Kiwi_Brad

Does anyone have experience with this.  I am keen to get one due to its long back focus as I use a DSLR and OAG. 

I have heard backspacing needs to be very accurate for it to correct properly but that is all good. 
 

I have heard it can introduce come aberrations as well though so interested in hearing peoples opinions after using it. 
 

Or any other recommendations with a long back focus for use with DSLR. 

I just use a SW130PDS at the moment. 
 

thanks 

10 hours ago, AstroMuni said:

Where in the train is your OAG? If you put OAG first thing after the scope and then CC, DSLR you should be able to get backfocus is my guess?? Guiding doesnt need coma free stars

No it does I had never thought about trying this to be honest.  I will def see what I can do.  Just always thought I wouldn’t be able to reach focus with it that early but will have a play around! Again great idea thanks. 

23 hours ago, AstroMuni said:

The overall image is looking much better. I think the reason for the oval shapes in the left hand side is a combination of tilt and collimation. If you are getting similar ovals on the right hand side which are like mirror images of the ones on the left then you will also need to look at adding or remover a spacer between CC and camera. 

And as alacant says, take a look at your processed images and decide if you still wish to improve it.

Great thank you to all it will be spacing of my baader cc. I am outside it’s backspacing and with a DSLR I can’t get any mess with my OAG. Sadly. 
 

Thank you for your help everyone. 

I blacked those screws, loosened the mirror clips and shortened the focuser tube. 
 

it seems to be pretty good now in terms of spikes. I do still see on the sides or corners where n a defo used star the edge of the star missing.  Is this a misalignment of the secondary and focuser tube? 

diffraction pattern is looking quite tidy and the additional spikes have gone.  Longer spikes on one axis than the other though  

why do I have the top quarter or more of the outer ring missing? 

this image is the centre of the fov 

5 hours ago, alacant said:

Hi

Assuming the optics are good, there's something interfering with the light path, but as we don't know the full story as to what has been changed,  perhaps the best (only?) way to diagnose is by elimation.

But before that struggle begins, I can see some bright areas around the new secondary spider rim. Perhaps screw heads? These coincide well with the new spike.

Next, go one at a time removing filter, cc... Then replace the original secondary holder, reverse whatever you did to the primary, remove the tube flock, try a friend's camera, remove 12mm from the protruding focuser barrel, blacken mirror edges, collimate and collimate again...

Here's hoping you find something obvious early on in the diagnosis.

Cheers and HTH

Yes I will blacken the cut screw heads tonight. I think the only things I have done that could be causing it are those screws or the focuser tube but of course that was there before but now with a darker flocked  tube and a lot of stray light being dealt with it is more directed into the focuser tube and creating the spike? Maybe… stretching. 
 

I will cut the tube slightly and blacken those screws and report back. 
 

Thanks

13 hours ago, AstroMuni said:

I would suggest taking images where the stars are slightly out of focus so you can see if its collimated properly. Its tricky to get the back focus distance correctly and it took me a multiple tries to achieve a situation where I was happy with it. Also worth checking the tilt as I struggle with getting the camera+CC perfectly in line with the focal plane. Have you upgraded the eyepiece clamp to a compression ring one so that this can be better addressed?

I have just replaced the eyepiece clamp to a compression ring so it wasn’t in those images but was in the latest close up stat image of Acrux.  Hopefully it will help as it is much better. 
 

I know I am outside the backfocus limits because of using a Nikon DSLR and OAG. I can’t find one smaller than 11mm which I use now.  So probably have to accept some issues through the corners.   One day I will find money for a new camera! 
 

Thanks 

13 hours ago, malc-c said:

Thanks for uploading the images.  The star image is not the same as when I was having similar issues.  Yours is even, and both sides.  I'm no expert, and hopefully someone with more knowledge of these thins will chime in, but my thought was that the focus tube is protruding a fair bit into the light path.  If I can use a clock to explain my logic, your 3d spider has vanes at 2, 4, 8 and 10 which looking at the image results in spikes at the same 2, 4, 8 and 10 O'clock positions.  The focus tube axis is a line through 9, and 3 which again the rouge spike appears in the same position.

