arc sec which is huge improvement from previous measurement of +-40 arc sec J

CG5 is slightly better than EQ5, so I guess if you want to use better mount over all, swapping synscan to CG5 makes sense.

ok, have done some tests and it is slightly better. calibration first time for long time was correct in N-S direction and most of the time graph was acceptable, but from time to time I do get peaks. I think I have to accept cheap mount will behave like that although still dont understand where this problem comes from and how to solve it completely.

I have also run PecPerp and while RA graph was most of the time between +-2 arcsec, DEC graph was between +-3 and highest peaks went to up tp 11 arcsec

Ouch. I hope it's not mechanical.

Just a thought Bamus but have you tried, once calibrated, reducing MxRA and MxDEC. Maybe PHD is over compensating? Try 500 ish?

Mark

Hi Mark

I don’t think overcompensating is an issue in my case. As you can see from EQMOD pulse guide monitor, PHD was not sending any long pulses at the time when star has moved rapidly to South.

Anyway, I have took apart my mount on Sunday and degreased all moving parts. It moves now more easily than before (perhaps resistance in DEC axis didn’t allow star to move as much as it should be and some kind of internal pressure was building up and was released from time to tome – hence this big star shift to South) . I have also slightly adjusted DEC motor position so now teeth in-between gears are tight together (hope not to tight) and any movement in DEC motor is translated immediately in DEC worm movement.

Hope this will help, if not that I have got no other idea what can help. First clear night I will give it a go.

regards

Adam

so here is promised update... not good one, but let me start from beginning.

I have removed guide scope and attached guide cam directly to main scope in order to increase focal length and improve DEC axis balance (which was pretty good).

calibration in RA went smoothly but mount could not calibrate in DEC, so I have changed DEC rate to 0.9 and DEC backlash to maximum in EQMOD. After that calibration in DEC in north directions went quick in about 15 steps but when it went to South direction star has hardly moved back to original position. PHD however started to guide.

I had to decrease DEC rate to 0.2 and DEC backlash to 0 in order to make DEC graph smoother. I have also changed guide in DEC to north only as my PA was slightly off on purpose.

So for few minutes tracking in DEC was as it suppose to be, but then old problem again. Star has jumped large distance to North and as guiding was in North only, nothing has stopped this movement.

From pictures below you can see that this was not caused by huge pulse guide. So it must be mechanical issue. I have tried to tighten and then loosen DEC clutch, but same happened again and again...

now only thing what I can think off which can help is taking apart mount and try to put it together hoping that this will solve issues I have got, but to be honest I am not sure where to look (which part can cause this what is happening)

I think I have to take few days off and dont walk into conservatory where mount is storred

Many thanks Mark! I went to bed very angry and frustrated last night asking myself why do I bother wasting my time, but today I am bit calmer and will try to solve this problem again.

I will keep you updated with my progress

Thanks Mark, any help/advise is more than welcome!

RA guiding is perfect. Calibration is done in about 15 steps and graph is within +/-1,5 arc sec, so there I have got no issue at all. I was doing yesterday 5 minutes subs and the one which have been in-between DEC graph peaks were perfect, other ones showed trails in Declination)

I am using EQMOD, so I will try to increase MAX DEC duration, is it done before calibration or after? (already have tried to increase DEC guide width to 150%, with little improvement). What about EQMOD backlash compensation. How can I measure how many ms I can use (at the moment it is on “0”)

Tonight I will try longer focal length guide telescope (at the moment I am using 135 mm lens and will change it to 300mm refractor) and will see if anything will improve. But to be honest I don’t expect huge improvement as I think there is mechanical problem in DEC axis as looking on the PHD DEC graph (with poor PA) I have noticed at the beginning small North corrections for a while (2-3 minutes) than it went back to South, small corrections at the beginning , then bigger and bigger (up to 1000ms) and then out of nowhere it went to huge North corrections and in this moment see-saw graph was appearing. It was very regular so it was almost like periodic error (I know DEC PE doesn’t exist but it almost look like one). If I am thinking correct, with poor PA declinations corrections should be only in one direction all the time, right?

Another issue is fact that calibration in DEC is not looking good as well. First off all clearing backlash takes about 5 minutes. It takes about 30 steps in North direction (not very regular steps, first 10 moves star only about 3 to 4 pixels, then there is huge jump in one step of about 7-8 pixels, some steps does not move star at all and in some stars is going south during North calibration. South calibration hardly moves star back to its original position).

So today, my final test night will be with longer focal length refractor, good PA (drift method) and I will check first how it will track with guiding in DEC off to reconfirm that problem has got mechanical nature, not software. If it is mechanical, then I will have to strip my mount completely down and put it back together. If it does not improve things I will throw the towel and put all my equipment in FOR SALE section (hope that I will not have to do it, but it will not make any sense to play astrophotography with this mount any more)

Dann - how was it last night? any improvement in DEC graph?

yes Merlin66, I am almost sure its something to do with "sloppy" dec axis.

2 days ago I have took apart upper part of mount head where DEC motor is, regreased everything and tightned all screws, but problem is still not solved. Could you explain what do you mean by :

"the usual fix is to pre-load the dec axis ( some out of balance load) so there's no need for reversal/ dead band"

(sorry need explanation - I am foreigner

)

I have got same issue and it’s not due to bad polar alignment (spent 1 hrs yesterday doing drift method).

With guiding with DEC turned off I got 3 to 4 minutes perfect tracking and then out of nowhere dx/dy graph starts sharply moving from middle line.

Same with guiding ON. I can get 10 minutes perfect tracking and then it start again, DEC graph is all over the place. Increasing Max DEC to 2000 has improved graph slightly, but its still far from perfect.

I am in the stage now where RA tracking is perfect and only thing limiting my ability to take longer exposures is DEC.

I suspect few things can cause such a behaviour:

- Telescope is not balanced well enough. Its not possible to achieve good balance with my WO72 as mounting foot is too short – I will have to find longer dovetail for it. But on the other hand my setup is light enough (3kg) and my mount (EQ5) should handle this without any problem

- Cable from guide camera and main camera are causing some pulling force which affects guide graph (but it does not affect RA graph, and after attaching cables properly to mount issue still existed)

- Mechanical error either in DEC motor, or DEC shaft/bearings – but why so many other people are getting it?

- Backlash – this is my main suspect. I think PHD does not handle clearing backlash properly. It takes ages to clear backlash and during N-S calibration star is not coming back to original position

Have you got any other ideas?

Great thread Can I just ask, as I was considering upgrading, once this is done how does the upgrade perform when your imaging with a guider plugged in. I want to do this but I'm worried it wont be worth it. I was given a star-guider and this would plug into the go to st4 port once the upgrade was done which would banish those double stars and shaky misalignment I'm used to..

all depends what kind of scope you will be using. If it is SW200/1000 then you will have problems, as mount will be on the very end of its capacity. I have got William Optics 72 Refractor on EQ5 with GOTO, and I have to say that I am very pleased how this cheap mount if performing

Love split roof idea. I also haven’t got a lot of room in my garden and to be honest I don’t like the view of roll on/off design. So one beautiful day when I will build my own obsy.