Thoughts on which imaging rigs to concentrate on

[Gina]

43 minutes ago, Demonperformer said:

Don't know if this would be of any use. I have one and the main body is genuinely 9mm. The threads on either side make the total 13, but the extra 4, of course, doubles up on whatever you attach to it. The catch is that, if you still need a filter wheel, that is likely to take you over the distance you have available!

There's nothing for it ... you are just going to have to design a combined FW/OAG that meets your exacting standards and get the 3D printer on the job. The only 'optical' bit (I think) would be the OAG prism - and as you have just bought an extra one that could be cannibalised ...

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.

Edited September 14, 2016 by Gina

[Gina]

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.

[russellhq]

19 minutes ago, Gina said:

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.

From what I've read, they add half their thickness to the optical path i.e. increase the overall focal length

[Demonperformer]

Yes, you get more backfocus. For extensive discussion:

 

[Gina]

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.

[Gina]

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.

[Demonperformer]

1 hour ago, Gina said:

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.

Now, does that mean I turn the focus knob towards ∞ or away from it ... ?

[Gina]

Away from ∞ I think.

Edited September 14, 2016 by Gina

[Demonperformer]

6 hours ago, Gina said:

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!

I agree with you that AT is about as much use as a choclate teapot for PA, but I have found it to be MUCH better at slew-and-solve. I will say, however, that it seems to be an awful lot faster with a 'lens' if I use the 41xx files (TYC2) rather than the 42xx files.

Last time I was out, first GOTO from start (with VERY rough home position - camera pointing vaguely forward, somwhere along the dovetail bar) was about 2½° out, but it got me to within 10" on one move. Considering the image size was about 12"/px, I thought that was probably good enough!

[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.

[Gina]

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!!!

[Gina]

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

[Gina]

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.

Edited September 14, 2016 by Gina

[Gina]

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.

Edited September 14, 2016 by Gina

[Demonperformer]

2 hours ago, Gina said:

tried running APT on 10s exposures - finished the exposure and locked up showing BUSY.  No image display. 

Yep, that's the problem I was having when I PM'd

[RichLD]

Incredible result Gina, my gut says longer and less if that makes sense. Given what you have with a single 120s sub, I would love to see what 20 x 200s looks like - deep and wispy I would imagine 

Truly fabulous and dare I say groundbreaking stuff - thanks so much for sharing your cmos journey so far!

[Gina]

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!!!

[RichLD]

Bet you could get a cracking bi-colour of the Flying Bat and OU4 with that rig 

[Davey-T]

Argh computers, I've wasted several nice clear nights trying to get autofocus to work on Win10, according to those who know the Win version shouldn't make any difference.

Tonight after a couple of false starts it's working (or at least it was before a big cloud arrived) not much help now there's a big annoying Moon, next dark clear night it probably wont work again 

Dave

[Gina]

16 minutes ago, RichLD said:

Bet you could get a cracking bi-colour of the Flying Bat and OU4 with that rig 

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. 

Edited September 14, 2016 by Gina

[Gina]

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.

[Gina]

Been thinking about what I shall do next time there's a clear night - tomorrow is looking hopeful.  Several options :-

1. More Ha data on a DSO I've already imaged
2. OIII data on a DSO already imaged
3. Ha on a DSO I've not tried with this rig
4. 55mm f1.8 lens and Ha on much larger area of Cygnus area - needs lens bracket and focuser parts printing
5. 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.

[Gina]

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

[Demonperformer]

Gina, I am sure people will be impressed whichever you choose, but, as you ask for a preference, I would say, do (5) as (i) it will be good to see if the esprit will perform without guiding, and (ii) you say you are "rather keen" - that is always a good thing.

 

[Gina]

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.

Edited September 15, 2016 by Gina