Gina

Thank you Wim I'll look into those.

About half of the lights so far are either totally duff or pretty poor. About 15 out of 35.

Thanks Rich Wish the clouds were as easy

Sky cleared after the 66 darks count so I went over to Lights. Removed the scope cover and set up on the Crescent, putting it near the corner of the frame so that the Soap Bubble comes near the centre. Found the focus had changed so needed to adjust that. Now running 120s lights with g500 and t-26°C. There are bands of cloud passing over so a lot of the subs are poor or unusable but I'll leave it running and see what I get. No problem from frosting of the sensor now nor condensation so the new desiccant tablets seem to be working. Here the latest light frame seems to be in a clear patch of sky Full frame, histogram stretched.

The 150s subs were a bit too much for the PA and show a bit of the oval star syndrome so I'm going for 120s subs tonight with full calibration sets if the sky clears. I already have 100 bias frames and 33 dark frames. I might stop the darks if the sky clears before they're finished.

I'm optimistic for tonight if the clouds part I have processed last night's 7 subs of 120s and 45 subs of 150s in PixInsight using an approximate set of darks but no biases or flats. I then saved the image as 16bit unsigned TIFF and transferred it to my Win7 desktop with Photoshop CS5 in which I applied histogram stretch and cropping - here is the result. These are full resolution - pixel for pixel, though first one is zoomed in to a smaller area.

Bias frames done and now taking darks for 120s g500 and t-24. Here's a couple of single frames just resized.

Just been out and covered the scope and now taking 100 Bias frames.

The camera is now running at -24°C and no sign of anything wrong - just taken 100 flats with gain of 500 and 0.03s exposure with Ha 3nm filter ready for an imaging run of Crescent and Soap Bubble later (clouds permitting). Here's a single flat sub. And histogram stretched from black to white.

Thanks

Thank you I have some small colour-change desiccant bags and might be able to fit two of them in the sensor chamber if the tablets don't work. I imagine these tablets are supposed to be better that the standard silica gel.

The replacement desiccant tablets and rubber pads had a moisture indicator card together with a desiccant bag in the sealed packet but the dot which is supposed to be blue is white. Wording says warning if the blue dot has gone completely pink - well not quite - not like the rectangular pink panel so maybe the tablets are alright. Anyway, I have now put them in the camera and screwed the cap on as tight as I can. "Proof of the pudding" will come tonight when I get the temperature to -30°C! FLO might be getting an email... I've also been back out and checked connections but my DMM only goes down to tenths of ohms. I found the spade connector a bit loose so I've tightened it up. That could have been where the problem was - again I'll find out when I get the camera back outside and connected up.

The camera sensor now has condensation around the edge which would become frost at lower temperatures. The end cap was definitely not fully closed and damp has got in so I will need to change the desiccant tablets and also clean out some bits. I've opened the camera sensor chamber and see that one tablet was slightly damaged and the stick-on cushion has been displaced. I found some of the glue on the cover and a few tiny bits in the chamber which I shall blow out with a puffer. The weather is dry, warm and sunny so the humidity indoors should be fairly low. I think not having anything to stop the cap unscrewing when trying to unscrew the camera from whatever it was screwed on to, is a design fault so I can't mark this camera as 10 out of 10. This problem has been mentioned before and maybe ZWO will change it in their next version of the camera. The end cap is only a few mm wide so it's not really practical to hold this to detach the camera from the rest of the optical system. The surface is smooth too. If it had some lugs or even a serrated surface it might be possible to grip it but as it is it's virtually impossible. That then is the first fault I've found. Anyone using the F-F gender changer adapter may be able to get something in to hold that and unscrew it from the rest of the rig but it's only 11mm wide so you can't get fingers in - it would have to be some sort of tool. If using the ZWO mini FW even that isn't an option as the adapter isn't used.

I shall certainly be investigating the connections - I don't like too much resistance in my power lines!

Yes, I've run 240v AC mains to the observatory and convert to 13.8v DC there. As for AC v DC, it's the volts and amps that matter not whether it's AC or DC. (From an Electronics and Electrical Engineering graduate with a career to match).

These are the big XLR connectors with 10A rating. The XLR connection gets undone and remade every time I set up the rig - last night, just before the imaging run. The pins and sockets are clean - I checked. The connector also has a screw ring to clamp the parts together as well as the plug an socket being very tight and needing considerable force to connect and disconnect. The pair of spade terminals have not been touched for some time. I'll check all connections either side and see if I can find where the problem is. Also the current wasn't 4A but 2A. And there isn't a problem anyway! The cooling electronics maintains constant power regardless of voltage by increasing the current at lower voltage. I now have the camera on cooling test but ATM I can only get it down to -14°C due to the ambient temperature. No sign of frosting or even dewing at this temperature. I have the camera powered from a bench PSU with variable voltage and digital voltage and current displays. When the voltage was lower the current was higher and vice versa so the power remains the same. That means that the supply voltage doesn't affect the cooling power after all!

I have brought the camera and laptop indoors to test the camera for frosting up. While I was out in the observatory I checked the supply voltage at the power distribution box on the scope and it was down to 11.6v rising to just over 12v once camera temperature set-point had bee reached. I have volt drop all over the place. At PSU its 13.8v, at battery it's 13.3v with another volt or so dropped in the cable from the warm room to the scope/camera. No wonder my cooling is not as good as others have reported. I think I'll have to do something about this. The cable from battery to camera is about 4 or 5m and quoted "Resistance per metre at 20°c 0.0185 ohms" so if 5m that's 0.09 ohms. Or near enough a tenth of an ohm. That should be 0.4v at 4A not over a volt. OK there's some drop in the earth cable but that's BIG stuff as used for house electrical earthing. Connections are by 6.3mm spade terminals and XLR connector plus standard car battery screw clamp terminals. These are supposed to be highly reliable for use in damp conditions. BUT there would appear to be excess volt drop somewhere. I guess I need to test further. The cable in question only feeds the distribution box on the camera/scope - the mount is fed through a separate cable of the same size. The only load I had on this morning was the camera cooler and EFW2 filter wheel (which only takes power when moving and very little then).

Just looked at the data I collected overnight and 45 out of 100 150s subs look as if they might be alright but at that point something went wrong with the tracking and the rest were spoilt. There are also 7 subs of 120s.

Thank you Chris Maybe I didn't get the camera tightened up enough and it's not sealed so the desiccant tablets have "worn out" I'll see it I can see ice when it's off the scope and powered up with cooling on. If so I guess I'll have to open it up and change the tablets.

I don't know what it is but I did accidentally partly unscrew the camera sensor chamber taking it off a T2 adapter and may have crushed the desiccant tablets when I tightened it up again. I have seen the odd bit on the sensor and had to shake it off. I've only had this much detritus on the sensor since I put the camera on the Esprit scope. I'll have to take it off and inspect it. I've previously had the temperature lower and not seen this.

Not the Atik OAG but this one.

Another 150s sub with same gain and temp of -27°C.

Decided to reduce the gain to 500 to reduce noise and increase exposure to 150s to compensate. Here's a single frame at -28°C.

Currently the sky is clear in the Cygnus area and I've been capturing images of the Crescent Nebula and may have the Soap Bubble in the frame. Cooler tonight and I'm getting to almost -30°C. This is 120s exposure with a gain of 600 with histogram correction in Ps. Full frame saved in PNG format.

I've had another idea to use the SX mini FW+OAG - turn a ring in aluminium with a 48mm female thread and about 75mm OD. This can be attached directly to the FW with three screws like the T2 adapter. That way I could save maybe 5mm.