ONIKKINEN

Was taking 60s subs of abell 1656, the coma cluster and a bright trail caught my eye. Found it amongst the subs and saw that it left what looks like a trail of some sort that persists for at least 2 frames, but i think the third one still shows a mark of the event. There was a dither in between so possibly visible for more than 3 minutes. Re-entry of a space rock or one of Elon musks toys?

Cygnus, and with it the summer milky way is rising again, had a look naked eye and with my 7x50 Nikons just cruising through the endless starfields. Nicely visible from a bortle 4 location without the moon in the way, but the feeling is bittersweet as Cygnus rising signals the end of the season is at hand.

M13 and M3 were also quite nice from these skies with the binos, if a little small. Usually have trouble finding them but not this time from much darker skies than i am used to.

Before the scope hits the tripod or some cable snags happen. If thats not happening then not maybe necessary, so the same as southern meridian crossings.

2 hours ago, Stu said:

I believe this is fairly standard practise from OO, I took a mirror out of a 12” scope a while back and found the same tape, actually there was much more than in Magnus’ picture, but no silicone. It was a pain to remove, I don’t understand why it is needed if the cell is doing it’s job properly (which it looks to be capable of)

My 8'' dated 2020 has the tape and some blobs of silicone, but not nearly as much silicone as this one here, i think the mirror cell in question here might be a bit of a monday morning product?

The tape in mine seems a bit redundant, but at least it doesn't feel like its in the way. It doesn't really hold the mirror tightly, it just sort of loosely sits there around the mirror and the clip holders so for me i doubt it could pinch the mirror, or really hold it in place so its just useless. I can wiggle the mirror a bit on the cell if i try, but i do have to try so i guess my cell is working more or less as intended.

13 hours ago, ninjageezer said:

Thank you but the HEQ5 pro mount has no usb port only the handset has one from what i can see ,no idea what its for.

You could do what i wrote above, connect to that with your PC and control the mount through the handset. In this configuration you can issue go-to commands from your PC and the handset, and both know where the mount is pointing towards.

Like above, i think less than half of imaging resolution and similar errors in both axis is good guiding. No obvious excursions in declination and a periodic error that is in check is key here. I use the predictive PEC algorithm in PHD2 and it seems to be doing a decent job of keeping my somewhat poorly figured RA worm gear in check.

But looking at the guide graph can be misleading, especially with a newtonian and you may have good guiding without round stars. That is, i believe, due to mechanical issues with most off the shelf newtonians including: Focuser slop, tube deforming, mirror cell stability issues, secondary holder issues and more. All of these issues will lead to effectively taking your scope out of collimation randomly and during the session. Your guide scope (if using a guide scope) can still report decent guiding because its not aware of the other issues, unless the guide scope attachment method is also sub par (also common with newtonians). Experts here recommend OAGs regularly for newtonians for these reasons, and im beginning to see why since some issues still persist for me even though i dont think they are related to guiding exactly.

I will probably make the jump from a guide-scope to an OAG some time in the near future because i see "good guiding" but still varying decrees of issues with the actual subs.

You can also use the USB port (assuming you have one?) on the mount or hand controller to connect to a PC. If you connect to the hand controller you can use both the hand controller and some software with your PC to control the mount. In this configuration EQMOD does not work.

If you connect to the mount USB port you can use EQMOD to control the mount, but now the hand controller cannot be used (or be plugged in).

With the handcontroller route you will need to use Skywatcher ASCOM drivers to control the mount, and need to download and install working Prolific USB to serial drivers. The one on Skywatchers website did not work for my AZEQ6, manufactured in 2022, but does for my EQM35 manufactured in 2020 so i believe Skywatcher just hasn't updated their site for a while.

The benefit of either of these is that you do not need to buy the extra cable. But the dedicated cable is probably a bit more reliable and most use that to connect to a Skywatcher mount.

1 hour ago, kirkster501 said:

Superb image, I love the double cluster and you've captured it perfectly.   However, there is more colour in the stars than you have been able to show and I think you should push the saturation up slightly more.  I;d love to see it when you have because I love the way you have tight stars and have it framed.

