CCD vs Film? Lots of time vs no patience? Alright, this is your place to discuss all the astrophotography what's and what's not. You can discuss about techniques, accessories, cameras, whatever....just make sure you also post some nice photos here too!
First time shooting from an open field at Lor Halus. Surrounded by severe light pollutions in most directions. But the open, unblocked views make a good observation site -- and a big plus is that it is not too far from home.
One of the targets of the day is Luhman 16. The brightest apparent magnitude of all the brown dwarfs -- those failed to become a true star.
Calculated the predicted position from the published proper motion data. And finally located it in the exposures after the deep-red - near-infrared 865nm pass filter. Brown drawfs are emitting mostly in the infrared range.
Quite happy with the result -- was very worried about the severe light pollution in the low sky region where the target was.
There is another brown drawf, WISE 0855−0714, just next to Luhman 16 on the list. But completely out of reach -- mag 25 in J-band -- only those huge professional telescopes can reach. Eh, actually it is now classified as a sub-brown-dwarf.
The then next closest stars are Wolf 359 and Lalande 21185, both at high altitudes at the time. Much easier to catch.
Both are at the centre spot of the picture.
What's next on the list after Lalande 21185? Oh the big dog star, Sirius!
NGC3201, in the deep southern sky, much affected by light pollutions. Otherwise, it should appear more "globular". Now it looks more like an open cluster.
Last edited by hhzhang on Sun Apr 11, 2021 8:26 pm, edited 1 time in total.
M104. Shot 18x120s (L) before I checked the gears and astonished by the water condensation everywhere.
But I began to question my own sanity shooting the skies under the poor conditions (light pollutions, humidity). Shall I revisit the target again when clear skies come upon Singapore in the next few days? Current answer is no. Might as well just stop here.
Aha, I borrowed color information from public pictures. So it is not completely my data.
100% crop of the central region of M3 image. Just try to figure out how much resolving power to expect practically from Singapore if I continue to use this scope or upgrade to something bigger.
Lower to the centre lies a pair of orange-color stars barely well separated. They are measured 3" apart. I think it is probably the limit of the setup (guided tracking mount+scope+sensor + seeing) for deep skies. Guided tracking RMS was usually .5" to .8" (RA+DEC total, 0.5 would be .3" in each axis! -- exceptional happy cases). The aperture of the scope at 115mm is equal to a theoretical resolution approx. 1.1". Even if I double the aperture (like C9.25) thereby increasing resolution to .6", it would be far from doubling the final resolution of the image.
Meteoblue.com shows that astronomical seeing in Singapore is about 2". Does it mean we should not expect significantly higher resolving power in actual deep-sky (long exposure) astrophotos from Singapore?
Now it becomes interesting to compare the best eyes out there with my small refractor. Yes, Hubble in space vs a small APO from poor Singapore's conditions.
Just for fun! At the centre is the aforementioned pair of stars ~3" apart that are barely separated in my image.
