The EQ3 DSO Challenge

[johnfosteruk]

I don't know why but I've not paid any attention to this thread, a wonderful collection of images that really push the boundaries of what the equipment can do, amazing

 

[Stub Mandrel]

8 hours ago, bobro said:

Slightly better Flame & Horsehead this time with the modified camera. Still need more subs to reduce noise. Polar alignment is causing trailing so will need to pay more attention to it. I like the blue of Alnitak though. 14 lights @ 6min, 1600ISO.

 

You've got the colour difference between the two nebulas nicely.

[Stub Mandrel]

8 hours ago, johnfosteruk said:

I don't know why but I've not paid any attention to this thread, a wonderful collection of images that really push the boundaries of what the equipment can do, amazing

 

We ain't pushing them, we're trying to find them

[Nigel G]

It's been quiet in here for a while, probably due to poor weather.

The weatherman promised a 2 hour gap in the clouds Friday evening, they were bang on. Why can't they be right when they say its going to be clear all night ?  

I made the most of the short gap. 13 x 360s is all I got.  At 800 ISO. 6 darks, 30 flats, 50 bias frames. 80ED, EQ3 guided, modified Canon 1200D. DSS & ST.

I tried binning less with StarTools at 75% with a much better result than 35% or 50%, I need to save up for a field flattener though.

For the short time taken I'm pleased with this  

IC 410, Tadpole nebula.

Nige.

 

[wimvb]

Wow, those tadpoles really stand out. Great.

If you can do that in a 2 hour gap, you must have a permanent setup, I guess. It usually takes me an hour at least to set up my rig and align.

Thanks for sharing.

[Nigel G]

1 hour ago, wimvb said:

 you must have a permanent setup, I guess. It usually takes me an hour at least to set up my rig and align.

 

 

I don't have a permanent setup, all I do is mark the patio where the tripod stands and just bring it in doors without adjusting it at all. Minimal aligning on setup, PDH does most of the hard work.

Scopes and cameras all get packed away.  

Nige.

[Peco4321]

My first ever capture of M101 Pinwheel Galaxy 35 x 25 sec ISO 1600, 11 x Darks, 20 x Flats, 20 x Bias, stacked as ever in DSS and stretched in GIMP, obviously need to get more time on this, but it was windy and cold, was a bit of a last minute session as the neighbours had bright lights on till late and I didn't quite have my mind on it, had lost my mojo for the night I think!!

Anyway, here you go, any pointers appreciated.

 

[wimvb]

Great catch. As you already noted, more data will improve the result. If you can increase exposure time to 1 minute, and catch 60 good frames, I think you can have a great image. It also seems to me that you are at the limit of what the Gimp can do. You can probably improve the image in photoshop or PixInsight.

Thanks for sharing

[happy-kat]

Or startools which is considerably less expensive.

[Stub Mandrel]

11 hours ago, Peco4321 said:

Anyway, here you go, any pointers appreciated.

A good start!

You can get more out of your data. I upped the gamma quite a lot, then moved the dark point until the background was dark again. I then duplicated the image as second layer, which I set to screen. If you 'pre stretch' in DSS by aligning the histograms, steepening the luminance curve and then moving the steep part you should get more out than this (yes this is your data!):

 

[Peco4321]

5 hours ago, Stub Mandrel said:

(yes this is your data!):

That's great, thanks for your efforts. Cloudy nights will give me plenty of time to improve processing, but it's great to see what's possible. 

[Stub Mandrel]

I posted this last night as a 'smash and grab' as I only had 31 subs before a cloud white-out and nearly half of those were useless because of haze/cloud. I retook my flats and got a better result, still a bit noisy, but hey, it was two months wait for that 60-minute session!

 

Edited March 3, 2017 by Stub Mandrel

[mikey2000]

I'm looking for guidance on guiding! (Sorry about the pun)

 

 

I had a clear night last night and finally got it all working without crashes, timeouts or anything bad.  But the PHD2 results were disappointing.  I had hoped to leap from 45s subs with a high fail rate to these 200s+ subs people seem to achieve.  Not so easy after all.

 

I find it hard to get RA guiding to less than 4 arcseconds RMS.   I seem to have DEC nailed down to consistently less than 1" RMS after using the PHD2 Drift Align tool (It's ace!).  It seems RA swings back and forth +/-4" with a short period (eg 3 up, 2 down corrections repeatedly overshooting the centre line).  I used 3s exposures to even out the seeing.

 

I'm using a Skywatcher EQ3 Pro Synscan, PHD2 EQMOD connected by USB to Serial Adapter to Handset (PC Direct Mode, No PEC applied in eqmod or handset) QHY5L-ii and  QHY130mm mini guidscope.  150PDS and Ascom Pulse Guiding.  Here's a guidelog It has two big downspikes (PE I think - they are about 11 mins apart) and a few big upspikes (wind, I think) PHD2 guidelog the new PHD2 beta AutoPecDetect algorithm  You can see the sawtooth quite clearly, it's the same with the usual Hysteris algorithm too.  I used the settings suggested for by the PHD2 Guiding Assistant.

 

I tried a few 60s frames at around 0 DEC and as expected, I saw star trails around 8" (arc seconds, not inches!) long.  That's the +/-4" swings then.   Now, I'm imaging at 24mpixels which is going to be quite demanding, I realise.  But if I resize the output to 1/4 size (ie, 6000x4000 becomes 1500x1000) I can still see slightly eggy stars.  Fainter stars look like little streaks.

