lux eterna

15 hours ago, wimvb said:

Simbad found some 3356 entries within your approximate field of view. In all fairness, some of these are stars, some are double entries, but most are galaxies, quasars, etc.

Here's what PixInsight's solver came up with

 

Eg, the one called PGC126753 (bottom edge) is some 2.5 Billion light years distant. Nice catch!

Let´s see now, if we add all the individual distances together... how many light years would we have present in that picture 😉

Ragnar

Thank you @vineyard, @wimvb, @Pankaj.

How many, that is a relevant question. Something to think about when we are standing there under a sparkling night sky... It´s just like fireflies, right !

It is taken just 10 km from where I live. During these two nights the sky was SQM 21.45 resp 21.55 so between Bortle 2 - 3. The altitude of the subject was approx 59 degrees so pretty high in the sky, which helps a lot.

Ragnar

With so little time left of this season, I pointed my Meade LX200-ACF to Coma Berenices so I would get as many galaxies as possible in one single frame. Used a Nikon D7000, HEQ5 Pro and NexGuide. Two nights gave a total of 6-7 hours of 10 minutes subs (1600mm F/7.8 iso200).

Ragnar

6 hours ago, CedricTheBrave said:

This is indeed very interesting. 

would this cause what looks like a star vibrating?

I posted a question a short while ago about my HEQ5pro. I don't usually use it for visual but while checking focus i noticed that the star i was looking at was indeed vibrating and this could account for my struggle to get sharp images with my setup!

Hi Cedric,

Interesting you have a HEQ5 Pro and a D7000, just like me. I can tell that if you can get the D7000 modded it gets very sensitive for H-alpha, I like that.

Vibrating star, no I would not call it vibrating from the issue described above. It´s more like jumping, bouncing or dancing. Only If you can notice a very small (it´s hard to see, you need good seeing otherwise the atmosphere will overwhelm this) and very rythmic (0.6 second interval) "jumping" in RA only, then you have spotted it. And as I said, I can bet my bottom Swedish Krona that other mounts in the same price range have similar behaviour. I do get sharp images with my mount, even before making this fix, it´s just a tad better now - but only when seeing is good (otherwise it makes no difference at all).

Ragnar

Looks great, just continue adding data when possible for more depth. Maybe I would have made the backgound not quite so dark - there are some faint galaxies out there that could pop out a little.

Ragnar

1 hour ago, pete_l said:

Interesting stuff.

So we have two issues with steppers: the lack of torque in microsteps, where competing currents hold the armature between "natural" full steps - and inherent non-linearity in the motor's response. Possibly due to only having approximate sin() / cos() values, but more likely due to the  properties of the permanent magnet: hysteresis and whatnot.
It might be illuminating to see how your mount responds to more or less OTA balancing.

Yes, it´s the mismatch between the driver´s implementation of cos / sin functions relative to the physical properties of the motor mechanics. So different motors can behave differently with the same driver.

There is a some unlinearity (as seen in the video) even with zero load in RA, and I have not seen any change at all under load (holding a finger against the pulley).

Ragnar

1 hour ago, SyedT said:

I tried altering the nebula and star colour with that tool but it ends up blowing out highlights and adding noise. Might have to look at it again and maybe approach with some more gentle processing. Thanks for the feedback! 

The stars are quickly fixed with this setting.

/Ragnar

I miss the red colour in M42 that is present in the bottom image. Star shapes are much better now though, but with a quick "selective colour" in PS it is also possible to make them more blue instead of green (on my screen both images have green stars).

Ragnar

It is very easy to see if your mount has this behaviour or not. Just attach a long paper or plastic index to the RA drive like I did. No need to measure, you can see just by looking at it. I think you are right, this happens each 64 micro steps (= each full step).

(EDIT:  posted by mistake, continued writing again... )

I found interesting explanation HERE (under "Limits of Microstepping").

Ragnar

On 14/04/2020 at 16:30, lux eterna said:

... I also made an Arduino based device that injects pre-defined and very short ST-4 pulses into the autoguide communication stream (yes it´s true - and it works 😁 ) It does not make a huge difference, but when seeing is good I can notice a slightly better guiding. The point is to compensate for the very small speed variations in the RA motor during tracking (should make a separate post for that).

Here it is.

Ragnar

Hi all,

I have been using this with my standalone Nexguide for more than 2 years now, so about time to tell the world... I guess it would work the same with any ST4 connected autoguider.
It is not intended to be critical of the HEQ5 Pro, I just love it. I guess things like these takes place in many mounts except the most expensive ones. This is a story of what often happens when a stepper motor is driven with microstepping.

It started during collimation of my Meade LX200-ACF and I was inspecting a star with maximum digital zoom. I noticed that the star was "dancing", or jumping, very very little in RA at a regular pace. Later I found out that the stepper motor does not have a 100% linear motion during tracking :

I took this as a challenge, and also a opportunity to learn something about using a Arduino microcontroller. I also got a reason to get myself a (very cheap, usb type) oscilloscope. This immediately showed me that there is a voltage spike on each of the two stepper coils, that could act as a trigger for the Arduino to send a pre-defined pulse train on the ST4 port (the probe was connected via a high ohm resistor directly over the stepper coils). Designing that pulse train was later done by trail and error.