As I said, I'm no expert in optics, so my logic could be way off. 

Thanks for that I do think you might be right. It protrudes quite far.  I have heard of people shortening the tube but the focuser itself really isn’t overly great but not sure I want to spend the money on that as an upgrade.  I certainly could trim a good 20mm off it  … 🤔

23 hours ago, malc-c said:

Can you post a picture of your new printed secondary holder.  I spent ages trying to eliminate a 5th spike on bright stars.  The cause was unsilvered edges on the stock secondary.  I'm just wondering if the edges of the minor axis of the secondary has been compromised by your new design.

Below is some images of the scope and my most recent collimation then star test. I think I have resolved most of my issues given my back spacing problem until I get a dedicated camera.  Focus looks better but still an extra diffraction spike just not split now.   I read and fixed this as the secondary mirror holder not be square to the OTA tube itself. So measure from the edge to the edge of the tube it was out about 2mm.   Also my laser collimated badly needs collimating so didn’t use that at all.   Don’t have an image across the whole field but any comments on collimation welcome. 
 

Thanks 

Just after some help with my 130PDS. I have taken it apart cleaned, flocked and added a few 3D printed parts.  Including a secondary mirror holder. 
 

I have attached an image before and after the rebuild. I was trying to help the primary mirror clip issues around bright stars mostly.   I have clearly introduced several issues into my images in doing all these. 
 

I believe I have aligned the focuser tube and secondary and collimated suitably well but I can’t tell the different between pinched optics bad collimation and the thousand other things I could have introduced. 
 

The two images are both of the southern pin wheel and a single frame.  Different exposures but you can see the differences in the images.  The second image is using the L-enhance filter.  I have a pds130. Eq6-r mount and use a Nikon DSLR which I am not convinced is all nice and square within itself let along the focuser tube.  I guide with an OAG and ZWO220mm mini (seemed to make my guiding worse from my 120mm). 

I am just outside the recommended back spacing due to my OAG etc. About 59mm to a Badder MPCC coma corrector.

Corners seem to be doing different things and now I have an extra diffraction spike?!

If someone could have a look at the images and give me some guidance that would be appreciated. 
 

Thanks Brad
 

14 hours ago, bottletopburly said:

Try guiding in phd2 multi star mode and 1.5sec exposure ,what  rate is ra/Dec setting in pulse guide settings default is 0.10 

Pulse guides are 0.70 I usually switch up exposure on guiding from 1.5-3 depending on conditions. 
 

I had excellent conditions last night but guiding would still blow out to 1.1 in some spots of the sky.  Bad moon glow as well. Was guiding better during all 53 minutes of dark sky.   Just wish the mount was a bit more consistent. 

Hi everybody. Just a quick updated. The above methods fix most of the issues for this mount for me. The end cap nut was far to tight and a quick work adjustment using a voltmeter to pick out high spots worked well.   
 

it is consistent now but still not great numbers. Comfortable around .7” mark but does drop right down to .5. This just get ruined by large erratic spikes. 
 

Short of pulling it apart to rebuild it (still under warranty so won’t do that yet) seems to be the best I can get out of this iteration of the mount. 
 

Any suggestions welcome. 
 

Cheers

I have now slackened off slightly the nut against the roller bearing in RA after have trouble balancing and this has significantly helped that process.  Slight adjustments on the meshing of both axis and using a ammeter confirmed there is no binding or backlash. 
 

It will be interesting to see how it goes now being a brand new mount and have those minor issues before like many other if these easy tweaks fix it. 
 

Cheers

Thanks Michael.  Yes it was on the finished pec curve was all very nice except one patch. Has done it twice I will try once more and post an image of it. I am guessing it’s binding but I don’t identify it on slew so may need some help. 
 

I have found a few settings in PHD which were wrong including saying I have as calibrating at Dec -60 so maybe those few little changes will help also. 
 

