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For what has seemed like forever, the clouds finally parted late last night and the Orion constellation was very clear from my balcony.
I had a brief window of opportunity earlier this week and had difficulty focusing on stars at all using my DSLR (Canon 450D) and APT.
Last night was a breakthrough; I was able to capture starlight in APT liveview and even bring the stars into (significantly better) focus!
I now face my next challenge; I am unable to focus sharply on any of the stars. Using my telescopes focusing wheel I seem to get only blurry spots of light coming through, despite very carefully adjusting the wheel for quite some time.
At the risk of embarrassing myself, I've attached the images of Rigel and Betelgeuse I captured last night (on both long and short exposures, details of ISO and exposure are detailed in the image titles). This is as sharp as I can them.
Is there anyway I can fine tune the focus? I've seen AP videos on Youtube where jam jar lids have been glued to the focus wheel or motorized focusers attached. Are these gimmicky or do they make a significant difference?
I should mention that I don't yet have a tracking mount: I've eyed the Skywatcher AZ-GTI wi-fi as good candidate for my first meaningful mount (with the EQ wedge coming shortly after). Having emailed a number of retailers it seems these are in very short supply, here's hoping stock replenishes post-Christmas! I think this will let me get to grips with the equipment I have right now, definitely would like to get a sharper image, even if I'm only capturing star trails.
to capture the images shown below I used:
- Celestron 100AZ (100mm Aperture, 660mm focal length)
- Canon 450d
- Barlow lens x2 (Celestron)
- APT (connected DSLR directly to laptop via USB)
- Stock Celestron Alt-Az Mount
All the best.
Single__0049_ISO400_0s4s__20C.CR2 Single__0034_ISO1600_30s__20C.CR2 Single__0027_ISO1600_30s__20C.CR2 Single__0012_ISO1600_1s__20C.CR2 Single__0011_ISO1600_30s__20C.CR2
I run a Youtube Channel and as part of that I like to live stream the telescope. But the problem is lack of consistency.
Orion EON 110, Meade 10" SCT
Orion Mount - Exos2-PMC. Meade Mount 'push to' alt az with clockwork drive
APT, SharpCap, PHD2, Stellarium, ASCOM Hub
Focal Lengths Orion 660mm, Guide Scopes 188mm, SCT 2500mm
Powered USB for ZWO cameras (120 and 294)
Here is what happens:
Cameras, sometimes work, sometimes don't. I am not making the mistake of trying to get APT and SharpCap to view the same camera. I used APT for the guide scope and SharpCap for the main tube and the 294. Sometimes APT will take an image, sometimes it will do live view, sometimes both, sometimes neither. It is very distracting to the stream to spend an HOUR turning the computer off and on, plugging, unplugging and replugging the cameras just to get them to image.
When I do get an image it plate solves at the NCP, but if you move away, setting the coordinates to the scope position or the object I am looking at, it doesn't consistently plate solve. Sometimes it does, sometimes not. It is completely irregular and can change within a session.
Not all three plate solving means even work, for blind solve,
ASTAP never seems to work, either in point craft or locally stand alone
PS2 and ASPS work intermittently, as above
I did download all the catalogs and they are in the default directories.
This is very frustrating and I was wondering if anyone else is having this issue or has suggestions.
By Padraic M
I spent the full night out last night and got 6 hours of Ha lights on the Bubble and the Horsehead. Reasonably pleased with the results, but even though I followed my usual process and got good focus statistics in APT, I am slightly out of focus with roundy stars and some are even slightly donutty. Samples are attached below.
- After getting close to spot-on focus, the APT Bahtinov Aid showed a focus distance oscillating from -0.02 to +0.02. Seeing seemed good to the inexpert eye. Not so sure about transparency as there was some thin, wispy cloud throughout the night. So, I started the night's imaging with focus 'Close' rather than 'On' focus.
- Different subs show different quality stars, ranging from small donuts to circles.
- HEQ5 Pro Rowan; SW Esprit 80 with field flattener, SW stock manual Crayford focuser; ZWO EFW Mini; Baader 1.25" 3.5nm Ha filter; ZWO ASI1600MM Pro binned 1x1 @ -20c.
- AA Starwave 50mm guidescope with ZWO ASI290mm Mini guidecam binned 2x2.
- All subs are 300s, gain 139, offset 10.
- Polar alignment with Sharpcap to 17 arcsec ("Excellent"); capture with APT; guiding with Phd2. Focus with Bahtinov mask and APT Bahtinov Aid. Stacked in DSS with Darks, Flats and Dark Flats.
- Mount is well balanced in RA, but is very camera-heavy in Dec.
- PHD2 guiding was around 2"/px. Imaging pixel scale is 1.9"/px.
- Do I put the round stars down to seeing, given that the Bahtinov Aid focus distance was bouncing equally above and below zero?
- Can poor seeing cause the donut stars?
- Would an electronic auto-focuser do any better in this situation?
- Would the Seeing Monitor in Sharpcap give useful information? I didn't think to use it last night.
- Could my guiding performance, and possibly the Dec balance, have affected the image quality in this way?
- What are my options in future - abandon imaging for the night? Bin all images in software 2x2 or 4x4 to sharpen the stars at the expense of lower resolution?
- Other suggestions?
Sample 1: Detail from a single 5-min sub of Bubble nebula at 100% showing round stars, and a blurred bubble.
Sample 2: Detail from a different sub of the Bubble nebula at 400% showing donuts
Sample 3: Detail from a 5-min sub of the Horsehead nebula at 100%, showing both round and donut stars
Finally, both images stacked, calibrated and stretched, scaled to 4x4 in Gimp. 28x300s Ha on bubble, 22*300s Ha on horsehead.
By Padraic M
How can I set up APT so that it always connects by default to my imaging camera? I have an irritating problem that APT will regularly connect to my guide camera, even though that camera is already connected in Phd2.
I have created two APT shortcuts on the desktop, one specifying camera 2 (which usually is the guidecam) and the other specifying camera 1 (which is usually the imaging camera), but it looks like cameras 1 and 2 are not absolutely assigned to the ASI1600mm (imaging) and ASI290MC (guiding).
At APT startup, in the log it will say 'Connected to ASI1600mm' and then imediately say 'sensor size 5.6mmx3.2mm'. Then I know I have a problem as it's obviously not the 1600! I can usually sort it out by disconnecting, Shift-Connecting (to get the camera selection dialog), and selecting cameras 1 and 2 until I get the correct sensor size.
There must be a better way?