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Hi, I've got a Skywatcher Heritage 130p reflector, and if i insert anything less than 10mm eyepiece, the image won't get crisp. I guess it's normal, but as I'm very new to astronomy, I'd like to know what the sharpness depends on exactly.
Is that the focal length (how fast the telescope is? ) or the size of the mirror and how much light it gathers? Or both affect it the same way?
Are things the same with refractors in this regard? Thanks.
I'm getting desperate over this hobby (but I refuse to give up); with every change new problems set in. I purchased a SVBONY SV106 (60mm - 240mm) guide scope to replace a 80mm - 400mm scope, I was using as a guide scope which was installed on the Orion 8 tube rings. I replaced the finder scope with the guide scope.
First issue balancing but that one I sorted out. Then I tried to focus the ASI120MM with the new guide scope. For the old one (80x400) , I needed 2 extensions (in fact the extensions are low cost barlows from which I removed the plastic lens) to get focus. To align the new guide scope, I used a 17mm eyepiece and that went ok while pointing at some far away trees. But I could not get the ASI120MM focused on the same trees, not with PHD2 nor with Firecapture; I turned the gain way down, but with or without extensions, no focus. As bad weather is (again) setting in and the scope is permanently outside I had to stop trying.
So I take on this break to get some assistance. Anybody any advice on this, for
As I said few days ago in my presentation I recently got my first scope (skywatcher 127) and over the last days I tried to test It.
Due to impossibility (temporary) to bring the scope in a decent location to make observations, I had to test it from home through a window (and under the sky of London - not the best at all). So i know that quality is of course affected.
On the other hand, I am sure that the performances are worse than I could expect also under these conditions (maybe you will correct me) and would asks for opinions to improve.
As a (mainly) planetary scope, I did not have a lot of choice: no Moon, Jupiter and Saturn out of my field of view. I pointed at Mars.
First sight, I see the very big central obstruction. I played with the knob of the focus to get rid of the big black spot in the centre of my target and here you are the issues that I would like to talk about:
1) the target became very small (ok) but still was not focus (very blurry and not a lot of clues to get atleast the shape of the planet well defined - can imagine to find any detail on it )
2) Also the colours did not convince me as no other colour than a light yellow was visible
3) Changing the eyepiece (10 instead of 25) for a magnification of 150x did not improve the situation: probably the image was even worse, more blurry with more irregular shape than before, no ability to focus at all. Differences from before : bigger (but still much smaller than expected) and very little variation in colours (I believe I saw a bit of orange).
To complete, later, I tried the scope to stars: Orion costellation was visible from my place and tried to all the stars. Although still a bit blurry (the brightest stars), I had impression of more sharp view, differentiation in colour and better shape (stars almost like a dot). Moreover, to give you a final idea, Mars (at the best focus I could get) did not appear that much bigger than Betelguese.
What do you think I can do to get better results? Could be a scope problem or some adjustments needed? Unfortunately I have no comparisons.
Thank you, Hope I was not too long 😅
I’ve just acquired the above (birthday prezzie!).
It’s a nice finder, and a definite boost from the 7x30 bundled with the scope!
However, I’m struggling to get anywhere near focus with my Pentax K50 on the end of it... anyone know why? There’s no focus mechanism to speak of, other than the objective lens’ mounting thread...
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.