Somethings not right, perhaps tracking?

[Peje]

As title,

I'm getting some strange results with my longish (up to 120s) un-guided exposures, I have seen it a bit down as low as 60s. Sometimes the stars seem obrounded / elongated and sometimes not. To get some test data I took three 120s exposures last night aimed at M42. Two images show the poor stars and one looks (to me) pretty much spot on. I've attached these below:

GOOD

BAD

My initial thoughts were that I simply wasn't getting a good enough PA. I'm using the Hour Angle method, I used the AstroShed youtube tutorial for guidance on this. With the results from last night, is it really likely its the PA? Surely if this was the case then all 3 images would be bad given it will need to track for a 120s exposure?

Another thought (after I'd packed up) was that perhaps I haven't unbalanced the scope enough, it is pretty balanced and I gather it should be made front heavy to compensate for backlash. A third potential issue is wind, perhaps wind is moving the scope a bit?

I have a guiding system (ST80 & QHY5L-II) but I'd really like to sort this out now to avoid complications later. One other thing (which is probably unrelated), last night when slewing my mount made a fairly noticeable 'clunk', this is only the second time it's done this in about 30 hours use. Anyone else noticed this? The scope was bought new from FLO in June so should be in good order.

Some additional info, I've been using FWHM focus option in Backyard Nikon to get the focus as best as i can (I've ordered a Bahtinov mask so I'll try that next week, weather permitting)

Any advice here would be greatly appreciated.

Pete.

[Pompey Monkey]

The NEQ6, as good as it is (I have a AZ-EQ6), still suffers from 20-30" of periodic error and this is not always smooth.

Take the plunge with your guiding set-up and you won't look back!

[Peje]

So you think this is just normal and it isn't the sign of something that's going to hamper my guiding?

I got the guide camera focused last night so just have to figure out PhD as I had some issues last night

[Pompey Monkey]

Yes, I think this is absolutely normal for this mount unguided. you could take half a dozen unguided 2 minute exposures: Five would be fine, but the sixth could be ruined.

Phd does take a little bit of fiddling, but it's worth it. My top tip is to set the exposure to "auto", but I don't know enough to say more than that.

Have fun!

[Starlight 1]

Had i same this week on Heq5 no PHD  working and was only doing 10s and 30s subs  so it do not add up ?

[dph1nm]

The trailing is in the RA direction. Given M42 is very close to the equator, polar alignment error would show up as trailing in Dec. So it is almost certainly periodic error (which is quite normal).

NigelM

[Starlight 1]

The trailing is in the RA direction. Given M42 is very close to the equator, polar alignment error would show up as trailing in Dec. So it is almost certainly periodic error (which is quite normal).

NigelM

Sounds good , did not think of this and I bin 300 subs

[Peje]

This is music to my ears. Though it is a bit disappointing but hopefully the guiding resolves this

[Starlight 1]

I just bin 300 like this as bad.

[Peje]

I just bin 300 like this as bad.

How long was the exposure for that one?

[Starlight 1]

30s you can see the Stars moving from right to left. I got some from 2 weeks ago when I had PHD on look better then this at 300s, So I am thinking he right about runing phd as it so low in the sky , so thanks for staring this post .

Les

[Peje]

That's great. I'm gradually building up the software, over the last month I've got using Stellarium, BYN, Astrotortilla so next on the list is PHD

[Starlight 1]

This is  what good programs are all about , I save a pic like this so when the program starts it use the pic and center on it , so every time you go back from night to night its all ways going to be in the same place as the last time out.

[Peje]

This is what good programs are all about , I save a pic like this so when the program starts it use the pic and center on it , so every time you go back from night to night its all ways going to be in the same place as the last time out.

Why not just use Astrotortilla? I'm amazed by how well it works

[Starlight 1]

For me SGpro as it do all . Go back to your post !!! may be best to check Subs as the night go on and save bining lots of Subs and take time in set up the mount even for little subs.