The below oscilloscope image is in fact two images (one for each coil), combined to one in PS. Time between a blue and a yellow spike is approx 600 ms (which corresponds to the dancing star that I estimated to be 0.5 sec). 

The above cirquit allows for the guider to have priority over the Arduino (via the two diodes to the right of the Arduino). I have set the HEQ5 guide speed to 1.0 (fastest) in order to minimize the pulse length of the guider, so it will free up more time for the Arduino pulses.
The "inpins" (#2 & 5) have no active role in this "RA fix", these are only used for monitoring the guide pulses which serves two purposes: 1) I can have a "clouds alarm" (= no active guide pulses) 2) I have programmed the RA fix to be active only when the guide pulses are active - this is because the RA fix could disturb the stepper motor during slewing (and guide pulses immediately stop when I start slewing so I use that for on / off switching). 

The pictures below show my first version which was built in under the hood of the HEQ5, but later I have included an intervalometer etc and put most of it externally (just the dual trigger devices are left internal).

Now things move smoother :

At last some live testing. The first image is during a manual slew in DEC (slowest possible) just to show the RA behaviour like in an oscilloscope. Of course no guiding here. The second is with guiding, while turning on or off this RA speed correction fix.

Having used this for a long time now, I think it needs good seeing to make any difference. But if that is the case, the autoguider will be less disturbed by the rather fast (0.6 sec) RA wobbling, and the result is clearly noticeable.

Ragnar

21 hours ago, Craney said:

 That just seems incredible....... from my back garden !!!!!!
 

I fully agree, and know exactly what you are talking about. Some time ago, I captured a quasar 12 billion LY away: This one 

So, "right after" Big Bang, this quasar was created and sent away photons in all directions - some of these in the direction that much later, when our galaxy was created, would hit our solar system, our planet etc. There was time for life and civilizations to arise, cameras were invented, the Sony factory made this specific sensor that happened to be the final endpoint for these photons - Splash. And we can see the result. Mind-boggling.

Ragnar

2 hours ago, Tommohawk said:

Yeah that's very nice - amazed that the HEQ5 can do that @ 1600mm. I'm hoping to do something similar with mine but my guiding is way off. Out of curiosity, any idea what your guiding RMS was?

Thanks Tom,

Me Too often gets amazed by this HEQ5 Pro. I have made some improvements to it, the simplest and one of the best is the DEC backlash killer. I also made an Arduino based device that injects pre-defined and very short ST-4 pulses into the autoguide communication stream (yes it´s true - and it works 😁 ) It does not make a huge difference, but when seeing is good I can notice a slightly better guiding. The point is to compensate for the very small speed variations in the RA motor during tracking (should make a separate post for that).

With the standalone NexGuide, I have no performance feedback from graphs etc so no idea about RMS.

Ragnar

16 minutes ago, alan potts said:

Superb image, as good as I have ever seen,, very well done Sir,

Alan

Thank you Alan, I am honored !

Ragnar

5 hours ago, Star101 said:

Please leave

 

Thanks ! (I promise 😉 )

Ragnar 

14 hours ago, vineyard said:

Hello, hope everyone healthy. So I went back to M81 earlier this month with my 4", and took longer exposures (and more of them) with guiding.  Still not a great image - too grainy for my liking & not a patch on some of the amazing M81 posted earlier today by @lux eterna (that's just incredible).

Stay safe,

Vin

 

Thank you Vin. One of the good things with this hobby is that you never reach any kind of finishing line, there is almost always room for improvement. My M81 is collected over several years, without intention when I started, but this time I just got the idea to add some more data to it. Because I had so many subs now, I could reject those with very small imperfections and still have 15 hours to stack.

So keep collecting, you have good data that deserves more company.

Ragnar

Thanks John !

Ragnar

Nicely processed, and still lots of details in the outskirts of the galaxy. Could be even better with colour...

I have done it myself but did not reach as far out as you have done.

Ragnar

Thank you @geoflewis !

Ragnar

Nice details there. I guess this is one of those that will not reveal much more without proffessional gear. So keep collecting colour data when possible and you will have one of the best M64 images out there.

Ragnar

Thanks @SyedT, I´m glad you liked it !

Ragnar

Thank you guys @silentrunning @Taman !

Ragnar

Hi Craig,

Yes, sometimes I have had the same issue. I usually run GX on a separate layer, then adjusting the opacity can lower that unwanted effect. And / or using a layer mask, (the mask can be made up from the main image, with extreme contrast to mask out this dark area to some degree). Experimenting with the detail & agressiveness settings can also help.

Ragnar

Hi Josh,

I would suggest to start with only the most obviously needed items (mount and scope). Use your unmodded camera without guiding, and try things out. Then add guiding, and maybe have your dslr modded. Or choose to get a (used) dedicated cooled astro camera by then. Or a already modded dslr to the same price as modding your own.

Ragnar

Thank you all @FaDG @JoshHopk @MarkAR @Craig a for valuable feedback. I have hesitated a bit, shoud I stretch it more or not, but I find this is more comfortable for my eyes.

Ragnar