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zwo asi 174

sooot

By sooot
in Discussions - Cameras

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JamesF

JamesF

Posted
Posted

Somehow DHL has transferred mine from Amsterdam to Brussels. Given that Groningen is about as far from Belgium as you can get, this is puzzling (apart from annoying). The status hasn't changed since 2:00 AM :(

It is however reassuring to see that DHL are promoting incompetence world-wide rather than just singling the UK.

James

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Davey-T

Davey-T

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Sounds like my Moonlight focuser that went on a World and UK tour and still got delivered to the wrong address by Parcelfarce, unfortunately the occupants were on a months holiday and after swearing it had been signed for they found it two days later and sent it to the local PostOffice who wouldn't let me have it without the postcard they'ed put in the wrong door  :grin:

Dave

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Luke

Luke

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There was a brief clearing here, I sort of blew the gap by testing new gear, not sure I will get anything useful out of it.

Anyway, what I discovered, is that the nosepiece supplied with the ASI174 is too long to be of use with a Quark and my 0.5x reducer, the reduction was far too strong it looks like, with a lot of vignetting (longer the gap to the sensor, the greater the reduction). I should have seen that coming, as I tried extending the reducer a little bit with my other camera, and that vignetted too, and is a smaller chip. So this was to be expected really! :rolleyes:

I removed the reducer and no vignetting I could see at all, wohoo! Quite a lot of small Newton's rings, but I am hopeful these can be treated with a flat, I didn't manage to test that in the brief time. The detail looked decent on screen. Slowly slowly, 10 seconds here, 20 messed up minutes there, I am looking forward to giving it a proper test. Hopefully before Christmas :grin:

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Amra

Amra

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Crappy cloudy weather all weekend, was hopeful on saturday morning, but it clouded over of course for the remainder of the day just when I had setup. Can't wait to try this sensor in white light on my Skywatcher 200P, I've had pretty good results with the QHY5L-II colour so this sensor should totally blow it away.

At least I did manage to clean my mirrors & colimate, so it's good to go as soon an opportunity presents itself. :)

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rwg

rwg

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I figures that everyone would be pointing these at Jupiter, so I'd try something a bit different for first light (actually, that's just my excuse... have a bit of a cold coming and didn't fancy fiddling around in the cold taking the ED81 off the mount and putting the SE8 or the Mak on it.)

Anyway, thought I'd go for some easy DSO targets to see if the amp glow and hot pixels do come out nicely with dark frames. Turns out that they do...

m42_asi174mc.jpg

3 minute exposures @150 gain. 8 lights, 12 darks. Just stacked in DSS and levels/saturation adjusted. A bit noisy (not enough total exposure) and I need to turn down the gain to avoid saturating the trapezium, but not too bad.

For a bit more of a challenge...

horsehead_asi174mc.jpg

4 minute exposures @200 gain. 10 lights, 6 darks. I suspect that the artifact to the right of the horsehead is a result of reflections between the window over the sensor and the CLS filter perhaps.

Quite pleased really - maybe Jupiter another evening :)

cheers,

Robin

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Luke

Luke

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Well I salvaged something from my session with my Tele Vue 85, Quark and of course the ASI174. Too much reduction, vignetting (cropped off), rushed focus, failure to grab a flat, so I limped home to get this. Not quite happy with how I processed it but glad I got something of the fab filaprom and observed it on the lappy screen. Hope the weather picks up for all and Michael I hope your camera makes it there soon, hope you don't get charged import duty twice or mulitple, or the Basler could work out cheaper!!

Postage, eh? My wife has been sent three out of four wheels for her car. Kinda needs the fourth as well really... :grin:

16359949819_bc8d7fa3e5_c.jpg

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Luke

Luke

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Sweet image, Michael, glad you got the killer fila too :laugh:

I just wouldn't want any folks thinking my effort was a good test of the ASI. I am trying an inverted version to see it I can get a little more detail out, I think that will give me a bit less of an issue with the lack of a flat because of how I process. Couldn't see any Newton's rings at all with the reducer, quite pleased about that. My Grasshopper showed rings last time I tried with  Quark and no reducer, so, hopefully, mild indeed?

A question for the CMOS folks: does 2x binning mean 4 times as long for the exposure? That's what I seem to get so far. With my Grasshopper 3 CCD, it was the other way round, 1/4 exposure time for 2x binning. Is this a CCD vs CMOS thing? What I love about CMOS is speed up when you reduce the width, my Grasshopper only got faster if you reduced height, width made no difference.

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Astroboffin

Astroboffin

Posted
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What does the gut mean when he says on the advert that he is sticking with the ASI120mm for the resolution on his set ups??

Is that something to do with getting the right size pixels to match the scope??

As I have an 8" SCT 2000mm fl @f10, so which would be the best match for me, and I sometimes use a TV powermate 25x to give f25

Cheers

AB

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JamesF

JamesF

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What does the gut mean when he says on the advert that he is sticking with the ASI120mm for the resolution on his set ups??

Is that something to do with getting the right size pixels to match the scope??

As I have an 8" SCT 2000mm fl @f10, so which would be the best match for me, and I sometimes use a TV powermate 25x to give f25

Cheers

AB

I'd not be surprised if you have the reason pretty much correct.

f/20-ish works nicely with the 120MM and is achievable for most people.  If your choice of scope for planetary imaging is, say, a large Skywatcher GOTO dob however, reaching f/30 to f/35 for the 174MM could be a bit of a pain.  I'm guessing there as it's not what I use, but it doesn't seem an unreasonable conclusion.

