Adam J

4 minutes ago, mightymonoped said:

Any particular aspects? Always looking for constructive criticism 🙂

Tony

You have lost the demarcation between OIII and H2 / SII in the second image. More so in the pelican. 

First one is much better in my opinion. 

43 minutes ago, Elp said:

As mentioned I have not had a single issue with a 485/183/600D/A6400 so it's NOT through a lack of experience. The 294 simply acts completely different.

I use multiple perspex to dim my flat panel with the panel itself on its lowest setting, from a casual view looking at it like this it doesn't even look like the panel is on. Usually I leave the asiair to calculate the right flats exposure and haven't had issues with other cameras, I've tried seconds long exposures and it still does it, if you do a histogram preview in Siril before and after background extraction the issue is clear to see, in fact it's worse after background extraction even when manually carefully selecting sample points but it's difficult due to the colour cast rendering the operation mostly moot as it's not a linear LP gradient.

I must note the majority of the time when I use the 294 is with an lextreme which I strongly suspect causes an issue but again, haven't had an issue with that and other cameras even daytime camera bodies with the filter on the front of the camera lens exposed to stray LP sources which optolongs don't like.

I'll try and find the CN forum post, it's quite long and people did multiple tests recording values etc, at the end it was concluded as the sensor glass causing the issue.

I don't think it was just one thread as multiple threads exist on the issue, here are two examples:

https://www.cloudynights.com/topic/611039-help-me-with-this-artifact-zwo-asi294/

https://www.cloudynights.com/topic/792863-asi294mc-pro-strange-recurring-color-pattern/

I was not calling you a beginner it was more of a general statement on the camera. 

7 minutes ago, PadrePeace said:

I take it you are employing calibration frames in your images? I use the 294MC Pro at 200 gain and 30 offset and with >4sec Flats and dark Flats I’ve never seen any of the mentioned colour patterns stretch through in post. Calibration sorts that entirely. 

This is true, at 200 gain and with good calibration frames it will work fine. I guess the issues is really with beginners getting all that correct. 

22 hours ago, Elp said:

I believe the OSC is a binned version of the mono

No its not there are both IMX294 and IMX492 OSC sensors listed on Sony's website. The sensor is not the same model between the 294mc and 294mm despite the common misconception. 

I posted about it above but no one seemed interested. 

Adam

3 hours ago, gonzostar said:

Sorry, OSC upto £850max

For that sort of price and with the scope you have i would consider this:

U.K. Astronomy Buy & Sell (astrobuysell.com)

or if you want new:

ZWO ASI 071MC-Pro USB 3.0 Cooled Colour Camera | First Light Optics

The 533 is a small sensor still and the 294mc has too many..."features" for me to recomend. 

The 071 on the other hand is going to give you a wide field of view and pixels that are well matched to your focal length. 

Watch this covering this camera:

IC4592 Blue Horse Head (Konstantin Firsov) - AstroBin

SH2-184 (Almos Balasi) - AstroBin

Cygnus Region w/ Samyang 135mm (Elmiko) - AstroBin

IC434 Horse Head Nebula - Just a dream in full... (Jocelyn Podmilsak) - AstroBin

IC5070 (Joel85) - AstroBin

The benefit of a lager sensor can outweigh the benefit of a more modern / sensitive but smaller sensor. As soon as you need to take multiple panels to cover any given target you double your required exposures. But also if you want a given FOV you can do so with a longer focal length and so usually larger aperture scope than with a smaller sensor. 

but then i would also recommend mono over OSC every time. 

Adam

You don't specify Mono or OSC, Also what is your actual budget?

5 hours ago, GTom said:

Exacty, not the first account where I hear that these little mounts can carry far more than expected by traditionalists🤔😎

Kinda, its also worth noting that i needed to adjust both RA and DEC to remove backlash before i was able to get that result. So it is not out of the box performance, although I have not modified it in any way beyond tweaking meshing of gears. 

