Planetary camera question...

[Twiggles]

Sky at night magazine had a review of the ASI034-mc camera this month, it is available for £118 (http://www.365astronomy.com/ZWO-ASI034MC-Colour-1-4-CMOS-USB2.0-Camera.html) and I assume it would at least be a step up from my Xbox camera. Has anyone used one that could give me any feedback on performance? I like the idea of limited DSO capture, at 60 second exposure limits I suppose it would just be brighter targets? Perhaps orion neb and Andromeda?

How would this compare to the qhy5l-ii? It can be had for £135, again for the one shot colour version. Which of the two would you reccomend and why?

For info, I intend to use it on a skywatcher 130m (900mm focal length) with motorised eq2 mount. I hope to get a skywatcher 127 mak later this year specifically for planets. Primary use would be solar system objects (including some white light solar and some lunar). As I intend to get a second scope later in the year budget limits me to the two cameras mentioned so please don't tell me to get an ASI120!

Kind regards

[ronin]

I would have thought the QHY5L, simply because it has more pixels and smaller ones so I would have said is a bit more suited to planetary as planets tend to be bright and so you can opt for a smaller pixel size. Well that seems the general opinion/rule but as there are numerous opinions/rules it all seems a bit arbituary.

The QHY5 chip is small at 4.83mm x 3.63mm although the same as the ZWO but the pixels are 3.75x3.75µm the ASI is 5.6x5.6µm. With the chip size moon shots will be partial or mosaics.

I think the chip in the QHY is one that the initial ASI-120 came with, I think that at some time they changed chips, check it out.

[jambouk]

You need to appreciate the how the size of the sensor will affect what you can capture.

Have a look on:

http://www.12dstring.me.uk/fov.htm

Plug in your telescope (I can't find a SQ Explorer 130 with a focal length of 900mm but one can alter the parameters); select the camera in question, then pick an object. You will see at 900mm with such a small sensor (1/4") the field of view is very narrow - fine for planetary, but I suspect will make anything else tricky. Even for planetary you will have trouble finding the planet, but that is the same even for bigger sensors. There is no way you'll get M42 or M31 unless you take a multiple image mosaic; probably 9 panel for M42, lots more for M31.

I don't know how the technology has changed since ZWO first made their 120MC to now with the 034MC, but there was a lot of noise with the 120MC with exposures over 30 seconds or so. Lots of noise. These are not cooled, and unlike the CCD sensors, they heat up throughout the exposure, not just on reading the sensor at the end of the exposure. What I'm trying to say if these are planetary cameras, not for DSOs. Yes a few people have got some images of DSOs with them, but I think you will be on a hiding to nothing if you have expectations to be imaging DSOs left right and centre with this camera.

Here is another image which goes some way to try and demonstrate what impact a small sensor has on imaging something big like M31:

James

[Twiggles]

You need to appreciate the how the size of the sensor will affect what you can capture.

Have a look on:

http://www.12dstring.me.uk/fov.htm

Plug in your telescope (I can't find a SQ Explorer 130 with a focal length of 900mm but one can alter the parameters); select the camera in question, then pick an object. You will see at 900mm with such a small sensor (1/4") the field of view is very narrow - fine for planetary, but I suspect will make anything else tricky. Even for planetary you will have trouble finding the planet, but that is the same even for bigger sensors. There is no way you'll get M42 or M31 unless you take a multiple image mosaic; probably 9 panel for M42, lots more for M31.

I don't know how the technology has changed since ZWO first made their 120MC to now with the 034MC, but there was a lot of noise with the 120MC with exposures over 30 seconds or so. Lots of noise. These are not cooled, and unlike the CCD sensors, they heat up throughout the exposure, not just on reading the sensor at the end of the exposure. What I'm trying to say if these are planetary cameras, not for DSOs. Yes a few people have got some images of DSOs with them, but I think you will be on a hiding to nothing if you have expectations to be imaging DSOs left right and centre with this camera.

Here is another image which goes some way to try and demonstrate what impact a small sensor has on imaging something big like M31:

James

Thank you for your response James, as I said in my original post, primary reason for the camera is planetary, if I could get the occasional DSO that would only be a bonus but its not the prime reason for selection of the cameras, price is. I have played around with the link you provided and ultimately I think the wider range of resolutions provided by the QHY5L-ii might make it a more attractive proposition than the ASI034, plus it has the ability to be used as a guide camera should I move in that direction in future, the ASI does not have the ST4 port.

Still, if anyone does have experience with either camera could they please post something with their opinion about the relevant device?

[JamesF]

I believe the ASI034MC would be a significant step up from the Xbox camera.

The QHY5L-II colour is disgustingly cheap on special offer at the moment.  I wonder how long that will last.

My thoughts on the QHY5L-II colour:

It's a lot of camera for £135

Larger sensor may be handy for solar/lunar imaging

Convenient camera body for moving around to achieve focus if you're short of focuser travel

Smaller pixel size means you don't have to go mental with barlows to get a good match to the OTA

The drivers can be a bit ropey

Can be used for guiding

And the ASI034MC:

Easy to fit to a nosepiece, T2 or 2" thread

Pixel size means the ideal focal ratio is around f/30

Small sensor is no big deal for planetary, but a bit more of a pain for anything bigger.

Support seems pretty good and responsive

Software seems fairly stable

I think either is going to be a struggle for DSO imaging as CMOS sensors can be quite noisy on long exposures, and the 034MC is really too small for most DSO targets anyhow (it might be ok for some globs).  The larger pixels of the ZWO camera might work in your favour giving increased sensitivity, but I've not seen a graph showing the sensor performance to compare to the QHY so I don't know.

