Thoughts on which imaging rigs to concentrate on

[Gina]

I did a search and I found Amazon were the cheapest for RPis.  I am definitely going down this route - just a matter of getting round to it.  Don't know why I'm hesitating, I've done lots with Linux in the past.

Downloaded the latest version of DSS and updated.  Then added all the lights and all the darks and set it going but when processing it said only one light was accepted for processing   It's been two years since I used it last and I haven't got the faintest idea of how to make it work   Maybe I should download the trial of PixInsight which I gather does the lot, including stacking.  If I can get used to PI it will help with the transition to Linux for processing as well as imaging.

[SilverAstro]

3 hours ago, Gina said:

Drive C: is just 5% fragmented so I don't think that's the problem.  One thing might be lack of RAM - it's got just 4GB.

Agreed, not the prob then, as long as your Swapfile is on C ? Might it be on D ? but why has the m/c become slow, 4GB RAM wouldnt explain it unless it used to be somewhat bigger and evaporated !

and is your swapfile still the same size as you thought it was, oh and did it get defragged as well, to make sure you have a contiguous big one for max speed you need to , , , ask an expert cos it is a long time since I did this on mine !! something like make it small, then defrag, then make it large again ? or the other way round ?

Just a few random thoughts for your consideration, prob a load of old . . .  !

[Gina]

There were some gaps in the cloud so I thought I'd have another go at imaging with my current setup but the software played up again needing a reboot.  Got the scope pointing almost right but after a couple of movements with the EQMOD buttons the mount carried on turning in dec until I switched it off as it was winding the umbilical round itself.   With that I thought "nuts", shut everything down and closed up.  No sign of any clear night sky in the next few days so I might have RPi control working by then.  The windows laptop is driving me up the wall

[Gina]

Back to desktop...  Can't find swapfile - been through Control Panel and can see no mention of swapfile.

[Gina]

OK - found it - virtual memory - used Windows Help   Size was 4055MB but system managed - help recommended custom size so I set it to 4096.

[SilverAstro]

3 hours ago, Gina said:

OK - found it - virtual memory - used Windows Help   Size was 4055MB but system managed - help recommended custom size so I set it to 4096.

Sorry ! my bad, my age showing, they used to be swapfiles and pagefiles and things in days of yore !

So that isnt the problem then, I mean not mis-set silly big or silly small by some misfortune

 

 

[Gina]

Would seem not - unless the system was working hard to work out the size required which seem unlikely.

The real answer is Linux, of course. 

[Gina]

Found out why I couldn't see the Cygnus Loop.  The field of view is a lot less than I thought it was.  I thought is was twice as big as the Cygnus Loop but it's only about half.  I don't know how this can be.  The FOV calculator app shows the coverage as around 7° across and the Cygnus Loop is about 3° so something is wrong somewhere.  I'll have to investigate.  If the FOV is indeed only about 1.5° I shall want a shorter FL lens.  I have 105mm and 55mm.  I feel like trying a 55mm f1.8 lens.

Here's a screenshot of the APT screen with a long enough exposure (240s) to show The witches Broom and Pickerings Triangle parts.

Edited August 26, 2016 by Gina

[Gina]

From first principles :- width of sensor = 4656 and pixel size is 3.8 microns giving a width of 4.636 x 3.8 = 17.6mm.  So the tangent of the subtended angle is 17.6 / 135 (focal length) = 0.13.  Inverse tan of 0.13 is 7.4° which is what the FOV calculator comes up with.

No I'm not using ROI.

[Horwig]

agree with your maths on subtended angle on the sensor, yes, the Cygnus loop should fit nicely on the sensor, In just compared it with what my QSI 6120 would give on my 105mm lens, and it fits, so your sensor on 135mm would give space to spare.

Just a thought, there's no subfame option on APT? It's not a piece of software I use.

 

Huw

 

Edit, sorry, you are not using ROI, my mistake

Edited August 26, 2016 by Horwig
not reading posts fully!

[Gina]

I tried SharpCap and that showed the right FOV so it's definitely something funny with the APT view.  ROI is definitely off and I couldn't find anything else to explain it such as zoom.  Anyway, I plan to use oacapture under Linux in RPi 3 when I get it sorted out.

[Gina]

Here's the view in SharpCap.  This isn't quite the full frame - it's cropped a bit particularly top and bottom.  The image is just a bit too big even at 25% zoom.

[Gina]

The FITS files saved by APT are fine - it's only the preview that's wrong   Here is one single Ha sub of 60s unguided from last night simply histogram stretched in Photoshop.  Two samples - firstly full frame and secondly rotated and cropped - then both resized to the maximum size of 1200px for upload here.  Saved in PNG format.  Tomorrow I'll see if I have time to stack and further process my collection of subs.

