Jezphil

On 05/07/2022 at 18:28, newbie alert said:

Mid Kent is that the bredhurst one?

I'm a SEKAS member

Yes, that's correct. 

22 minutes ago, newbie alert said:

Great that you have it sorted..

Eden bridge isn't too far from me,. I'm in Ashford 

Ah - it's within striking distance of London and Bortle 4(ish) in the countryside there. I'm an MKAS member, so another Kent astronomy link there.

On 02/07/2022 at 21:20, newbie alert said:

A couple of points here flag up, the parts circled can show up as tilt... You don't need the nose cone on the reducer as it can screw directly onto the focuser with maybe an adapter... And the thumbscrew on the extension can throw things off line...

Btw, what's the spec on the spacing distance, yours looks quite a bit more than usual..

Good job that you're using solid baader shims rather than delrin, as they introduced tilt on my 460

Thank you - yes, you nailed it. Many thanks and I tested the corrected spacing last night in a field outside Edenbridge and I now have round stars. The camera now screws rather than clamping to the filter wheel which I am sure was indeed a dodgy connection. The other clamp you highlighted goes into a Starlight Feather Touch focuser which seems very finely engineered and snug and doesn't seem to create an issue. 

On 03/07/2022 at 16:50, david_taurus83 said:

Yes, I'd say that's a tad too much! Do you have a 20mm spacer?

Okay, I ran test frames last night after switching in a 20mm spacer and screwing rather than clamping the camera to the filter wheel to avoid sensor tilt. Back focus was the correct 55mm. I have round stars in the margins at last!

Thanks so much for your help on this - you totally nailed something I hadn't understood and that's been bugging me for a long time and I am hugely grateful. I am sending a virtual beer to Birmingham which, apologies, I know isn't as good as an actual one.

I got back home to London, after testing in a field out of town, at 5am this morning and accidentally set off the house alarm, waking up the family. So if you also offer marriage guidance counselling... ?

13 minutes ago, david_taurus83 said:

Yes, I'd say that's a tad too much! Do you have a 20mm spacer?

Correction: I measured to the wrong part of the camera, but it is still well over...

filter wheel: 22mm

sensor set back 13mm

cone to edge of camera housing 32mm

total 67

...so I am 12mm over.

I don't have a 20mm spacer but will get hold of one. I need to figure out the correct widths and thread sizes.

16 hours ago, david_taurus83 said:

That looks like way too much between the camera and filter wheel. If the EF2 is 22mm and the Atik has 13mm to sensor, you should only have a 20mm spacer to make up the difference as the SW reducers are usually only 55mm requirement. That spacer looks more than 20mm to me. Also, you should have the camera threaded as close as possible to the filterwheel and the spacer between filterwheel and reducer if possible. 

 

Edit: You should have this much spacing between end of camera to the reducer.

Hello David

Thank you for this. That total distance is: the filter wheel at 22mm + 55mm to the end of the camera housing as illustrated by your blue lines above. So that is 22+55=77mm, plus an extra 13mm to the sensor. So 90mm! And this should be 55mm? Blimey. Does this make sense? I am way, way out, right?

6 minutes ago, Budgie1 said:

If you decide you need the rotator linked above, make sure to check that it will fit where you want it too. This rotator normally screws directly onto the standard Sky Watcher focuser draw tube and the reducer/flattener then screws onto the rotator. This configuration won't work with your Starlight focuser so it will have to be located somewhere else in the train.  

Thank you - yes, I need something to screw at one end to the ATIK 460EX camera and at the other end to the EFW2 filter wheel, keeping that distance 34mm so the back focus is correct. I think the rotator is less than 34mm, so I am looking into a solution. I think the weak point is likely to be the camera filter wheel connection, rather than the reducer/focus tube. 

11 minutes ago, newbie alert said:

A couple of points here flag up, the parts circled can show up as tilt... You don't need the nose cone on the reducer as it can screw directly onto the focuser with maybe an adapter... And the thumbscrew on the extension can throw things off line...

