QHY5L-II opinions

[Lee_P]

Hi all,

I'm toying with the idea of getting my first dedicated astro camera. QHY5L-II (http://astronomia.co.uk/index.php/ma-qhy5l-ii-01.html) seem to have quite a good reputation; fit my price point; and can be used as a guide camera as well as for imaging. I wonder, does anyone have experience of using them for long exposures to image deep sky objects?

I'd also be interested to hear recommendations for other similar cameras.

Thanks!

  - Lee 

[JamesF]

The impression I have is that the CMOS sensors used in these cameras aren't brilliant for long exposure imaging.  There's a fair bit of noise and the hot pixels show up quite rapidly based on my mucking about with them whilst testing with them.

The ASI120MM is based on the same sensor and if you're not in a hurry it might well be that there are a few around second hand later this year, assuming the new USB3 version does the business from a planetary point of view.

James

[Andy Milner]

I plan to sell my qhy5l-II c when the new ASI120mc-s (usb3) is released. The fps increase is reportedly insane.

I'm loving my qhy5l-II colour camera at the moment. I've only had it a few weeks and shot a great Mars and Saturn. I plan to try and guide with it soon when I properly attempt long exposures with my DSLR.

Here's Saturn from Wednesday evening this week. My best yet.

Hope the image is not too compressed on here...

Andy

Sent from my iPhone using Tapatalk

[hobsey]

You can't go wrong really with the QHY5L-ii unless you want to do long exposures.

I think the number of people who own this particular camera on SGL pretty much speaks for itself.

[wuthton]

I use one for guiding, no complaints here.

[Lee_P]

Thanks for the replies everyone. Regarding DSOs, I'm currently using a Nikon D700, which has great high-ISO performance but the huge sensor makes most objects seem tiny. I suppose part of my motivation behind looking at other cameras was having a smaller sensor to get a bigger view. Would I actually be better off just putting a Barlow lens in there and then using the QHY5L-II to guide the longer exposures?

...and when considering the QHY5L-II as a guide camera, can anyone recommend a good (but cheap!) guide scope that it will work with?

Thanks again!

[JamesF]

The QHY5L-II works fine with a finder-guider for me, though perhaps the most common choice for a guidescope is the ST80.

Regarding the apparent size of DSO images, you may be thinking about the size of the sensor the wrong way.  What would be the difference, for example, between using the D700 and cropping the frame down to the size of the QHY5L-II, or using the QHY5L-II to start with?

Instead you probably need to be concentrating on pixel size and focal length (or focal ratio, if you prefer -- with a fixed aperture one is as good as the other).  If you want an image that covers more pixels then you either need smaller pixels or a larger image on the sensor.  The D700 has relatively large pixels, but hardly excessively so.  They are over twice the size of those on the QHY5L-II, but halving the pixel size also means that only a quarter of the photons arrive per photosite in the same period of time, dramatically increasing exposure times.  The same applies if you increase the focal length -- the available light is spread out more across the sensor, so the exposure takes longer to capture the same amount of data per pixel.

I'd suggest that if you want to start imaging small-ish DSO targets at fairly long focal lengths (M27 and M57 spring to mind as immediate possibilities) then you need to look at what sensor size is required at the local lengths available to you and then what cameras would suit.  It may well also be sensible to consider mono cameras as a means of recovering some of the additional exposure time required for long focal length exposures.

To keep the budget under control, perhaps the simplest way forward would be to increase the focal length using with the D700 and use the QHY as a guide camera to compensate for the longer exposure times required.

James

[Astral Enigma]

I think I'm currently asking myself the same question. I know I need a decent dedicated camera for planetary use but want to move onto DSOs later. Currently I've borrowed a Phillips SPC900 but it's not giving great results - I guess the seemingly clear but actually hazy weather isn't helping... In fact I'm getting images pretty much as good with my Pentax K5 DSLR.

The QHY5L is on my possible list - along with the Neximage5, or possibly the Skyris132 - or Opticstar PX-75C or PX-137C.... too many to choose from (there are others of course).

I know I need a decent barlow too, which could well improve the SPC900. A 3x has been suggested - perhaps Skywatcher (3 or 4 element) or the Celestron XCel-LX ? 

Thoughts, anyone? They'll be going mostly on my 925 SCT, but also Nexstar SE6. Thanks as ever!

[JamesF]

You can't really choose the barlow before the camera.  The "optimal" focal length/focal ratio for the imaging setup depends on pixel size, so ideally you pick the barlow to match your camera and OTA.