It can very much be a "balancing of compromises" issue though.  For example, with my C9.25, secondary focuser and filter wheel together with a 2x barlow it's quite hard to keep the focal ratio out of the high 20s with the 120MM.  Put a flip-mirror in and it's nigh on impossible.  Sorting that out to my satisfaction has proved awkward.  It may actually be easier just to go with the 174MM and increase the focal ratio a little.

As to what might be best for you, there's probably no definitive answer that anyone else can give you.  If I were just using the C8, powermate and camera then I'd probably go for the 120, but that may change over time as you decide you want to modify your setup, say.

James

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Astroboffin

Astroboffin

Posted
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I'd not be surprised if you have the reason pretty much correct.

f/20-ish works nicely with the 120MM and is achievable for most people.  If your choice of scope for planetary imaging is, say, a large Skywatcher GOTO dob however, reaching f/30 to f/35 for the 174MM could be a bit of a pain.  I'm guessing there as it's not what I use, but it doesn't seem an unreasonable conclusion.

It can very much be a "balancing of compromises" issue though.  For example, with my C9.25, secondary focuser and filter wheel together with a 2x barlow it's quite hard to keep the focal ratio out of the high 20s with the 120MM.  Put a flip-mirror in and it's nigh on impossible.  Sorting that out to my satisfaction has proved awkward.  It may actually be easier just to go with the 174MM and increase the focal ratio a little.

As to what might be best for you, there's probably no definitive answer that anyone else can give you.  If I were just using the C8, powermate and camera then I'd probably go for the 120, but that may change over time as you decide you want to modify your setup, say.

James

Thanks for that James, so what scope would suite this new 174 camera, would it be the smaller refractors?

And if I were to put one of these camera on my 8" SCT with 2.5x powermate at f25 what would be the issues, would I be getting too many arc seconds of sky per pixel, or not enough?

I don't really understand this pixel scale stuff, it was more luck that judgement that I explained it correctly in my earlier post.....

Sorry for all the questions

:)

AB

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nicoscy

nicoscy

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OK, if I am wrong, please someone correct me. Here goes:

The ideal focal length depends on your seeing conditions which determine what the ideal arcseconds to a pixel number you can aim for.

In my case here in Cyprus, one can regularly aim for 0.13. Given this number, there is a formula for determining the ideal focal length to image to get full use of the camera.

S=(205 x P)/FL therefore FL = (205 x P) / S where P is Pixel Size and S is ideal arcseconds you would like to aim for.

To make life easy, I have an EXCEL sheet for you in my Dropbox if that helps. I have my Nexstar camera and I added the two ZWO (120 and 174). Obviously the focal length must not be ridiculously long, so with my upcoming Intes M500, I should not work above FR 25 to 27 for planetary, but I can work on the moon with the ASI 120 hence I will pick that as well.

Basically just plonk your scope's diameter and you are set to go. Also the ideal arkseconds where you are located. People should be able to make a recommendation given your local conditions and their experience in the UK. Then you must consider if that focal length is within your instrument's reach.

OK, people, please correct me if I am wrong here as I am a noob when it comes to imaging and just getting into it...

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JamesF

JamesF

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The idea with the image scale is that you match the resolution of the camera to the resolution of the OTA by changing the effective focal length of the OTA.  Generally this means trying to achieve a particular focal ratio for a given camera pixel size.

The ASI174 has large pixels, so requires a long focal length relative to the aperture (that is, a large number for the focal ratio) to match the camera and OTA resolutions.  SCTs and Maks are probably the easiest of scopes to do that with.  They're not without their own little wrinkles however, which is why I started to have problems when I added all the extra bits to the back of my C9.25.

But it's not a case of "this one works" and "this one doesn't".  It's more about whether you're willing to do what's necessary to get one or the other where you want it to be.  For example, using a flip mirror massively increase the focal ratio for me.  I then had to decide whether I could live without the flip mirror or find another solution (which may have involved throwing a load more money at the problem).

There's another side to the 174 cameras that isn't particularly relevant to planetary imaging however.  It has a large sensor.  Some people will certainly use it for, say, solar Ha imaging and accept that the resolution may not be the best possible purely because it means they either don't need to make mosaic images, or can significantly reduce the number of panes required.

There isn't really a right or wrong answer here.  There's what is probably the optimal solution, and there's what works for each individual.

James

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Luke

Luke

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Interesting thoughts, James. I found the rule of thumb you mentioned in another thread helpful:

Or, as someone pointed out a while back, around five to six times the numerical value of the pixel size in um.  The ASI120 has a pixel size of 3.75um, giving a range for the focal ratio of 18.75 to 22.5.

I had concluded with my Grasshopper 3 camera (3.69um, similar to ASI120) from a number of captures that about F20-ish was right. F10 SCT and 2xBarlow seemed good, 3xBarlow seemed pushing it a bit. With my F7.5 frac, 3x Barlow just about okay, 5x Powermate a bit pointless.

So... I wonder if the 174 with its bigger pixels will be nice for Quark and no reducer. With its integrated 4.3x Barlow, it's putting my F7.5 scope at about F32... Of course, I'll need good conditions at that focal length.

One thing I am hoping with this camera is that I can move up one Barlow level for best conditions (or use Quark without reducer, at its defaut 4.3x) and effectively gain a new mag level at prime focus, with the bigger pixels giving a lower power image (on top of the wider chip, of course).

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