symmetal

4 hours ago, Laurieast said:

A bit less motley 😉 

Yes, I think that looks like a more 'natural' result. 🙂

Alan

As you're using a filter drawer with the flattener, then the easiest way to maintain the spacing is to put a clear glass filter in the filter drawer when you don't want a specific filter. This avoids you having to remove a spacer to compensate. A UV/IR cut filter also called a luminance filter is commonly used as a 'clear' filter as it has the benefit of blocking out of focus IR wavelengths from the sensor.

Alan

Back focus spacing is only important if using a field flattener or coma corrector in your imaging train, as an exact distance is required between the flattener/corrector and the image plane for them to work correctly. Adding a filter between the flattener/corrector and the camera will increase this critical distance due to refraction through the filter so an extra mm or so spacing is necessary. You;re right that if the filter is removed then the extra mm spacer would need to be removed.

Getting the spacing right is more critical with larger size sensors. With smaller sensors the spacing distance is not so critical and the change when adding a filter is likely not worth worrying about.

If not using a flattener/corrector them there is no critical back spacing requirement, so as long as you can focus the image then your're fine. Adding a filter will move the focus point back a small amount but your standard focus knob will take care of that for you. 🙂

Alan 

@Laurieast Thanks, you've accentuated some detail there Laurence. 🙂 If you're using Registax wavelets, then the noise reduction parameter associated with each slider, particularly the top slider is good at mitigating the noise mottling effect. 

Alan

@neil phillips @CraigT82, Ahh, good tip. You've obviously done more planetary processing than me. 😊

Alan

43 minutes ago, CraigT82 said:

Nice one, love playing with other peoples data... good practice!  Here's my attempt, using Astrosurface and Gimp.

11 minutes ago, neil phillips said:

Pushed it as much as I could without artifacts. Its good data

Like both your versions. Thanks. In comparison mine is a bit green. You've avoided the curved artifact on the left edge which I have. Will have to look into Astrosurface. 😉

Alan

@neil phillips Thanks. It might be worth bracketing the initial exposures with focus so see which one is best but that means stacking each exposure which takes some time. Probably worth it to save a lot of potentially soft videos. Also repeat every 30 mins or so. Using a bahtinov mask to mentally integrate a collection of a few seconds worth of exposures and determine the average is a bit of a challenge which I have yet to master. 🙂

@Kon Thanks. Yes the seeing was pretty good as the video image wasn't dancing around much during capture. 🙂

@CraigT82 Thanks. My monitors aren't colour calibrated so it's quite likely off colour. 😉 I'm not sure what colour Jupiter should be so choose what makes it look pretty. 😊

If anyone wants to have a go at processing it, here's the stacked tif from Autostakkert3

2022-09-20-0018_5-U-RGB-ZWO ASI224MC_Gain=350(off)_Exposure=5.0ms_4_Jup_lapl4_ap330.tif

Alan

40 minutes ago, neil phillips said:

Hi Alan unsure why you are limiting your time frame so drastically.

Hi Neil. I did take videos of 1 min and 2 mins as well to do some comparisons, but I think the focus must have shifted as every stacked video after this first 30 sec one was noticeably softer so I just went with the sharpest image before using Registax. 🙂

I'll have another go if it's clear and do a focus check more often. The scope had been outide for 4 hours in the dark beforehand so assumed it had stabilized. I did readjust the ADC slightly at one stage. I had checked before with a bahtivov mask on a star and moving the ADC levers didn't seem to affect focus which surprised me but maybe I need to check more closely.

I have used WinJupos in the past and it did improve the image a little but it takes a bit more dedication to use it. 😁

Alan

First time planetary for this year with the LX200GPS, 2x Powermate, Zwo ADC, ASI224MC. Found the collimation was way out, possibly due to the wild temperature changes in the shed up to 45C in summer even though there is an extractor fan which comes on at 20C. All the weather satellite receivers and processing PCs in the shed give out a fair amount of heat. The spiders don't mind the heat though as it's like a scene from Aracnophobia when you open the shed. Had to disconnect several large web anchors from the scope before wheeling it outside causing a bit of a scuttling frenzy. 😬

Took several videos near the Meridian of various lengths and exposures. Found 5mS for 30 seconds gave the sharpest result. 45s and 60 secs were noticeably softer though it was likely the focus drifting. Others at 2 to 4mS were softer too so must remember to check focus more often.

Anyway here's the sharpest result. 5mS exposure, 30 secs video at 200fps. Stacked in AS3 using 15% (900 frames). 5 and 10% were sharper but more noisy. Wavelets in Registax 6. Colour and slight curves adjustment in Photoshop.

