Jupiter with Nexstar 102slt and cheap webcam!!

[tarqs101]

Hi,

As you know I'm very new to astrophotography, had a couple of attempts over the last fortnight. Tried again last night with my Celestron Nexstar 102 SLT and a very cheap webcam (10 quid from tesco!) Stacked 360 frames and tweaked.

Here is the final result. Please be as critical as you like but remember it was a very cheap webcam!!

Gavin

Jupiter-200809 editied.bmp

[rawhead]

That's better than I managed at the start.

Definite banding on show.

A few more subs may help? (Not always easy with a max of 10fps.)

Are you using an IR filter?

Cheers

Jon

[tarqs101]

Hi Jon,

I'm not using any filters, would you recommend a IR filter? I got 370 frames and stacked 30, how many would you recommend?

Also, I can get 30FPS out the webcam, would that be better?

Sory about all the questions!

Gavin

[rawhead]

Hi Jon,

I'm not using any filters, would you recommend a IR filter? I got 370 frames and stacked 30, how many would you recommend?

Also, I can get 30FPS out the webcam, would that be better?

Gavin

Hi Gavin,

An IR filter is recommended though not essential.

I think you are only supposed to image Jupiter for about 1 minute before you start to get rotational blurring. If you are using 10fps this equates to a stack of 600 images. You would hopefully want to stack at least half (300) 10X more than you used on your image.

Don't go above 10fps. The image quality will suffer.

Look here for an excellent tutorial:

http://stargazerslounge.com/primers-tutorials/40665-primer-planetary-imaging-toucam.html

Cheers

Jon

[tarqs101]

My mistake Jon. I made a typo in my second post, I did stack 360 frames but can't remember if I used 10FPS or 30FPS.

Thanks for your advice.

Gavin

PS. Love your site and Observatory!

[rawhead]

PS. Love your site and Observatory!

Thanks mate

[omneferuss]

Hi Gavin, that's real progress you've made!

I won't say a uv/ir-cut filter is mandatory, but it will help.

Try 'WXAstrocapture' software (free download ) it's a simple interface to all the camera settings.. ( I can't guaranty it'll work with your camera tho')

I'll disagree with rawhead on fps.. more fps can sometimes help against "seeing" being poor, but the other settings must be juggled with it to find the best exposure.. eg, see my avatar.. done in poor seeing @ 30 fps. All settings are interdependant and camera-specific, and dictated by the target and conditions. There are no rote rules to 'one size fits all'.

I've seen mentioned that 1-1/2 to 2 min max on Joop before smearing of details.. I use 90 secs or 800 frames, or thereabouts, whichever comes first... tweaking settings for every capture.. trying to learn what a good one looks like live on screen, with my setup, to my eyes. ( I've only tried this about six nights last year, and the once sofar this 'season'.. the last is my new avatar :o:rolleyes:

.... many many avi's never processed, just by-products of 'learning to drive'.

keep it up Gavin, you're well on the way!

( ..now if we could get a lil more aperture and a DBK.. )

Russ

[tarqs101]

Cheers for your comments Russ.

I have just downloaded WXAstrocapture so will give that a try.

It really is a great learning journey to be on! I think what has really helped is I've regreased the focusing dial on the 'scope so it's a lot more smooth and I seemed to be able to get Jupiter looking much more clear on the laptop. I've also felt more confident just to tweak the settings as I see fit, whereas before I was trying to follow 'how to' guides, and, as you said, every camera, 'scope, tripod is different so there is no one rule fits all.

Guess it's a matter of confidence!

Gavin

[Milamber]

Hi Gavin - nice pic and I applaud your attitude of doing it yourself and making your own mistakes as you learn... those that buy mountains of kit then ask how to use it are missing the point I feel - in imaging, the fun is in the journey as well as the destination.

Here's some piccies from my archive from when I started with webcams a long time ago ...

Beginning with the smallest, Feb 18 2003 actually. Which would mean it was with the NS8GPS

Second pic, middle size, is same setup but a hard week of trial later, Feb 23rd, 2003.

Third and largest image, a bit later still - 18th March 2003.

Press on, results come fast if you persevere.

Arthur

Jupiter_20030318_2105UT.BMP

[tarqs101]

Wow Arthur you can really see the progression! It just shows that perseverance is key!!

[rawhead]

I'll disagree with rawhead on fps..

Concerning webcam compression. Was further discussed in a thread I started here: http://stargazerslounge.com/imaging-discussion/77449-planetary-imaging-upgrade-path.html

Cheers

Jon

[Milamber]

Jon - you are assuming people are correct, and also assuming a non-RAW modified webcam. Compression and webcams is a funny subject and unless you have the information from the webcam manufacturer you are in a very grey area where statements like "above 10fps compression kicks in..." are dangerous indeed.

