Autostretch with BYEOS?

[Gasman]

Hi guys

New to the forum!. I`m deciding on which camera to buy (Canon 750D is favourite at the moment!) . I have been using another software package designed for DSLR/CCD use and although it has a histogram it doesn`t have an autostretch feature yet. The sort of observing I do is spectroscopy and my Lodestar guide ccd is constantly giving say 2-3 second shots in Liveview to display a fine slit in the FOV but without autostretch I`m having to adjust the histogram settings regularly to show the slit which can be invisible without adjustment and the slit is needed to get the star on my spectroscope . Does BYEOS have anything like an autostretch setting which could enable the slit to be seen without constant histogram tweaking please?.

thanks

Steve

[Gasman]

Rick

Yes on second thoughts perhaps not a good idea using a nice expensive DSLR as a guide cam . I do like the idea of a self contained unit for use on the road ie storage,power, focus etc such as comes with a DSLR.

You will enjoy using the Alpy its an excellent piece of equipment. Do checkout other spectro software such as ISIS from Christian Buils` site and also BASS both excellent packages and both unbelievably free, but maybe we are veering off topic and maybe subjects for another post.

cheers

Steve

[astroman133]

Steve,

 

So are you doing real-time spectra for public outreach?

 

When I have tried spectroscopy it was with a slitless grating, so i am having a bit of a problem trying to understand what you are struggling with. Also the software that I have (RSPEC) which controls the camera and displays the spectra only works in real-time with DirectX compatible high frame rate webcams, like the ZWO ASI120, StarlightXpress Loadstar, or NexImage 5. Of course you could use any camera and software that  can capture an AVI file or a still image (a T6i with BYE, for example) and use that video after the fact for spectroscopy.

 

If your issue is that the star is shifting in the field-of-view between successive images then it seems that your issue is with tracking, polar alignment, and/or autoguiding.

 

That said, the Premium version of BYE (also in the free trial version) has the ability to stretch images for display on the screen, but it is not automatic. You have to drag a curve, via the provided control points, to brighten the displayed picture.  The adjusted curve does then apply to successive images. It does not work with LiveView images in Frame and Focus mode, only with still images in Imaging mode. 

 

Canon's LiveView is based on taking short duration (say 1/30th of a second) images in succession and displaying them on the LCD display or, for BYE, downloading them to the PC. For nighttime astrophotography use the short exposure means that only the very brightest stars or bright solar system objects (Moon, Venus, Mars, Jupiter, or Saturn) will be visible in LiveView.  It is useful only for 2 purposes...planetary imaging and focusing. It is not possible to slow the frame rate to brighten the image.  The only way to brighten the images is by increasing the gain of the analog-to-digital conversion. This is accomplished by means of the ISO and shutter speed controls, but the frame rate still stays constant.

 

Another thing with the DSLR cameras is that you have the ability to shoot and download RAW and/or JPG images.  The RAW images are unstretched, linear data, but the JPG images have been stretched in the camera prior to download and are therefore brighter.

 

If you replaced your current camera with a T6i and still had to take 2-3 second exposures, I am not sure what the advantage would be.

 

Canon DSLRs are certainly suitable for astrophotography and BYE is an outstanding product for controlling the camera to get the most out of it, but I don't know how this would solve your issues.  Perhaps I don't understand what you are trying to do.  Also understand that larger images, because of their size, take more time to download from the camera and to display on the screen since you are limited by the bandwidth of the connection (usually USB 2.0) between the camera and the PC.

 

If you still have questions, please feel free to ask them.  Guylain, principal author of BYE and moderator of the forum, has said that any astrononomy-related discussion is appropriate on these forums.

[Gasman]

Hi Rick

Many thanks for the helpful reply. The setup I have for my ccd`s is similar to an OAG set up except the mirror has a 25 micron slit in it and the light goes through this slit to my Atk 314/Alpy 600 spectroscope. My Lodestar fitted at right angles to the Atik has a FOV showing the slit which is quite faint off centre in the FOV. The chosen star is seen in the Lodestar FOV and then tweaked with the hand control so it goes on to the slit for the spectro. Its this Lodestar FOV where the slit can appear/disappear depending on the available light in the image. When it disappears I then have to nudge the histogram to bring it back again but this is only carried out on the last image taken so an evening can be spent moving the light/dark points left and right.

