Quote:
Originally Posted by montewilson
Hmmm - I'll think about that. It΄s an interesting idea. I enjoy doing Ha stuff. Any suggestions on a suitable object that we could consider?
BTW - are you having troubles focusing? I use RoboFocus and although I can get focus it is rarely quick or easy and the @Focus feature in CCDsoft is not much chop if you don't have an absolute encoder value for the focus position. The backlash in the stepper motor confuses it.
|
Monte, I’ll let you pick the first target if you like. There are endless objects in the night sky to target with the FSQ. There is nothing it won’t frame well with exception to small planetary nebs and galaxies as you generally need a longer focal length. Try to pair two interesting objects in the FOV, such as a neb and cluster to provide something unique. In future, we can use TheSky mosaic tool to ensure both our frames are centered as we collectively acquire data. I’m presently working on a small mosaic project at the moment, of which I’ve only collected 3 hours worth of one frame. I’ll come back to that when the moon disappears again.
The hardest part will be the differences in CAA rotation. If my CAA is slightly different to yours, we’ll crop data. In the grand scheme of things, this is only a minor issue. A plate solve may sort it out, but we will need to test this. Just take exposure of the target – full frame and upload it to my website. I will provide you with login details via PM. I can then center the object and commence data acquisition.
Re: Focusing… You don’t have to teach Robofocus so it moves the focuser physically all the way in from out. I’ve only taught it ~400 steps of either side of critical focus. Also adjust the step size so it is reasonably small. You can also tune backlash in the Robofocus control panel. I’d imagine it wouldn’t be much, perhaps 5 to 10 steps. The critical focus zone for the FSQ is only 55 microns so the lower step size will assist. I usually work around 5 or 6 microns per step. Providing you consistently hit this zone, you’ll be fine. Not all my filters are parfocal so I refocus regularly. You get focus shifts as the temp. changes anyway. Mine haven't been large enough to worry about. I've actually acquired RGB data in one night without having to refocus. Imaging in an observatory does provide a stable environment.
I have no focusing problems, but I don’t use @focus which I believe is CCDSoft specific. I use MaximDL for image acquisition which has a similar automated focusing routine, but I don’t use it either. FocusMax all the way my friend. I reach precise focus generally under a minute every time. Works a treat once you’ve built a good v-curve model – around 40-50 steps as it moves through the critical focus zone (you’ll need at least 6 v-curve runs to build a good model). What I like about FocusMax is that as it begins to reach close to focus, it stops and takes five or six exposures. This allows the software to accurately determine the FWHM and other measurement calculations on the star based on seeing conditions. Using this information it calculates where precise focus is located and moves focuser to that position. There is no way I could obtain this level of focus accuracy and consistency manually The only time I’ve experienced issues is when the star automatically targeted to focusing is in a cluster. Hope this helps. FocusMax - Highly recommended.
Quote:
Originally Posted by glenc
Jase you wrote "Interesting both James and John missed the reflection neb considering it’s rather predominate."
Here is my theory about that.
Modern aluminium mirrors reflect 85% of the blue light, at 400nm, and 89% of the orange light, at 600nm.
I estimate that the speculum mirrors used by Dunlop and Herschel reflected about 47% of the blue light and 76% of the orange light. Maybe that is the reason why they missed the blue reflection nebula.
Silver on glass mirrors were first used in 1856. Schmidt discovered NGC 6726-7-9 in 1861.
Copper only reflects 35% of the light at 400nm and tin 76% at 400nm.
Speculum was 12 parts copper and 5 parts tin according to:
http://www.saao.ac.za/assa/html/his-...el__14ft_.html |
Thanks for the info Glen.
Good point. Mirror coatings were very different back then.