May I show mine on your thread by way of comparison??? I like your framing better but I managed to get more colour. You've inspired me to have another go at it in autumn so that I can get rid of the slight haze I have in my version.

Double Cluster with FSQ 85 and Atik 460 | SK Astro

 

Yours is very nice! I kinda like the "ethereal" look to the haze in your shot. Almost makes it look like a galactic halo sort of thing, really nice touch 👍. You could have spun it as a choice in processing rather than something you wanted to get rid of and i would have believed you 100%.

I do agree seeing yours that my reds are not as vibrant, but yours still doesn't look oversaturated at all to me. Maybe ill have another go, i still have the data somewhere in the terabytes of data i have stored in one of my hard drives.

For me this target is available round the year at 60 degrees north, one of the perks of northern astrophotography that some targets are always available. Well maybe a bit too low at its lowest, but visually no problem and i check this every time i convince myself to put an eyepiece in rather than a camera.

2 hours ago, mackiedlm said:

I dont generally get much out of star cluster images and tend not to image them myself. But I think that image is strikingly beautiful.

I sometimes image them as secondary targets like i did with this one, doesn't need a long integration and the worst thing that could happen is loss of 30 minutes. Most dont look nearly as interesting as the double cluster though.

There are several bright stars within a few degrees of NGC 4236 and some of these can be in a sweet spot where they just about hit the edge of your coma corrector and cause reflections off the lenses, at least thats what i think happened for me (i am also imaging the galaxy).

See the rainbow reflection thingy in the bottom left? That happens when i have a bright star at just the right distance from my image center.

Also had the same happen on a few other targets so its not unique to this target, but i do find that the range of distances is quite narrow. Just a bit closer or further and this goes away, but it can actually be worse than it is in my shot if i get just a bit further away from the bright stars.

Now it doesn't really look the same to me, yours looks more like a flats/gradient removal issue rather than a well defined halo like mine, but something like this could play a part as well.

19 minutes ago, vlaiv said:

I have algorithm that will keep all the data and use most of it .

I just don't have time to implement it - but hopefully that will change soon.

We often use deconvolution on final stack to sharpen it up - but that is really not the best way to use deconvolution. Most deconvolution algorithms are designed with simple premise in mind - there is some read noise and some Poisson / shot noise and image has been blurred with known kernel.

When we deconvolve stacked image - it is no longer simple statistics. We have changed noise statistics when using interpolation for aligning and stacking combines individual PSFs / blur kernels into very complex shape. We then use approximate blur kernel for deconvolution.

My idea goes like this.

We split data into three groups - subs at target FWHM (with very small variation from target FWHM), subs below target FWHM and subs above target FWHM.

We stack subs with target FWHM to get reference PSF.

For each sub below target FWHM we derive convolution kernel by deconvolving reference stars with sub stars and averaging result. We use this kernel to convolve stars in sharper images to make them same as reference frame. We do similar but opposite thing with subs that have higher FWHM - we find deconvolution kernel and then deconvolve subs.

After this operation all subs will have about the same FWHM (this will also correct for star elongation if we form reference from subs with round stars). Subs from below FWHM group will have improved SNR, while subs from above FWHM will have worse SNR.

In the end we need very good adaptive algorithm that can take into account different levels of SNR (per pixel not per image as there is no single SNR value per image). I already have that bit implemented.

Above should produce better SNR than throwing away poor subs - without loss of resolution.

If i understood you correctly with how it works, i think this kind of automated process on subs of various quality would be almost revolutionary for astrophotography processing?

You are a seemingly endless well of knowledge and wisdom when it comes to this hobby, thanks for sharing some of that with us mere mortals.

2 hours ago, Catanonia said:

The process for those wanting to follow - Basically a summary

For my scope and camera combination I should be aiming at 1.5"/px

If I bin my data by 2x (software or hardware) on 2000mm @F8 then this will be almost twice as fast as using a 0.67 reducer @1400mm and F5.3 and no loss in resolution.

Therefore I will only use the reducer "if and when" I need a larger FOV for a target.