James

[riklaunim]

ASI034MC can be replaced with Altair Astro GPCAM which is ASI120/QHY5L-II clone in much lower price.

as planets tend to be bright and so you can opt for a smaller pixel size.

Pixel size is irrelevant for planetary imaging (aside of extreme values). The smaller pixel the faster the optimal f/ratio will be. Result the same. "Brightness" the same.

[jimbo747]

I've not managed to get my qhy5l iic to work yet despite many attempts in day light and a lot of swearing. I reckon its either because my laptop is USB 3.0 or my dot net installation is corrupt. CBA to reinstall windows. Sharpcap et al will detect a camera but just show a gray image, nowt on histogram even shining a bright led torch on the chip. I'll try it with the little tablet I have, otherwise it will just go in the bin. Modern astronomy isn't exactly amazon so won't be able to return it after so many months.

[rwg]

I've not managed to get my qhy5l iic to work yet despite many attempts in day light and a lot of swearing. I reckon its either because my laptop is USB 3.0 or my dot net installation is corrupt. CBA to reinstall windows. Sharpcap et al will detect a camera but just show a gray image, nowt on histogram even shining a bright led torch on the chip. I'll try it with the little tablet I have, otherwise it will just go in the bin. Modern astronomy isn't exactly amazon so won't be able to return it after so many months.

Try turning the 'high speed mode' (I think it's called that) for the QHY to off/zero. SharpCap currently defaults it to on, but some USB chipsets seem to take exception to it. I'm going to change the default to off in the next version.

cheers,

Robin

[rwg]

Pixel size is irrelevant for planetary imaging (aside of extreme values). The smaller pixel the faster the optimal f/ratio will be. Result the same. "Brightness" the same.

Some people think this is a heretical statement, but it makes sense to me. A sensor with 4 micron pixels at f/30 should give the same result as a sensor with 2 micron pixels at f/15 (providing the sensor have equivalent quality - certainly the number of photons falling on each pixel will be the same). Of course you might even say that the lower f ratio is preferable - after all taking *out* the barlow lens will reduce light loss and distortion...

cheers,

Robin

[Twiggles]

Thanks to everyone who commented. In the end (and out of curiosity!) I ended up purchasing an Altair GPCam (colour) from the folks at Tring astro. It arrived on Monday so I set about downloading the drivers and getting latest version of SharpCap. Now I know it is not designed for DSO's, but as there are no planets to try it on that are in a reasonable viewing position I decided to try for some anyway.

First off, an easy target and went for Vega. Showed up nicely in both Sharpcap and altairs own capture software (which I found quite easy to use in all fairness), tried for the ring nebula but no joy, couldn't get Andromeda galaxy either. That was Monday or Tuesday night (whichever was clear I forget!). Biggest issue I had was trying to find focus.

Tonight, had a little bit more success. Tried a few of the stars in Cassiopeia and they showed up fine and when loading Sharpcap had a dialogue tip box popup telling me about the focus aid. That is great! Had lots of fun just trying to get the lowest numbers on FWHM? Unfortunately as I have only got a red dot finder, having to search for an object, then centre it using eyepieces etc makes refocusing with the camera quite difficult. I tried for the ring nebula again, but still couldn't pick it out on the camera, probably due to the refocusing issue or not being correctly centered.

Had some success with M13 (Hercules Cluster), being able to get it on the camera and achieve some focus. The downside to this was that it highlighted how inadequate my EQ2 mount is. It has the RA motor, but a combination of not being able to get accurate enough polar alignment and suffering from the shakes everytime you focus, the wind blows or someone sneezes, meant that it just wasn't worth trying exposures longer than a few seconds. Instead I just set it to as long as I dared and watched it travel across the screen, amazed more than anything that I had managed to actually get it there in the first place.

So, am I happy with the camera? Absolutely, even focusing on stars is an opportunity to learn how to focus the camera, get to grips with the various capture software options and generally get ready for Jupiter later in the year. It's definitely a step up from the old webcam and I look forward to seeing how my images might improve. Its also motivating me to get outside a bit more and look for DSO's. ST4 point mean that in the future, funds and ability allowing, it can be put to use as a guide cam.

The bad points? Well I guess the main ones are that it is now showing that I really should consider a sturdier mount and possibly changing to a guide scope rather than RDF. The light pollution is also killing my ability to find DSO's leading to huge frustration, even if I cant image them it would be nice to be able to find and then look at it! Long exposures do get very noisy so its not going to perform well there, but its not supposed to, so who cares?

[Scorpius]

I tried for the ring nebula again, but still couldn't pick it out on the camera, probably due to the refocusing issue or not being correctly centered.

The Ring Nebula is small and not extremely bright so don't expect it to jump out at you at a focal length of 900 mm with that camera. It would be very small on the screen and it would take exposures longer than a few seconds to spot it if you could even pick it out at all with dodgy tracking. Perhaps a better DSO to view on screen with your setup would be M27 which is also a planetary nebula but both brighter and larger than M57.

As far as focusing - get a Batinhov mask. They're inexpensive and work very well. Focus on a bright star near the intended target then point the scope as accurately as possible to where M27 should be while setting the camera to take longer, looping exposures while you attempt to zero in on its exact location.

For me personally - I'd be lucky to find the moon if it weren't for the goto capabilites of my AVX...