Thoughts on which imaging rigs to concentrate on

[Gina]

My camera can barely get down 35°C below ambient let alone 40-45!   Don't know why but if the absolute limit is -30°C it doesn't really matter.

For planetary I bought an ASI185MC camera but the only real difference would be that it's a colour camera - cooling wouldn't be necessary.  The pixel size is almost identical - 3.75 v 3.8 microns.  A mono camera of the same pixel size will give better resolution as the colour needs sets of 4 pixels per coloured pixel.  So the 1600 will beat the 185 for planetary for resolution.  I'm not sure whether RGB filtering would be possible due to planetary rotation.  It would with three cameras and three scopes of course but that's out of the question for the very long focal length required.

[wimvb]

Haven't read all of your posts in detail. But it struck me that if you want to measure camera characteristics, PixInsight has scripts for that. (Of course.) What you are after might just be somewhere among all the tools...

[wimvb]

As for minimum temperature, there may well be a practical limit. Electronic components have a temperature dependence, and may very well go out of specs for too low temperatures. So even if the cooling can go lower, the electronics may set a limit. That limit can be - 30 C. There is no contradiction, the camera cools to - 40 C below ambient, down to - 30 C.

 

[Gina]

Yes, 40°C below ambient or -30°C absolute whichever is higher.  And yes, the tool for measuring the camera sensor characteristics is from PixInsight.  I now have the appropriate captured frames so now I have to find the reference and set things going   I also have the flats for the 55mm lens rig and matching master dark and master bias to calibrate with.  After that I can process all the data I captured last night.  I'm never short of things to do

[Gina]

Looks like there could be some clear sky tomorrow night with luck but still time enough to change completely!  Moonrise is around 11pm so could have some time with a dark sky   Maybe getting to the time to think about OIII and SII - the 3nm SII filter came today so I now have a full set of 3nm NB filters   I might see about doing the Cygnus area in three wavelengths.  Actually, I think I've covered pretty much all I can do at this time with what DSOs are available in Ha. 

There is some vignetting with the f1.8 lens and 1.25" filter even right up against the body of the camera (inside the adapter ring).  Probably sorted out with calibration with flats though but I wouldn't want to move the filter further away from the sensor so a manual filter change will be in order.

[Gina]

Just back home from a meeting and saw the sky was clear and the stars were out - moon not up yet - so I opened up the observatory and set everything up for some imaging.  Got to the point where I had an image on the preview screen and the camera cooling nicely when all of a sudden the image disappeared.  Went outside and looked at the sky and - guess what - yep!!!  cloudy!   Grrr...  Still, I enjoyed the meeting and can't be in two places at once

Edited September 21, 2016 by Gina

[wimvb]

Same here, it started out nice, but then clouds moved in. It's typical for this time of the year: warm sunny days with evaporation that will turn into clouds when the air cools down in the evening. Didn't even bother to haul my gear out.

[Demonperformer]

"Clear Outside" is promising me zero cloud from 7pm tonight until 4am tomorrow ...

even now there is a squadron of pigs coming-in over ASDA ....

[Gina]

" a squadron of pigs coming-in over ASDA " - I love it

[Macavity]

I MUST read this thread! I suspect it encompasses some/many of the issues
of current concern here... That of being a "Generalist" - Too thinly spread? 

At the moment, I have divided my activities according to focal length - With
specific scope and / or camera! My memory for "setups" ain't what it was!

• 2.6mm f/1.0 Computar + Watec 102N+ "All Sky" meteor/cloud Cam.
  (Remote VIDEO setup - Not really all-sky... coincides with rooftops!)
• 20-70mm Canon EF f/4 (non-stab) lens + EOS100D for Wide Field.
  (My current excitement! Constellation and "Open Cluster  scope".
• Lunt 50Tha f=350mm H-Alpha scope + ASI120MM camera... The
  START of the rot! lol. Still need to work on Newton's Rings etc.
• Altair ED66 f/6 f=400mm (Sometimes wish I'd gone for an ED80)
  Currently White Light Solar with Lunt Wedge. Needs 1/2" Cam!!!
• TS 200mm F/4 (modded!) "Astrograph". My VIDEO Astronomy
  machine! Watec 910HX (Fully "remote"... focusser, HEQ5 etc.)
• Skywatcher MAK150 + Monorail Focus,  Barlow(s) + ASI120MC
  for "Planetary" (Colour rather than RGB wheel, for simplicity?) 

