First light with 1600MM

[Demonperformer]

Last night was the first time I had used my new ZWO ASI1600MM-cooled "in anger". It is now busy taking some flats, after which I will get the result processed and see what it looks like.

I was using APT, and the first thing I noticed was that I was unable to get the camera down to the sort of temperature I had been managing during my "test" sessions. The lowest I was able to achieve stably last night was -17°C. Well, that is a lot lower that I could achieve with my DSLR, so I decided to go with that. I was using the camera unfiltered and my first set of subs were of NAN - at least, that was the theory. It was not showing up in the individual subs and there was a bright star close to the middle of the screen - I have been wondering if I forgot to realign the scope after I centred on Deneb? When I get a result, I will do a plate-solve. I was using 20s subs and set the gain to a mid-range 300. This was not really producing round stars. I know from previous tests that the PE on my mount is about 30" p-to-p, which averages to about 2.5" in a 20s sub. My image scale is 3.91"/px so I would have thought they would not be too bad. Mmmm.

After this,I moved onto M31, and found that reducing the exposure time to 15s produced a much less saturated image than 20s, so decided to run with that. Unfortunately, I started getting a lot of high intermittant cloud during these subs, so I do not know how many of them are going to be useable.

I was going to take my flats at the end of the evening, but could not get my ELP to light. This morning I discovered why when I realized it helps if the power is connected the right way round! I was also going to do my darks this morning, but again ran into cooling problems. I could not get the camera below about -12°C/-13°C. I am definitely going to have to keep an eye on this and get in touch with 365 (from whom it was bought) if the problems continue.So, anyway, I am going to have to do the initial stack without any darks.

All-in-all, it was a bit of a "messy" session, but I think it does hold some promise for the future.

One other thing I discovered last night was in relation to the tripod height. I normally use it at minimum height - I find it hard enough to attach my big scope to it, without having to lift it to head-height. But I found that my LP is a whole mag worse at that level than if I raise it to eye-level (as measured on my SQM). So, in future, when using just the camera and lens, I think I will use the extra height. I suppose the positive in this is that it shows that the light from the streetlights is actually quite directional downwards, if a couple of feet in height makes such a difference.

I will add results of stacking when I have them (if they are worth it!). In the mean time, here is a photo of my setup taking the flats [the camera and lens had been left bolted to the dovetail bar overnight, so everything was still in the same orientation].

Thanks.

[wimvb]

I guess there is a learning curve for any piece of equipment.

How did the images turn out?

[Demonperformer]

The M31 image turned out GHASTLY. 60/100 subs did not even get into the filelist, and it seems they are just a bunch of zeroes (thread). The Deneb region ones are being done at the moment.  What with that and the fact that the cooler seemed to be more limited than spec is giving me serious cause for concern over this camera (the individual one, rather than the make). I will be doing some more tests, but, if problems persist (and others using this camera do not seem to be having them), I will go back to 365 (from whom it was purchased) and have a 'quiet word' with them ...

[Gina]

I got mine from FLO - my favourite supplier by far

[Demonperformer]

Well, I have no doubt that, if necessary, 365 will act as any reputable retailer would. If not, there is always the SCC - in which case, this will be reported on the forum.

[Jokehoba]

5 hours ago, Demonperformer said:

... the fact that the cooler seemed to be more limited than spec...

What current rating is the power supply you are using? Maybe it's not powerful enough. I use a 4A rated PSU.

[rwg]

My 1600MM hits -20C at pretty much max power when used indoors. Last night it was at about 24% cooler power to hit -20C outside (air temperature about 6-8C).

The missing FITS data sounds like it may be an APT bug perhaps?

cheers,

Robin

[Demonperformer]

1 hour ago, Jokehoba said:

What current rating is the power supply you are using? Maybe it's not powerful enough. I use a 4A rated PSU.

It's one of these, which gives 4.0A @ 12V.

[Demonperformer]

42 minutes ago, rwg said:

My 1600MM hits -20C at pretty much max power when used indoors. Last night it was at about 24% cooler power to hit -20C outside (air temperature about 6-8C).

The missing FITS data sounds like it may be an APT bug perhaps?

cheers,

Robin

I will try the cooler on Sharpcap this afternoon and see what results I get. Certainly, if the problem is with APT rather than the camera, this would make life easier.

Thanks.

[Demonperformer]

What a BOZO! - I've just checked the power supply and (for some unknown reason) the voltage was turned down to the minimum of 5V. Have no idea when or why I did this, but have a pretty good idea that this would not help the camera in operating at peak efficiency. In fact, I am rather amazed that I was getting anything at less than 50% operating voltage.

OK, will now give it a go at the proper voltage, and see if this makes a difference.

[wimvb]

Nice to see it wasn't the camera. I made the same mistake with my mount once. Electronics worked fine, but motors seemed dead. Until I found out that the power supply was at 5 V. "Welcome to the club." 

[Gina]

My camera reached -30°C last night - ambient temperature was in single figures.

[Demonperformer]

Well, that certainly made a difference.

