johnturley

2 hours ago, johnturley said:

I think I get it now

The first of the 2 attached images  is virtually the same image taken the same night but using a capture area of 800 x 600 instead of 1936 x 1096, the second image is actually the same image but enlarged by approximately 100% in GIMP.

I was confused by the fact that when I saved the first image back to my laptop, although it appeared approximately 100% larger on the laptop screen when imaging, it appeared to be the same size as the original image (but it wasn't), the second image though did appear approximately 100% larger on the laptop. 

I did not realise that had I posted the 800 x 600 image onto this site, unlike when viewing on my laptop it would in fact appear about 100% larger than the original

It looks therefore that had a done a capture at around 400 x 300, it would appear the same size as the second of the 2 attached images (enlarged in GIMP), but would probably been sharper.

John 

This is the first image after being additionally processed in Lightroom, so hopefully getting there slowly, 2 of the Galilean satellites show up quite nicely,  

John

On 26/08/2022 at 17:24, johnturley said:

Had my best views of Saturn and Jupiter of the year so far last night, Cassini's Division was clearly visible in Saturn's rings, plus the satellites Titan, Rhea, and Iapetus. 

Quite a lot of detail was visible in the Jovian cloud belts, but unfortunately the Great Red Spot was not on show, it should be tonight, but the forecast is cloudy.

Finally turned the telescopes towards Mars, a hint of markings were visible on the tiny 9 arc second disc, plus suspected both the South Polar Cap, and the North Polar Hood.

Also obtained the best images I've taken so far through my Esprit 150, using a ZWO ASI 462 planetary camera, a 2.5x Tele Vue Powermate, and stacked and processed in Registax, I might be able to improve the images further in Lightroom, but not had time to do that so far. I also had a Baader Neodymium filter in the light path, not sure whether this helped.

 

These are virtually the same images, but captured at 800 x 600, instead of 1936 x 1096, and additionally processed in Lightroom, two of the Galilean satellites show up quite nicely. 

I think I get it now

The first of the 2 attached images  is virtually the same image taken the same night, but using a capture area of 800 x 600 instead of 1936 x 1096, the second image is actually this same image but enlarged by approximately 100% in GIMP.

I was confused by the fact that when I saved the first image back to my laptop, although it appeared approximately 100% larger on the laptop screen when imaging, it appeared to be the same size as the original image (but it wasn't), the second image though did appear approximately 100% larger on the laptop screen. 

I did not realise that had I posted the 800 x 600 image onto this site, unlike when viewing on my laptop, it would in fact appear about 100% larger than the original

It looks therefore that had a done a capture at around 400 x 300, it would appear the same size as the second of the 2 attached images (enlarged in GIMP), but would probably been sharper.

Maybe my 5x Powermate might now be redundant, I originally thought that I would need this to get decent sized images with the Esprit 150. I don't think I'll need to use GIMP either, but this program would have been useful for enlarging planetary images taken with my Canon 6D digital SLR, where you can't vary the capture area. 

John 

1 hour ago, vlaiv said:

Have you seen any Jupiter images produced with TAK that is better than say mass produced 8" newtonian?

But they are not.

You are confusing (still) two things:

FOV and scaled image and 100% zoom 1:1 pixel image.

This is the size of your Jupiter:

It is the same size of Jupiter that you will get if you open image you posted above in new window (right click, open in new window) and then - set zoom to 100% instead of image being scaled to display size.

Whenever you have image that is larger in pixels than display device - it will be scaled down to fit the screen and objects in the image will look smaller.

You don't need that much FOV around planetary images. That is why people use ROI of say 640x480px. It is more than enough for even 14" telescope to fit Jupiter.

Look at image posted by Neil above - it is only ~450x450 px - yet Jupiter is large in it.

Your image is full format 1936x1096. Compared to image itself, Jupiter that should be something like 136px or so - will be tiny - it will be less than 10% in width and height.

On the other hand - if you put image that is 400x400 - it will occupy 1/3 in height and width.

You should really try to understand:

- FOV vs pixel count and pixel size

- Scaling - especially "fit to screen" and 100% zoom level

1 hour ago, vlaiv said:

Your planets are already larger then they should be.

I know this might sound strange, but just hear me out for a second.

Maximum planet size that you can record - that is not over sampled - meaning "just enlarged without any detail" (which is what you also get when enlarging in software) - is governed by aperture size.

There is only so much detail that you can get with given aperture size - that is called resolving capability of the telescope. It is down to laws of physics and does not depend on quality of the telescope.

