Gina

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.

I've replaced the Arduino Nano with a new one and the USB connection is alright now. Should last for a while and give me time to sort out a Raspberry Pi version The earlier forecast couple of hours of clear sky tonight has evaporated and turned into partly cloudy all night Might get the odd gap I can use - have to see. OTOH there is now some clear sky forecast for tomorrow night but that might go when the time comes!

Yes, but that gives you a male thread, requiring a female thread in the filter wheel. With the SX wheel you can get either male or female adapter plates and these are the same both sides so yes the deficit can be eliminated but this means that the focus is brought forward and the OAG stalk becomes too long by about 11mm. It might be possible to get the hacksaw out and take 9mm off the stalk allowing the SX Lodestar to reach focus (I think). I might try this. Having the filters closer to the camera will reduce the slight vignetting. Alternatively, I can look into using the Atik EFW2 with separate OAG though the OAG doesn't have as much accuracy as I would like and there could be an error in the focal plane angle. The EFW2 is extremely well engineered and made but all this lovely optical accuracy may be spoilt by a poor OAG! The SX wheel with built in OAG should give better optical alignment and if I can get the guide camera to focus I think this would be the best way to go. For the smaller DSO such as galaxies, I would probably use the MN190 and the focal plane is much less critical with a 1000mm FL so the separate OAG and EFW2 will be fine giving me all the filters I want in one wheel.

Right then, let's have another look at filter wheels and add up the dimensions. EFW2 :- As I recall, the distance from front face to rear camera adapter plate is 22.3mm. The M48 to T2 adapter is 10mm and the 1600 camera with 11mm adapter back focus is 17.5mm. Total = 10 + 22.3 + 17.5 = 49.8mm. Actually less than the 54.9mm back focus of the FF and needing a T2 spacer of 54.9 - 49.8 = 5.1mm Workable without OAG. SX MiniFW+OAG :- Looking at the dimension drawing, the thickness works out as 4.3+28.2+4.3 = 36.8mm. This is with a T2 front and T2 rear thread so we need the 10mm M48 to T2 adapter and camera back-focus of 17.5mm including adapter. Total = 10 + 36.8 + 17.5 = 64.3mm. OH! That's 64.3 - 54.9 = 9.4mm too much! So the SX wheel will not work with the Esprit field flattener and 1600 camera!

Distance from rear element to mating surface of M48 adapter is about 20mm. Take that from 75mm and we get 55mm or near enough 54.9mm, the quoted back focus

I'm a bit confused about the Esprit field flattener. Mine has a rear thread of about 53mm with a 10mm long adapter reducing to 48mm which fits the OAG I have but the FLO web site quotes the rear thread as 48mm. I wondered if this was including the adapter but the photo doesn't show an adapter. If the FF back focus of 54.9mm includes the adapter to 48mm, I'm in business. They also quote the back focus as 75mm from the rear element so I'll go out and measure it.

Regarding the star drift due to imperfect PA, I guess I could improve this by further attention to accurate PA. Maybe I'll try drift alignment. The forecast for tonight has worsened with only an hour of clear sky forecast and by the time tonight comes the clear sky could have disappeared completely. This leads me to think about further PA fine adjustment rather than imaging - if even that's possible.

Thanks for the suggestion but I tried fixing the cable but to no avail. Think I'll try a new Nano but the long term solution is going to be more radical - either replacing the Nano with a UNO or better still a Raspberry Pi 3. Have to see if I can revise my Python Shouldn't be too difficult to translate my Arduino script in C++ to Python

Capture at 10:25pm or 23m after alignment of cross-hairs.

Changed to Lum filter and focussed on the moon - slewed to Alpha Cygnus, reduced the exposure to 2ms, adjusted slew to put star in centre of field, changed zoom to 200% and refocussed, changed zoom to 400% to show 4 pixels clearly and finally adjusted for fine focus. Seeing was causing the star to wobble by 6-8 pixels. Enabled cross-hairs and took a screenshot. Left it for five minutes and took another screenshot just as cloud was coming in. Here are the two screenshots separated by 5m. The star drift is clear. I estimate this as something like just over a pixel per minute. This is at 3x the focal length of the lens - 135mm to 400mm. Aperture from f2.5 to f5 or two stops and needing 4x the exposure for similar light on sensor. So 30s becomes 2m and the drift at this position in the sky is about a couple of pixels. This will be alright for reasonably bright DSOs.

There's a hole in the clouds so I'm off out to the observatory to open the roof and point the scope at the hole

Now have the Esprit on the EQ8 with the camera, EFW2 and OAG plus FF attached and all connected up. Everything is working except the remote focuser which is suffering from bad USB connection on the Arduino Nano. If I wiggle the plug it will connect but it won't stay connected whatever I try. These mini USB connectors are just not up to it!! Think I'll see if I can sort out an alternative tomorrow. Anyway, I cna probably manage with manual focussing tonight - if the cloud clears at all and doesn't turn into thunderstorms!