Btw, what's the spec on the spacing distance, yours looks quite a bit more than usual..

Good job that you're using solid baader shims rather than delrin, as they introduced tilt on my 460

Thanks - yes I think there were indeed too many spacers. However, there are fewer spacers now than you see in the image - 2mm of spacers - as I removed a couple. It didn't make any noticeable difference to the issue. And that reduced amount was what I used for the test frame above. The cone on the reducer fits into a Starlight FeatherTouch focuser which I use as replacement for the original SkyWatcher one. It doesn't have a screw thread, just a clamp. But it's quite a high quality part with a wide opening/fitting for the wide cone, so perhaps the issue is more likely to be the camera with it's thinner cone going into the filter wheel clamp which doesn't seem to be as well engineered. It has just one screw operating the tightness for example. The star-shape issue was the same before I fitted the new focuser - i.e. when the reducer was screwed directly into the original SkyWatcher focuser. So this also makes me think maybe the camera into filter wheel junction could be the culprit. 

The distance between the camera with cone screwed off to the filter wheel is 35mm, so I think the rotator in the link above would need an added piece of tubing to keep the back focus correct. I will have to try to figure that out. 

Ah - thank you so much guys. I really appreciate the time you have taken to respond to this issue, which has been bugging me for a long time.  What an amazing community astrophotographers are.

Regarding the red lines above showing the direction of elongation - yes, this makes complete sense and yes, the camera is clamped to the filter wheel. This had been a concern to me and I had tried to solve it by loading the image train vertically, and very carefully, but was always concerned that the clamping mechanism was still creating an issue. Obviously the electrical tape you can see in the image was a slightly desperate and vain attempt to keep things perpendicular.  I will definitely try a threaded connection now. 

Regarding the SkyWatcher Evo rotator link above - thank you for this really helpful guidance and I will now go down this route. I will need to make sure the back focus is correct.

17 minutes ago, newbie alert said:

Can you attach a JPEG of the image as I presume it's a fits file? Can't open on my phone.. also what's the scope and method of attachment, ie solid screw fittings ?  Any spacers like delrins?

 

Thank you - here you go. Scope is a SkyWatcher Evostar 120ED Pro refractor with a SW 0.85 flattener/reducer. There is also an ATIK EFW 2.2 filter wheel in the image train. I have tried the delrin-type spacers in various combinations but they don't help. The camera slots into the filter wheel. Image of this is also attached. 

10 minutes ago, Nigella Bryant said:

I suspect it's coma as there's evidence of elongation on all four sides. Less so top right but nonetheless it's there. Most elongation seems equal on the other three side's. I'm definitely no expert so I'll take my leave and leave it to much more experienced deepsky imagers, which no doubt will give a better understanding of what's going on. All the best. 

Thank you Nigella - useful and much appreciated. Yes, there is the effect on all four sides. Oriented in different directions though - wonder whether that still means it is coma? 

Am I experiencing sensor tilt here? This is a stretched single sub-frame. My guiding was good at around 0.6 px RMS. I have tried spacers in various configurations but they haven't helped. I am using an ATIK 460EX mono CCD, which doesn't have a large sensor: a  SONY ICX694AQG, 12.49mm x 9.99mm. Any thoughts would be very welcome.

WR134_300sec_1x1_WR134OIIILightsn2_0019 stretched.tif

13.8V supply now ordered for this. Thank you everyone for your help and advice. Much appreciated - what a great community this when you need help 👍

Just now, Jezphil said:

Yes, it's the branded one actually supplied by SkyWatcher that came with the mount and is noted on the back as 12V and 5A. I am using it purely for the mount, nothing else. Why wouldn't they do it for slightly more than 12V to avoid issues with under powering? Posing this HEQ5 with slightly more eradicates the issue, I have found. And I think that's what others have found also, from what I have seen.

Mount and adapter are around two years old btw. 

2 hours ago, StevieDvd said:

Did that psu come with the mount - and are both new? It's 12v but what amperage.