RA is still very tight. I would say there is some level of stiction there. Does anyone know how to help that like that end shaft cap in DEC which was over tightened. 

Thanks 
 

1 hour ago, newbie alert said:

For pulse guiding In the northern hemisphere we should be calibrating on the equator ( so pointing south and on DEC 0/ meridian intersection.... 

For a oag the .5 camera loop might be far too short.. I use 2- 3 sec loop but I'm using a sct.

With multi star,  click the loop button, click the button to the right of it and it will pick it's own stars, then press guide button.. 

sweet thanks for that that’s where I calibrate now so all good. 
 

I always let PHD pick the guide star it just never picks multistars now for some reason. 
 

thanks for the info.  Always appreciated. 

On 09/11/2021 at 00:14, michael8554 said:

Hi Brad

Calibration looked good. The steps were slightly bunched up into pairs, indicating some stiction, but this didn't appear to affect guiding.

PA was good, 1.1arcmins.

You guided for 50 minutes, THEN ran Guide Assistant.

A shame, because then you mostly only made runs too short to see the trends with the suggested settings.

Best to Cal, then GA, then guide.

Your 9 minute session had good figures, RA = 0.58 arcsecs, Dec = 0.66, these should yield round stars.

With your final 7 minute run you slowed exposure from 2.5 to 3 seconds, and enabled Multistar.

MultiStar tries to compensate for Seeing, so exposures can be increased to as fast as 1 second, not decreased to 3 seconds.

At the end of your final run, RA and Dec shot off on their own and the guide star was lost.

If that wasn't you "shutting down", then there was probably a cable snag.

Michael

 

 

Thanks Michael

Good to know I am not doing anything weird contributing to errors. 
 

Ran GA after that time because I was recording PEC Curve. Which was great except one patch of vertical movement so I scrapped it.  Clearly something going on there. 
 

The multi star guide is odd as I always have that on and didn’t touch it at all. It never seems to work with OAG even if I can see multiple stars. Is there a way to force it? 
 

The following nights numbers were much worse which was frustrating as I have no idea why. I’ll get a couple of hours tonight to just go through it again. 
 

Can someone confirm for calibration what RA and Dec I should be looking to do this at. I thought it was easy or west and low to horizon? 
 

Thanks

Hello again,

The Dec seems to be MUCH better with the end shaft cap loosened and certainly balance is much better now. 
 

I think overall the mount is probably doing what it is supposed to although not great it’s under 1” mostly so I guess I can’t complain?

I was just wondering if someone with a bit of knowledge could take a quick look at a log from last night. Was perfect conditions so nothing else to blame.  At times where I calibrated it would settle to .5-.6” which I was happy. Still getting some spikes in RA. 
 

There is every chance I could do things better / differently and improve but I don’t know what I’m doing wrong unless someone tells me. 

Thanks very much for anyones times in advance! If anything else is needed please let me know. I’m planning on getting out again in a few hours. 
 

Cheers 🤙🏿

PHD2_GuideLog_2021-11-07_201900.txt

46 minutes ago, michael8554 said:

An interesting link Starflyer,  I will digest that TAE theory.

So Brad, a MinMo of 0.50 pixels will be equivalent to this many arcsecs:

Your guide image scale in arcsecs/pixel  x  0.50 pixels.

Michael

 

Perfect thank you Michael. That’s fairly obvious isn’t it but exactly what I wanted. 
 

My scales and min move are all good then. Just higher than I am use to seeing with guide scope. 
 

I always run guide assistant for a full work cycle and apply the recommendations. It’s very rare I try to be smarter than computer software! 
 

Thanks again. 
 

i will try to dig out some logs etc from my last run and then when I get out again after loosening off the end shaft cap as I have seen other guide graphs identical to mine on here. 

Can someone tell me if the min motion settings being recommended at .5 etc and quite high would be to do with switching to an OAG at 650mm?  I’m presuming it is and hasn’t thought about that. 
 

i did set up a new PHD2 profile as I switched over. 
 