 

I'd like to somehow remove the +/-4" oscillations from the guiding.  Even +/-2" would be much better.  I wonder if a big increase in the RA min-move parameter would be a solution, or perhaps decrease the agressiveness.  Or maybe there is some kind of lag between guide commands and mount response?  I could see how that could result in overshooting.

Any tips would be much appreciated!

[mikey2000]

Just in case I'm doing something really silly.... In PHD2, I chose EQMOD ASCOM HEQ5/6.  I think I got that from the QHY website when setting up the camera initially.  Is that the best choice?

[bobro]

20 minutes ago, mikey2000 said:

 

I'm looking for guidance on guiding!

 

As I'm hoping to soon start testing out PHD via an Arduino, I spent a bit of time today looking at your guiding graph. Initially  I didn't think I could offer anything in the way of help as my current setup is Lin_guider. Nevertheless there are obvious similarities, so here goes.....

My comments assume that a good guide star was used and so wasn't a source of the instability - I don't know enough about PHD to tell from the graph. RA guiding continually oscillating about zero is often a sign of overguiding. I can see this with my setup if the gain (Aggressiveness) is set too high, so this is something to look at. I'm not convinced this is the real reason for the oscillation though. Your setup is using a 3 second guiding exposure. This seems quite high and will limit the responsiveness of the guiding, possibly resulting in guiding corrections being large. As a comparison, my guide camera cannot do long exposures, which results in Lin_guider issuing guide corrections of up to about 8 guide corrections each second. Due to the frequent guide corrections I need to set the RA Aggressiveness to a low value. The end result is guiding that is relatively responsive. 

I note that your setup typically issues a guide correction each 3 seconds - this is also a sign of an overguided system as there should be periods where guide corrections are not required, especially with a stepper motor driver (my setup is a simple dc motor so underlying accuracy isn't great). 

Some suggestions -

1) capture a guide graph with RA guiding disabled to see the underlying accuracy of the setup

2) shorten the guide camera exposure to allow more frequent guide calculations

3) try reducing the RA aggressiveness 

Hope this helps - perhaps someone with more experience of PHD will come along and offer better advice.

[Nigel G]

1 hour ago, mikey2000 said:

 

I'm looking for guidance on guiding! (Sorry about the pun)

 

I found these videos very helpfull, my first try was spot on.

Nige.

 

[bobro]

Not much opportunity for imaging recently, so I've been putting together a DIY 1.25" Coma Corrector. See :

Hope to be posting images here with it before too long! (If it works .)

Bob

[mikey2000]

Nigel - thanks for the video link.  I think I learned a lot and I can't wait for the next clear night (probably some time in November judging by how February was....)

[alacant]

On 3/3/2017 at 21:28, mikey2000 said:

I'm looking for guidance on guiding!

Hi. I think the saw-tooth could be reduced by lowering the aggression and upping the hysteresis. But using hysteresis for RA, not ppec. HTH. 

**send your logs to the devs anyway as they are testing the ppec beta ATM.

[Nigel G]

I had a couple of hours Monday night with clearish sky's so I done a little test.

I set the tripod up on its marks, checked Polaris and it was in the right place in the polarscope. ( using polar finder ).

2 star aligned then aimed at M51.

Fired up PHD2 and chose a star in the field of view, done a manual nudge to get North and West correct. then calibrated.

I did not enter the star altitude.

I did not do a drift align, but went straight to guiding.

Just 20 minutes to start imaging.

The mount guided perfect for 1.5 hours until the star was lost due to dew on the guidescope  

I need to sort out dew heaters or something, only an hour and it started building up which has ruined the image.

Cheers

Nige.

 

[wimvb]

14 minutes ago, Nigel G said:

Just 20 minutes to start imaging.

The mount guided perfect for 1.5 hours until the star was lost due to dew on the guidescope  

I need to sort out dew heaters or something, only an hour and it started building up which has ruined the image.

Cheers

Nige.

 

Done that, been there. (Never got the t-shirt ). Made a dew heater for my st80 guide scope, but didn't really solve the dew problem until I also made a dew shield, which extends about 30 cm or more in front of the scope lens.

[Filroden]

21 minutes ago, Nigel G said:

Just 20 minutes to start imaging.

That's amazing. It takes my 25 just to get the kit into position and connected!

[mikey2000]

That's quick, Nigel.   Could you give me an idea of how well your PHD2 works, maybe in terms of arc seconds (eg peak to peak "normal" deviations)?

[Nigel G]

Will do Mikey as soon as I  get home ?

[Nigel G]

On ‎08‎/‎03‎/‎2017 at 17:03, mikey2000 said:

That's quick, Nigel.   Could you give me an idea of how well your PHD2 works, maybe in terms of arc seconds (eg peak to peak "normal" deviations)?

As I set up Polaris was in the right place so polar alignment was good.

PHD2 was peaking at 6" maximum normal adjustments 2-3" main adjustment was on the dec, ra was good with very few inputs from PDH.

I thought I should mention that my EQ3 has had an Astrotec service before I got it which apparently improves the mount a fair bit.

If you get a good result from PDH drift aligning you shouldn't have any trouble.

Make sure you manual drift to let PDH know whats North and West, then calibrate.

I use the ST4 cable and on camera mount connection so I still use the Synscan handset to choose stars and objects, not EQmod.

Nige.