Gina

Problems as soon as it starts to get dark - again No image in SharpCap. Rebooting - see if that cures it - I've already tried restarting SharpCap.

Away from ∞ I think.

Rig cleaned and reassembled, attached to EQ8 and connected up. All functions tested OK, moved Home mount position 2 or 3 degrees anti-clockwise to line up with my N mark. I'll check position of Polaris when it's dark enough and further adjust as necessary. Means the DSO's should appear in the FOV when slewed to from CdC. Another warm night forecast and lots of moon so I plan to try longer NB exposures with lower gain to reduce the noise at higher temperature. Always assuming the forecast clear night becomes true.

Thanks Just been reading that thread from 2015 which shows the confusion but it does seem the consensus is that filters add to the focal distance from the flattener (or whatever). Good - adding a mm is no problem - saving a mm would be virtually impossible.

Did forget something - filters change the optical path length but I can never remember whether it's more or less and however I work it out I get it wrong! Astrodon filters are 3mm thick and change the focus be 1mm. Maybe that will not affect things for this size of sensor. If it means it moves the focus further away I could turn an extra mm onto the camera ring for the FW.

I only need an OAG for scopes - with good PA that I now have, I can do without for lenses. Might even try without on the Esprit. Yes, I've been looking at the TS OAG and was going to post about it. I was trying to make out just what the threads were on each side but I found it confusing. As for 3D printing, I already have a design I was going to use with a debayered DSLR but I've given up on that project - life's too short!! But I don't think plastic is stiff enough for optics for imaging. It really needs machined aluminium but that would be a lot of work. Anyway, I have another solution for the Esprit scope, that involves much less machining - just a replacement camera ring for the Atik EFW2. This has a rectangular groove in the edge to take the grub screws that allow this ring to rotate to change the camera angle but hold it fast when tightened up. I can save 11mm if I do away with the T2 female to female connector ring and place the camera right up against the FW. To achieve this the camera rings needs a T2 female thread rather than a protruding T2 male thread. I had to bring the rig indoors anyway because I saw a great big dust bunny last night so need to do a spot of cleaning so with it all apart I did some more measuring. With the OAG screwed onto the 10mm thick adapter for the field flattener of the Esprit, the EFW2 + OAG gives a thickness of 38.4. 10 + 38.4 + 6.5 = 54.9mm. Distance from optical face to focal plane of FF is 54.9mm - an exact match This is with the camera against the EFW2 which could be achieved with a new EFW2 camera ring with a T2 female thread/hole as mentioned above.

The so-called 10mm optical length OAG has arrived but it isn't! It's 19mm and exactly the same as the one FLO sell and the one I've got. I did come with a whole heap of adapters and extension tubes of various lengths though which may be useful. Don't think I can be bothered to send it back - it was half the price of the FLO one so I might be able to sell it at a profit

I've now realised why the DSOs were not appearing in the middle of the view when slewing to target from CdC - I think I must have moved the azimuth a couple of degrees or so when I adjusted the PA last night. That means the Homed mount is no longer pointing due north after the azimuth adjustment so it's no longer star aligned. AstroTortilla left me with an enormous PA error! It's a wonder I could do much good imaging even with guiding! I think the first thing to do tonight is to adjust the mount Home position to bring Polaris to the centre of the FOV. And no! I'm not using AstroTortilla to plate solve - I'm so disgusted, I've dumped it - I no longer have any confidence in it! Maybe the new version has solved the problems but my confidence in it has been destroyed, and that's that I'm afraid. I'll see how I feel when I go back to longer FL with telescopes but I hope to be using Linux by then. I believe INDI or KStars or PixInsight or ekos or whatever has plate solving anyway.

Thank you DP and Rich When I used AstroTortilla I found results were not repeatable and it drove me up the wall! What with repeated iterations of plate solving on a view to the east and then to the south, with adjusting the mount in between, and not really getting anywhere anyway, I just gave up having lost hours of clear sky I could have used for imaging!! PoleMaster has saved my sanity and well worth the money

No joy with that - the mist has come in so I've packed up for the night. Quite satisfied though - I've got the PA very much better Not sure how long I could expose for without getting oval stars - I only went up to 5m and the movement was a pixel or less. Looks like I won't need guiding with a lens of this FL or shorter. I plan to do some even wider field covering something like 15° x 20° later on with a 55mm f1.8 lens.