Thanks

6 hours ago, newbie alert said:

Before you take it apart you need to cross off all the  other avenues first  such as balance, calibration, PA , shaft locking ring over tightened, belt over tension,  pulley oscilaton, too short a camera loop etc..

Have you got  a screenshot of your guiding?

A friend's eq6 r pro guides fantastic straight out of the box, no need to potentially introduce other issues.. taking it apart should be a last resort after you've eliminated all the other options ,and certainly not if it's within it's warrenty as opening it up voids it..

Yeah thanks. I’m still in the tuning phase. I don’t have the mount computer on at the moment. 
 

i spent today re tuning Dec backlash. The shaft end cap was def too tight and on d I backed that off enough so it was just holding the roller bearing etc all in place with no play the second axis was much easier to accurately balance. 
 

I’m pretty sure balance wasn’t right it as accurate as it could be but now it should be much better.  I also redid the back lash which needed some work. 
 

I will try this the next clear night. That shaft end cap issue straight of the box could be a regular occurrence. 
 

Thanks for your help team. 

45 minutes ago, rnobleeddy said:

I'd guess the belt mod might be the easiest solution? 

Thanks

It’s an EQ6-r it’s already belt driven. 

Hello everybody,

Such a great source of information here so thank you to everyone who shares their knowledge and I am after some more of anyone can help. 

I have a new EQ6 pro and the same issues that everyone else has with Dec backlash issues and saw tooth spikes randomly (not periodic). 
 

Excepting I can still do some Dec backlash adjustment to tune some of this out I am going to go full noise and replace the bearings, grease, and check for any anomalies. 
 

I will follow Astroblokes bearing replacement guide and tear down and have read a few others. 
 

What I want to know is if there is a guide for other areas or things to check along the way and parts I can or should clean up and polish. If I have it apart I want to tune and clean up anything that may help. 
 

Has  anyone tried the spring loaded worm gears for these? I saw them on an Australian site. 
 

The plan following that will be to get it back together and then concentrate on settings etc.   i don’t get any alerts from PHD2 but the backlash graph isn’t great and as I say guiding has plenty of corrections and saw tooth spikes randomly on Dec only. Guiding assistance gives me min move settings of .6-.9! RA is pretty good but still sets min move what I think is high at .3-.5. 
 

Cheers

8 hours ago, michael8554 said:

Hi Brad

650mm FL and 3.75um pixels gives a image scale of 1.19arcsecs/pixel.

Binning would up that to 2.38, IMO a more sensible value.

But depends on the guidestar shape.

Many setups have less than ideal star shapes.

PHD2 seems to cope, but worth testing both Bins on the same night in case Binning makes guiding worse :-<

Michael

Great thanks Michael. 
 

if anyone has any experience or updates from the above conversation I would like to hear how it went. 
 

Thanks 

Looking to switch over to my OAG on SW130 and ASI120mm has anyone got an update on this. I have very good dark skies and good seeing so would binning be better or am I better spreading the guide stars over more pixels or am I totally wrong with everything I said… cheers. 

I am having similar issues and PHD2 always throws up errors after calibration about not being able to make sufficient adjustment or similar. 
 

I have managed to get some decent images from this as an entry level mount for the price but the support and help is non existent.  They reply but have not actually offered parts of solutions to any of my issues. Terrible binding wobble and backlash.  I am still a beginner so don’t know what is ‘normal’ and not but I suspect a lot with this mount is not. 
 

it just adds to the learning curve of all the things you need to get across mount troubles are something you could do without.  
 

if you are across mounts already for the price as a beginner it’s good enough but don’t expect help fixing it. 

Multiple issues with obtaining good tracking mount wobble and backlash issues. Lots of fiddling around and it’s a good beginner mount. For the price it’s decent. 
 

I have not had any help at all from questions to Explore Scientific directly around the binding of the worm gears and issues. In NZ so I’m on my own for servicing and no offers of parts or assistance so be wary of the support.