Trust me.

Arthur

[rawhead]

Jon - you are assuming people are correct, and also assuming a non-RAW modified webcam. Compression and webcams is a funny subject and unless you have the information from the webcam manufacturer you are in a very grey area where statements like "above 10fps compression kicks in..." are dangerous indeed.

Trust me.

Arthur

Fair enough. Point taken

[Milamber]

Ah, that reads back as being rather arrogant - for which I apologise Jon - the point I was trying to make really is that there are as many different opinions as there are webcams, and therein lies the problem. Just exactly which webcam are we talking about? Which sensor? Even Logitech (and Philips at one point) sold the same cameras with totally different systems inside the case. We are not even sure which webcams we are talking about most of the time and it was the big sweeping statements that presume to take in "webcams" that I was trying to reel in.

The old truism though still remains - ccd-equipped webcams will allow a much higher frame rate before any compression (if any) kicks in. This is simply because cmos-based cameras have most of the processing on-chip and you cannot stop it, whereas the ccd-based cameras just collect light and dump it out to be played with - where the data can be hi-jacked and read RAW into the computer before the camera has a chance to mess it up.

Arthur

[omneferuss]

Hi Jon, I read the thread.. I won't argue re any assertions about 'compression'. My point being that regardless of any theory, I 'suck it n see' at the coalface, so to speak... on the night, whatever compression that may have been occuring nevertheless gave superior image-quality @ 30fps compared to other framerates under the prevailing seeing conditions with my equipment.

Sofar, I'd say 20fps has seemed to give the best image in better seeing, for me, ..but nothing is hard and fast set in concrete.. I always sample the mix to see what might be possible

Concerning webcam compression. Was further discussed in a thread I started here: http://stargazerslounge.com/imaging-discussion/77449-planetary-imaging-upgrade-path.html

Cheers

Jon

[brianb]

The old truism though still remains - ccd-equipped webcams will allow a much higher frame rate before any compression (if any) kicks in. This is simply because cmos-based cameras have most of the processing on-chip and you cannot stop it, whereas the ccd-based cameras just collect light and dump it out to be played with - where the data can be hi-jacked and read RAW into the computer before the camera has a chance to mess it up.

Actually the processing is also (in my experience. mainly) a function of the capture software running on the PC - the if driver supports raw capture & the software sets it, you get raw capture.

Lots of the capture software also seems to get frame rate & exposure time confused. Getting a high frame rate is good, but you're wasting bandwidth if you're recording more frames than the camera is seeing.

There is a balance somewhere between high frame rate / short exposure and longer exposure meaning less gain meaning less noise meaning less frames are needed to get a smooth imaging - but the balance keeps shifting because wobbly seeing makes longer exposures less sharp.

You really need lots of experience with your camera & capture software on your scope in your local seeing conditions to get close to the "right" balance, and the only way you get that experience is by getting things wrong most of the time. Just keep detailed records of what you're doing so that when you get it right (or nearly so) you can use that as a starting point next time.

CMOS / CCD technology is of minor import. CCDs are inherently "quieter" but only provided they're read out relativel slowly - rushing to empty the chip is a good way of increasing electronic noise. And much of the reason for the apparently worse sensitivity of modern CMOS based webcams is because they have much denser pixel sensors, higher pixel count on the same size sensor chip means that the signal at each pixel is smaller hence more noise.

The Celestron NexImage camera still has a 640x480 CCD chip & the supplied capture software is more flexible & more appropriate to astro applications than that which comes with consumer webcams, even the excellent but discontinued Philips SPC900NC. It also comes with a nosepiece already attached so you don't have to "butcher" it to remove the lens. I used to consider it expensive when good consumer webcams were available at around £20, but now it looks good value - if you can't afford to upgrade to a Imaging Source DBK21.

Almost all targets, when imaged with a refractor (unless it's a very good triplet apochromatic) or at altitudes less than about 45 degrees (moon & planets almost all the time), benefit from the use of a UV/IR blocking filter as this reduces smearing due to false colour - the atmosphere acts as a prism. Such a filter is also useful as a "dust cap", permanently left on the camera. Just remember that it's there before trying to image in the UV or IR....

As for rotational smearing of details on Jupiter - 2 mins is an extreme for high resolution systems. With smaller scopes or in poor seeing you can keep recording for longer because there is less detail in the image to smear.

In one minute Jupiter rotates (about) 0.6 degrees or 0.01 radian so the apparent rotational blurring is 0.01 times its radius; now Jupiter at opposition is around 50 arc secs in diameter so the rotation blurring is approx. 0.01 x 50 / 2 = 0.25 arc seconds per minute of elapsed time.

[rawhead]

I am continually flabberghasted by the volume of info associated with this hobby of mine.