Found the galaxy BUT the sky isn't very clear and the moon is giving a strong gradient so RGB imaging is not on. I'll just have a little play with longer exposures and lower gain in Ha 3nm.

I now have the rig pointing towards M31 - except that there's no sign of the galaxy! Anyway, with zoom at 200 in SharpCap showing individual pixels I can see no star movement in five minutes which is an considerable improvement, so it seems the PA is definitely better Best cooling temperature I can get is around -20°C so long subs at high gain are not on but I could reduce the gain. Anyway, I'm doing what I said - M31. When I find it

Adjusted both axes and onto the fine adjustment. But I couldn't quite get the red and green circles exactly lined up. As I got nearer and nearer I got to a point where the green circle started dancing all over the place. I noticed that this corresponded to Polaris moving out of the green square. Both axes needed altering to perform this alignment, particularly the Azimuth. I just hope I've got the PA right and not totally undone the PA I got from AstroTortilla a couple of years ago!!. I guess an imaging run will tell me!

Clear enough for a run - this shows the misalignment.

Hmmm... waiting...

Clearing now

Cloud beginning to break up.

Sky around Polaris cleared for a few minutes and I was able to run PoleMaster for the first run. The PA looks well out! Now the clouds are back

After umpteen attempts to install the PoleMaster driver I finally have it working Now I just want the clouds to go away. I have the Allen screws loosened ready to adjust the mount PA - the elevation locking wheels are still tight but they are handwheels so I can easily undo or tighten these in the dark. I shall be interested to see how far my PA is out The other thing I want to do tonight is RGB on M31 when it's high enough. Really must try not to do too much or I'll only get confused It's very warm again so I won't be able to get the imaging camera cool enough for short, high gain subs.

Installed PoleMaster driver and software on my observatory laptop in the hope of some clear sky tonight to check and correct my PA.

I've ordered an OAG from ebay purporting to have an optical length of just 10mm. This may work with the EFW2 for use with the Esprit. I still prefer an OAG if possible. I've also been thinking about the ZWO filter wheel with the possibility of taking the Astrodon filters out of their carriers and mounting them with the M2 screws and washers provided, as unmounted filters. I think I will be returning the SX EFW+OAG as I don't think I can use it.

My last post leads on to another thought. I could use the triple scope rig mounting plate and put the WF rig where the second ST80 was then I could use the remaining ST80 for guiding. This idea is fine while I'm using the EQ8. That would give me medium FOV and wide FOV in one setup. For smaller DSOs I would remove that rig and replace it with the MN190 scope with OAG.

I've been looking further into using the Atik EFW2 plus OAG (FLO model) on the Esprit field flattener and I think I might be able to make it work. The EFW2 has a rotating camera adapter and I might be able to turn a replacement with a female thread to replace the Atik one with a male thread. That would enable me to use the 1600 camera straight on the FW saving 11mm. The OAG is 18mm long leaving me with 7mm to find. The adapter on the field flattener adds 10mm and I might be able to turn a shorter adapter for the FW. OTOH I'm not sure it's worth it - I could just use a guide scope on a dual mounting. I already have the triple scope rig and could simply use one of the ST80s as guide scope and remove the other. My lathe isn't really up to optical precision turning.

Thanks rich I did look at this idea a while back but not recently - sounds like quite a good idea for this new rig I'll look into it. This one looks a beauty but I'm rather reluctant to buy from the USA. Maybe I don't need that much quality I guess I don't really need a medium format lens, as you say I already have a lot of top quality glass.

I've put the rig back together and back on the EQ8, connected everything up and run all the software to check it all works still - which it does. So I'm all set up for next time we get a hour or so of clear night sky. Focussed on tree on distant hill which gives a good starting point for star focus. Weather forecast looks good for 2am tomorrow morning but I'm not staying up that late just in case they're right!