[Gina]

Here's a further crop showing full scale (not resized - just cropped) pixel for pixel from the original same sub.  Same histogram stretch and no other processing.  I have high hopes for when I can get a full set of Ha, OIII and SII subs.  I think this ASI1600MM-Cool looks like doing better than the Atik 460EX.  This magnified view is showing oblong stars at this exposure (60s) without guiding but in view of the amount of data I think I could easily halve the exposure and still get adequate subs for stacking.

[Demonperformer]

Some nice images starting to come out of this setup now. Are you using the camera lens at its full f/2.5 to get that much data, or have you stopped it down at all?

Thanks.

[Gina]

Thank you   I'm using it at full aperture - it doesn't seem to be showing any aberrations - these are superb lenses

[Gina]

Ran subs through DSS and after several goes at fiddling with the settings eventually got it to stack 26 lights out of 53 without darks because the darks I had were different exposure.  These lights are 30s with Ha 5mn Astrodon filter - 135mm lens f2.5 at full aperture and ASI1600MM-Cool camera at -23°C.  Processed in Photoshop:- Rotated and cropped to include just the Cygnus Loop.  Histogram stretched (actually I think I've squashed the whites), Enhanced DSO & Reduced Stars then Space Noise Reduction.  Resized to fit upload frame max size of 1200 px (about 50%) and saved in PNG format.

[Gina]

Here is what I captured of the North American and Pelican Nebulae, again 30s Ha exposures.  Run through DSS which chose 4 of 8 subs then in Photoshop, cropped and histogram stretched only followed by resize to 1200 px wide and saved in PNG format.

[Stu]

Some really nice images there Gina. Something solid to build upon.

I must confess, I'm enjoying the fact that you are able to get some imaging done, it's great to see. Simple is good sometimes  

[Gina]

Thank you very much Stu   Yes it's really great to be imaging again after so long.  Have to say I'm very impressed by the new ZWO ASI1600MM-Cool CMOS camera.  Also by the quality of the Asahi Super Takumar 135mm f2.5 lens even at full aperture.  The large image sensor with 16Mpx is much bigger than I've used before, other than DSLR.  It gives me much more scope to cover a wider view of the DSO I'm imaging and crop it without losing too much resolution.  And it's equivalent to mosaics on the larger ones.  Have to say, I'm really enjoying this combination

This is only the start and the first night for a couple of years that I've had a really decent clear night sky.  I plan to go on to add OIII and SII to the images and process to Hubble Pallet.  There are also a huge number of DSOs to go for. 

I have ordered the Astrodon 3nm Ha filter in 1.25" size from Ian King Imaging.  Though the 5nm seems to be doing quite well ATM the 3nm will be a benefit when the moon's out and probably also for fainter DSOs.  I might need to increase the exposure for these but so far 30s subs seem to be doing pretty well and don't need guiding.

Edited August 28, 2016 by Gina

[Davey-T]

Coming along nicely Gina, it's been a real boost to get some decent skies recently even though I've only been setting up a new mount.

Be interested in your conclusion on the 3nm veresus the 5nm HA filter, been considering this for a while and comparing folks images but difficult when they're from different set ups.

Dave

[Gina]

Thanks Dave

Several members have said the improvement with the 3nm filter is considerable and well worth the extra cost so I'm hopeful and much looking forward to trying it 

Edited August 28, 2016 by Gina

[Gina]

A couple of hours of clear sky last night and I managed about 70 x 30s Ha subs on the NAN & Pelican.  I was going to change to OIII but Artemis Capture couldn't find the filter wheel, just when I wanted it.  It was working...  So that's something to sort out.  As I had already captured a fair number of Ha subs on the Cygnus Loop I decided to find another DSO to grab in Ha. 

Having looked up the positions of several and found them in CdC I decided on IC1396 in Cepheus, a large nebula which includes the Elephant Trunk, as all the others were too low down.  After slewing to it with CdC, all I could see was a misty disc with a bright star on the edge.  Yes, this was it but...  I checked the lens and it was misted up.  Very heavy dew   Cleaned that and still misty - thin high cloud had rolled in   Gave it half an hour but no joy so I packed up for the night.

Tonight looks more promising from the forecast but I think dew could still be a problem so I shall be sorting out a dew shield and maybe dew heater for the lens.  I also hope to find out what's the matter with the filter wheel.  Yes, it was connected to power and USB just as before.  Meanwhile I have a nice crop of Ha subs to process.  I'll be back soon with the results...

Edited August 29, 2016 by Gina

[Gina]

35 of 71 subs stacked in DSS (it's still choosing about half the total), rotated 180° to put it the usual way up and histogram stretched in Photoshop.  Reduced in size and saved in PNG format for upload here.  No other processing as yet.

Edited August 29, 2016 by Gina

[Gina]

I'm going to try something - what happens if I try uploading the full size image of 4656×3520 pixels...  Please wait - uploading will take a long time with such a poor internet connection...  1m  2m  3m  4m  5m ...  Ah here it is