Adam

9 hours ago, TiffsAndAstro said:

• Weight (including tube-rings and mounting dovetail) approx 4 kg

4kg is a lot less than i was expecting. the sa gti official payload is 5kg, but the conventional wisdom is to use half that value.

this could be quite cool, but i'd be concerned about the guiding performance before i did it. don't mind someone else trying it out first though to see

i've read these sorts of newtonians can need quite a bit of mods to make them more suitable for imaging though.

 

Conventional wisdom is wrong i have been getting <1 arcsecond rms with the SAGTI and a 5kg payload. 

Adam

3 hours ago, vegaandarctures said:

So I’m considering picking up a small frac for some wide field imaging. Currently have a SWED80 but want something with less focal length for those super wide shots. On the lookout for a little 60mm and I’ve come across two from Altair. 

This one: the Starwave 60ED (£379)

https://www.harrisontelescopes.co.uk/acatalog/altair-ascent60.html?gad_source=1&gclid=EAIaIQobChMI7sjzoPPGhgMVTolQBh0e7SfwEAQYAyABEgKsWPD_BwE
 

And this one: The Altair 60EDF (£499)

https://www.harrisontelescopes.co.uk/acatalog/altair-60edf-refractor.html#SID=1706

The Starwave has FCD100 glass whereas the EDF has fpl53. Other than this are they optically different enough to justify the rather large jump in price of the EDF? 
 

There are lots of great reviews for the EDF but pretty much none for the Starwave. Does anyone have any experience with the Starwave? I’d be tempted by that if I know it’s just as good as the EDF, as it saves a considerable amount of money especially when you add the cost of the reducer too.
 

Any insight/advice welcome

 

 

EDF looks to include a Interferometer report with it and so it likely has superior quality controle and a guaranteed level of optical finish to it. 

On 17/05/2024 at 20:59, Ags said:

I'm slowly cogitating upon this weighty matter. I think the 183MM might be the camera for me. I need a mono camera with small pixels for white light solar, as well as a larger mono sensor for Ha solar and the Moon. For DSOs I need the small pixels for my refractors and binned 2x should be ideal for the the RC.

Probably not a bad idea. But got to say a 533mm is a better choice. 

Adam

On 03/05/2024 at 10:25, Tom33 said:

I have been considering purchasing a long focal length scope for galaxies as I currently use a SW Esprit 100 and an ASI 294MC PRO for wider field imaging but am wondering if I am better changing my camera to say an ASI 533 MC PRO with a smaller chip and smaller pixels to get the same result. Just wondered if anyone had opinions on this ?

Can you give some example of images of galaxies you have already taken?

This is my image of NGC4565 with an esprit 100 and a ASI1600mm pro. Are you already getting this kind of resolution? I doubt you will get much more than this from that scope.

Adam

With my mobile phone braced against the roof of my car. 16s ISO3200

Saxilby UK

Amazing night!

Great images all. 

Adam 

On 06/05/2024 at 18:54, cloudyweather said:

Hi all,

First let me say that I've read as much as I can find online and I'm looking for help.

I'm fairly new at astronomy, retired and a  semi-professional photographer in the past (love HQ lenses).  Not sure about all the image processing/stacking that seems to be needed for astro but may give that a go (I have an APS-C Fuji). But I'm also looking for Visual and somewhat portable (car / easy setup).

Consider the Starfield 102 + 0.8 reducer/flattener and the Askar 103mm + 08. reducer/flattener to be the same price and both in stock.

I've read nothing but glowing reports of the Starfield everywhere. Praising the quality build, finish & optics for both Visual and Imaging.

The Askar seems to have split views. Concern about cheaper glass than perhaps more expensive triplets. I did read of possible focuser issues on one site.

Why am I asking?  The Starfield has been out of stock for a few months and I could get the Askar, but I'll wait a little longer if needed.

Has anyone actually used both telescopes?  First hand experience of both? For Visual and Imaging?

Many thanks

You will get the TS Optics 115mm triplet for a similar price. Its well established as a good imaging scope. 

Adam

49 minutes ago, vlaiv said:

Sorry, my bad, did not understand that correctly.