Alan

A luminance filter is a UV/IR cut filter so yes they would be the same thing. Many colour cameras incorporate a UV/IR cut filter in the protect glass but the ASI224MC doesn't, so I use a separate luminance filter with it.

Alan

Your video stats are reasonable Ian though you could try adjusting them a bit.

Your exposure could be reduced to 4 or 5mS and camera gain increase to compenstate. High gain is not an issue in planetary as stacking will remove the noise. This will enable a higher framerate. Also select 'high speed' option in camera config and use 8 bit capture to maximize framerate.

Depending on your camera you should manage 200fps at 5mS exposure and a ROI big enough to just surround the planet. At 4mS I was getting 237fps with my ASI224MC.

You stack percentage in AS3 is rather high. I usually select multiple stack percentages from 5 to 20% depending on what the quality graph looks like. You need around 1000 frames as a minimum stack amount and 20% will give 1000 frames from your video. At a higher framerate this will be higher.

The quality graph gives a good indication of best stack percentage. The grey graph is the frames as recorded while the green graph is them sorted in order from best to worst. You don't want frames below 50% quality in the stack if you can avoid it. 25% includes those frames from the left up to the first blue line. Your 60% would include some rather poor frames which degrades the result.

Alan

Looks pretty good for a first attempt. If you mention what the exposure, video duration, fps, percentage stack in AS3 was etc. we could possibly offer some tips. 🙂 Did you use the ADC?

I took some Jupiter videos tonight, first time since last year, at different exposures from 2 to 5mS, and varying video durations, so will see how they compare when i process them tomorrow. The ADC tuning in Firecapture showed quite a large red/blue split and still needed about 20 deg on each ADC lever to correct it at the meridian.

Alan

Your latest image is actually very good and many people would be happy with it. 🙂 Here's the CCDI analysis. Your min and max FWHM figures are much better compared to your previous postings.

Pixel peeping, the top left is visually the worst showing slight triangular stars which I've found with my WO scopes means that corner FF spacing is a bit too much. Stars on the left are a bit larger than those on the right so slightly out of focus down the left. The tilt looks like it's purely left to right.

Fixing tilt like this requires very small adjustments and the tilt jig is really the only way to improve this. As you have the bits you may as well build it. 😊 Using the tilt shims, it depends a lot on how tightly the parts are screwed together so is hard to reproduce reliably. On the jig you should be able to fit your Zwo tilt adjuster with a spacer between it and the filter wheel to allow allen key access, followed by the camera, such that you have the correct 55mm FF backspacing when it's fitted back on the FF. You'll then appreciate the tiny adjustments needed on the tilt adjuster which you would never manage trying it in the field. If you need to use the shims instead you can easily see the effect of rotating them and how tight they need to be screwed together.  

Alan

Oh dear! And AST are launching 100 even larger LEO BlueBird satellites from 2024. 😬

Alan

Starizona adapter with NBZ fitted easily once 'complete' clear filter removed. 😊 Focus was significantly out after changing so expected to have some odd shaped stars requiring a shim spacer but good stars all over after refocusing and still no tilt. 🤗

5 min exposures gave a sky background ADU of 711 where 717 ADU is the point where the read noise is swamped by 5, though there is a partial moon so on moonless nights 6m may be better.

Alan

Eventually found a topic on CN concerning the glass filter and helpful images confirms that the outer knurled ring is just part of the filter assembly and can be removed without affecting anything else.

Currently outside with original setup imaging RGB but will try removing the 'whole' filter assembly later and try some NB when the Moon gets higher. 🙂

Alan

I've highlighted the knurled ring on this image from the RASA white paper and it doesn't appear to clamp the corrector lenses as they butt up against the flange behind it. The ring just seems to hold the clear glass. Shall I remove it? 😖

Alan

My RASA 8 Starizona 2" filter holder for 17.5mm backfocus cameras arrived today and was hoping to try it with an NBZ filter tonight, but the filter projects out the back of the adapter far too much and when you fit the whole assembly to the RASA with the RASA locking ring, after 1 turn the filter mounting ring hits the knurled ring on the front of the RASA, as shown on the first image, and jams.

I have removed the RASA glass filter locking ring and the clear filter as required from the front of the RASA but it seems I have to remove the large knurled locking ring too for the NBZ to fit into the space left, but this looks like it is what is holding in the front corector lens. 😬

Without the filter installed it all fits together like the original RASA M42 adapter, with the correct camera spacing, but I can't see any other way to fit the filter, as there is only one 2" filter thread, and when fitted with just one turn available on the locking ring, it puts the camera about 6mm further forward than it should be.

