Gina

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!

I'll see what I can do and the see what it can do

Seems I need a FLO M48 to T2 adapter - that should do the trick. A short test should show if the PA is good enough for unguided imaging with the Esprit though.

Just measured up the actual rig and the distance from OAG to camera face is 53mm. Add 6.5mm camera back focus gives 59.5mm + 10 FF adaptor gives 69.5mm. Specified back focus is 54.9mm so error is 69.5 - 54.9 = 14.6mm That's even worse!!

I've looked back through this thread and yes, I did have the 1600 camera working with the Esprit and FF BUT it was with the OAG and EFW2 in the optical path. Strangely the focus seemed consistent across the field! The back focus was 11mm out!! ie. image sensor at 65mm from the optical face of the FF rather than 54mm. Could it be that the back focus of the Esprit field flattener is really that tolerant? Seems unlikely. Looks like there could be some night sky with just partly cloudy tonight so I might just set up the Esprit and just take a frame or two and see how good the focus is. I can use SharpCap for this and eyeball the result immediately.

Yes, and I've been looking into that as I think that would be my preference too. I seem to be missing and adapter though Strange because I'm sure I had the 1600 camera on this scope with the field flattener and if so the adapter can't be far away! Rather tired today and maybe not quite with it as I had a late night or rather an early morning from imaging (or trying to) last night.

Does anyone have any preference as to which sort of imaging they would like to see me do? If so, please say

Been thinking about what I shall do next time there's a clear night - tomorrow is looking hopeful. Several options :- More Ha data on a DSO I've already imaged OIII data on a DSO already imaged Ha on a DSO I've not tried with this rig 55mm f1.8 lens and Ha on much larger area of Cygnus area - needs lens bracket and focuser parts printing Esprit on the Crescent and Soap Bubble in Ha Some options depend on the ambient temperature. Options 4. and 5. seem the most exciting I think the PA might be good enough for imaging with the Esprit without guiding. If so it will save me either turning a new EFW2 camera ring or fitting up a guide scope. I am also rather keen to see if I can catch the Soap Bubble. I seem to be getting star shape problems on one side of the image with the current 135mm lens. This seems to get worse as time goes on in an imaging rig. I suspect it could be partial dewing of the lens but not sure. The dew was very heavy last night and the rig was pointing almost straight up which could well mean dew falling onto the lens more on one side.

Here is a 120s Ha sub of the Crescent Nebula area of Cygnus. Again gain of 500 and temperature -25°C. Histogram stretched. Full frame.

I'll have a go at that later One thing I'd like to do is change over to the 55mm f1.8 lens and do a mosaic of the whole Cygnus area so that I can see where everything is Might not even need a mosaic.

Yes. I don't know why it happened earlier this evening - that was all I had running. Then it just suddenly started working alright again! Modern computers are pure "Black Magic" and I'm not referring to chocolates!!!

I'm trying to decide on whether to stop at 50 Ha subs or go on to the full 100 as I did with the 30s subs. 50 will already be twice the total time of the 30s runs and I've heard it said that the rule of diminishing returns applies. I'm think I'm still in the experimental phase. There's the decision of many short exposures or fewer longer ones too.

APT working now and I'm capturing 120s Ha subs of IC 1396. Gain reduced to 500 with temperature of -25°C. This is a single sub histogram stretched.

Tried another reboot and SharpCap is working but APT isn't.

I didn't - tried running APT on 10s exposures - finished the exposure and locked up showing BUSY. No image display. There's a few bits of cloud about but I think it's clearing - now the gear won't work!!!! AAAARRRGGGHHH!!!