Sometimes I wonder why I ever started this, lol! My ENTHUSIASM is still
intact, but lack of clear skies, having a life, WEIRD neighbour(s) etc. etc. 
Determined to give it a few more seasons (Can I hire an "assistant"?) 

Aside: I also remembered this, which made me chuckle:

Quote

“When you are a Bear of Very Little Brain, and you Think of Things, you find sometimes
that a Thing which seemed very Thingish inside you is quite different when it gets out
into the open and has other people looking at it.” -- A.A. Milne

Honourable mention for Skywater 102 + modded AZ3-2. "Pimped" +
Monorail focusser! Envisaged for Astro Soc "Observation Nights" but...

Edited September 22, 2016 by Macavity

[Gina]

Calibrated master flat for 55mm lens and 1.25" 3nm Ha filter up against camera body.  100 subs each of biases, darks and flats.  Firstly as is - just resized and saved in PNG format and secondly fully histogram stretched from black to white.

Edited September 22, 2016 by Gina

[Gina]

Here is the histogram before stretching.

Edited September 22, 2016 by Gina

[Gina]

Clear tonight and capturing images   Widefield Cygnus area with 55mm lens.  Frame alignment done and currently imaging Ha.  I'll be changing to OIII or SII shortly.  Here's a 60s g500 t-25°C 3nm Ha sub.

[Demonperformer]

Good! With the breeze here coming from the west, that gives me a little hope the skies might clear a bit later.

[Gina]

I only captured a few subs like this so I'm going for the full 100 before changing filter.  I guess the OIII will be next.  At least when the moon comes up it will be something like 90° away from the area of sky I'm imaging and with 3nm filters, it should be alright.  I may stay up most of the night if it stays clear - I would love to grab the full set of NB images at this FOV, then I can go back to the 135 lens for the next session.

There are several possibilities for the next few sessions.

1. The Cygnus Loop
2. NAN & Pelican
3. Cygnus Wall
4. IC1396 the one that contains the Elephant's Trunk
5. Andromeda Galaxy M31 - depend on there being no moon

[Gina]

Some cloud about now but it's supposed to clear a bit later.

[Demonperformer]

Well, I've got zeroes across the board until midnight. And zero is about the size of the gaps between the clouds at the moment!

[Davey-T]

51-ish N - 1-ish E so let's hope they're right 

Dave

[Gina]

Changed to OIII filter and refocussed - now capturing subs.  Here is the first OIII 60s sub, flipped and rotated only then saved in PNG format.  Here's the full size image.

[Gina]

Still getting some clouds passing over so these subs will need going through with the Blink tool in PixInsight.

I could do with my all sky camera operating so that I can see what the sky looks like from indoors but I only have one Windows laptop and that's capturing NB ATM.  I must have another go at Linux and the Raspberry Pi 3 with INDI and KStars which I now see has image capture without external capture software.

Edited September 22, 2016 by Gina

[Gina]

Had a look outside and the clouds have gone (for now).  No sign of the moon on the eastern horizon yet. 

Just turned down the cooling set point to -30°C and the cooling has reached that with no problem - it's cold out tonight!  I could see a reduction in the noise in the image.  I think the OIII exposure is alright at 60s though could possibly be increased a bit but I'll leave it at that for now.  I expect to need more exposure for SII.

[Gina]

The mount hit the end stop so I had to do a meridian flip and then readjust the framing to match the previous frames.  Decided to increase exposures to 90s too.

Here's a 90s sub g500 t-30°C 3nm OIII just flipped and rotated left as linear, full frame.

[Gina]

Been looking at FOV and the various DSOs.  Several DSOs are only half as big as the FOV with the 135mm f2.5 lens so would benefit from just under twice the focal length - say between 200mm and 250mm.  I have 200mm f4 Super Takumar lenses which would be better than 135mm for FOV but just over a stop slower.  May be worth a try.  Certainly on M31 with its high brightness but also the Cygnus Loop and IC1396.

[Gina]

Captured 85 90s subs in OIII and decided to try SII as the target was about to be obscured by the observatory roof.  Tried 120s and the only DSO visible at all was the Cygnus Loop and that very faint.  Now running 5m subs to see if anything shows up.

[Gina]

Beginning to   Here's a 5m g500 t-30°C 3nm SII sub, flipped & rotated plus a bit of histogram stretching and size reduction.  Next time there's some clear night sky I'll finish off the OIII and take a load of SII subs perhaps with longer exposures but not sure that will help.  Might be able to get some useable SII data though.