Thoughts on which imaging rigs to concentrate on

[Gina]

Now for some calculations...  EFW mini is 20mm (I measured 20.25mm), camera back focus is 6.5mm so total so far of 26.75mm.  Asahi Pentax SLR M42 thread lenses have a back focus of 45mm so there's an extra 21.45mm available for an OAG if wanted - my OAG is 18.7mm including a T2 to M48 adapter ring leaving about 3mm for either a slimline "Russian adapter" or for cheating and screwing the lens M42/1mm into the M42/0.75mm T2 thread  

For use without OAG...  My standard "Russian adapter" is 8.9mm so adding the lens + adapter to the FW requires an extra 21.45 - 8.9 = 17.55mm ie. 10mm + 7.5mm T2 extension tubes.

[Alien 13]

8 minutes ago, Gina said:

Now for some calculations...  EFW mini is 20mm (I measured 20.25mm), camera back focus is 6.5mm so total so far of 26.75mm.  Asahi Pentax SLR M42 thread lenses have a back focus of 45mm so there's an extra 21.45mm available for an OAG if wanted - my OAG is 18.7mm including a T2 to M48 adapter ring leaving about 3mm for either a slimline "Russian adapter" or for cheating and screwing the lens M42/1mm into the M42/0.75mm T2 thread  

For use without OAG...  My standard "Russian adapter" is 8.9mm so adding the lens + adapter to the FW requires an extra 21.45 - 8.9 = 17.55mm ie. 10mm + 7.5mm T2 extension tubes.

I have found that the cheat works well because the thread depth is quite small, I do however make this sort of adapter semi permanent with a drop of Araldite like the M42 to 15mm T extension tube I use on my scope.

Alan

[Gina]

Yes, I've found the "cheat" works pretty well but if the Russian adapter fits in with the measurements then the optical alignment may be more precise.

[Gina]

Slight miscalculation above   45 - 26.75 = 18.25mm.  Subtracting 8.9mm gives 9.35mm then adding 1mm correction for filter gives 10.35mm so a 10mm extension tube should be right with changing the lens focus to a bit less than ∞   I'll run a check.

[Gina]

Yes, that's fine

Here's a screenshot of the preview screen with imaging rig pointing out of east window of living room towards far hill.  Focus is on 50ft/15m.  3nm Ha filter chosen.

Edited September 28, 2016 by Gina

[Gina]

Weather forecast is amazing!!!  Both the BBC and Clear Outside are showing solid cloud all afternoon and evening but we currently have wall-to-wall sunshine with barely a cloud in the sky - just a couple of small cumulus clouds!

[Gina]

Downloaded the ZWO EFW mini ASCOM driver ZWO EFW ASCOM Setup V1.0.0.7(Add support for editing filter name and focus offset ) and installed on my imaging laptop. Needed reboot to work.  Then ran SharpCap and from Settings in the File menu selected the Hardware tab and filter wheel from the list.  EFW mini recognised and selecting a filter ran the filter wheel to the right position   Then tried in APT and same result - all working fine.  Edited the filter names to Ha, OIII and SII - so that's that set up and tested

Both SharpCap and APT allow for changing the focus according to which filter is selected so it's looking like it's getting near time I made my remote focuser ASCOM compliant   Then, having determined the focus settings for each filter I could put them into the system and run a complete NB imaging run under APT as process controller.

[ChrisLX200]

1 hour ago, Gina said:

Weather forecast is amazing!!!  Both the BBC and Clear Outside are showing solid cloud all afternoon and evening but we currently have wall-to-wall sunshine with barely a cloud in the sky - just a couple of small cumulus clouds!

I can think of a lot of words for it - Amazing isn't at the top of the list though.  My gear and I sat outside for 3 hours last night in the expectation of the clear sky forecast by both Met and CO, of course there was only solid cloud.

ChrisH

[Gina]

The weather seems to have caught up with the forecast   Now clouded right over and starting to rain!  I was about to take the imaging rig and laptop out to the observatory to set up but I'm not taking gear out in the rain!  I'll take a photo of the rig with new filter wheel on the table shortly then instead of on the mount.  Unlike the Atik EFW2, the ZWO filter wheel needs no 12v power - it works entirely off USB and at least it has a full size type B USB socket rather than the dreaded mini USB.

Just the one power cable from the distribution box to the camera plus USB cables from camera built-in USB hub to focuser and FW.  The only other USB connection required is for the EQ8 and that's run directly from the laptop.  USB from laptop to camera completes the wiring.  (Apart that is, from power from umbilical to distribution box and power from pier to mount.)

