Need advice on webcams

[mostlyemptyspace]

Hi all. I have a Celestron Nexstar 8SE 8" SCT. I would like to get started with some planetary imaging using a webcam. 

I would love to get a ZWO ASI120MC, but it's a little out of my budget right now. I'm wondering, what other good, less expensive webcams are there that can compete with the ASI120MC?

I read about the ASI034MC, and while that is less expensive, the resolution is much much less. I'm hoping for something in between, or even better, an off-brand version with similar specs to the ASI120MC.

Also, what brand/magnification Barlow would you recommend I get for imaging Jupiter, Saturn, and Mars? 

[GuillermoBarrancos]

Did you check out the QHY5L-IIc color camera?

[DonFitzg]

Why not have a bash at modding up one of the recommended Philips webcams ? The best price I've seen on the QHY5L is US$ 197.54 excluding shipping (www.cyclopsoptics.com). There are a  few Toucam Pro's and SPC900's on sale on eBay right now, and plenty of advice on modifying these on this website. I've just used the advice to mod two webcams myself - can't give you the results yet as the weather is just too cloudy over Exmoor. The 1.25" adapters can be picked up on eBay for about £12-13. The total cost (apart from your time) would probably be in the region of £60-70.

[jambouk]

My first webcam was off ebay, a modified logitech 4000 with a nose piece, about £38 i think. Did the job nicely; i keep meaning to do a side by side comparison with it and the zwo120mc.

Barlows / powermates, an age old debate; get the best you can afford probably, and 2x or 2.5x will be ok:

http://stargazerslounge.com/topic/210059-barlow-lenses-vs-powermates/

I suspect the frequent poor seeing and low altitude of saturn will be more limiting factors than the glass in your barlow or powermate.

Good luck.

Jd

[JamesF]

I'd suggest that there's nothing terribly wrong with the resolution of the ASI034MC if you wanted to go that route.  The difference is that with the ASI120 you'd probably aim to use it with a 2x barlow in the C8, whereas with the ASI034MC you might be better off with a 3x barlow.  In both cases the resolution of the camera will be exceeding the resolution of the telescope.

I've never used the 034MC so I don't know how well it performs.  It would be nice to see some example images, certainly.  Alternatives (though I'd hesitate to buy these at new prices because I think they're a bit too much these days) might be the DFK21.AU04 or DFK21.618.

James

[JamesF]

I've just used the advice to mod two webcams myself - can't give you the results yet as the weather is just too cloudy over Exmoor. 

Ain't that the truth?  I think I could count the number of clear nights in the last six months without needing to take my socks off

James

[jambouk]

This is just like mine:

http://m.ebay.co.uk/itm/400672194481?nav=SEARCH

Easy to use and does the job. If it goes for under £35 i'd be tempted to get it.

Jd

[jambouk]

There's a few spc900 too but these often go for silly money (£70-80) which seems overly steep to me:

http://m.ebay.co.uk/sch/i.html?kw=spc+900&isNewKw=1&pgn=1&epp=24&cid=28179&cnm=Telescopes+%26+Binoculars&mfs=KWCLK&acimp=0&autoComplete=true&sqp=spc900&_trksid=p2056088.m2428.l2632.R2.TR3.TRC2.Xspc900

Jd

[mostlyemptyspace]

So do you guys think these modded webcams can really stack up to a ZWO ASI120MC, or even an ASI034MC?

[GuillermoBarrancos]

So do you guys think these modded webcams can really stack up to a ZWO ASI120MC, or even an ASI034MC?

No. You can´t compare a 20-40 pounds webcam with a 300 pounds dedicated planetary camera.

But if you are on a small Budget, then a modified webcam is a great place to start.

It´s all about budget. If you are looking for something similiar to the ZWO cameras, but at a lower price, then the QHY5L-II color is a great alternative for 184 pounds.

http://www.modernastronomy.com/camerasPlanetary.html#QHY5L-II

[catman161]

My opinion would be to go for an SPC900 it flashed 880. Great starter cameras and what I started with. Keep an eye on astro buy sell UK for second hand powermates (much better than a Barlow in my own opinion) or you can go down the Barlow route. I wouldn't worry about a webcam being comparable to the ZWO cameras. Unfortunately in astro (as with most things in life) you get what you pay for. I have attached a Jupiter image I did with a Philips SPC900 and 2x televue powermate so you can see what kind of results are possible Let us know what you go for in the end.

[jambouk]

As said above, the modded £30 webcam is not a £250 dedicated planetary camera. It's like asking "is this 12 year old golf GTI as good as this brand new Porche" - daft comparison but trying to give some point of reference.

You've suggested you can't afford the zwo/porche, so the other options are:

- modified webcam

- buy one second hand already modified

- buy the bits and modify one yourself

- DSLR

- second hand other planetary camera as indicated above

- buy the cheaper ZWO

Now there are limitations to each of these, which you can find out about in the forum, and as jamesf says, we've not seen anything yet from owners of the cheaper zwo so it's difficult to know how they compare.

Felix has given you some pointers about the spc900, i could try and find the images i got with my logitech 4000 (but they are in the depths of an external hard drive so i'm not sure i have the energy to hunt for them), and there is plenty of other stuff on the forum of peoples results using other cameras.

Even if you don't get on with your chosen camera, the good thing is you'll be able to sell on reasonably easily and not lose too much money.

Else save up and go for the porche in the first instance... As i said earlier, i'm still keen to do a side by side comparison of my logitech 4000 and the zwo, and see how much difference there is; i suspect frames per second will be the most obvious difference.