 

I will do software binning in PI

The workflow is as follows for me on OSC ZWO 2600 MC Pro

• Calibrate all images with darks, flats and bias
• Blink images and remove bad ones
• Perform a SplitCFA process on the calibrations to split them into CFA0 (R), CFA1(G), CFA2(G), CFA3(B) channel directories
• Combine the 2 greens directories into 1
• Align all the images to a reference one with ImageRegistration
• ImageIntegration to produce Red, Green and Blue channels
• Perform an IntegerResampling 2x bin on each of the RGB channel integrations
• Use LRGBCombination to bring them back to a RGB image
• Process as normal

 

This workflow is more or less what i do in Siril to my data. It looks scary but once you get used to it its just another step in the voodoo magic of astrophoto processing and its not that big of a hassle in the end. Splitting has some very small benefits to debayering and then binning, but everything in AP processing is done to get a small gain so why not do it i think.

I dont blink my data, or really visually inspect the subs in any way for that matter. I just use statistics measured from the subs to weed out the bad ones. I use measured FWHM, star roundness, background levels and SNR to make the decisions. In Siril i use the dynamic PSF function to create a plot of all the subs and its just a few clicks to determine what gets kept and what gets thrown out. I think in PI you could use the subframe selector tool to do the same, but with much better stats than what Siril can provide. Blinking can be fun to see asteroids and other anomalies in the subs, but other than that i dont give it much value for determining whether the sub is kept or not.

Sometimes after a night i see that almost all the subs are less than ideal and they get thrown out, but with long integrations i care less about losing a few hours of data since its nowhere near done anyway. I have 2 in progress projects that are at 15+ hours so far and i estimate i may need to double that to reach a result that i really like, so whats losing a few hours when im looking at 15+ hours of more in the end? For the most demanding objects i see that i not only need a long integration, but also will need all of the data to be better than average to get a sharp and deep image in the end.

Actually i have not used Pixinsight either, the script i use is for Siril.

The command in question for Siril is seqsplit_cfa "your sequencename".

I would be surprised if PI doesnt have the same feature though.

14 hours ago, Grant93 said:

Cheers! Ill try this

Uhm it was around its meridian, about 40/50 degrees. But this has been happening a while on many of my captures on many different targets using the ZS61, I've been aware of it, just blissfully ignoring it 😅 Now wanting to perfect things I wanted to figure out the issue..

Right, that altitude will have an effect but its probably not the thing you're after.

I have 2 different T-rings for my 550D and both are loose fitting and i can rattle the camera in them a bit. I fitted some aluminium tape around the "groove" which the camera flange attaches to and they were snug afterwards. If you have the same kind of T-rings its an easy fix. Not sure how much that helps if there is tilt but it wont hurt and will make subsequent troubleshooting easier with that out of the way

Rising Cam to the rescue again?

Be interesting to see if they lowball ZWO and QHY prices like with the IMX571 cameras.

To me it looks like atmospheric dispersion is playing a not insignificant role in the elongation of your stars. Blues and reds are on the opposite side, as they refract through the atmosphere at different rates and so can land a few pixels apart on your sensor.

How high was Leo when shooting? I find this issue just about perceptible at somewhere around 50 degrees and increasingly distracting at lower altitudes. Anything lower than 40 and i find colour channel alignment after stacking a necessity rather than a bonus.

Im not a refractor owner myself so couldnt tell if chromatic aberration from the optics could separate colours like this but the atmosphere definitely will.

Decreasing light pollution as the night progresses, or the target getting higher in the sky, probably both.

Some street lights are dimmed in the AM hours of the day, or even shut down. I notice that some patches of highway around here have only every second light on at the lowest traffic hours of the night. Some folks might also have their yard lights off for the night. Most businesses shut down lights at least partially at some point of the night and car traffic producing extra lights is at its minimum. All of these are small effects but it adds up and there can be a real noticeable difference in light pollution in the weird hours of the night.