[Peje]

Yeh I'll probably keep a closer eye on it. I generally set up a queue with BYN then head back into the house for some heat and tv

[Peje]

I'm trying to justify buying pixinsight but it is pretty expensive software

[Pompey Monkey]

I'm trying to justify buying pixinsight but it is pretty expensive software

But it has DBE and SCNR and STF. And DBE

Certainly once I moved to a CCD, PI is the dogs proverbials for these two functions alone.

[Peje]

Those acronyms are?

[steppenwolf]

So you think this is just normal and it isn't the sign of something that's going to hamper my guiding?

I agree that this all looks quite normal - once you start auto-guiding all will be well and the guider will easily cope with what we are seeing here.

[Pompey Monkey]

But it has DBE and SCNR and STF. And DBE

Certainly once I moved to a CCD, PI is the dogs proverbials for these two functions alone.

Dynamic Background Extraction: gets rid of gradients in the image due to light pollution.

Subtractive Chromatic Noise Reduction: gets rid of the unnatural green (or red or blue) in the image.

Screen Transfer Function: does not do anything to the image per se, but does a superb stretch of the data so you can see wha'ts actually going on while the image is still linear  (much of the processing should be done before stretching).

[Peje]

No clear skies here so just had a crack at plugging everything in a faking a nights imaging to debug some errors I was seeing. Glitches were:

- EQMOD connection timeout to mount when taking a long exposure through BYN.

- BYN loosing connection to the camera.

- PHD2 crashed when I clicked 'loop'.

Last night I noticed that if I plugged the EQMOD USB into the PC directly the timeouts ceased. Tonight I did some digging in device manager and noticed an error associated with the powered USB3.0 hub I have outside for running cables to the mount, etc. I unplugged the hub and when I plugged it back in the error was gone and everything seemed to work perfectly.

I turned on tracking, set a 20min exposure, activated PHD2 (garbage image but it didn't crash at least)...after 20 mins I had no errors

So in short I think I just need to only switch on the hub when it's needed. Fairly simple but could make my life much easier, this way I'll be able to close the door and get some heat into the shed

[Pompey Monkey]

No clear skies here so just had a crack at plugging everything in a faking a nights imaging to debug some errors I was seeing. Glitches were:

- EQMOD connection timeout to mount when taking a long exposure through BYN.

- BYN loosing connection to the camera.

- PHD2 crashed when I clicked 'loop'.

Last night I noticed that if I plugged the EQMOD USB into the PC directly the timeouts ceased. Tonight I did some digging in device manager and noticed an error associated with the powered USB3.0 hub I have outside for running cables to the mount, etc. I unplugged the hub and when I plugged it back in the error was gone and everything seemed to work perfectly.

I turned on tracking, set a 20min exposure, activated PHD2 (garbage image but it didn't crash at least)...after 20 mins I had no errors

So in short I think I just need to only switch on the hub when it's needed. Fairly simple but could make my life much easier, this way I'll be able to close the door and get some heat into the shed

Welcome to the murky underworld of USB connected hardware.... 

My best tip here is to get it all working and then reboot your computer without disconnecting anything. If it all still works after that, reboot again and repeat a few times. If it still works, then set a system restore point. I call mine "Astronomy".  You can then always go back to a working configuration.

USB can be very fickle.

[Peje]

LOL I hope that's not necessary, that seems extreme...though perhaps in a few years when all the hardware isn't new I may need to employ such tactics. The astro PC will not be getting upgraded for quite some time given the money it cost to build. Can't even bring myself to move up to W10 as I'm afraid of driver issues. Think I'll wait til Spring in the hope that others have debugged the issues and the good winter nights are over

I've labelled all the ports with which device goes where & purchased high quality cable so fingers crossed this is the end of the issues for now.

[Peje]

PHD2 worked a treat, got a 7 min exposure of Deneb with no trails. I did a 8 min one but got a slight trail, this might have been a one off though. I am noticing a bit of flare on the stars, perhaps a focus issue??

7min ISO400

One new problem I've discovered, after a couple of hours the front lens on the ST80 was covered in condensation. Admittedly it was EXTREMELY wet today so it's likely the humidity was very high. Would dew heaters help with this?

Pete