Jd

[JamesF]

So do you guys think these modded webcams can really stack up to a ZWO ASI120MC, or even an ASI034MC?

Generally, no.  The dedicated cameras have the benefit of being designed specifically for astroimaging.  They can usually achieve high frame rates without data compression and in the case of colour cameras often allow access to the raw colour data from the camera sensor.  They also tend to have firmware that allows better access to the camera controls.  The design of webcams is often a compromise based on how the manufacturers perceive them being used and those compromises are rarely ones that a planetary imager would choose.

The SPC900 (or SPC880 flashed to 900) has the same sensor as the DFK21.AU04 which has in the past meant it was a good budget camera choice (especially when they could be bought for the price of a couple of beers), but it is only USB v1 so the frame rates are limited and unless the frame size is kept very small it will use lossy compression on the image at anything above 5fps.  It's a very good webcam for planetary imaging, but it will still struggle to compete with a dedicated camera.

There are other budget planetary cameras, but despite most of them being on the market for some time it's not common to see people posting images from them.  I honestly don't know why that is.  There may be a very obvious conclusion to be drawn, but I don't know if it would genuinely be a valid one.  It may just be that people tend not to buy them because they don't see anyone else posting images from them.

James

[leelee970]

Generally, no.  The dedicated cameras have the benefit of being designed specifically for astroimaging.  They can usually achieve high frame rates without data compression and in the case of colour cameras often allow access to the raw colour data from the camera sensor.  They also tend to have firmware that allows better access to the camera controls.  The design of webcams is often a compromise based on how the manufacturers perceive them being used and those compromises are rarely ones that a planetary imager would choose.

The SPC900 (or SPC880 flashed to 900) has the same sensor as the DFK21.AU04 which has in the past meant it was a good budget camera choice (especially when they could be bought for the price of a couple of beers), but it is only USB v1 so the frame rates are limited and unless the frame size is kept very small it will use lossy compression on the image at anything above 5fps.  It's a very good webcam for planetary imaging, but it will still struggle to compete with a dedicated camera.

There are other budget planetary cameras, but despite most of them being on the market for some time it's not common to see people posting images from them.  I honestly don't know why that is.  There may be a very obvious conclusion to be drawn, but I don't know if it would genuinely be a valid one.  It may just be that people tend not to buy them because they don't see anyone else posting images from them.

James

You do have a good point James, you just do not see images captured by the cheaper dedicated planetary cameras.

I myself use the SPC900, but I feel I've reached its limits and will now be moving on.

The options for me are ASI120MC and the QHY5L or maybe DMK21AU618.

recently I've seen alot of the new CELESTRON NEXIMAGE 5 for sale which leads me to think they may not be up to the job.

Lee

[Russe]

In both cases the resolution of the camera will be exceeding the resolution of the telescope.

I just never understood that...

Could you explain resolution of scope vs camera for a complete numpty? Please?

[JamesF]

I just never understood that...

Could you explain resolution of scope vs camera for a complete numpty? Please?

The smallest detail that can be resolved using a telescope can be calculated.  It works out to be related to the aperture of the telescope.  The greater the aperture the smaller the detail that can be resolved.  If you google for Rayleigh Criterion you should find loads more detail on the web.

Obviously with a fixed optical system there's a limit to what can be resolved with a camera, too.  You can't expect to see details that end up appearing on the camera sensor smaller than a single pixel.  By increasing the effective focal length of the telescope however and therefore making the image on the camera sensor larger (or indeed reducing the camera pixel size) it may well be possible to resolve such a detail.

In general when planetary imaging one would be using a focal length such that one pixel would be receiving light from an area smaller than the smallest detail that the telescope can resolve due to its aperture (there are good reasons for wanting to do this, but I have to take the kids swimming so I can't go into them now

Does that make sense?

James

[Russe]

Yes, and how would one calculate things to estimate if the camera is suitable or not?

[jambouk]

Theoretical resolving power of the scope is:

4.56 / aperture in inches

Answer is in arc seconds.

Jd

[jambouk]

The third online calculator works out arc seconds per pixel:

http://www.wilmslowastro.com/software/formulae.htm

Jd

[JamesF]

Yes, and how would one calculate things to estimate if the camera is suitable or not?

I wrote up all the maths behind it here, but the long and the short of it is that you end up balancing an "optimal focal ratio" against the camera pixel size.  You don't have to get it perfect -- it's more of a target to aim for really.  I've always tried to achieve a focal ratio of f/35-ish with my SPC900 and that would be a reasonable target for any camera with 5.6um pixels.  With the ASI120 I go for f/20 to f/25 because of it's smaller 3.75um pixels.  With both my 127 Mak and C9.25 that means I go for a 3x barlow with the SPC900 (the native focal ratio of the Mak is about f/12, so 3x gives f/36) and 2x or 2.5x barlow with the ASI120 (f/24 with the Mak and 2x barlow, or f/20 with the C9.25 and 2x barlow, or f/25 with the 2.5x).  Those SGL planetary imagers using the big f/5-ish dobs tend to be using a 5x barlow with similar cameras I think.

There are practical limits to what can be achieved (if you make the image too big on the sensor by using too large a multiplier barlow you just end up with a useless dim image, for example), but it is perhaps easiest to get whatever camera works for you and then adjust the focal ratio using suitable barlows to reach the optimal focal ratio.

Remember also that these are theoretical figures assuming that the seeing is perfect.  If the seeing won't play then you're never going to get the best results.

James