Last night's session at least gave me some information - the viability of unguided imaging.  Guiding was not necessary for up to two minutes exposures, maybe three but not quite four - that was showing star trailing.  I have the OAG built into the SX wheel if needed but I will need to get access to another USB for the guide camera and that will mean a USB hub.  Fortunately I have a selection including a highly recommended professional metal cased powered USB hub that I bought a while back for my multiple imaging rigs.

[Demonperformer]

1 hour ago, ChrisLX200 said:

I can think of a lot of words for it - Amazing isn't at the top of the list though.  My gear and I sat outside for 3 hours last night in the expectation of the clear sky forecast by both Met and CO, of course there was only solid cloud.

ChrisH

Been there, done that, T-shirt being printed ...

 

[Gina]

I think I shall use the bad weather to do a bit of a tidy up of the rig.  The power distribution and focussing control box could do with re-making and given a proper bracket rather than attached with rubber bands.  But rather than stripping the current circuit down I think I'll make a new one just in case the clouds go away before I've finished.  The wiring could do with tidying up too - with fixing in place.

[Gina]

This is the circuit diagram of the power distribution and focus box.  This shows the filter wheel power which is not needed for the lens rig.  For the Esprit scope rig the second power plug can be used for the USB hub which runs off 12v (nominal).  I'm not currently using dew heaters with the lenses or the Esprit scope but it might be needed for extreme dewing conditions.

[Gina]

The circuit for the lens version could be a bit different and include a ULN2003AN stepper motor driver chip on the circuit board with stepper motor socket rather than having an external motor driver module.  That would be tidier.  And it would only want 3 fuses as the filter wheel is USB powered.

[Gina]

Looks like I shall need some extra bits to build a new power distribution and focus box so I'll be using the current one for now.

Here are some photos.  On table, on EQ8 homed, on EQ8 and pointing at far trees.

Edited September 29, 2016 by Gina

[Gina]

Clear sky ATM and imaging NAN&P.  Here's a 60s Ha sub at -28C and gain of 500.

[cosmojaydee]

how amazing is that for 60s, can't wait for this years clear night to come 

[Gina]

Trying to do OIII now but try as I might, I can't get APT to work - just stops at Busy at the end of the first sub

[Gina]

Got to find something other than APT!!!!!!!

[Gina]

Tried rebooting and APT still won't run   And now SharpCap is playing up!!   Maybe it's bedtime....

[cosmojaydee]

Have a look at SG pro Gina

[Gina]

I thought about SGPro but it's Windows again and I'm afraid I'm just fed up with Windows!!

This new ZWO camera is showing great promise as is the rest of the hardware I'm using for widefield DSO imaging.  Now if only I can get the software working I foresee some very presentable images emerging   CdC frequently disconnects from EQMOD, APT sometimes just stops at the BUSY point in a capture session and even SharpCap plays up at times - currently failing to stop imaging at the end of the exposure set up.  I'm hoping I can get Linux software working better but I'm having problems with the Raspbian OS on the RPi.  I may try using a laptop running Linux Mint and using that with INDI.

[Allinthehead]

Hi Gina. Did you have two programs connected to the camera at the same time? I found the only time APT would stall on busy was when i connected sharpcap and APT simultaneously.

[Gina]

No I didn't, but thanks for the suggestion   A cold boot with several seconds off time seemed to help a bit but things were still not working so I closed the roof, packed up and went to bed.

[Gina]

Now have the hardware to construct another power distribution and focus box though with reasonable progress with the Linux based system and Raspberry Pi I might leave it for now and see how I get on with that.  I've also bought another ex film SLR camera lens - Asahi Pentax SMC Takumar 28mm f3.5 which I can use either for even wider FOV or as an electronic finder scope with astro camera.  As the 55mm f1.8 lens seems to give problems at full aperture, an f3.5 lens might be better.  The 28mm FL will cover twice the FOV of the 55mm, of course, so that something like 40° by 30° - should be interesting

[Gina]

Used as a finder with ASI185MC camera the FOV would be 7.3mm x 4.6mm divided into 28mm giving tanθ of about 0.25 and 0.16 and θ of about 15° x 10°.  With a 460EX and 12.49mm x 9.99mm sensor - tanθ of 0.45 x 0.36 and FOV of 25° x 20°.  The latter would be a useful FOV for an electronic finder.   OTOH with KStars/Ekos/INDI having plate solving an electronic finder may not be needed.