But usually this isn't a shocking difference, but maybe a 10% reduction overall. Did you check your secondary mirror for dew? Or a coma corrector lens (probably the tube facing one) if you have one. A thin film of dew can be difficult to spot without shining a light directly on it so it might just seem like there was no dew but really there was. I sometimes got dew on my secondary before i started using a dew shield, which then made the problem go away even for the worst nights.

Great detail in the core and everywhere else, beautiful image!

I do agree with cajen2 with the greens though. Try running SCNR (green noise removal) to fix it? Tried it in SiriL and seems to fix the green cast very nicely.

Also, forgot a simple method of testing the flats.

Just look at your calibrated frames from all over the session. All of them should have their flats applied the same way, but if some of them have the donut or some other problem in them and some dont you will know that some subs were in a different collimation (due to anything, focuser, mirror etcetc) than the flats.

Yes, you do need darks even if the camera is low noise. Its a pretty clear cut case, examples below:

First calibrated without darks:

Then calibrated with your bias frames as darks (and bias frames):

Now the problem isn't completely gone as i can still see the outline of the 100% illumination zone as the darkened area, because you really would need to use darks to make this work properly.

Another issues to keep in mind would be more mechanical rather than data handling. Did you move the camera before taking the flats? Did the scope sit in sunlight and warm up? Many things can happen with newtonians that ruin flats because the primary mirror can move in the bottom. Thermal differences between night and sunlight could probably also deform the tube enough to take you out of collimation. Flats being offcenter and showing this kind of weird center pattern could be due to that, miscollimation because of either the mirror cell itself being sloppy or the tube deforming, or the focuser being sloppy or really anything. I would try to take flats at night in the middle of the session to make sure they are the best they can be. You can test whether your scope has some mechanical issues by taking one set of flats at the beginning of the session, one in the middle and one in the end. The tube will be in different orientations and so mechanical issues will manifest themselves to the flats. If you see these issues, you need to fix the root problem before flats will ever work consistently.

But you can take darks now and see if it fixes, or makes the issue better (it will). The mechanical thing is somewhat of an eternal migraine for newtonian users, myself included, but think of that later.

What does a single flat frame and the flat master look like?

Did you use all calibration frames? You have over correction, which to me looks like you might have skipped darks or bias, or both. Depending on the camera and flats exposure time you may need to use darkflats to calibrate the flats too. If you used one of the newer low thermal noise cameras then bias works just fine for that (i do this, no issues).

This image does look like the skyflats had some gradient to them with one corner much better than the other, but the over correction is what bothers me most.

What does a single sub look like?

Difficult to tell if you have just stretched it to this point or if it was like this in the subs. But i am going to guess that there is no way 120s on M51 would be overexposed. Its a bright object for a DSO, but its not really bright enough for you to accidentally saturate pixels with it.

Looks pretty good to me. Sharp galaxies and nice detail even if the background is a bit noisy, but i dont think it detracts from the image. If you want to denoise the background, the best way would probably be to just shoot more subs as its not a super long integration yet?

I shoot at a similar resolution as you, but with 5x the aperture area as your scope (assuming its the FSQ85?) and still think that my background is weak at this kind of integration time, so must be with your scope as well. Maybe it looks worse because there is a lot of background in this image and with nebula images there isn't nearly as much?

6 hours ago, Iem1 said:

 

I think it's because I'm racing against the clock, using a DSLR, I have two batteries. An old Canon battery that lasts around 45-60 minutes out in the cold and a newer Duracell that will last ~2.5 hours. So I'm always conscious of wasting time in set up

 

I know what you mean, running on camera batteries is so stressful. I had 4 old and dubious quality batteries with my 550D and if it was very cold outside that got me just 2 hours of subs, of which most were junk due to many reasons so there was always a sense of urgency with getting things going quickly.

There are dummy batteries that insert one end to the camera and the other to 12v DC or mains power if you want to run cabled and not worry about batteries. Most astro vendors have these, including FLO of course.

17 minutes ago, powerlord said:

Big gun out tonight. Surrender wee galaxies, resistance is futile!!

Tonight, sunflower, silver needle and ngc2903.

Stu

 

Does look a bit like some napoleonic era field artillery piece with the mount hidden like this.