Have you posted the comparison?

no I am on my phone, would need to do it later. 

Just now, vlaiv said:

I would advise against this as stacking would not make sense after you alter noise distribution.

In any case - why don't you simply try it out on existing data you have? Make comparison between two approaches.

Maybe best way to do it would be to create "split screen" type of image. Register both stacks against the same sub so they are "compatible" - prepare the data one way and the other and compose final image prior to processing out of two halves - left and right copied from first and second method.

That way final processing will treat both datasets the same as you'll be doing it on single image.

Alternatively - if you can't make it work that way - just do regular comparison - do full process one way and then the other.

I'd be very happy to see the results.

I didn't say that though, I said I would apply it after stacking. 

I have tried it and the thread is to ask if others have observed the same thing. 

Adam

42 minutes ago, vlaiv said:

We seem to be having different concepts of what the binning is for.

I see it as a data gathering step - integral into data reduction stage, rather than final processing tool.

In my view - if you choose to bin your data - there is no sense in up sampling it. You don't up sample your data from regular pixels either, right?

You choose to bin your data because you'll be happy with final sampling rate that binned pixels give you - as if you were simply using larger pixels in the first place.

If you leave your image binned - it won't be any different than shooting "natively" at that sampling rate. It can loose detail versus properly sampled image - but that is not due to binning, same would happen if you compared two images taken with regular pixels - ones being bigger and under sampling and ones being smaller and properly sampling. Under sampled data will not show the same level of detail - simply because it's under sampled (not because it was binned - because in this case it was not).

 

I would say there are two reasons to bin, 

1) You want to improve SNR by effectively making the pixels bigger. 

2) You are oversampled, likely due to seeing and you want to present your image at a scale at which it appears sharp to the eye as opposed to soft. 

In the case of two I would argue that the AI noise reduction will provide a better result if used before you software bin and in this case I would apply noise reduction as a first step following stacking then resample. In the case of one I would just let the AI noise reduction do it's thing if the image is critically sampled or undersampled. If oversampled see case two. 

Adam

53 minutes ago, gajjer said:

That was my thought. I always use binning to get a higher gain but at the cost of resolution. But then I'm no expert.

cheers

gaj

Yes that's correct, but it's a blunt tool applied across the whole image, even the brighter areas. 

29 minutes ago, vlaiv said:

Can you explain this?

When is binning detrimental to image quality?

yes, it's detrimental when you are undersampled and you loose detail in bright areas to gain SNR in faint areas of the image. Something that occurs in wide field imaging quite allot. The point being in wide field you are almost never limited by seeing. 

My example is that when I processed my M45 wide image at 180mm focal length, the surrounding dust looks better if you bin the image as you might expect. But in binning the whole image you loose detail in the core of M45. 

Yes it would be possible to bin an image, resample back up to original level and then mask the brighter areas of the unbinned image back in but the AI noise reduction seems to achieve this with better granularity and minimal effort. 

19 minutes ago, vlaiv said:

With some things I agree 100% and with others 0% . I'll explain.

1. Yes, QE does matter, but only up to a point.

Nowadays, most cameras have very similar QE. There is really not much difference in 81% vs 83%. Transparency on the night of imaging and position of the target can have greater impact on speed than this. So does the choice of stacking algorithm if one uses subs of different quality. My reasoning is to go with higher QE only if it fits other criteria below

2. Read noise is in my view completely inconsequential for long exposure stacked imaging where we control sub duration at will.

Since we can swamp the read noise with selected exposure length and again CMOS cameras have much lower read noise than CCDs used to have - I again don't see it as very important factor. I would not mind using 3e read noise camera over 1.4e read noise camera if it fits with other criteria

3. Sensor size is very important for speed - because it lets us use larger aperture while having enough of FOV to capture our target. I guess this is self explanatory

4. Binning is the key in achieving our target sampling rate with large scopes and large sensors.

Speed is ultimately surface_of_the_sky_covered_by_sampling_element * QE * losses in telescope * aperture

In above equation there are only two parameters that can be varied to a greater extent - one is aperture and the other is sampling rate or sky area. Latter determines the type of the image we are after - do we want wide field image with low sampling rate or we aim to be right there on the max detail possible for our conditions. If we aim for latter - well we don't have that much freedom in this parameter. This leaves aperture. We can choose to go with 50mm or 300mm scope, but in order to hit our target sampling rate we must have equal range of pixel sizes - that we don't have. Binning to the rescue.

