Thoughts on which imaging rigs to concentrate on

[Gina]

This may be alright when I get faster broadband in a few months but 5m to upload and over 2m to download the full size image is not good.  But it does seem to work and the full size image may be good for others to view.  I didn't have this "problem" with the Atik 460EX because the frame size is much smaller. 

These large sensors with huge megapixel numbers are in a whole different ball-park!  Wonderful!   The new ZWO CMOS cameras are fantastic! - to the point where I'm wondering if I will ever use the 460EXs again.  But I am preparing myself for a fall - can this really be?  Can these CMOS cameras really beat CCD hands down??  I think it's blown my mind!

Edited August 29, 2016 by Gina

[SilverAstro]

2 hours ago, Gina said:

I'm going to try something - what happens if I try uploading the full size image of 4656×3520 pixels...  Please wait

Very nice ! ( and only 2min to download on my slow 3G, followed by 1.5min whilst my lappy untangled its VirtualMemory and returned control to me )

Shame about DSS not liking 50% of your subs, wonder why that is ?

Have you done any exposures in white/mono light and/or RG&B ? with it for comparison. Presumably the 5nm filter cuts out a lot / needs a lot longer exposure ( me never having done anything like this should probably ask that in the beginners section ! )  ie. in what way does the 5nm image differ from, for example, a broad band red as given by a moded dslr (apart from needed exposure duration and noise !? )

 

Edited August 29, 2016 by SilverAstro

[Gina]

I think I need to look into the DSS settings further - it's a complicated beastie with lots of settings, many of which I don't understand - must read some more tutorials on it!

I haven't done any other imaging but Ha so far with this camera though I did set the FW to the Luminance filter to try and find a DSO I was hunting (without success).  Yes, the NB filters reduce the general light enormously - which is their function - only letting through light of a certain wavelength and a little bit either side.  The amount of the unwanted light either side of the wanted wavelength depends on the bandwidth.  The narrower the less unwanted light comes through.  Unfortunately, the production costs rocket as the bandwidth decreases eg. a 3nm Astrodon Ha filter costs 4 or 5 times the price of a 7nm Baader one.  Both firms make excellent quality filters but narrow costs more.

To answer your specific point, a red filter will let about the same amount of Hydrogen alpha light through as a narrow band one but the red filter also lets a lot of red light of other wavelengths through.  So hydrogen gas emissions tend to get lost is other light wavelengths.

RGB filters come in for galaxies mainly which have a wide spectrum of light.  Nebulae consist of clouds of gasses, mainly hydrogen but also oxygen and sulphur (I don't like the newer American spelling of sulfur! Nor does my English spell checker).  These gases emit light of several discrete wavelengths and have been labelled hydrogen alpha and beta - oxygen I, II and III etc.  Don't know if there are other wavelengths for H and O.  The usual wavelengths used for narrowband imaging are Ha, OIII and SII though there are other wavelength emissions they are weaker and less used.

[Gina]

I've made a Blue Peter style dew shield using an empty plastic bottle (contained peanut butter) with the ends cut off and sticky backed plastic in the form of flocking paper from FLO, to line it with and prevent reflections.  I'm hoping that will be enough.  I've checked that there isn't any vignetting of the view across to the next hill.  If I still get dew problems I'll have to add a heater.

The filter wheel problem is USB connection woes.  I've tried rebooting the laptop to no avail - neither the FW nor my focussing system are showing in the Device Manager   The focuser was working last night, the FW wasn't, now it's neither!!!  The camera is working and the mount is working though from another laptop port.  FW and focuser run off the USB hub in the camera.  Strange thing is that the laptop beeps when these are connected but they don't show in DM.

[Gina]

Been trying again.  Got FW showing in DM with a ?  "No Driver Installed" so I reinstalled the driver and Artemis Capture now recognises the FW.

A little later... Tried changing filters and it works   Hooray - one problem solved - next is the focuser.  I often get problems with the USB connection on this.  It's an Arduino Nano with a mini USB connector and these are notoriously troublesome!  I'll go out and waggle it...

[SilverAstro]

31 minutes ago, Gina said:

I think I need to look into the DSS settings further - it's a complicated beastie 

The amount of the unwanted light either side of the wanted wavelength depends on the bandwidth. 

Don't know if there are other wavelengths for H and O.

Thanks for that explain ( and no I dont like sulfur neiver ) !

I had been thinking that the only wanted light was that of the nebula, but now you explain I suppose the 'unwanted' is light pollution and/or the moon. Yes I am seeing now I think. Ancient physics reminds me of the Hydrogen Balmer(sp?)  series producing beta gamma &etc, I have seen discussion somewhere about a Hbeta filter, but there was doubt if it was needed as it produced only the same hydrogen region image, something like that.

As for DSS yep, I know, a little mysterious at times , but I have only used it for simple stacks of camera&tripod pics. of lots of short exposures. It is throwing away 1/2 your life ! so you must beat it into submission !

Good luck with the usb.

 

[Gina]

H-beta is a sort of pink colour and one quarter the strength of H-alpha and yes, it's produced by the same gas as H-alpha so adds nothing.  I think that's right   As for other wavelengths, there are thousands of stars in the Milky Way so any DSO in this region will be swamped by the stars. An Ha filter will block most of the light from stars making them much weaker in the image and allowing you to increase exposure until the emissions from the hot gasses show up.  Yes, the moon and earth borne light pollution also add to the background unwanted light.

[SilverAstro]

8 minutes ago, SilverAstro said:

Ancient physics reminds me of the Hydrogen Balmer(sp?)  series producing beta gamma &etc, I have seen discussion somewhere about a Hbeta filter,

54 minutes ago, Gina said:

labelled hydrogen alpha and beta -

Ooops, sorry, re-read and I see you have already found the Hb ! 