You can calculate this size for any given aperture and also calculate needed F/ratio for given pixel size.

ASI462 has 2.9um pixel size. Optimum F/ratio for planetary imaging is x4 this number at F/11.6. You are already at F/7 with your esprit, so you need only x1.65 barlow (not x2.5 or higher. Take x1.5 or x2 barlow element and dial in distance to sensor to get x1.65 magnification - by the way, this only works with barlow, not with telecentric like powermate).

At F/11.6, 150mm of aperture will result in 1740mm of focal length. With 2.9um pixel size - that is 0.3438"/px.

Given that Jupiter is now 48" in diameter - that results in 139px image of Jupiter's disk. That is maximum that you can get with full detail.

With planetary camera you need to consider only a few things:

- QE of sensor

- Read noise level

- how fast the read out is.

Maximum frame rate of ASI224 is over 300fps (640×480 299.4fps, 320×240 577.9fps in 8bit mode) and it is still one of the best planetary cameras.

ASI462 is not bad either. Both can produce excellent results. Only difference is in pixel size and F/ratio needed. ASI224 needs F/15 while ASI462 needs F/11.6

 

TOTALLY CONFUSED, the images are way smaller than those most people post !

At f11.6 (the supposed optimum for the ASI 462) the images would have been even smaller !

Looks like I would have been better off with the ASI 224 (maybe I should get one of these), but FLO recommended the 462 over the 224, maybe I was given the wrong advice.

'There is only so much detail that you can get with given aperture size - that is called resolving capability of the telescope. It is down to laws of physics and does not depend on quality of the telescope'

Try telling that to the owner of a 3-4 in TAK !

John 

John 

On 25/08/2022 at 20:18, neil phillips said:

Again no I was just pointing out the native FL of the scope. Not being F5

 Ok Here's the deal. I never resize my Jupiter images the way your considering. I don't have to.

First I use a Barlow lens attached to the ADC. I often do a Registax 1.5x drizzle that will increase the size a third. ( because i like the way it effects registax wavelets is one reason)

Then I downsize by varying degrees. Most often a 25% reduction. sometimes 30% Putting the image back much closer to the original pre drizzle size. I am slightly perplexed on your interest on resizing images. As Vlaiv has correctly pointed out. If your correctly sampling, with a semi planetary scope like a 10" F6.3 Newtonian. The image size will be healthy as is.

Especially as ive pointed out I do a 1.5 x drizzle that I can downsize to taste. With the ZWO ADC  in the train I am often oversampled. Because of the extra amplification that occurs with the extra distance between the Barlow and camera sensor.. Not by choice I might add. But because of limitations of barlow powers that I own. 

(Also something perhaps that is throwing you off when you try to understand my image size) So that should hopefully clear up Your interest in resizing images.

Being correctly sampled with the right instrument.  I personally would aim for slightly oversampled. As opposed to slightly under sampled) If it can not be achieved exactly

But that's a choice you can make through experimenting. I said it before. Try correctly sampling with your 14" Newtonian. And your image scale should be fine. If you feel you need extra ( I personally like the way 1.5 x drizzle Effects my sharpening routines ) Perhaps that's something you also could try. Though drizzle is primarily  used for under sampled images. And will have no other benefit than the one I suggested earlier. Other than perhaps be easier to see two close points. With my somewhat aging eyes while processing before downsizing. 

Good luck

 

Neil

Thanks for your detailed and informative reply.

The attached images of Saturn and Jupiter (which I have also posted on the 'What did you see last night thread'), show the size I get with the Esprit 150 and a 2.5 x Powermate, (which I acquired this week) which gives an effective focal length of 2,600 mm, not too bad maybe, but still a bit on the small side. I originally tried imaging with a 5x Powermate, but it didn't give very good results (maybe because the dim image reduced the frame rate too much), although it might work ok under very good atmospheric conditions, and might be required for the tiny disc of Mars.  Obviously with the same 'barlow' 'arrangement, with an effective focal length of  4,500 I will get larger sized images. I did try some imaging with the 14in last week, but I can't say the results were dramatically different, and as I've menti0ned preciously, it makes it more difficult to balance the telescope. 

I've tried the 1.5x 'drizzle function in Registax a few times, but it just didn't seem to work, more often than not the image just 'disappeared' during the stacking process in Registax (don't know why). I've also tried enlarging the image in GIMP as suggested by Vlaiv, which does work, but the results are not always that great, I think that you are limited in practice to a 1.5 to 2x amplification.