I`m not replacing my CCD`s but want to also take my smaller ED80 out on the road with my DSLR and Star Analyser (with a portable equatorial I`ve yet to decide on!) hence my interest in BYEOS to use out in the field as well as on my main scope in place of the Lodestar. So obviously the stretch would only apply when its on my main scope.

hope that makes sense

Steve

[astroman133]

Steve,

 

So the Atik 314 is the science camera and the Lodestar is the guide camera. Once you have the target star visible through the slit in the 314, you should start autoguiding with the Lodestar.  This should keep the star visible through the slit for as long as necessary.

 

You haven't said what spectroscopy software you are using, so I will assume that it is RSpec.

 

Unless I am missing something for your road show (80mm refractor and DSLR with StarAnalyzer, I do not believe that you can feed a Canon LiveView stream from BYE to RSpec. You would need to shoot moderately long duration images (a guess would be 10-30 seconds) with the DSLR and then open those image files in RSpec. As long as you have a reasonably good polar alignment you should be able to get exposures up to a minute or so that would be good enough to bring into RSPEC, but since you are not looking at live images, the autostretch question becomes moot. It is only for stretching an image that has already been taken and is being displayed on the PC monitor.

 

I do hope that I understand your issues correctly and that my reply is useful.

 

 

It still seems like autoguiding

[astroman133]

I hit the Post button before finishing...

 

it still seems like autoguiding would solve your issue with using the 314 as the science camera and the Lodestar as the centering/guiding camera.

 

I hope this does help.

[Gasman]

Sorry Rick I think I`m over complicating things the way I`m describing it, perhaps a few screen grabs would help, next time I`m out.

I`ll try another way.

The DSLR I decide on I would like it to perform 2 operations if possible -

1. Act as a guide camera on my main scope/spectroscope where it would monitor a field of view which has a slit visible in the image. This slit can be visible in the shot providing the histogram settings are correct for that shot. The Lodestar at the moment takes a 3 sec (or longer if the chosen star needs it) shot then another, then another ...and so on each shot may or may not show the faint slit. When the slit is visible I tend to manually guide with the hand controller why? well the slit is 23 microns (sorry not 25) wide and my Lodestar has 8.2 micron pixels so the accuracy has to be within 3 pixels to get any spectrum at all and I`m not sure I could achieve this level  of guiding automatically??. Maybe this is achievable but I`ve not cracked it yet .

2. Use my DSLR with a Star analyser with my ED80 (plus mount) while away from home. This level of spectroscopy is fine without guiding or stretching and as its slitless there is no slit to keep the star on.

My Lodestar is getting a bit long in the tooth now and gives me the odd hiccup so the thinking is maybe killing two birds with one stone ....!!!.

I use a few different software packages for post processing of the spectra including Rspec occasionally so I have no problem there its just getting the spectra in the first place.

It seems like BYEOS will offer me the same post stretching as other packages but I do like the look of its interface and when I get my DSLR I`ll be happy to download BYEOS and try it.

Hope that describes things a little better

regards

Steve

[astroman133]

With the ALPY 600, the off-axis camera performs 2 functions: 1) to put the star in the slit, 2) to keep it there by allowing you to  automatically autoguide the mount with software, using some other star that is in the same field-of-view.

 

You are doing 2) manually, which is tedious, but OK. Depending on your mount's characteristics (periodic error, polar alignment, backlash), autoguiding with PHD2 could work just fine.  When I image, I get autoguiding with less than +/- .5 pixels movement with guiding and Periodic Error turned on. And, even if the star momentarily moves out of the slit, autoguiding should act to return it to the slit faster than you probably can with a manual adjustment.

 

Newer cameras have more sensitivity and smaller pixels (in the range of 2.8-3.5 pixels) and may do even better.

 

If you use a DSLR as the off-axis camera with your ALPY, I would not call it a guide camera.  It would lead some people to think that they could autoguide with the DSLR, and that is not what you are doing.  You are merely using it as a centering camera to put the star into the slit and to re-adjust it back there as it shifts out. That would work, but you would still need to use still exposures, as opposed to LiveView "movies" to see the star and the slit. Over a long period of time it would definitely contribute to wear and tear on the DSLR's mechanical shutter.

 

Our club has a new ALPY 600 that we will hopefully start to use over the next few weeks. It should be fun!