There is also an interesting hydrogen at 21cm - but a little outside these types of sensor lol !

 

[Gina]

OK...  Waggled USB connector and got connected.  Laptop lost its pointer though so another reboot   Now have pointer back and connections to both FW and focuser and both working.  Phew!  Just hope they stay working until dark!

[Gina]

Here are a couple of photos of the dew shield.  BTW in resizing these images I noticed that the DSLR has fewer pixels than the ASI1600MM-Cool sensor!

[Gina]

The dew shield is a nice push fit on the lens

[sloz1664]

42 minutes ago, Gina said:

The dew shield is a nice push fit on the lens

Hi Gina,

It's got that William Otics look about it

Steve

[Gina]

Amazing what you can do with rubbish   I have such a lot to be thankful to Blue Peter for   I was going to 3D print one but then I had a thought...

[Gina]

Have captured another 50 Ha 30s subs of the Cygnus Loop and now changed to OIII filter and taking 100 subs.  The preview looks alright

Refocussed for the new filter.  Count for Ha was -3 and now for OIII is 31.  The remote focuser is working fine - using SharpCap for focussing with zoom at 200% so that I can see individual pixels and I can get the focus to about 1-2 pixels.  The focussing resolution is adequate after all - I had thought it needed to be a bit finer but it's just alright.  The focus was changing slightly due to the seeing and this was around 2 counts.

[Gina]

I won't have any OIII subs to analyse until I've finished transferring all the Ha subs from obsy laptop to desktop PC and that will be over an hour.  I'm capturing umpteen gigabytes of data with this new camera!  Data collection is running at nearly 64MB a minute.  That's over 3GB an hour   Yes, it is that much.  Each frame is 32MB and I'm capturing 2 frames a minute (nearly).  Each frame takes a few seconds to transfer from camera to HD.  Probably running at about 60MB a minute then or 3600MB/hr!

I shall be capturing 100 OIII subs to get 50 stacked and that is 3200MB = 3.2GB.  Just over half way ATM - should be finished by 11pm then I shall change filter to SII and grab a hundred of those.  After that I shall go to a different DSO if it's still clear. 

I could be up all night - I haven't got this process automated yet as I need to be on hand to move GBs of data about.  Plus focus needs changing between filter wheels and that's manual currently.  I'm hoping I can get things more automatic once I get the RPi/Linux system worked out.

Edited August 29, 2016 by Gina

[Gina]

Now have the first OIII sub to show.  Changed from FITS to TIFF and then histogram stretched in Ps, resized and saved in PNG format.

[Gina]

Here's the first SII sub histogram stretched in Ps, resized and saved as PNG as usual.

[Gina]

Nearly finished the Cygnus Loop   IC1396 next I think.

[Gina]

Capturing 30s Ha subs of IC1396

[SilverAstro]

1 hour ago, Gina said:

Nearly finished the Cygnus Loop   IC1396 next I think.

A fine clear night

and I have taken another liberty with your pics Stars from the Ha +Ha,neb +the single O,neb (didnt notice the SII in time !) I wondered why I had lost a lot of red then realised it had turned into most of the yellow, I suppose that should happen ?

[Gina]

Single 30s Ha sub of IC1396.  Histogram stretched and resized.

[Gina]

Captured the best part of 100 OIII but then the fog came in and I packed up and went to bed just after 4am.  Good session even if I didn't get to complete the series

[Gina]

This DSO is much fainter than Cygnus ones and has needed a lot more histogram stretching.  I think this would benefit from longer exposures as I'm capturing very low data in 30s subs.  To go longer I shall need to get the polar alignment better of use guiding - maybe both.  Not surprised, I expected to reach the limit of this super simple rig on fainter DSOs and I have been looking at adding guiding.  Mind you, the PA could well be out and I think I might use the next night with some clear sky to use PoleMaster to check the PA.

Here is the full frame with just histogram stretching and resizing.  Stack of 40 subs of 80 captured.

[Gina]

Been thinking about guiding.  As usual - two choices separate scope/lens guider or OAG.  I have always preferred OAG as I've found it more accurate and also doesn't need a separate scope or lens with its mounting problems. 

Using a lens I have a back focus of 45mm which can be pushed a mm or two by focussing the lens and there is simply not enough room for a standard OAG and filter wheel.  I'm considering the idea of buying the Starlight Xpress USB Mini Filter Wheel (1.25") with OAG.  This would make for the most compact and lightweight setup with no alignment problems or flexibility between guider and main imager.  It's just a pity the wheel only takes 5 filters - I would like Ha, OIII, SII, R, G and B making 6.

I guess I could use this FW for narrowband only as the only time I want RGB is for galaxies and the only galaxy that wants a wide FOV is Andromeda (M31) the rest would want a scope with plenty of room for a normal OAG.  M31 being bright and wideband won't need guiding.  I may have a go at M31 tonight as there are a couple of hours before midnight forecast for tonight.  I think M31 should be above the trees

The other thing I want to do is check/improve PA using the QHY PoleMaster.  I think the PA is almost certainly a bit off.

[Gina]

Looks like I won't be doing anything tonight - ASCOM is throwing up an error when trying to connect to the mount   The USB-to-serial adapter is being recognised and showing in the Device Manager as COM3 which it has been on each imaging night lately so it's not that.  I have never had this error before.  I guess the solution will be to reinstall the software   Oh well...  I guess I must be satisfied with a good session last night and I am a bit tired tonight from the very late night - um... early morning   Any suggestions as to whether this can be fixed without reinstalling ASCOM?  Or is this the best way forward?