Thoughts on which imaging rigs to concentrate on

[Gina]

Had a think and decided I'm not up to sorting out RPi software tonight - maybe I'll feel better tomorrow.  I think all I'll do tonight is plan further work on the project and consolidate my ideas.

I think I'll go straight for putting the RPi on the rotation rig and leave the current imaging rig basically untouched so that I can just put it back on the mount and use the laptop if it looks like a possible clear night.  That doesn't mean tonight as it's cloudy and there's rain forecast and I'm not going outdoors tonight anyway - need to look after my health.

[Filroden]

Sounds sensible. It also sounds like you have a plan at least, so once you've rested it should hopefully work.

I'm managing to add a little data to my Rosette Nebula. My first attempt on Tuesday was ok, but I didn't get a lot of data and the Ha dominated the LRGB by some margin!

[Gina]

Thanks Ken

The RPi software I though I'd messed up is still quite adequate for my daytime colour ASC - I only need the camera driver and that's fine.  I'll just use the other RPi for my main imaging rig.

[Gina]

Yesterday the forecast for tonight looked dire, now it's looking good both on BBC and Clear Outside - amazing!!!  Will that stand or will it flip back to 100% cloud though, I wonder   Anyway, depending on what the weather does a bit later I might take imaging rig and laptop out to the observatory and set it all up.  Very unlikely to have the rotation rig ready by tonight but I'm expecting to do some work on it today.

[Filroden]

9 minutes ago, Gina said:

Yesterday the forecast for tonight looked dire, now it's looking good both on BBC and Clear Outside - amazing!!!  Will that stand or will it flip back to 100% cloud though, I wonder   Anyway, depending on what the weather does a bit later I might take imaging rig and laptop out to the observatory and set it all up.  Very unlikely to have the rotation rig ready by tonight but I'm expecting to do some work on it today.

Grr, mine has done the opposite. Yesterday the forecast was for clear and winds weakening. Today it's now forecast for mist/low level clouds all day/night. I only managed 60 images last night and I think the last 30 might have been ruined by mist rising too. And I'm now in a permanent circle with my camera. I must have slightly ground one of the tablets and every time I open the chamber to blow the dust away, as soon as I close it, more dust appears. I think I will need to remove all four tablets, give the whole thing a good blowing over, dust the tablets down somewhere away from the camera and gingerly put it back together. The problem I have is any time I unscrew the EFW, it sometimes also unscrews the chamber which I think then disturbs the tablets  This isn't usually a problem but I've been trying to improve my spacing so there has been lots of dismantling/rebuilding over the last few days.

Good luck getting the rotation rig ready. 

[Gina]

I had that trouble but have now cured it.  I used THIS TOOL from FLO to tighten the front of the camera.  I too had the camera front unscrew like you and screwed it back on but I didn't get it screwed right down - caught one of the desiccant tablets and the chamber wasn't air tight so I got frost after a while.  Opened it up again, found a tablet had a bit broken off and dust in the chamber.  So I gave it a good blowing out with my rocket blower and replaced the tablets with the replacement ones, carefully attaching the little rubber discs.  Then carefully reattached the cover and tightened it up using the holes in the face and the Baader tool.  It's now good and tight and hasn't come undone again.

Edited January 26, 2017 by Gina

[Gina]

Weather still windy, cloudy and cold

[Gina]

Well unless something quite magical happens to the weather I'm staying indoors in the warm!!

[Gina]

The clouds almost parted a little while ago and it looked like clearing but it changed its mind!!  Now it's looking brighter again!  The weather just can't make up its mind!

Decision - leave the imaging rig all set up ready to go outside or strip it down and check how everything fits together again in the rotation rig.  May be able to arrange it to be used with that without the RPi, using the same Arduino Nano and power circuit as it is now all connected to the laptop.