I do have a ZWO ADC, which I could put in the light path with the Esprit (but there would be insufficient in travel with the Newtonian), I do find that the ADC (to which I have attached a Baader Neodymium filter) helps a bit with visual views through the Newtonian, but not much gain with the refractor, but then from what you've said it has a similar effect to using a higher amplification barlow or Powermate. 

I'm a bit confused at what you mean by 'Being correctly sampled with the right instrument', I've done some captures by reducing the native capture area of the ASI 462 from native 1936 x 1096 to around 800 x 600, this does give a much larger image on the laptop when imaging, I gather also allows a faster frame rate, and takes up less computer memory, but after processing the image size is exactly the same. 

Maybe the ASI 462 was not the best camera for me for planetary imaging, but FLO recommended this model over the cheaper ASI 224 for planetary imaging, the latter has a slightly smaller sensor size of 1/3 as opposed to 1/2.8 (so not much difference), but has at maximum 30 fps at it's maximum resolution of 1280 x 960, as opposed to 136 fps at 1936 x 1096 of the 462, hence I thought that I was getting a better camera.

I've also tried Autostakkert, which some recommend over Registax, but what not impressed with my first results, also pre-processing in PIPP (which I needed when using my Canon 6D for planetary imaging), but couldn't see any improvement, and its slows down aligning and stacking in Registax. Some also recommend imaging in RAW rather than RGB 24, as it allows a faster frame rate, but then I gather you then need PIPP or Autostakkert to Debayer the monochrome images to get them back into colour.

Had my best views of Saturn and Jupiter of the year so far last night, Cassini's Division was clearly visible in Saturn's rings, plus the satellites Titan, Rhea, and Iapetus. 

Quite a lot of detail was visible in the Jovian cloud belts, but unfortunately the Great Red Spot was not on show, it should be tonight, but the forecast is cloudy.

Finally turned the telescopes towards Mars, a hint of markings were visible on the tiny 9 arc second disc, plus suspected both the South Polar Cap, and the North Polar Hood.

Also obtained the best images I've taken so far through my Esprit 150, using a ZWO ASI 462 planetary camera, a 2.5x Tele Vue Powermate, and stacked and processed in Registax, I might be able to improve the images further in Lightroom, but not had time to do that so far. I also had a Baader Neodymium filter in the light path, not sure whether this helped.

5 hours ago, neil phillips said:

Just for clarity its actually F6.3 Not F5 John And thats native not Barlowed

Sorry I forgot that its f6.3, I used to have a Fullerscopes f6.3 10in Reflector many years ago, which was good on planets.

If you are using that scope un-barlowed , then the focal length will be the native 1,575 mm, which will produce quite small images with approx 1/3 sensor sized planetary cameras, such as the ZWO ASI 224 and 462, so unless the camera you are using produces much larger images, then I assume that you must be  increasing the image size around 3 - 4x with software like GIMP, to produce the images of Jupiter that you post on this site.

The attached image shows the size of the Jupiter image obtained with my ZWO 462 planetary camera, through my 14in Newtonian un-barlowed, which has a native focal length of about 1,800 mm. 

John 

2 hours ago, Cosmic Geoff said:

I'd agree that the experience of a direct view can be great, and the screen view limited. But what if you can't see anything at all through the eyepiece? There are plenty of objects I have seen only with camera assistance, e.g. M1, M33, the spiral arms of sundry galaxies, and various planetary nebulae. 

Agree, I was referring just to the view of the major planets.

John 

12 minutes ago, johnturley said:

Will give that a try, I tried it in Registax, but it didn't make any difference to the size of the saved image.

John 

I've just tried it now, and it appears to work, it actually saves as a PNG rather than a JPEG file, I didn't realise that you have to do 'Export' rather than 'Save as', similar to as you do in Lightroom.

Maybe you can do something similar in Registax, rather than having to load GIMP, will look into this.

I've been asking the question about how to enlarge images in various threads for about the last 12 months, and previously nobody has been able to answer this question.

John 

14 minutes ago, vlaiv said:

Ok, so your image size is 4000x2264 px

That is way too big image to be shown on 1920x1080 FullHD screen - and will always be resized to fit the screen.

First thing you need to do - is select area around Jupiter and crop image so that only sensible size of pixels around Jupiter is contained in the image.

Select crop tool:

Make selection around Jupiter with it:

Say around 800x600 px.

Then press enter to perform actual crop.

Next, to save it as jpg - choose Export as option in File menu:

Now you can save it as jpeg.

Given that it is now smaller than your computer screen - it will no longer be scaled down and it will look like this:

Will give that a try, I tried it in Registax, but it didn't make any difference to the size of the saved image.