There are many SW mounts that can use a 12v supply but the amps may differ slightly, for example the AZ-GTi needs far less amps (min  750mA) and a psu from 7-14v

 

Yes, it's the branded one actually supplied by SkyWatcher that came with the mount and is noted on the back as 12V and 5A. I am using it purely for the mount, nothing else. Why wouldn't they do it for slightly more than 12V to avoid issues with under powering? Posing this HEQ5 with slightly more eradicates the issue, I have found. And I think that's what others have found also, from what I have seen.

1 hour ago, StevieDvd said:

To answer the last part of the question about higher voltage, the answer is that they do.

See HEQ5-Pro specs it can take 11-15v so a 13.8v supply  (like a car battery etc) is within the range allowed.  Always good to see what the manufacturer states as required.

I read in later SW mount manuals where 11-15v is specified that the 11v needs a higher amp rating quote:

"Output Current: 4A for power supply with 11V output voltage, 2.5A for power supply with
16V output voltage."

So perhaps the psu you have does not have enough amperage to supply a steady 11V.

 

Thank you. I was referring to the power adapter which only supplies 12V as I understand it. Why not make that, say, 13V when 12V can create intermittent issues like I experienced? Great that the mount itself can go to 15V but they could bump up the power from the adapter. It just seems that 12V adapters are on the edge of being too low for the HEQ5, or that they aren't that reliable and maybe can easily be delivering below 12V. It doesn't allow much margin for error if the voltage from the adapter is slightly low maybe? 

Ah - apologies. Yes, I ended up getting volts and amps confused!  Anyway thank you for this link below, which is really helpful and I will go for this as a solution...

https://www.firstlightoptics.com/batteries-powerpacks/nevada-psw-30-25-30a-switch-mode-power-supply.html 

14 minutes ago, fozzybear said:

I use one of these left over from my Amateur radio days and serves me fine with various outputs 

Thank you. So that's 10A. Is that what you are using? I was thinking 12A was too low. Or is your one higher amps?

3 hours ago, Padraic M said:

Yes the HEQ5 doesn't like a voltage below ~11.5V. When you draw current from the PSU, the voltage will drop and the mount can behave erratically. I use a 13.8V Nevada Radio PSU and it works perfectly.

Thanks for this. Would it be this you are using?...  https://www.firstlightoptics.com/batteries-powerpacks/nevada-ps-08-6a-8a-regulated-linear-power-supply.html

When I use my 12V Skywatcher power adapter for my HEQ5 mount, it works only intermittently. Sometimes simply refuses to budge or react in any way on instruction to do so.  If I run the power at 12.8V however, from a Primalucelabs Eagle4 mounted on the scope, the mount works fine. I've read somewhere that 12V is actually slightly low for an HEQ5 mount. Anyone else encountered this issue? Why don't SkyWatcher slightly bump up the voltage, say to 12.5 or 12.8 to account for this?

On 23/12/2021 at 14:51, david_taurus83 said:

Can't say I've seen this effect on mine or any other 460's. Below is a single sub but no sign of microlensing.

Hmmm... looks perfectly clear. Thanks.

9 minutes ago, david_taurus83 said:

Are you using an ASI1600 or similar camera with same sensor? This is well known issue with this sensor and bright stars. Yours doesn't look too bad though. I have seen worse! Still a great image. Nice, tight stars!

Hi

Thanks - I am using an ATIK460 CCD monochrome cam.

On 19/12/2021 at 09:07, Ags said:

A lovely image, regardless of the grid!

Thank you! Here is the finished version.

Please can anyone help explain what the grid is that is appearing over the stars in the bottom right quarter panel of this mosaic (from a blue filter only)? There is a criss-cross effect and I have no idea what has caused this. It appears very subtly in the other frames also.  Thanks in advance.

Thank you for your help. The coordinates of my location in EQMOD had, inexplicably, reverted to default, giving a location thousands of miles from where I am. That was the issue - the scope is up and running now successfully. All good.