This cold is still making me feel pretty grim so maybe it would be better just to abandon all thought of imaging tonight and stay in the warm.  At least I can play about with the rotation rig   If I were to set up outside I would need to take the laptop back out as well as the imaging rig so a couple of trips out into the cold and some time setting up in the cold observatory.  I would have to do that in the daylight and before it got even colder and still the cloud or fog could come in. 

I'm currently watching Countdown and can usually beat the contestants from the comfort of my settee but I'm not doing very well today which shows I'm not up to scratch   At least I've just solved the numbers, though so have the contestants

Edited January 26, 2017 by Gina

[Gina]

The weather didn't improve until after dark when the clouds dispersed and the fog in the valley didn't come over here.  So there's a clear sky with masses of stars visible.  Might have guessed - well I did guess and made the decision to look after my health rather than ambition!  I know it was the right decision but I hate missing out on imaging time.

[Gina]

Astroberry driver install...

DEBIAN PACKAGE
================
1) Download latest binary package from http://sourceforge.net/projects/astroberry/files/Astroberry/
2) Install downloaded package $ dpkg -i indi-astroberry_*.deb

 

[Gina]

Just installed the BCM2835 INDI driver and subversion which will enable me to get the source code for INDI drivers, modify and install later.

sudo apt-get install subversion cmake libgps-dev
wget http://www.airspayce.com/mikem/bcm2835/bcm2835-1.50.tar.gz
tar xvfz bcm2835-1.50.tar.gz
cd bcm2835-1.50
./configure
make
sudo make install

 

[Gina]

Installed indi-astroberry...

pi@raspberrypi:/ $ cd /home/pi
pi@raspberrypi:~ $ ls
bcm2835-1.50         Desktop    Downloads   indi-astroberry_1.0.4-1_armhf.deb  Pictures  python_games  Videos
bcm2835-1.50.tar.gz  Documents  index.html  Music                              Public    Templates
pi@raspberrypi:~ $ sudo dpkg -i indi-astroberry_*.deb
Selecting previously unselected package indi-astroberry.
(Reading database ... 152862 files and directories currently installed.)
Preparing to unpack indi-astroberry_1.0.4-1_armhf.deb ...
Unpacking indi-astroberry (1.0.4-1) ...
Setting up indi-astroberry (1.0.4-1) ...
pi@raspberrypi:~ $ 

 

 

[Gina]

I think I may have done something wrong installing the INDI driver for the BCM2835 or maybe not done something needed as I get an error when trying to use either of the Astroberry drivers I want when they call bcm2835_init.  eg.

pi@raspberrypi:~ $ indiserver -m 100 -vv indi_rpibrd
2017-01-27T18:49:04: startup: indiserver -m 100 -vv indi_rpibrd 
2017-01-27T18:49:04: Driver indi_rpibrd: pid=2877 rfd=3 wfd=6 efd=7
2017-01-27T18:49:04: listening to port 7624 on fd 4
2017-01-27T18:49:04: Driver indi_rpibrd: sending <getProperties version='1.7'/>

2017-01-27T18:49:04: Driver indi_rpibrd: bcm2835_init: Unable to open /dev/mem: Permission denied
Child process 2877 died

 

[Gina]

I have found my box of lenses   These include a Russian made Jupiter 9 85mm f2 lens which is quite a heavy chunk of glass, plus zoom lenses 18-55mm, 35-105mm and 75-300mm all around f4-f5.6.  The shortest and longest are Canon and the middle one a Vivitar with M42 thread.

None of these lenses will fit in my current rotation rig but I knew I would need more than one variation on this rig.  The stock Canon 18-55mm zoom lens has a possible problem for remote control - the focus ring moves in and out with the zoom so will need a long motor pinion so that the teeth of the gear attached to the focus ring can slide up and down the teeth of the pinion.

I have still to test zoom lenses to see if they are of sufficient quality for imaging use and I guess I should make up a rig to test the zoom lenses before making special rotation rigs for these lenses.

[happy-kat]

The Jupiter lens sounds worth a try, I have the Canon 85mm f1.8 which is nice for day time but does get CA which makes using the f1.8 less attractive.