I haven't given out any info here that I have not picked up here from other users whose knowledge and experience I respect... In some cases that's been contradidcted and then contradicted again.

Thanks for all the techy info, I have certainly learnt plenty

I have pretty rigidly stuck to max of 10FPS with my webcam. That is going to change. 'Suck it and see' Will also be investigating the Celestron NexImage.

Gavin,

I hope like me this thread has been of help

Cheers

Jon

(will also think twice before chipping in with 'good advice' in future )

[omneferuss]

Ditto here Jon. We're all learning and unlearning/relearning as we go

It'd be a bit dull if it was all just "step1, step2, ..you're done" ..wouldn't it..

Not to mention the variability of circumstances that differ between us, but also the individuality of experience and personality with which we each approach the task, there's a wealth of permutations to be shared...

nothing is immutable! (beyond the 'Laws' of physics ) .....and besides, it's all about experiencing doing it one's self..

.... I personaly wouldn't bother if all I could aspire to was exactly replicating a formulaic rendition of an ossified iconic totem reifying the quo ad nauseum...

Vive la difference! and enjoy the uncertainty ...of course it might be different if one is imaging for scientific purposes where 'control' is crucial to analysis of a collective database of images, I don't know..

but for my part, to Gavin I'd say "Give it a go, mate.. don't limit yourself with artificially imposed limits... there's no adventure without 'danger', and no success without 'failure'."

[tarqs101]

I stayed quiet for a moment as you all lost me!!:)

Thanks for loads of comments and advice!!

Gavin:)

[omneferuss]

Goodo Gavin pardon my sermonising above.. I need to get out more..

But allow me to comment that, for the aperture you are using, and a 'non-descript' webcam, your results to date are a fine achievement already.

...and you are bound to improve on it yet

Russ

ps..has WxAstrocapture worked with your webcam?

[tarqs101]

Thanks Russ really appreciate that.

I am now seriously considering a DSLR...

Gavin

[Mattius]

How does the first Picture at the start of this topic compare to viewing through the scope with no camera?

[Clayton]

Actually the processing is also (in my experience. mainly) a function of the capture software.

There is a balance somewhere between high frame rate / short exposure

You really need lots of experience with your camera & capture software on your scope.

CMOS / CCD technology is of minor import.

Almost all targets, when imaged with a refractor (unless it's a very good triplet apochromatic) or at altitudes less than about 45 degrees (moon & planets almost all the time), benefit from the use of a UV/IR blocking filter

As for rotational smearing of details on Jupiter - 2 mins is an extreme for high resolution systems. With smaller scopes or in poor seeing you can keep recording for longer because there is less detail in the image to smear.

All good points. Just as an experiment I tried 3min on the 22nd Oct and could detect no smearing. I routinely use 120sec as it is a convenient size for me to work with on the old lappy re HDD size and my impatience with processing time

My CCD is 640 x 480 pixels, Jupiter takes up about 100 wide of those with my setup. 5h=300min/100pixels = 3min in perfect seeing before any detail at the centre of the planet moves a single pixel. Poor seeing will routinely cause much more smearing by visibly distorting the image. Just to try to keep it in perspective

[Clayton]

I have adjusted levels ( hope you don't mind? )

[neil phillips]

Good stuff for a cheap webcam Gavin

I tried 15 fps and didnt like the result at all, more noise than extra detail aquired, through more frames, I found using a spc 900.

Also i didnt like 5 fps either, yes the frames were smoother but it just could not beat the seeing.

I was convinced that 30 fps on jupiter was the way to go with a dfk and no compression, however my best result was dropping the frame rate because i found by having smoother frames with less gain needed. I needed to stack less frames, Important why ?

By stacking less frames, k3 ccd tools often gets it wrong, and adds a lot of bad slightly smeared frames into the mix by increasing frame quality, and hence needing less to stack. the final result surprsed me.

by stacking less frames i felt the blur aquired by shooting at 30 fps was reduced when i filmed at 15 fps.

because i was having far fewer slightly smeared frames into the mix. probably half as many, the math 30 fps to 15 fps if the error of k3 ccd tools quality estimation remined the same. which i assume it would, seemed to explain that

but this is a quality estimation problem not a large stack problem. stacking by choosing the frames by eye might have reversed this effect, but its not something i enjoy doing even though there is ways of speeding it up with virtual dub for example.

one has to be careful though, because its possible i was getting better seeing on this particuar capture or better focussing ( i often re focus ) but i suspected this really was happening for sometime.

And feel it actually is true, it makes perfect sense if you think about it. further study will refute or confirm this. but i suspect confirm.

Hope you dont mind me showing you the image that really got me thinking

Heres the image in question aquired at very high mag, actual capture size here not resized. taken with my custom f6 spx 300 about 20 degrees elevation 2009 uk

Interesting thread here guys