How are other peoples 2" filters fitted. I know some of you have the Artesky adapter but any help with this dilemma and whether the large knurled ring need removing is appreciated. None of the instructions imply that it does, just to remove the clear glass filter for correct optical spacing with an external filter.

Starizona adapter on the right

Alan

1 hour ago, Stratis said:

Wow.... does anyone know how to get in touch with Robert Dalby, he'd know  

His Astronomy and Nature TV Youtube channel is still active by the looks of it, with the last video posted 8 months ago. You could try asking on his facebook link. 😃

Alan

Jupiter is around 39 deg elevation from the UK at the moment, and the chart shows 0.7 arc sec dispersion between red and blue at that elevation. With lucky imaging, your imaging around something like 0.1 arcsec/pixel, so an ADC is still useful if you have one. 🙂

Alan

As well as being 1.4x larger across, the new sensor has pixels around half the size so the field curvature effect of the focused image will be much more apparent with the new sensor.

This will be fixed by buying the field flattener, but this means you do have to worry about spacing but it's fairly straightforwand. 🙂

You will need 55mm between the rear mounting face of the FF and the sensor of the 490EX.

Atik 490EX front plate to sensor = 13mm +/- 0.5mm

EFW2 thickness = 22mm

So the extra spacing required between the rear of the FF and the filter wheel is 55 - 13 - 22 = 20mm

The filter glass thickness does effect this spacing though and you need to add 1/3 the filter thickness to the original 55mm quoted for the FF. For 2mm thick filters this is around 0.7mm making 55.7mm spacing required. Therefore your 20mm spacing mentioned above should be nearer 20.7mm.

However, as your new sensor isn't that large compared to say an APS-C size sensor the FF spacing isn't so critical so you can probably forget about the extra 0.7mm and the 20mm extra spacing should be fine.

The FF has an M48 rear thread and I assume your EFW2 is M42 so the thickness of any M48 to M42 adapter used will count as part of the 20mm.

So your new optical train will be

Skywatcher Esprit 100ED > Field flattener > 20mm spacing > ATIK EFW2 (Filter) > 490EX 

Hope that helps 😊

Alan

Sony haven't released info on how the HCG and LCG actually works, at least I couldn't find anything, and manufacturers just give similar rough indications and no specifics. It does appear that three separate settings are available on the later sony sensors with HCG which affect gain.

HCG on/off. If off it's in LCG mode.

HCG gain multiplier

'Normal' camera gain

Zwo have tried to make it simple with having a fixed HCG gain multiplier and turning HCG on when the normal gain is set to 100 or above. 😃

Some manufacturers have the HCG on/off separate to normal gain, giving more control but needs more consideration to avoid conflicting settings. 🤔

Atik have possibly made all three available in the Horizon but in preset steps with confusing names which doesn't really tell you what mode it's in. 😬

The newest Sony sensors have a Dual-Conversion Gain mode which has two ADCs available for each pixel, so each pixel is converted twice simultaneously, one with a low gain and the other with a higher gain. The two ADC outputs are then combined to give a HDR, high dynamic range, signal output. Whether this is a HCG ADC combined with a LCG ADC, or two different 'normal' ADC gain settings, or a combination, I don't know.

Alan

Hi Paul,

I suspect the shorter one is an earlier version of the AC519 and the other is an improved version having an undercut and I presume anti-reflection ridges on the front. It was intended for the small size CCD chips of the time. Here's a nostalgic AE video showing their barlows and the Imagemate, (the longer one). 😃

Alan

HCG was introduced to give a higher quality picture in low light conditions primarily for security or industrial use cameras.

LCG is really just HCG turned off and is the way cameras operated before HCG was available. In normal lighting conditions LCG is preferable as you get a larger well depth and camera read noise is not an issue.

Astrophotograpy has found that HCG has a distinct advantage, due to the very low light conditions the camera is operated in.

Alan

Did you not make the test jig Stefan? 🤔

If you post a full size sub it would be easier to assess what the actual tilt effects are. From your test image the stars look OK but it's too small really to tell.

Even if there was tilt elsewhere in the system reversing the orientation of the shim would have made a difference if it was actually working. It's possible your threaded pieces are too well meshed, and not allowing enough free movement to react to the shim face, and are just locking down on the thickest part of the shim, and not introducing any 'wanted' tilt at that point. I imagine you only want a few mm of thread meshing where the shims are introduced to enable some free movement to occur.

Alan