[Gina]

I get over the CA problem with these vintage terrestrial lenses by imaging in narrowband.

[Gina]

Been looking at what I would like to image and DSOs that need capturing soon if I'm going to get them this season.  One I particularly like is the Rosette Nebula plus the Orion Sword including the HorseHead and Ha nebulosity in the area which fits in the 135mm lens quite nicely for a wide view.  Also, as far as equipment is concerned I would like to try zoom lenses to see if they are up to DSO imaging.

The Rosette Nebula would be a good candidate for the 75-300mm lens, with maximum magnification of 300mm.  At that zoom the aperture is f5.6 similar to my Esprit 80ED scope which is 400mm but I doubt the lens would be anything like as good as the scope.

Here's a screenshot of CdC and the Rosette Nebula showing frames of 200mm and 400mm focal lengths.  I would like to be sure of getting the whole nebula in the FOV plus a bit of space around it, so I think 400mm might be a bit too much.  OTOH 200mm looks like being too wide.  So 300mm, in between the two would seem to be a good focal length to try.

Edited January 28, 2017 by Gina

[Filroden]

I found the 400m frames the Rosette wonderfully. I have to crop mine back as I use an alt-az mount and I have to deal with field rotation, but with your set up I think it will show the nebula and capture some of the extensions that link it up to the Cone Nebula.

[Gina]

Do you have an image you could show me of the Rosette with 400mm FL and ASI1600MM-Cool please?  Maybe it's time to work on my Esprit 80ED with field flattener + SX EFW with OAG + ASI1600MM-C.  Might be worth seeing if I can get away without guiding

[Filroden]

This is a single 60s sub at 300 gain/50 offset and -20C on the Esprit.

.

And the result after I had to crop the stacking artefacts from field rotation (probably losing a good 10% around the borders which won't affect you).

[Gina]

Thanks very much Ken   That looks very promising - great images   That settles it - Rosette imaging with Esprit.

[Gina]

If I were to increase the gain from the 300 that you're using I should be able to considerably reduce the exposure time and maybe capture unguided.  I can get 5m with 135mm lens and a 400mm is about 3x as long so should be able to use 60s at 400mm unguided   Seems the Rosette is brighter than I thought   15s exposure would want an extra 12dB gain (I think) meaning a gain setting of 420.  Going down to 10s would mean a further gain increase of just over 3dB. ie. 450.

However, with the KStars/Ekos/INDI system a download takes 8s for a setting of 16bit data so reducing the exposure too much would loose too much overall imaging time.  A 16s exposure time would mean losing a third of the total time downloading at least until I can work out how to buffer the data and download during the next capture period.  It doesn't do that as INDI and ASI driver is ATM - I've tried it.

[Filroden]

60s was about my limit. The mount tracks well enough but anything above 60s and you can see rotation in the stars (oh, the problems of alt-az mounts). I originally captured the Rosette at 15s then went up to 30s and eventually a mix of 30s and 60s depending on filter. I can't go much higher than 30s with LRGB as the sky background becomes too bright and I lose all dynamic range. However, with the Ha, if the target was better positioned to the east I could probably have gone longer than 60s (field rotation is less a low altitudes and towards the east/west).

I'd give 60s a try and you may even want to try 120s with your mount. It certainly saves pushing the gain.

[Gina]

I've found that increasing the gain and decreasing the exposure gives better results.  Of course this increasing data processing time considerably but a few hundred frames is not too bad with my fast Linux Mint desktop.  I find processing with PI in Linux is much faster than Photoshop on my Win7 desktop.  A faster machine plus faster OS makes a big difference   Admittedly, I have found 60s exposures gives good results generally but mostly I have been imaging fainter DSOs.  I think I'll probably use 30s exposures as a compromise.

Have you found any SII in the Rosette?  I know it emits Ha, NII and OIII and that would probably do for the 3 colours.  I could see considerable NII in the widefield images with Ha 5nm - Ha 3nm and I've seen Ha, NII, OIII combination in published images.