John 

In my opinion the view through the eyepiece at the telescope is vastly superior to what you seen on the screen of a laptop using a planetary astro camera.

Its only when you stack and process the various images, do you get a superior view, and as Cosmic Geoff has posted, you can't vary the magnification and field of view like you can by changing the eyepiece, although you can zoom in by adding Barlows or various amplifications.

John 

1 minute ago, vlaiv said:

When you say this, what do you actually mean?

The same small physical on the computer screen, as with the above image of Jupiter, showing a shadow transit of Jupiter. 

On 23/08/2022 at 12:33, CraigT82 said:

Gimp is completely free John 👍🏼

Hi Graig

I downloaded GIMP, and gave it a try, but I didn't have much success with it.

I'm probably missing something obvious, but I tried altering the image size as you suggested in GIMP, from about 1,920 to 4,000 (which incidentally is the same as what you can do in Registax), but after saving the image back into a folder on my laptop, the saved image ended up the same size as it was before, which is the same as what happens in Registax.

Moreover in GIMP, unlike Registax, the image does not save as a JPEG image, but as a GIMP image which then has to load GIMP in order to view, and I couldn't find a way of saving as a JPEG image (see for example attached image of Jupiter. showing Io Shadow Transit, and still the same size after enlarging it about 2x in GIMP)

Jupiter B 29.08.21 with Io Shadow Transit..xcf

On 23/08/2022 at 00:33, Maurizio83 said:

Hello everybody,

a few days ago I had an evening of good seeing, and I was able to shoot a series of good quality videos. Thus, I also tried to increase the focal length to F / 25. The resulting scale is about 0.12 "/ pixel which for a C8 is perhaps excessive, but it seems to me that the fine details are a bit sharper than the first videos taken at a focal length of about F / 18. I don't know, maybe it's just a matter of settings in the elaborations ...

I am very happy with the result. The old "orange" C8 still works well 😀

Full resolution image and detailed info visible here:

https://flic.kr/p/2nFZSrg

👍

Excellent image, what type of camera, and stacking/processing programs did you use, at f25 with a C8 I assume that this would be an effective focal length of around 5,000 mm.

I'm very dubious about suggestions that you should be aiming for a focal ratio of about 3x the pixel size of your camera in um, it just results in small images.

John 

Excellent images again, I'm still a bit confused as to how you manage to produce such large size detailed images with no more than a 2 x Barlow, I expect that JPEG images saved from processing programs such as Registax would have been much smaller. Is it possible to cut and paste larger images directly onto this site direct from the processing programs.

Is your Stella Lyra CC f12, so that with a 2x Barlow the effective focal ratio would have been f24, a lot more than the supposed optimum of around f10 (based on 3x the pixel size) for a lot of planetary cameras.

John  

19 hours ago, Altair8389 said:

Thank you John.

Thats very informative. At the moment, I do not envisage spending big on a heavy mount which can support a C14 telescope which is also quite expensive and I do not have the room in my home at present for such a large scope (too heavy) and big.

But maybe in the future (I would perhaps need a helper to setup my C14)...

 

Magnus

You don't need a long focus SCT to produce excellent planetary images, some observers have posted excellent images taken with 150 mm Newtonians, 127 mm MAC's, and Neil Phillips in particular with a 250 mm f5 Newtonian.

It's just that the former allow you to get closer to the supposed optimal focal ratio for some planetary cameras, based upon 3x the pixel size. 

John 

25 minutes ago, Dragon_Astro said:

Restacked with better alignment point placement, and a reduction in size and colour. Previous version was a bit too yellow.

 

 

Excellent image, what stacking and processing programs did you use.

John 

45 minutes ago, CraigT82 said:

John the best way to enlarge an image is to do it right at the end of the processing, once you have aligned, stacked and sharpened the image. 
 

I don’t know what you use for image finishing (photoshop?) but in GIMP you can enlarge for shrink the image by any factor using the ‘Scale Image’ tool under the ‘Image’ tab (shown below). You just enter the new image size in pixels that you want, so for a 2x enlargement of this particular image I would enter 3,292 into the circled box (1646*2) and then hit the  ‘Scale’ button. 


 

Edit: Should probably add a note on the interpolation method for the scaling. Choosing no interpolation method will result in a blocky ‘pixelated’ appearance. In GIMP the Cubic method gives a nice smooth interpolation. Here is an 800% image of the two methods, ‘cubic’ top and ‘none’ bottom:

 

I don't have GIMP, just Lightroom (which doesn't allow me the option of increasing the size of the saved image, or if it does I haven't figured out how to do it.