Off the top of my head I don't think there's too much more planetary imaging to be had here in the UK until getting towards mid November when Jupiter reappears so I'd be quite tempted to sit on my hands for a while and see what happens.  ZWO have announced their new USB3 version of the ASI120 which means there may be a few USB2 models on the second hand market over the next six months.

If you're not getting the quality of image you'd like with the SPC900 then a change of barlow may help if the one you have isn't great.  With my 127 Mak I used to use the Revelation 2.5x barlow which is well-regarded and add extensions between it and the camera to get higher multiplier values.  If you eventually plumped for either the QHY5L-II or ASI120 though you'd probably want to stick with 2x.  There are other things that may help too though.  For instance, checking the collimation of the OTA, making sure you're using sensible settings for the SPC900, motorising the focuser to allow more accurate focusing, practise at processing, too.  If your current barlow is poor then it makes sense to replace it.  I wouldn't blame the camera before checking everything else though.  It won't (these days) produce images that set the world on fire, but it certainly is capable of producing quite decent output.  If you can't get images that show the turbulence following the GRS or the festoons in the region north of the NEB then the camera is probably not the place you should be looking.

James

[Astral Enigma]

Thanks James - at the moment I don't have any barlows! So getting one is high on my list of priorities, but as the web camera is borrowed I'm planning to get something myself...

My thoughts for a 3x barlow were that 2x is an improvement but probably not noticeable enough and 5x is pushing it (I could always get that later too if the need arose). So it comes down to which - Skywatcher do a couple, Celestron do their XCel LX, Opticstar have one, all in the £50-£70 region, otherwise I could look at Televue but that triples the cost! On the other hand if I know they are incredibly much better and that's what I'll end up feeling I need, I'd do better to get it to start with (though rather hoping I don't need to!).

[JamesF]

The intent behind using a barlow is (or perhaps "should be" to match the resolution of the camera to the resolution of the telescope.  There's little point in massively exceeding the resolving power of the telescope as it just makes life harder and doesn't really achieve much that you couldn't do in processing.  As it turns out the "optimal" focal ratio is related to the pixel size of the camera.  There's a fair bit of leeway, but I worked out that with the SPC900 you really want to be somewhere around the f/35 mark, though anything between f/30 and f/40 is probably reasonable.  To achieve that with my 127 Mak (which is a smidge under f/12) I used the Revelation 2.5x barlow with an extension to get the factor up to a bit over 3x.  Now I'm using the ASI120 which has a much smaller pixel size and really only needs to be at around f/20 I've stopped using the Revelation barlow altogether and bought a Tele Vue 2x second hand.  This holds regardless of the telescope being used.

The Revelation 2.5x also has the benefit of being criminally cheap for how good it is.  I think it's sub £35 these days at Telescope House.  You could easily spend double that or more and get nothing better.

James

[hobsey]

The Revelation 2.5x also has the benefit of being criminally cheap for how good it is.  I think it's sub £35 these days at Telescope House.  You could easily spend double that or more and get nothing better.

I second this, lovely piece of optics for the money.

[Astral Enigma]

Thanks James, Anthony. The Revelation is now an option! Although the Celestron XCel LX is high on the list too.

[Astral Enigma]

I resolved the barlow question by upping the budget and, for once, buying what I probably ouight to buy in the first place rather than something less and having to upgrade.... so now I have a 2.5x Televue Powermate. Still not decided about the cam era yet though... NexImage5 or QHY5L-II are the front runners although perhaps they each have some advantages over the other. Prices seem similar. Thoughts, anyone please?

[lensman57]

Hi all,

I'm toying with the idea of getting my first dedicated astro camera. QHY5L-II (http://astronomia.co.uk/index.php/ma-qhy5l-ii-01.html) seem to have quite a good reputation; fit my price point; and can be used as a guide camera as well as for imaging. I wonder, does anyone have experience of using them for long exposures to image deep sky objects?

I'd also be interested to hear recommendations for other similar cameras.

Thanks!

  - Lee 

Both QHY5L ii and the ASI 120 are decent planetary cameras. They can be used for up to 10s exposure with a fast F ratio scope to play around with some very bright DSOs for fun if enough frames are stacked, 100 or so at the very least, to reduce the thermal noise but as a dedicated DSO imagers these are hopeless.  They also work well as a guide camera.

A.G

[Merlin66]

I recently "upgraded" from the ol' original QHY5 camera to the QHY5L II(mono) for spectroscope guiding.

The chip size is smaller in the QHY5L and I'm not convinced the smaller pixels add anything to my guiding ability.

The improved sensitivity however is noticeable (as are the hot pixels!)

2x2 binning for guiding works well for me with the C11 at f10 (similar to an on axis guide system)

HTH