I didn't quite manage to get to 40 below ambient (15.2C) - only managed 39.6. Made a note of some times as I was going [get something positive out of my fiasco]:

15 below ambient: 3m, 23 below ambient: 6m, 32 below ambient: 10m, 37 below ambient: 14m, 39.4 below ambient: 19m.

I will have to give some thought as to how much those extra 2.4 degrees are worth in terms of the extra time taken to get there.

Thanks.

[Demonperformer]

3 minutes ago, Gina said:

My camera reached -30°C last night - ambient temperature was in single figures.

That would be on a par with the figures I have got this afternoon. How long are you taking to get there, Gina? [I guess you are using APT's cooling aid?.]

[Gina]

Yes, APT Cooling Aid for imaging runs but I haven't actually timed it.  I use SharpCap for setting up and the temperature goes down much more quickly in that though it's still regulated and doesn't run the cooler at 100% initially.  It starts off at a low cooling power and gradually increases it.  I just set the temperature at -30°C or whatever I want as the set-point if that's less.  I've been using -25°C set-point temperature for more consistent results and matching darks for calibration.  APT seems to take a lot longer to reduce temperature than SharpCap.

Another thing I've noticed is that the temperature actually goes up for a while after starting cooling, before starting to go down.

[Demonperformer]

Right, APT's warm aid has raised the temperature back up to where I started, so off to have a go on Sharpcap and see how that does ...

[rwg]

SharpCap runs the sensor all the time, which will generate more heat than it sitting idle. Also, I'd expect it to generate more heat running 20fps @ 50ms exposures than running 15s exposures, so you might find the temperature that you get to depends on your exposure setting.

cheers,

Robin

[Gina]

I use just a 1s pause in APT so the sensor is running almost continually when doing DSO imaging and around 60s exposures.  Whether more or less heat is generated when reading out than imaging I don't know.

[rwg]

17 minutes ago, Gina said:

Yes, APT Cooling Aid for imaging runs but I haven't actually timed it.  I use SharpCap for setting up and the temperature goes down much more quickly in that though it's still regulated and doesn't run the cooler at 100% initially.  It starts off at a low cooling power and gradually increases it.  I just set the temperature at -30°C or whatever I want as the set-point if that's less.  I've been using -25°C set-point temperature for more consistent results and matching darks for calibration.  APT seems to take a lot longer to reduce temperature than SharpCap.

Another thing I've noticed is that the temperature actually goes up for a while after starting cooling, before starting to go down.

SharpCap actually doesn't do anything smart with the cooler power - that's all down to the camera driver. SharpCap just tells it the target temperature and the driver gets on with it. I believe that the driver uses a PID algorithm (https://en.wikipedia.org/wiki/PID_controller ) to set the power percentage and ensure that the final temperature is stable. The soft start may just be a byproduct of this algorithm.

cheers,

Robin

[Demonperformer]

Well, that was instructive.

In 3m, instead of getting to 15 below ambient (APT), I was 34 below ambient. It stalled-out at 38.7 (cf 39.6) below ambient, but it got there in 5m (cf 19m).

However, switching to APT after the temperature was at that level, I connected the camera and started cooling aid as quickly as possible, and it had already risen by 21 degrees! And I had started APT running before closing Sharpcap. I have a feeling there is something wrong with those figures somewhere, but cooling aid started dropping at the same sort of rate it had been doing when I ran my first test.

Even though temp drops quickly in Sharpcap, if it rises so quickly while swapping programs, I feel it would be a bit of a hollow exercise. But, as I say, I am not totally convinced that the temp given by APT when I connected was reliable [I have no real evidence to support that assertion!].

[Demonperformer]

Let me just clarify that last post.

Sharpcap - start temp: 16.7, final temp -22.0

Start APT while camera still running on Sharpcap

Once APT ready, close sharpcap, press connect, press cool aid (as quickly as possible)

APT temp starts showing at -0.3.

[Gina]

Yes, I've noticed that too.  It's amazing how quickly the temperature rises.  I think APT must switch the cooler off as soon as it starts so leaving SharpCap on while starting APT doesn't actually help - APT immediately takes control.

[Demonperformer]

OK, so if the figures are right ...

Sharpcap took 5m to get to its stable temp, which rose to ~zero for when APT started to cool it down again. But to get to ~zero using APT only took 3m, so I don't see that doing it that way is going to be very efficient (not to mention the risk of thermal shock during the rapid reheating between programs).

I think I will take a look at Sharpcap's 'longer exposure' options, as this could be my best way forward.

[rwg]

The peltier gets very hot on the hot side and the sensor kicks heat. As soon as the peltier gets turned off the combination of the heat leaking back through from the hot side of the peltier and the generated heat warm things up pretty quickly. I think you might see the same if you were to shut down SharpCap and then re-open it again to see the temperature.

cheers,

Robin

[SonnyE]

On 10/4/2016 at 05:55, Demonperformer said:

What a BOZO! - I've just checked the power supply and (for some unknown reason) the voltage was turned down to the minimum of 5V. Have no idea when or why I did this, but have a pretty good idea that this would not help the camera in operating at peak efficiency. In fact, I am rather amazed that I was getting anything at less than 50% operating voltage.

OK, will now give it a go at the proper voltage, and see if this makes a difference.

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