Is GIMP available as a free download, or do you require a subscription.

John 

2 hours ago, vlaiv said:

Another way to achieve the same effect is to sample at F/10 and then simply enlarge finished image in software.

 

Several people have stated this or similar, but I've yet to find any satisfactory software to enlarge the finished image.

Yes, you can enlarge the image  in processing programs such as PIPP and Registax, or enlarge the image when imaging at the telescope by reducing the capture area, but when you save the final image after processing back to your PC as a JPEG file, it still ends up EXACTLY the same physical size.

The only things that seems to effect the size of the saved image, are the size of the sensor of the camera, and the effective focal length of the telescope. 

John 

On 10/08/2022 at 18:00, Altair8389 said:

I have the ASI 462MC (2.9 micron), and ASI 120mm-s (3.75 micron). 

So the F20 rule is wrong then (I think the author was talking about native F10 telescopes). I saw some highly detailed Jupiter images with the SW 150pds, not sure how common that is though.

Even bigger scopes seem to get average images. 
I will test out my x2 Orion shorty barlow, and x3 barlow on Jupiter and see what you think.

 

The focal ratio required to get a decent sized image, and the optimum focal ratio for your camera based on pixel size can be quite different.

With a Skywatcher 150 PSD, focal length 750 mm, you will need around f20 (4 x Barlow) to get a decent sized image, at f10 (2 x Barlow) the image size will be very small. 

To get good sized images of Jupiter and Saturn I think you need an effective focal length of around 3000 - 4000 mm, this would explain why long focal length SCT's such as the C11 and C14 are popular with many  planetary imagers, as they have this order of focal length without requiring any amplification with a Barlow, and have focal ratios close to the optimum for most planetary cameras. 

John 

1 hour ago, Adam J said:

The ASI224mc is a good starting place as people have stated above. 

Adam 

I was a bit torn between the ASI 224 and the ASI 462, I asked FLO's advice, and they recommended the 462, but for planetary photography through my Esprit 150, it transpires that the cheaper 224 may actually have been the better choice. If you go by (as some people recommend) that the optimum focal ratio should be 3 x the camera pixel size, then this gives 2.9 um x 3 = about f9 for the 462, and 3.75um x 3 = about f12 for the 224, which equates to effective focal lengths of about 1350 and 1800 mm, roughly achieved by 1.5 x, and 2 x Barlows respectively.

The former in particular however gives an image size that is far too small with this telescope.

John 

1 hour ago, CraigT82 said:

You don't have to use either, I don't.

My workflow is Firecapture (capture) > Autostakkert 3 (registration and stacking) > Astrourface (Sharpening) > Affinity photo or Gimp (finishing).

PIPP is still a very handy bit of software though and I do use it for some things, usually to automatically reject frames without a planet or an incomplete planet due to windy conditions as AS3 can struggle with those frames.

Been struggling to learn Sharpcap, PIPP, and Registax over the last 12 months, don't think I can face learning 3 or 4 completely new programs, but may give Autostakkert a try, as quite a few people seem to prefer it to Registax for stacking.

Not sure however whether you can use it in conjunction with Registax, can you go straight into the Wavelet function, skipping stacking, if pre stacked in Autostakkert 3.

John 

Thanks for the info, I can understand now why some people use PIPP as well as Registax.

John

19 minutes ago, CraigT82 said:

Regarding exposure and gain settings for capture, there is a great feature is sharpcap (pro - well worth £12 imo) called smart histogram. If you do a sensor analysis prior to using it it will use that analysis to give you a live readout of your SNR when you mouseover the histo peak. 
 

By altering your exposure and gain you can see what gives you the best SNR. (Hint: the best SNR values come from longer exposure and lower gain). The gotcha here though is that you have an upper limit on your exposure length which is the seeing. In good seeing you can use longer exposures and in poor seeing you will be forced to use shorter ones. 

The idea really is to use the longest exposures the seeing will let you get away with. And don’t worry about then increasing the gain to get the histogram up to 75% or whatever, that doesn’t matter. Keep the gain low and If the image is dim then that’s fine, you can brighten it later in post processing (eg. By using the ‘normalise’ function in Autostakkert).  You don’t want to go too low with the gain though as if the noise on the image is very low that can cause issues further down the line after stacking - the stack may retain a lower bit depth which can lead to artefacts after using wavelets.
 

 

 

Thanks for the info, I note that you use a small capture area (640 x 480) and RAW 8 rather than RGB 24, what is the advantage, doesn't using RAW 8 give you a black and white image.

John