I simply don't like AI side of things. We have very good conventional algorithms that do wonders as well if applied correctly.

 

I think it's better to say they have a similar peak QE, although legacy cameras do have lower QEs, the main difference for OSC is in what the bayer matrix is doing to that QE. 

In terms of read noise. At a dark site my understanding is that Narrowband will take significant time to burry the read noise with LP at least. Now it may be so low even in that case that shot noise from a faint target is still the biggest factor. 

My personal current struggle is to replace my ASI1600mm pro with a higher QE camera or buy a second and use in a duel rig. I am leaning towards a duel rig as the used coat has come down. 

All in all to op I would say get the largest sensor you can afford with the possible exception of wanting to specialise in galaxy imaging. 

12 hours ago, vlaiv said:

Yes, provided it is used with the same optics and nothing special is done to the data.

If you have the choice of telescopes you can use with your cameras, and you can bin your data - then it depends.

If you want to get really faint stuff in "reasonable" amount of time, then this would be my advice:

- figure out your working resolution in arc seconds per pixel (one that will capture all the detail you are after and will not over sample)

- get the biggest aperture that will give you focal length in combination with pixel size you have and any binning factor that will provide you with wanted working resolution - and will have enough FOV to capture the target.

(of course, consider all other variables like ability to mount the said largest aperture scope, costs involved, quality of optics and so on ...)

 

Am starting to think that the only things that matters are QE, Read noise per unit area and sensor size. 

And this is why, 

I don't think software Binning for increased SNR is the way to go anymore. 

Interested in your thoughts. 

Adam

My basic theory is that when used purely for the purpose of noise reduction the use of Binning is made redundant by the advent of modern AI noise reduction techniques and in some cases my be detrimental to image quality. 

In effect AI noise reduction is making best use of available information contained within the raw image to reduce noise dynamically across the image dependent on local SNR. By binning the image you are simply depriving the AI algorithm of information and potentially missing out on detail in areas of already high SNR if whole image binning is applied. 

In the case of a oversampled image I would always now apply AI noise reduction and then as a final step resample the image to present it at an appropriate image scale. 

Thoughts? 

Adam

42 minutes ago, ollypenrice said:

The only reason to use a reducer is to increase workable field of view. If it's not going to do that, it's not worth bothering.

If you would like to swap more signal for less resolution you can resample the image downwards before processing. Beware the F ratio myth when it comes to reducers.

Olly

I disagree you are exchanging Resolution for both FOV and Reduced time to reach a given SNR. As a Rasa owner its exactly the same thing as your scope is doing only it is preconfigured to do that.

Resampling is worse because you exchange resolution for speed without also gaining FOV.  Can only do both with a reducer. 

Adam, 

18 minutes ago, Giles_B said:

Can you explain why - because of the small image circle? square stars? pixel size? Or just personal preference because of all of the above?

Its a complex thing to put into words but in the end what you are doing with a corrector is correcting the field curvature as a function of distance from the optical axis. The amount of correction needed changes with distance from the optical axis, so with a faster corrector you have a steeper correction "gradient" (not the right term but I am having a go here), you need to compensate for that gradient more precisely, That means that you need a better match between the original profile of the field to be corrected and the correctors profile itself. So you will need more precision back focus, but also any miss match in that gradient is more significant. On top of this you are also going to increase vignetting with a faster corrector. The larger the chip the worse it all gets.  It also gets more sensitive to tilt in the corrector relative to the principle optical axis. 

That is the best i can explain it.  In essence 0.8x is the standard for a reason, its a design balance. 

Adam

I generally think that 0.6x reducers only work really well on small chip cameras like a IMX533 or smaller. 

Adam